[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"$fxLN3MUwXCdr5RPjwZYIDpOj8CHyjOmngWTgoKXPtZbg":3,"$fjgVfZFbFKabqNMHqV0dLn4Aikwjx61XgkhVh2-Nwwpk":36,"$f3Ft0rKFJHppdzE-vuveecxx1BUcg9iOlMLtyzf_MJDg":249,"$fucxFBm2ZjZfGSdmdRaSNGBI_F0jJme4f0GTvzUhQfL8":314},[4,8,12,16,20,24,28,32],{"title":5,"slug":6,"path":7},"About Microbeonline.com","about-microbeonline-com","\u002Fabout-microbeonline-com\u002F",{"title":9,"slug":10,"path":11},"About Me","about-me","\u002Fabout-microbeonline-com\u002Fabout-me\u002F",{"title":13,"slug":14,"path":15},"Advertise with Us","advertise-us","\u002Fadvertise-us\u002F",{"title":17,"slug":18,"path":19},"Privacy Policy","privacy-policy","\u002Fprivacy-policy\u002F",{"title":21,"slug":22,"path":23},"Authors","authors","\u002Fauthors\u002F",{"title":25,"slug":26,"path":27},"Microbes","microbes","\u002Fmicrobes\u002F",{"title":29,"slug":30,"path":31},"Books","recommended-books","\u002Frecommended-books\u002F",{"title":33,"slug":34,"path":35},"Tags","tags","\u002Ftags\u002F",{"type":37,"data":38},"blog",{"slug":39,"title":40,"description":41,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":44,"lastUpdatedDate":45,"draft":46,"category":47,"image":42,"body":48,"faq":49,"commentsClosed":46,"tags":50,"related":52,"comments":245},"bacteriology-mcqs-zoonoses-stis-spirochetes","Bacteriology MCQs: Zoonoses, STIs and Spirochetes","\u003Cp>Twenty clinical MCQs with explanations on zoonotic and sexually transmitted bacteria: plague, tularemia, \u003Cem>Pasteurella\u003C\u002Fem> bites, gonorrhea, syphilis serology, chancroid, and leptospirosis.\u003C\u002Fp>",null,"Acharya Tankeshwar","2025-08-21","2026-08-28",false,"mcqs","Twenty clinical multiple choice questions on zoonotic bacteria, sexually transmitted infections, and spirochetes, with a full answer key and explanations at the end. Write down your answers first, then check against the key.\n\n## Zoonoses and high-consequence bacteria\n\n**1.** Which of the following is generally not considered a potential agent of bioterrorism and biologic warfare?\n\na. *Yersinia pestis* \\\nb. Botulinum toxin\\\nc. *Streptococcus pyogenes* \\\nd. *Brucella* species \\\ne. *Bacillus anthracis*\n\n**2.** Which of the following species of *Pasteurella* has been associated with infections of the female genital tract and a newborn?\n\na. *Pasteurella multocida* \\\nb. *Pasteurella pneumotropica* \\\nc. *Pasteurella ureae* \\\nd. *Pasteurella bettyae*\n\n**3.** In a patient who has the bubonic form of plague, all of the following specimens are acceptable for diagnosis except:\n\na. Stool culture on Hektoen Enteric agar \\\nb. Blood culture using routine laboratory media \\\nc. Culture of a lymph node aspirate on blood or MacConkey agar \\\nd. Acute and convalescent serology \\\ne. Immunohistochemical staining of lymph node tissue\n\n**4.** An 8-year-old boy was bitten by a stray cat. Two days later, the wound was red, swollen, and draining purulent fluid. *Pasteurella multocida* was cultured from the wound. The drug of choice to treat this infection is:\n\na. Amikacin \\\nb. Erythromycin \\\nc. Gentamicin \\\nd. Penicillin G \\\ne. Clindamycin\n\n**5.** All of the following statements regarding the epidemiology of infections caused by *Yersinia enterocolitica* are correct except:\n\na. Most human infections are caused by serotypes O:3 and O:9 \\\nb. Humans acquire the infection from ingesting food or drinks contaminated by animals or animal products \\\nc. Person-to-person spread is quite common \\\nd. A large inoculum is required to cause infection \\\ne. Infection is more prevalent in persons with histocompatibility antigen HLA-B27\n\n**6.** Intimate contacts of patients with suspected plague pneumonia should receive which of the following agents as chemoprophylaxis?\n\na. Gentamicin \\\nb. Cefazolin \\\nc. Rifampin \\\nd. Penicillin \\\ne. Doxycycline\n\n**7.** Which of the following subspecies of *Francisella tularensis* is the most virulent for humans?\n\na. tularensis \\\nb. holarctica \\\nc. mediasiatica \\\nd. novicida\n\n**8.** All the following statements regarding the etiologic agent of chancroid are correct except:\n\na. The organism is a small gram-negative rod \\\nb. The organism requires X factor but not V factor\\\nc. The organism grows well on standard chocolate agar \\\nd. On Gram stain of lesions, the organism occurs in strands \\\ne. The organism is susceptible to erythromycin\n\n**9.** Which of the following cell components produced by *Neisseria gonorrhoeae* is responsible for attachment to host cells?\n\na. Lipooligosaccharide \\\nb. Pili (fimbriae) \\\nc. IgA1 protease \\\nd. Outer membrane porin protein \\\ne. Iron binding protein\n\n**10.** An 8-year-old girl was playing in a slowly moving stream when she cut her foot on a sharp object. Three days later, she was brought to the emergency room of Tribhuvan University Teaching Hospital because of pain and swelling at the site of the wound and drainage of pus from it. The most likely cause of the infection is:\n\na. *Vibrio vulnificus* \\\nb. *Escherichia coli* \\\nc. *Aeromonas hydrophila* \\\nd. *Proteus mirabilis* \\\ne. *Salmonella* Typhimurium\n\n\u003Cfigure>\n\u003Cimg src=\"https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002Fmcqs-in-sexually-transmitted-infections-1.jpg\" alt=\"MCQ on STIs and Spiral Bacteria\" width=\"1024\" height=\"726\" draggable=\"false\" contenteditable=\"false\">\u003Cfigcaption>Figure: MCQ on STIs and Spiral Bacteria\u003C\u002Ffigcaption>\n\u003C\u002Ffigure>\n\n## Sexually transmitted infections and spirochetes\n\n**11.** A 70-year-old woman with severe chronic lung disease presented in the OPD of Tribhuvan University Teaching Hospital with fever, productive cough with purulent sputum, and worsening hypoxemia. A sputum sample was collected and sent to the microbiology lab. The lab reported plenty of polymorphonuclear leukocytes with both intracellular and extracellular gram-negative diplococci. This organism grows well on 5% sheep blood agar and chocolate agar. Later, a butyrate esterase test was done and found to be positive. What is the most likely organism involved in this illness?\n\na. *Haemophilus influenzae* \\\nb. *Moraxella catarrhalis* \\\nc. *Neisseria gonorrhoeae* \\\nd. *Neisseria lactamica* \\\ne. *Neisseria meningitidis*\n\n**12.** A 32-year-old woman who is 10 weeks pregnant presents to the Obstetrics clinic for prenatal care. She has a history of treatment for syphilis 7 years previously. The results of serologic tests for syphilis are: non-treponemal test (RPR) nonreactive; treponemal test (TP-PA) reactive. Which of the following statements is most correct?\n\na. The baby is at high risk for congenital syphilis \\\nb. The mother needs a lumbar puncture and a VDRL test of her CSF for neurosyphilis \\\nc. The mother needs to be treated again for syphilis \\\nd. The mother's previous treatment for syphilis was effective\n\n**13.** A 26-year-old sexually active woman presents to the OPD with purulent vaginal discharge and dysuria. She reports unprotected sexual intercourse with a new partner a week ago. Which of the following diagnostic tests will be the most sensitive method to find the etiologic agents involved in this case?\n\na. An enzyme immunoassay \\\nb. Bacterial culture on selective media \\\nc. Gram's stain \\\nd. Molecular diagnostic methods \\\ne. Serology\n\n**14.** A 20-year-old woman who reports unprotected sex with a new partner 2 weeks previously develops fever and left lower quadrant abdominal pain, with onset in association with her menstrual period. *Neisseria gonorrhoeae* is cultured from her endocervix. The diagnosis is gonococcal pelvic inflammatory disease. What is a common sequela of this infection?\n\na. Cancer of the cervix \\\nb. Infertility \\\nc. Urethral stricture \\\nd. Uterine fibroid tumors \\\ne. Vaginal-rectal fistula\n\n**15.** A 40-year-old man is suffering from multiple episodes of disseminated gonococcal infection over the last few years. Cultures of his urethra and knee fluid yield *Neisseria gonorrhoeae*. What is the most likely cause for this recurrence?\n\na. A polymorphonuclear cell chemotactic factor deficiency \\\nb. Absence of lymphocyte adenosine deaminase activity \\\nc. Deficiency of a late-acting complement component (C5, C6, C7, or C8) \\\nd. Myeloperoxidase deficiency \\\ne. Selective IgA deficiency\n\n**16.** Infection with which of the following agents can result in a biological false-positive non-treponemal (VDRL or RPR) test for syphilis?\n\na. *Borrelia burgdorferi* \\\nb. Epstein-Barr virus \\\nc. *Streptococcus pyogenes* \\\nd. Varicella-zoster virus \\\ne. All of the above\n\n**17.** A false-positive non-treponemal (VDRL or RPR) test for syphilis is a common diagnostic problem. In which of the following conditions can you expect false-positive VDRL or RPR results?\n\na. Leprosy \\\nb. Lupus erythematosus \\\nc. Malaria \\\nd. Measles \\\ne. All of the above\n\n**18.** A 22-year-old woman presents with a 2 cm ulcer on her labia majora. The lesion is painless and has a raised border. The differential diagnosis of this lesion includes:\n\na. Adenovirus infection \\\nb. *Chlamydia trachomatis* infection \\\nc. *Neisseria gonorrhoeae* infection \\\nd. Papillomavirus infection \\\ne. *Treponema pallidum* infection\n\n**19.** After returning from a community posting in a rural village in Nepal, a 20-year-old medical student was admitted to the hospital with fever (39°C) and headache. He had been swimming in a pond where cows are also bathed. Based on clinical examination, leptospirosis is suspected. Which of the following tests will help to confirm the diagnosis?\n\na. Culture of CSF on blood and chocolate agar \\\nb. Culture of urine on human diploid fibroblast cells \\\nc. Testing acute and convalescent-phase sera for anti-leptospiral antibodies \\\nd. Testing acute and convalescent-phase sera using the RPR test \\\ne. Testing serum by dark-field examination for the presence of leptospires\n\n**20.** Which of the following animals is a reservoir or source of *Leptospira interrogans*?\n\na. Cattle \\\nb. Dogs \\\nc. Mice \\\nd. Swine \\\ne. All of the above\n\n## Answer key\n\n 1. c. *Streptococcus pyogenes*\n 2. d. *Pasteurella bettyae*\n 3. a. Stool culture on Hektoen Enteric agar\n 4. d. Penicillin G\n 5. c. Person-to-person spread is quite common\n 6. e. Doxycycline\n 7. a. tularensis (Type A)\n 8. c. The organism grows well on standard chocolate agar\n 9. b. Pili (fimbriae)\n10. c. *Aeromonas hydrophila*\n11. b. *Moraxella catarrhalis*\n12. d. The mother's previous treatment for syphilis was effective\n13. d. Molecular diagnostic methods (NAAT)\n14. b. Infertility\n15. c. Deficiency of a late-acting complement component (C5, C6, C7, or C8)\n16. e. All of the above\n17. e. All of the above\n18. e. *Treponema pallidum* infection\n19. c. Testing acute and convalescent-phase sera for anti-leptospiral antibodies\n20. e. All of the above\n\n## Why these are the answers\n\n**1.** *Streptococcus pyogenes*. High-consequence pathogens are categorized by the CDC as potential bioweapons: [*Bacillus anthracis* (anthrax)](https:\u002F\u002Fmicrobeonline.com\u002Fbacillus-anthracis-properties-pathogenesis-diagnosis\u002F), *Yersinia pestis* (plague), and botulinum toxin are Category A agents, and *Brucella* species are Category B. [*Streptococcus pyogenes* (Group A Strep)](https:\u002F\u002Fmicrobeonline.com\u002Fstreptococcus-pyogens-gas-common-characteristics-virulence-factors-diseases-key-tests), though it causes severe suppurative infection and necrotizing fasciitis, is a ubiquitous community pathogen and is not classified as a biological warfare agent.\n\n**2.** *Pasteurella bettyae*. While *Pasteurella multocida* is overwhelmingly linked to animal bites and scratches, *Pasteurella bettyae* is distinct because it is isolated mainly from human genitourinary infections and Bartholin gland abscesses, and it can be transmitted vertically to a newborn during delivery, causing neonatal septicemia.\n\n**3.** Stool culture on Hektoen Enteric agar. Bubonic plague is characterized by painful, swollen regional lymph nodes (buboes), where [*Yersinia pestis*](https:\u002F\u002Fmicrobeonline.com\u002Fyersinia-pestis-properties-disease-diagnosis\u002F) multiplies rapidly before spilling into the blood. So lymph node aspirate culture, routine blood culture, serology, and tissue immunohistochemistry are all valid. [Hektoen Enteric agar](https:\u002F\u002Fmicrobeonline.com\u002Fhektoen-enteric-agar-composition-principle-uses\u002F) is a selective medium for intestinal pathogens such as *Salmonella* and *Shigella*; it has no role in bubonic plague, because the organism is not shed in feces in this form of the disease.\n\n**4.** Penicillin G. *Pasteurella multocida* is an exception to the usual gram-negative treatment pattern, because it stays highly sensitive to narrow-spectrum penicillins. For animal bites empirically, a beta-lactamase-inhibitor combination such as amoxicillin-clavulanate is preferred, because it also covers the mouth anaerobes in the wound. But for a confirmed, isolated *P. multocida* infection, penicillin G (or oral amoxicillin) is the definitive drug of choice. It responds poorly and unpredictably to macrolides such as erythromycin and to lincosamides such as clindamycin, which is why those distractors are wrong.\n\n**5.** Person-to-person spread is quite common. This is the false statement, so it is the answer to an \"except\" question. *Yersinia enterocolitica* is a zoonotic enteric pathogen acquired by the fecal-oral route, classically from undercooked pork or contaminated water; direct person-to-person spread is rare. The other statements are true: most human infections are caused by serotypes O:3 and O:9, a relatively large inoculum is needed, and there is a well-documented link between *Y. enterocolitica* reactive arthritis and the HLA-B27 tissue type.\n\n**6.** Doxycycline. Pneumonic plague spreads by respiratory droplets and is rapidly fatal if untreated, so close contacts need post-exposure prophylaxis. Oral doxycycline or a fluoroquinolone such as ciprofloxacin is the standard choice to halt infection before it establishes. Aminoglycosides such as gentamicin are reserved for treating active, systemic plague rather than for prophylaxis, which is why gentamicin is the tempting but wrong option here.\n\n**7.** tularensis (Type A). [*Francisella tularensis*](https:\u002F\u002Fmicrobeonline.com\u002Ffrancisella-tularensis-properties-pathogenesis-lab-diagnosis\u002F) is divided into subspecies of differing virulence. Subspecies tularensis (Type A) is the most lethal for humans, often causing severe disease from an infectious dose of fewer than 10 organisms. Subspecies holarctica (Type B) causes a milder tularemia, and novicida is generally of low virulence in immunocompetent people. This extremely low infectious dose is also why *F. tularensis* is handled as a high-risk laboratory pathogen.\n\n**8.** The organism grows well on standard chocolate agar. This is the false statement and therefore the answer. The cause of chancroid is *Haemophilus ducreyi*, an extremely fastidious organism that does not grow well on standard chocolate agar. It needs specially enriched media (supplemented with fetal bovine serum and vancomycin to suppress competing genital flora) incubated under humid, capnophilic conditions. The true statements: it is a small gram-negative rod, it requires exogenous X factor (hemin), it lines up in a \"school of fish\" or parallel-strand pattern on Gram stain of lesions, and it responds to macrolide therapy.\n\n**9.** Pili (fimbriae). Pili are hair-like appendages projecting from the outer membrane of [*Neisseria gonorrhoeae*](https:\u002F\u002Fmicrobeonline.com\u002Fneisseria-gonorrhoeae-properties-disease-pathogenesis-and-laboratory-diagnosis), and they are the primary virulence factor for initial attachment to the microvilli of non-ciliated urogenital epithelium. The distractors each have a different job: lipooligosaccharide (LOS) drives endotoxic inflammation, porin proteins (PorB) modulate phagosome fusion, and IgA1 protease cleaves mucosal antibody, but attachment is the pilus's role. This is also why a gonococcus that loses its pili loses much of its ability to establish infection.\n\n**10.** *Aeromonas hydrophila*. This is a classic freshwater wound infection. *Aeromonas* species live in fresh water (streams, rivers, lakes), so when a wound is exposed to fresh water or mud, *A. hydrophila* can colonize it rapidly and cause aggressive cellulitis with purulent drainage. Contrast this with *Vibrio vulnificus*, which causes similar aggressive wound infection but after exposure to warm salt or brackish (marine) water. The freshwater history points to *Aeromonas*.\n\n**11.** *Moraxella catarrhalis*. [*Moraxella catarrhalis*](https:\u002F\u002Fmicrobeonline.com\u002Fmoraxella-catarrhalis\u002F) is a gram-negative diplococcus that commonly causes respiratory infection in elderly patients with COPD. Under the microscope it resembles *Neisseria*, but it grows on standard blood and chocolate agar (unlike the fastidious pathogenic *Neisseria* such as *N. gonorrhoeae*), and a positive [butyrate esterase test](https:\u002F\u002Fmicrobeonline.com\u002Fbutyrate-disk-test-principle-procedure-results-uses\u002F) separates it cleanly from *Neisseria* species. Both features in the vignette point to *M. catarrhalis*.\n\n**12.** The mother's previous treatment for syphilis was effective. Treponemal tests (TP-PA, [FTA-ABS](https:\u002F\u002Fmicrobeonline.com\u002Ffluorescent-treponemal-antibody-absorption-fta-abs-test\u002F)) detect antibody to *Treponema pallidum* antigens and usually stay reactive for life, whether or not treatment succeeded. Non-treponemal tests ([RPR](https:\u002F\u002Fmicrobeonline.com\u002Frapid-plasma-reagin-rpr-test-principle-procedure-and-interpretations\u002F), [VDRL](https:\u002F\u002Fmicrobeonline.com\u002Fvenereal-disease-research-laboratory-vdrl-test\u002F)) track anti-cardiolipin antibody, which falls with disease activity and reverts to nonreactive after cure. A nonreactive RPR with a reactive TP-PA in someone treated years ago is the pattern of past, successfully treated syphilis, so there is no current risk of congenital transmission and no need to re-treat.\n\n**13.** Molecular diagnostic methods (NAAT). Nucleic acid amplification tests are the most sensitive method for urogenital gonorrhea and chlamydia. They outperform culture (they do not depend on keeping the organism alive during transport) and vastly outperform a cervical Gram stain, which has poor sensitivity in women. NAAT is the current gold standard for these infections.\n\n**14.** Infertility. Pelvic inflammatory disease occurs when a lower genital tract infection ascends to the endometrium and fallopian tubes, triggering inflammation, mucosal scarring, adhesions, and tubal occlusion. The most important long-term consequence of untreated or recurrent gonococcal PID is infertility, along with a raised risk of ectopic pregnancy from tubal scarring.\n\n**15.** Deficiency of a late-acting complement component (C5-C8). The immune system relies on the membrane attack complex (MAC), built from the terminal complement components C5b through C9, to lyse *Neisseria*. People with a genetic deficiency of these late components cannot assemble the MAC, so they cannot lyse [*N. gonorrhoeae* or *N. meningitidis*](https:\u002F\u002Fmicrobeonline.com\u002Fdifferences-neisseria-gonorrhoeae-neisseria-meningitides\u002F) directly, and they suffer recurrent, disseminated neisserial infections. Anyone with recurrent meningococcal or disseminated gonococcal disease should therefore be evaluated for terminal complement deficiency.\n\n**16.** All of the above. Non-treponemal tests (RPR, VDRL) detect antibody to a cardiolipin-cholesterol-lecithin antigen rather than to the treponeme itself. Because cardiolipin is a phospholipid found in host cell membranes and in many microbes, diverse infections, including Lyme disease (*Borrelia burgdorferi*), infectious mononucleosis (EBV), acute varicella (chickenpox), and severe bacterial infections such as streptococcal disease, can trigger transient cross-reactive antibodies that produce a biological false-positive. This is exactly why a reactive non-treponemal test must always be confirmed with a specific treponemal test.\n\n**17.** All of the above. Beyond acute infections, chronic conditions are a frequent cause of a biological false-positive VDRL or RPR: lepromatous leprosy, autoimmune disease such as systemic lupus erythematosus (through antiphospholipid antibodies), malaria, and acute exanthems such as measles all cause tissue inflammation and cell breakdown that release cardiolipin and mimic a reactive syphilis screen. Questions 16 and 17 together are worth learning as a pair: acute or infectious causes in one, chronic causes in the other.\n\n**18.** *Treponema pallidum* infection. A 2 cm, indurated, painless ulcer with a clean base and a firm, raised border is a hard chancre, the hallmark of primary syphilis, caused by the spirochete *Treponema pallidum*. The key contrasts: chancroid (*Haemophilus ducreyi*) produces a painful, soft ulcer, and the primary lesion of lymphogranuloma venereum ([*Chlamydia trachomatis*](https:\u002F\u002Fmicrobeonline.com\u002Fchlamydia-trachomatis-properties-disease-pathogenesis-and-laboratory-diagnosis\u002F) ) is a small, painless ulcer that is transient and heals before the prominent inguinal lymphadenopathy appears. The painless, firm, indurated quality points to syphilis.\n\n**19.** Testing acute and convalescent-phase sera for anti-leptospiral antibodies. Leptospirosis is confirmed most reliably by serology, tracking a fourfold or greater rise in specific antibody titer between acute and convalescent samples (by the microscopic agglutination test, MAT, or ELISA). Leptospires are fastidious and do not grow on routine blood or chocolate agar, nor on viral fibroblast cell lines, and dark-field microscopy of blood or serum gives many false results because fibrin strands are easily mistaken for spirochetes.\n\n**20.** All of the above. [*Leptospira interrogans*](https:\u002F\u002Fmicrobeonline.com\u002Fleptospira-interrogans-characteristics-pathogenesis-and-lab-diagnosis\u002F) is a zoonotic spirochete that sets up chronic kidney infection in a wide range of wild and domestic animals, including cattle, dogs, rodents (mice and rats), and swine, all of which shed the organism in their urine. Humans are incidental hosts, infected through skin or mucous membrane contact with water, mud, or soil contaminated by that animal urine. The village pond shared with cattle in question 19 is a textbook exposure.",[],[51],"bacteriology-mcqs",[53,87,111,143,153,177,186,211],{"slug":54,"title":55,"description":56,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":57,"lastUpdatedDate":58,"draft":46,"category":59,"image":42,"faq":60,"tags":85},"bacillus-anthracis-properties-pathogenesis-diagnosis","Bacillus anthracis: Anthrax Toxin, Clinical Forms, Diagnosis, Prevention","\u003Cp>How anthrax toxin (protective antigen, lethal factor, edema factor) causes disease, the four clinical forms of anthrax, and how \u003Cem>B. anthracis\u003C\u002Fem> is diagnosed, treated, and prevented.\u003C\u002Fp>","2020-04-21","2026-08-07","bacteriology",[61,64,67,70,73,76,79,82],{"question":62,"answer":63},"\u003Cp>What are the three components of anthrax toxin and what does each do?\u003C\u002Fp>","\u003Cp>Protective antigen (PA) binds host cells and forms a pore that delivers the other two into the cell. Edema factor (EF) is an adenylate cyclase that raises cAMP and causes edema. Lethal factor (LF) is a protease that cleaves MAPKK signaling proteins, causing cell death and shock. PA plus EF is edema toxin; PA plus LF is lethal toxin.\u003C\u002Fp>",{"question":65,"answer":66},"\u003Cp>Why is protective antigen called \"protective\" if it helps the toxin?\u003C\u002Fp>","\u003Cp>The name refers to immunity, not to the host during infection. Antibodies against protective antigen protect a vaccinated person, because they block the delivery step of the toxin. On the organism's side, PA is actually the component that forms the pore and lets the harmful factors into the cell. That is also why PA is the target of the anthrax vaccine.\u003C\u002Fp>",{"question":68,"answer":69},"\u003Cp>Why are both plasmids pXO1 and pXO2 important?\u003C\u002Fp>","\u003Cp>pXO1 carries the toxin genes and pXO2 carries the capsule genes. The organism needs both for full virulence: the capsule protects the bacteria from being eaten by phagocytes while they multiply, and the toxin then causes the tissue damage and shock. Removing either plasmid strongly weakens the organism, which is how some vaccine strains are made.\u003C\u002Fp>",{"question":71,"answer":72},"\u003Cp>How is Bacillus anthracis distinguished from Bacillus cereus in the lab?\u003C\u002Fp>","\u003Cp>\u003Cem>B. anthracis\u003C\u002Fem> is non-motile, non-hemolytic, capsulated, and string-of-pearls positive with penicillin. \u003Cem>B. cereus\u003C\u002Fem> is motile, beta-hemolytic, and non-capsulated. These features reliably separate the two.\u003C\u002Fp>",{"question":74,"answer":75},"\u003Cp>Why is the skin lesion of cutaneous anthrax painless?\u003C\u002Fp>","\u003Cp>The lesion is caused mainly by the toxin rather than by a pus-forming inflammatory response, so it is typically painless even though it looks severe, forming a black eschar with marked surrounding swelling. The painlessness is a diagnostic clue.\u003C\u002Fp>",{"question":77,"answer":78},"\u003Cp>Is inhalational anthrax the same as anthrax pneumonia?\u003C\u002Fp>","\u003Cp>Not exactly. Inhaled spores travel to the mediastinal lymph nodes and cause hemorrhagic mediastinitis, which shows as a widened mediastinum on chest imaging, rather than a typical airspace pneumonia. This is why it is called inhalational anthrax rather than anthrax pneumonia.\u003C\u002Fp>",{"question":80,"answer":81},"\u003Cp>Is anthrax contagious from person to person?\u003C\u002Fp>","\u003Cp>No. Anthrax is acquired from spores in soil, in contaminated animal products, or in a deliberate release, not by spread between people. Routine laboratory diagnosis is done under standard BSL-2 conditions.\u003C\u002Fp>",{"question":83,"answer":84},"\u003Cp>Why must anthrax be treated as early as possible?\u003C\u002Fp>","\u003Cp>Antibiotics kill the bacteria but do not neutralize toxin that has already been released. Early treatment limits how much toxin is produced. In severe systemic disease, antitoxin against protective antigen can be added to neutralize circulating toxin.\u003C\u002Fp>",[86],"gram-positive-rods",{"slug":88,"title":89,"description":90,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":91,"lastUpdatedDate":92,"draft":46,"category":59,"image":42,"faq":93,"tags":109},"streptococcus-pyogens-gas-common-characteristics-virulence-factors-diseases-key-tests","Streptococcus pyogenes (GAS): Properties, Pathogenesis, and Lab Diagnosis","\u003Cp>\u003Cem>Streptococcus pyogenes \u003C\u002Fem>(Group A Strep) morphology, virulence factors like M protein and streptolysins, and bacitracin, PYR, and other tests for lab diagnosis.\u003C\u002Fp>","2015-11-08","2026-08-25",[94,97,100,103,106],{"question":95,"answer":96},"\u003Cp>What is the difference between\u003Cem> Streptococcus pyogenes\u003C\u002Fem> and \u003Cem>Streptococcus pneumoniae\u003C\u002Fem> on a Gram stain?\u003C\u002Fp>","\u003Cp>Both are Gram-positive cocci, but \u003Cem>S. pyogenes \u003C\u002Fem>forms chains while \u003Cem>S. pneumoniae\u003C\u002Fem> forms lancet-shaped pairs (diplococci). Hemolysis also differs: \u003Cem>S. pyogenes\u003C\u002Fem> is beta-hemolytic (complete clearing), \u003Cem>S. pneumoniae\u003C\u002Fem> is alpha-hemolytic (partial, green discoloration).\u003C\u002Fp>",{"question":98,"answer":99},"Can a positive ASO titer diagnose an active strep throat infection?","No. Antibodies against streptolysin O take one to three weeks to develop, so a patient with active pharyngitis often still has a normal ASO titer. ASO is used retrospectively, to support a diagnosis of rheumatic fever or post-streptococcal glomerulonephritis after the throat infection has resolved.",{"question":101,"answer":102},"What is the difference between rheumatic fever and post-streptococcal glomerulonephritis?","\u003Cp>Both are non-suppurative sequelae of\u003Cem> S. pyogenes\u003C\u002Fem> infection. Rheumatic fever follows pharyngitis and results from M protein's molecular mimicry of cardiac tissue, leading antibodies to attack the heart. Post-streptococcal glomerulonephritis can follow either pharyngeal or skin infection and results from immune complex deposition in the kidney.\u003C\u002Fp>",{"question":104,"answer":105},"\u003Cp>Why doesn't \u003Cem>S. pyogenes\u003C\u002Fem> form a walled-off abscess the way \u003Cem>S. aureus\u003C\u002Fem> does?\u003C\u002Fp>","\u003Cp>\u003Cem>S. pyogenes\u003C\u002Fem> lacks coagulase. Instead, it produces streptokinase and hyaluronidase, enzymes that dissolve fibrin clots and connective tissue rather than building a barrier, which is why its infections tend to spread diffusely instead of localizing.\u003C\u002Fp>",{"question":107,"answer":108},"\u003Cp>Why is \u003Cem>Streptococcus pyogenes \u003C\u002Fem>called Group A Streptococcus?\u003C\u002Fp>","\u003Cp>Lancefield grouping classifies beta-hemolytic streptococci by differences in their C-carbohydrate cell wall antigen. \u003Cem>S. pyogenes\u003C\u002Fem> carries the Group A antigen, hence Group A Streptococcus (GAS).\u003C\u002Fp>",[110],"gram-positive-cocci",{"slug":112,"title":113,"description":114,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":115,"lastUpdatedDate":92,"draft":46,"category":59,"image":42,"faq":116,"tags":141},"yersinia-pestis-properties-disease-diagnosis","Yersinia pestis: Plague, Its Pathogenesis, and Laboratory Diagnosis","\u003Cp>How \u003Cem>Yersinia pestis \u003C\u002Fem>causes plague: the flea-rodent cycle, bubonic, pneumonic, and septicemic forms, why it is so deadly, and how the laboratory recognizes it (bipolar safety-pin staining, the F1 antigen).\u003C\u002Fp>","2020-04-24",[117,120,123,126,129,132,135,138],{"question":118,"answer":119},"\u003Cp>What disease does\u003Cem> Yersinia pestis \u003C\u002Fem>cause?\u003C\u002Fp>","\u003Cp>Plague. It occurs in three forms: bubonic (swollen lymph nodes from a fleabite), pneumonic (a lung infection that spreads person to person through the air), and septicemic (bloodstream infection). Untreated plague can be fatal within days.\u003C\u002Fp>",{"question":121,"answer":122},"\u003Cp>Why is \u003Cem>Yersinia pestis \u003C\u002Fem>stain called a safety-pin appearance?\u003C\u002Fp>","\u003Cp>On Wayson or Giemsa stain, the two ends of the cell take up more stain than the middle, so the organism looks like a safety pin with two dark ends and a pale center. This bipolar staining is classic for \u003Cem>Y. pestis\u003C\u002Fem>, but other organisms can look similar, so it is not proof on its own.\u003C\u002Fp>",{"question":124,"answer":125},"\u003Cp>How is plague transmitted?\u003C\u002Fp>","\u003Cp>Mainly by the bite of an infected flea from a rodent. It can also spread by contact with infected animal tissues, and, in the pneumonic form, from person to person through airborne droplets.\u003C\u002Fp>",{"question":127,"answer":128},"\u003Cp>Why does\u003Cem> Yersinia pestis\u003C\u002Fem> grow best at 27°C?\u003C\u002Fp>","\u003Cp>Because its natural home is the flea and rodent cycle, not the human body. Its optimum growth temperature is around 27°C, cooler than most human pathogens. It also senses when it has entered a warm human host and switches on its main defenses at 37°C.\u003C\u002Fp>",{"question":130,"answer":131},"\u003Cp>Is \u003Cem>Yersinia pestis\u003C\u002Fem> motile?\u003C\u002Fp>","\u003Cp>No. It is non-motile at both 25°C and 37°C. This separates it from the other \u003Cem>Yersinia\u003C\u002Fem> species, which are motile at 25°C but not at 37°C.\u003C\u002Fp>",{"question":133,"answer":134},"\u003Cp>What is the F1 antigen?\u003C\u002Fp>","\u003Cp>It is the protein capsule of \u003Cem>Y. pestis\u003C\u002Fem>. It protects the organism from being engulfed by immune cells, and it is also the target of rapid diagnostic tests, which detect F1 directly from a bubo aspirate or sputum.\u003C\u002Fp>",{"question":136,"answer":137},"\u003Cp>Why is Yersinia pestis handled only in high-containment laboratories?\u003C\u002Fp>","\u003Cp>Because it is extremely dangerous, can cause fatal infection from very few organisms, and the pneumonic form is airborne. Suspected isolates are worked with in a BSL-3 laboratory and referred to a reference laboratory.\u003C\u002Fp>",{"question":139,"answer":140},"\u003Cp>What is the difference between Yersinia pestis and the other Yersinia species?\u003C\u002Fp>","\u003Cp>\u003Cem>Y. pestis\u003C\u002Fem> causes plague and is flea-borne and systemic. \u003Cem>Y. enterocolitica\u003C\u002Fem> and \u003Cem>Y. pseudotuberculosis\u003C\u002Fem> cause intestinal infection (diarrhea, mesenteric lymph node inflammation) from contaminated food, and are motile at 25°C. All belong to the Enterobacteriaceae.\u003C\u002Fp>",[142],"enterobacteriaceae",{"slug":144,"title":145,"description":146,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":147,"lastUpdatedDate":148,"draft":46,"category":149,"image":42,"faq":150,"tags":151},"hektoen-enteric-agar-composition-principle-uses","Hektoen Enteric (HE) Agar: Composition, Principle, Colony Characteristics, and Uses","\u003Cp>Hektoen Enteric (HE) Agar is a selective and differential medium for \u003Cem>Salmonella\u003C\u002Fem> and \u003Cem>Shigella\u003C\u002Fem> with better \u003Cem>Shigella\u003C\u002Fem> recovery than SS agar. Learn its green-medium principle, three-carbohydrate differentiation, H₂S indicator system, and colony colors.\u003C\u002Fp>","2015-01-27","2026-08-14","culture-media",[],[152],"bacterial-culture-media",{"slug":154,"title":155,"description":156,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":157,"lastUpdatedDate":58,"draft":46,"category":59,"image":42,"faq":158,"tags":176},"francisella-tularensis-properties-pathogenesis-lab-diagnosis","Francisella tularensis: Tularemia, Clinical Forms, Pathogenesis, Diagnosis, Treatment","\u003Cp>How \u003Cem>Francisella tularensis \u003C\u002Fem>escapes the macrophage to cause tularemia, why the route of entry decides the clinical form, why the infectious dose is so low, and how it is diagnosed and treated.\u003C\u002Fp>","2020-10-13",[159,162,165,168,171,174],{"question":160,"answer":161},"\u003Cp>Why does the way you catch tularemia change the symptoms?\u003C\u002Fp>","\u003Cp>The route of entry determines the clinical form. If the organism enters through the skin, it causes an ulcer with swollen nearby lymph nodes (ulceroglandular). Through the eye, it causes conjunctivitis with a swollen node near the ear. By inhalation, it causes pneumonia. So the same organism produces different pictures depending on where it got in.\u003C\u002Fp>",{"question":163,"answer":164},"\u003Cp>Why is Francisella tularensis so dangerous to handle in the laboratory?\u003C\u002Fp>","\u003Cp>Because its infectious dose is extremely low, as few as about 10 organisms can cause disease. This means routine bench work, such as Gram staining or examining plates, can infect laboratory staff. Suspected tularemia must be handled under biosafety level 3 conditions, and the laboratory should always be told when it is suspected.\u003C\u002Fp>",{"question":166,"answer":167},"\u003Cp>How does Francisella tularensis survive inside the body's immune cells?\u003C\u002Fp>","\u003Cp>After being engulfed by a macrophage, it escapes from the phagosome into the cytosol of the cell, where it multiplies safely away from the cell's killing machinery. Because it hides inside cells, the body relies on cell-mediated immunity to clear it, and effective antibiotics are ones that penetrate cells.\u003C\u002Fp>",{"question":169,"answer":170},"\u003Cp>What is the most common form of tularemia?\u003C\u002Fp>","\u003Cp>Ulceroglandular tularemia, which follows entry through the skin. It causes an ulcer at the site of entry together with swollen, tender lymph nodes draining that area, usually on the same side.\u003C\u002Fp>",{"question":172,"answer":173},"\u003Cp>How is tularemia diagnosed?\u003C\u002Fp>","\u003Cp>Mainly by serology (detecting antibodies), because culturing the organism is slow, requires special cysteine-containing media, and is hazardous to laboratory staff. PCR can also be used, and culture is done only under strict biosafety conditions when needed.\u003C\u002Fp>",{"question":175,"answer":175},"",[],{"slug":178,"title":179,"description":180,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":181,"lastUpdatedDate":182,"draft":46,"category":59,"image":42,"faq":183,"tags":184},"neisseria-gonorrhoeae-properties-disease-pathogenesis-and-laboratory-diagnosis","Neisseria gonorrhoeae: Properties, Pathogenesis, Virulence Factors, and Lab Diagnosis","\u003Cp>\u003Cem>Neisseria gonorrhoeae\u003C\u002Fem> causes gonorrhoea: the second most common STI globally. Learn its Gram-negative diplococcus properties, virulence factors (pili, Opa proteins, IgA protease, LOS, PorB), diseases (urethritis, PID, ophthalmia neonatorum), lab diagnosis (Gram stain, culture, NAAT), and AMR resistance timeline.\u003C\u002Fp>","2013-06-10","2026-08-06",[],[185],"gram-negative-cocci",{"slug":187,"title":188,"description":189,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":190,"lastUpdatedDate":92,"draft":46,"category":59,"image":42,"faq":191,"tags":210},"moraxella-catarrhalis","Moraxella catarrhalis: Identification, How to Tell It from Neisseria, and Disease","\u003Cp>How \u003Cem>Moraxella catarrhalis\u003C\u002Fem> causes otitis media, sinusitis, and respiratory infection, and how the laboratory tells it apart from \u003Cem>Neisseria\u003C\u002Fem>, since the two look identical on Gram stain as Gram-negative diplococci.\u003C\u002Fp>","2021-05-27",[192,195,198,201,204,207],{"question":193,"answer":194},"\u003Cp>How do you tell \u003Cem>Moraxella catarrhalis\u003C\u002Fem> from \u003Cem>Neisseria\u003C\u002Fem>?\u003C\u002Fp>","\u003Cp>They look identical on Gram stain (both Gram-negative diplococci), so the distinction is biochemical. \u003Cem>M. catarrhalis\u003C\u002Fem> produces acid from no sugars (asaccharolytic), is DNase-positive, butyrate-positive, and nitrate-positive, and grows on plain blood agar. \u003Cem>Neisseria\u003C\u002Fem> ferments at least glucose, is DNase-negative, and is more fastidious.\u003C\u002Fp>",{"question":196,"answer":197},"\u003Cp>Is\u003Cem> Moraxella catarrhalis\u003C\u002Fem> a Gram-positive or Gram-negative organism?\u003C\u002Fp>","\u003Cp>Gram-negative. It is a Gram-negative diplococcus that closely resembles \u003Cem>Neisseria\u003C\u002Fem> under the microscope.\u003C\u002Fp>",{"question":199,"answer":200},"\u003Cp>What diseases does \u003Cem>Moraxella catarrhalis\u003C\u002Fem> cause?\u003C\u002Fp>","\u003Cp>In children, otitis media (middle ear infection) and sinusitis; it is one of the three main causes along with \u003Cem>Streptococcus pneumoniae\u003C\u002Fem> and \u003Cem>Haemophilus influenzae\u003C\u002Fem>. In older adults with chronic lung disease, it causes bronchitis and bronchopneumonia. Rarely, it causes invasive disease.\u003C\u002Fp>",{"question":202,"answer":203},"\u003Cp>Why does penicillin not work against\u003Cem> Moraxella catarrhalis?\u003C\u002Fem>\u003C\u002Fp>","\u003Cp>Because nearly all strains produce a beta-lactamase, an enzyme that destroys penicillin and ampicillin. Treatment uses beta-lactamase-stable drugs such as amoxicillin-clavulanate.\u003C\u002Fp>",{"question":205,"answer":206},"\u003Cp>Why is Moraxella catarrhalis asaccharolytic important?\u003C\u002Fp>","\u003Cp>Because it separates \u003Cem>M. catarrhalis\u003C\u002Fem> from \u003Cem>Neisseria\u003C\u002Fem>. \u003Cem>Neisseria\u003C\u002Fem> species ferment sugars (at least glucose), while \u003Cem>M. catarrhalis\u003C\u002Fem> produces acid from none. An organism that looks like \u003Cem>Neisseria\u003C\u002Fem> but ferments no sugars is likely \u003Cem>Moraxella\u003C\u002Fem>.\u003C\u002Fp>",{"question":208,"answer":209},"\u003Cp>What does a Moraxella catarrhalis colony look like?\u003C\u002Fp>","\u003Cp>Grey-white, dry, and brittle, and it can be pushed intact across the agar with a loop, sometimes described as a \"hockey-puck\" colony. This is a useful clue that separates it from the buttery colonies of \u003Cem>Neisseria\u003C\u002Fem>.\u003C\u002Fp>",[185],{"slug":212,"title":213,"description":214,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":215,"lastUpdatedDate":216,"draft":46,"category":217,"image":42,"faq":218,"tags":243},"butyrate-disk-test-principle-procedure-results-uses","Butyrate Disk Test: Principle, Procedure, Results, Uses","\u003Cp>The butyrate disk test detects butyrate esterase to presumptively identify \u003Cem>Moraxella catarrhalis \u003C\u002Fem>by a blue color. Learn the principle, procedure, how to read the result, and why it matters for beta-lactamase-producing \u003Cem>M. catarrhalis.\u003C\u002Fem>\u003C\u002Fp>","2015-05-25","2026-08-16","biochemical-tests",[219,222,225,228,231,234,237,240],{"question":220,"answer":221},"\u003Cp>What does the butyrate disk test detect?\u003C\u002Fp>","\u003Cp>It detects the enzyme butyrate esterase. When present, the enzyme hydrolyzes the substrate on the disk and releases indoxyl, which forms blue indigo.\u003C\u002Fp>",{"question":223,"answer":224},"\u003Cp>What does a positive butyrate disk test mean?\u003C\u002Fp>","\u003Cp>A blue to blue-violet color (or fluorescence with the MUB substrate) is positive. In an oxidase-positive, Gram-negative diplococcus with typical morphology, this gives a presumptive identification of \u003Cem>Moraxella catarrhalis\u003C\u002Fem>.\u003C\u002Fp>",{"question":226,"answer":227},"\u003Cp>What does a negative result mean?\u003C\u002Fp>","\u003Cp>No color change. The organism does not produce butyrate esterase. \u003Cem>Neisseria\u003C\u002Fem> species, including \u003Cem>Neisseria gonorrhoeae\u003C\u002Fem> and \u003Cem>Neisseria lactamica\u003C\u002Fem>, are butyrate-negative.\u003C\u002Fp>",{"question":229,"answer":230},"\u003Cp>Why is the butyrate test used for Moraxella catarrhalis?\u003C\u002Fp>","\u003Cp>\u003Cem>M. catarrhalis\u003C\u002Fem> looks identical to \u003Cem>Neisseria\u003C\u002Fem> species on Gram stain and oxidase testing, since all are oxidase-positive, Gram-negative diplococci. The butyrate test separates them quickly, because \u003Cem>M. catarrhalis\u003C\u002Fem> is butyrate-positive and \u003Cem>Neisseria\u003C\u002Fem> species are not.\u003C\u002Fp>",{"question":232,"answer":233},"\u003Cp>Why must the disk be read within 5 minutes?\u003C\u002Fp>","\u003Cp>Reading later than 5 minutes can give a false positive, because color develops nonspecifically over time.\u003C\u002Fp>",{"question":235,"answer":236},"\u003Cp>Can organisms other than M. catarrhalis give a positive result?\u003C\u002Fp>","\u003Cp>Yes. Some other \u003Cem>Moraxella\u003C\u002Fem> species, \u003Cem>Acinetobacter\u003C\u002Fem>, \u003Cem>Eikenella\u003C\u002Fem>, staphylococci, and pseudomonads can be positive. This is why the test is only interpreted on an oxidase-positive, Gram-negative diplococcus with typical morphology.\u003C\u002Fp>",{"question":238,"answer":239},"\u003Cp>What should I do if the organism looks like M. catarrhalis but tests negative?\u003C\u002Fp>","\u003Cp>Repeat with a heavier inoculum, since a small inoculum can cause a false negative. If it is still negative but fits the other criteria, DNase testing can be used as a further confirmatory step.\u003C\u002Fp>",{"question":241,"answer":242},"\u003Cp>Does a positive butyrate test tell me about antibiotic resistance?\u003C\u002Fp>","\u003Cp>Not directly, but identifying \u003Cem>M. catarrhalis\u003C\u002Fem> is a strong hint, because most strains produce beta-lactamase and resist penicillin and ampicillin. Beta-lactamase is confirmed separately with the nitrocefin test.\u003C\u002Fp>",[244],"enzyme-tests",{"enabled":246,"threads":247,"total":248},true,[],0,[250,256,263,270,276,281,287,292,298,301,308],{"slug":251,"name":43,"description":252,"image":253,"body":254,"postCount":255},"acharya-tankeshwar","Editor-in-chief","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Ftankeshwar-acharya-author-microbeonline.jpg","***Tankeshwar Acharya, MSc (Medical Microbiology)***\n\n*Tankeshwar Acharya is an Assistant Professor in the Department of Microbiology at Patan Academy of Health Sciences (PAHS), Nepal, where he has been teaching and practicing clinical microbiology for over 14 years. He is the founder of Microbe Online, one of the leading free microbiology education resources on the web, covering bacteriology, mycology, parasitology, immunology, and clinical laboratory diagnostics written from direct experience in both the classroom and the diagnostic laboratory.*",480,{"slug":257,"name":258,"description":259,"image":260,"body":261,"postCount":262},"ashma-shrestha","Ashma Shrestha","SEO Copywriter and Science Communicator\nKathmandu, Nepal","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Fashma-shrestha.png","Ashma Shrestha holds a Master of Science in Medical Microbiology from the Institute of Science and Technology (IOST), Tribhuvan University, Nepal, where she developed a strong foundation in virology, molecular biology, and diagnostic microbiology.\n\nShe now works as an SEO Copywriter at Resolution Digital, where she combines her scientific training with research-driven content strategy. She is certified in Google Analytics and Google Business Profile (GBP), and brings a data-informed approach to science communication writing content that is not only accurate but structured to reach and serve the students who need it most.\n\nAt microbeonline, Ashma contributes articles primarily in virology and molecular biology, areas she finds most compelling for their mechanistic depth and their growing clinical relevance. Her writing reflects the same standard the site is built on: factual rigor, clear explanation of the *why* behind microbiology concepts, and content that helps students move from memorization to genuine understanding.\n\nShe is passionate about making complex microbiological concepts accessible without sacrificing accuracy; a skill that sits at the intersection of her scientific training and her professional work in content and SEO.",79,{"slug":264,"name":265,"description":266,"image":267,"body":268,"postCount":269},"sushmita-baniya","Sushmita Baniya","Author \u002F Contributor","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Fsushmita-baniya-1.png","Sushmita Baniya holds an M.Sc. in Medical Microbiology from Tribhuvan University (National College), with a research focus in Genetics and Molecular Biology. She is actively involved in teaching and research in the field of microbiology.",26,{"slug":271,"name":272,"description":266,"image":273,"body":274,"postCount":275},"samikshya-acharya","Samikshya Acharya","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Fsamikshya-acharya.jpeg","Samikshya Sharma completed her postgraduate studies in Medical Microbiology at the Central Department of Microbiology, Tribhuvan University, Nepal. She contributes to Microbeonline with the goal of making foundational and clinical microbiology concepts clear and useful for students in medical, laboratory science, and allied health programs.",20,{"slug":277,"name":278,"description":266,"image":42,"body":279,"postCount":280},"alisha-tripathi","Alisha Tripathi","Alisha Tripathi holds an M.Sc. in Medical Microbiology from National College, Tribhuvan University. With over a year of teaching experience, her academic interests span Molecular Biology, Immunology, and Genetics.",6,{"slug":282,"name":283,"description":284,"image":42,"body":285,"postCount":286},"aastha-shrestha","Aastha Shrestha"," Author \u002F Contributor","Aastha Shrestha is a Biotechnology graduate with an M.Sc. from National College, Tribhuvan University. Her academic interests center on Molecular Biology and Immunology; two fields that are increasingly converging in modern diagnostic and clinical microbiology. \n\nShe contributes to Microbeonline with the goal of making complex concepts in these areas approachable and exam-relevant for students across medical, biotechnology, and laboratory science programs.",9,{"slug":288,"name":289,"description":290,"image":42,"body":42,"postCount":291},"guest-author","Guest Author","Guest Author \u002F Contributor",1,{"slug":293,"name":294,"description":266,"image":295,"body":296,"postCount":297},"srijana-khanal","Srijana Khanal","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Fsrijana-khanal-1.png","Srijana Khanal is a microbiology educator with nearly a decade of teaching experience, including her role as faculty in the Microbiology Department at National College, NIST. \n\nHer time in the classroom has given her a clear sense of where students struggle and what explanations actually work, a perspective that directly shapes how she writes.\n\nHer academic interests span Immunology, Genetics, Basic Sciences, and Research Methodology, and she brings the same rigor to her writing that she brought to teaching. Alongside academic writing, she has a passion for creative writing -- an instinct that shows in her ability to make dense scientific material readable without sacrificing accuracy.\n\nShe contributes to Microbeonline to extend her teaching reach beyond the classroom, helping medical and laboratory science students across the region build a stronger foundation in microbiology.",15,{"slug":299,"name":300,"description":290,"image":42,"body":42,"postCount":291},"dr-poonam-acharya","Dr. Poonam Acharya",{"slug":302,"name":303,"description":304,"image":305,"body":306,"postCount":307},"nisha-rijal","Nisha Rijal","Microbiologist and AMR Specialist Kathmandu, Nepal","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Fnisha-rijal-1.png","Nisha Rijal is a microbiologist with nearly 15 years of frontline diagnostic and surveillance experience at the National Public Health Laboratory (NPHL), national reference laboratory under the Department of Health Services, Nepal. She currently works as an AMR Support Officer at the World Health Organization (WHO), Nepal, where her work focuses on strengthening antimicrobial resistance surveillance systems and translating AMR data into actionable public health response.\n\nHer research, published in peer-reviewed journals and cited over 220 times, spans some of the most clinically significant infectious disease challenges in Nepal and South Asia: antimicrobial resistance trends in *Vibrio cholerae* across an 11-year national surveillance dataset, sero-epidemiology of scrub typhus in patients with acute febrile illness, lower respiratory tract infections in HIV-positive patients, and gonococcal resistance surveillance. She was a contributor to Nepal's National Antimicrobial Resistance Containment Action Plan, a foundational policy document for AMR governance in Nepal. You can find list of [Nisha Rijal's article here in Google Scholar.](https:\u002F\u002Fscholar.google.com\u002Fcitations?user=N-Ruq54AAAAJ&hl=en)\n\nThis depth of experience is visible in her writing at Microbeonline. Her 53 published articles cover bacteriology, parasitology, mycology, immunology, and laboratory techniques, and are consistently among the most detailed and clinically grounded content on the site. She brings to every article the same standard that national reference laboratory work demands: methodological precision, awareness of real diagnostic constraints, and an understanding of what results actually mean for patient care in resource-limited settings.\n\nHer areas of particular expertise include antimicrobial susceptibility testing and resistance mechanism detection, quality assurance in clinical microbiology, and laboratory-based infectious disease surveillance.\n\n---\n\n*Nisha Rijal contributes to Microbeonline in a personal capacity. Her views and writing do not represent the positions of the World Health Organization or any other institution.*",54,{"slug":309,"name":310,"description":311,"image":312,"body":313,"postCount":291},"padma-shrestha","Padma Shrestha","Author","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Fpadma-shrestha.png","Padma Shrestha is from Kathmandu, Nepal. She has completed Masters degree in Medical microbiology from Tribhuvan University. She has great interest in Microbiology and Molecular Biology.",[315,321,327,331,336,340,344,348,351,356,360,365,369,374,379,383,387,391,396,401,405,409,413,418,422,426,430,433,438,443,447,451,455,459,463,467,471,475,479,483,487,491,495,499,503,507,511,515,520,524,528,532,536,540,543,547,551,555,559,563,567,571,575,579,583,587,591,595,598,602,605,608,611,614,617,620,623,626,629,632,635,638,641],{"slug":185,"name":316,"description":317,"image":318,"body":319,"postCount":320},"Gram-Negative Cocci and Coccobacilli","Neisseria, Moraxella, Haemophilus and related gram-negative coccal organisms","https:\u002F\u002Fassets.microbeonline.com\u002Ftags\u002Fgram-negative-cocci.png","# Gram Negative Cocci\n\nNeisseria gonorrhoeae, Neisseria meningitides, Moraxella catarrhalis, and other Neisseria spp. are clinically relevant gram-negative cocci.\n\nN. gonorrhoeae is the leading cause of sexually transmitted disease whereas N. meningitides is a leading cause of fatal bacterial meningitis.",14,{"slug":322,"name":323,"description":324,"image":42,"body":325,"postCount":326},"microscopy","Microscopy","Microscope types, components, and microscopy techniques","These are list of blog posts related to microscopy. ",12,{"slug":110,"name":328,"description":329,"image":42,"body":42,"postCount":330},"Gram-Positive Cocci","Staphylococcus, Streptococcus, Enterococcus, Micrococcus — organisms, diseases, and identification tests",11,{"slug":332,"name":333,"description":334,"image":42,"body":42,"postCount":335},"gram-negative-rods","Gram-Negative Rods (Other than Enterobacteriaceae)","\u003Cp>Gram negative rods other than members of Enterobacteriaceae family such as  Pseudomonas, Acinetobacter and related organisms\u003C\u002Fp>",5,{"slug":86,"name":337,"description":338,"image":42,"body":42,"postCount":339},"Gram-Positive Rods","Bacillus, Clostridium, Listeria, Corynebacterium, Actinomyces and related organisms",8,{"slug":341,"name":342,"description":343,"image":42,"body":42,"postCount":330},"mycobacteria","Mycobacteria","Mycobacterium tuberculosis, leprosy, atypical mycobacteria, and acid-fast organism diagnosis",{"slug":345,"name":346,"description":347,"image":42,"body":42,"postCount":326},"anaerobic-bacteriology","Anaerobic Bacteriology","Anaerobic organisms, anaerobic culture methods, and anaerobic infection diagnosis",{"slug":142,"name":349,"description":350,"image":42,"body":42,"postCount":326},"Enterobacteriaceae","Identification, differentiation, and clinical significance of Enterobacteriaceae family members",{"slug":352,"name":353,"description":354,"image":42,"body":42,"postCount":355},"spirochetes","Spirochetes","Treponema, Leptospira, Borrelia and spirochetal infections",7,{"slug":357,"name":358,"description":359,"image":42,"body":42,"postCount":320},"food-microbiology","Food Microbiology","Food-borne pathogens, food safety, spoilage, and preservation",{"slug":361,"name":362,"description":363,"image":42,"body":42,"postCount":364},"antimicrobial-susceptibility-testing","Antimicrobial Susceptibility Testing","Methods for testing antibiotic susceptibility in clinical microbiology",21,{"slug":366,"name":367,"description":368,"image":42,"body":42,"postCount":320},"antimicrobials-moa-amr","Antimicrobials (MOA & AMR)","Mechanisms, detection, and clinical significance of antimicrobial resistance",{"slug":370,"name":371,"description":372,"image":42,"body":42,"postCount":373},"sterilization-disinfection","Sterilization and Disinfection","Methods of sterilization and disinfection in healthcare and laboratory settings",10,{"slug":375,"name":376,"description":377,"image":42,"body":42,"postCount":378},"specimen-collection-transport","Specimen Collection and Transport","Collection, handling, and transport of clinical specimens for microbiological testing",27,{"slug":380,"name":381,"description":382,"image":42,"body":42,"postCount":364},"bacterial-structure-physiology","Bacterial Structure and Physiology","Bacterial cell structure, growth, physiology, and environmental factors affecting growth",{"slug":384,"name":385,"description":42,"image":42,"body":386,"postCount":280},"horizontal-gene-transfer","Horizontal Gene Transfer","Articles related to **Horizontal Gene Transfer**",{"slug":388,"name":389,"description":42,"image":42,"body":390,"postCount":373},"chromatography","Chromatography","Information about chromatographic techniques.",{"slug":392,"name":393,"description":394,"image":42,"body":395,"postCount":355},"electrophoresis","Electrophoresis","Information about Electrophoresis Techniques ","Detailed information  about Electrophoresis Techniques ",{"slug":397,"name":398,"description":399,"image":42,"body":400,"postCount":280},"pcr-techniques","PCR Techniques","Information about various types of Polymerase Chain Reaction Techniques ","More detailed information about various types of Polymerase Chain Reaction Techniques ",{"slug":402,"name":403,"description":404,"image":42,"body":42,"postCount":280},"bacteriophage","Bacteriophage","Description about Bacteriophage.",{"slug":406,"name":407,"description":408,"image":42,"body":42,"postCount":280},"malaria","Malaria","It is the collections of articles regarding malarial disease. ",{"slug":410,"name":411,"description":412,"image":42,"body":42,"postCount":280},"anaerobic-culture-techniques","Anaerobic Culture Techniques","Posts related with Anaerobic Culture Techniques.",{"slug":414,"name":415,"description":416,"image":42,"body":42,"postCount":417},"immunoassays","Immunoassays","You will get information about all the diagnostic tests that rely on the specific binding between an antigen and an antibody to detect or quantify a substance.",19,{"slug":419,"name":420,"description":421,"image":42,"body":42,"postCount":355},"biosafety-levels","Biosafety levels ","Articles related to Biosafety Levels",{"slug":423,"name":424,"description":425,"image":42,"body":42,"postCount":335},"environmental-factors","Environmental Factors ","In this case we are talking about growth requirements of microorganisms with deep dive in environmental factors that affect the growth. ",{"slug":427,"name":428,"description":429,"image":42,"body":42,"postCount":280},"pipette","Pipette","Posts related with Pipette. ",{"slug":51,"name":431,"description":432,"image":42,"body":42,"postCount":355},"Bacteriology MCQs","This sections lists MCQs in Bacteriology.",{"slug":434,"name":435,"description":436,"image":42,"body":42,"postCount":437},"parasitology-mcqs","Parasitology MCQs","This section lists MCQs in Parasitology.",2,{"slug":439,"name":440,"description":441,"image":42,"body":42,"postCount":442},"virology-mcqs","Virology MCQs","This is the collections of Multiple Choice Questions in Virology.",4,{"slug":444,"name":445,"description":446,"image":42,"body":42,"postCount":335},"mcqs-in-microbiology","MCQs in Microbiology","This section lists the collections of Multiple Choice Questions in General Microbiology Topics. ",{"slug":448,"name":449,"description":450,"image":42,"body":42,"postCount":339},"immunology-mcqs","Immunology MCQs","In this section; we are posting collections of Multiple Choice Questions about Immunology. ",{"slug":452,"name":453,"description":454,"image":42,"body":42,"postCount":373},"microbial-curiosities","Microbial Curiosities","In this clusters, we are posting interesting and unique information about Microorganisms. ",{"slug":152,"name":456,"description":457,"image":42,"body":42,"postCount":458},"Bacterial Culture Media","Posts related to Bacterial Culture Media. ",23,{"slug":460,"name":461,"description":462,"image":42,"body":42,"postCount":280},"fungal-culture-media","Fungal Culture Media","Posts related to Fungal Culture Media.",{"slug":464,"name":465,"description":466,"image":42,"body":42,"postCount":335},"motility-test","Motility Test","This lists the procedure regarding various tests methods for bacterial motility.",{"slug":468,"name":469,"description":470,"image":42,"body":42,"postCount":373},"bacterial-enumeration","Bacterial enumeration","These posts are related to isolation and enumeration of bacteria. ",{"slug":472,"name":473,"description":474,"image":42,"body":42,"postCount":437},"gram-positive-coccobacillus","Gram-positive coccobacillus","List of Gram Positive Coccobacilli",{"slug":476,"name":477,"description":478,"image":42,"body":42,"postCount":442},"dimorphic-fungi","Dimorphic Fungi","This is about various dimorphic fungi. ",{"slug":480,"name":481,"description":482,"image":42,"body":42,"postCount":355},"bacterial-classification","Bacterial Classification","These posts are related with various approaches used for the classification of Bacteria. ",{"slug":484,"name":485,"description":486,"image":42,"body":42,"postCount":335},"immunofluorescence","Immunofluorescence ","Various Tests related to Immunofluorescence ",{"slug":488,"name":489,"description":490,"image":42,"body":42,"postCount":286},"antibody-mediated-immunity","Antibody-mediated Immunity","This clusters links the articles that are sharing insights about Antibody-mediated immunity. ",{"slug":492,"name":493,"description":494,"image":42,"body":42,"postCount":355},"hypersensitivity","Hypersensitivity","Articles related to Hypersensitivity.",{"slug":496,"name":497,"description":42,"image":42,"body":42,"postCount":498},"haemophilus","Haemophilus",3,{"slug":500,"name":501,"description":502,"image":42,"body":42,"postCount":442},"sexually-transmitted-infections-stis","Sexually transmitted infections (STIs)","This is the clusters of infections that are transmitted sexually. ",{"slug":504,"name":505,"description":506,"image":42,"body":42,"postCount":326},"adaptive-immunity","Adaptive Immunity","Blog posts related to B Cell Immunity and T Cell Immunity.",{"slug":508,"name":509,"description":510,"image":42,"body":42,"postCount":320},"fungal-diagnostics","Fungal Diagnostics","Various methods used for the Diagnosis of Fungal Infections. ",{"slug":512,"name":513,"description":514,"image":42,"body":42,"postCount":335},"laboratory-storage-and-preservation","Laboratory Storage and Preservation","Articles about Laboratory Storage of Antimicrobial Disk, Test organisms and Equipment used for this process. ",{"slug":516,"name":517,"description":518,"image":42,"body":519,"postCount":280},"laboratory-heating-equipment","Laboratory Heating Equipment","A guide to laboratory heating equipment, including hot plates, water baths, Bunsen burners, incubators, and dry baths, and how to choose the right one for each task.","Laboratory heating equipment covers the instruments that warm, melt, incubate, or sterilize samples and media in a microbiology laboratory. Each one delivers heat differently. \n\nA hot plate gives high, direct, dry heat; a water bath gives gentle, even, wet heat up to about 100°C; a Bunsen burner gives an open flame for rapid, very high heat; an incubator holds cultures at a steady temperature over hours or days; and a dry bath heats small tubes without water. Choosing the right one depends on the temperature you need, how precise it must be, and whether the sample can tolerate direct or open-flame heat.\n\nThe articles below cover each piece of heating equipment in detail, including its parts, working principle, uses, and the mistakes that most often go wrong at the bench.",{"slug":521,"name":522,"description":523,"image":42,"body":42,"postCount":286},"laboratory-glassware","Laboratory Glassware","Posts about Laboratory Glassware. ",{"slug":525,"name":526,"description":527,"image":42,"body":42,"postCount":280},"helminths","Helminths","In this section, we are covering properties, life cycle, pathogenesis and laboratory diagnosis of Helminths\u002FHelminthic infestations. ",{"slug":529,"name":530,"description":531,"image":42,"body":42,"postCount":355},"protozoan-parasite","Protozoan Parasite","In this cluster, we are covering protozoan parasites. ",{"slug":533,"name":534,"description":535,"image":42,"body":42,"postCount":291},"tests-for-gram-positive-cocci","Biochemical Tests for Gram Positive Cocci","This is the lists of Biochemical Tests that are used for Gram Positive Cocci. ",{"slug":537,"name":538,"description":539,"image":42,"body":42,"postCount":373},"bacterial-staining-technique","Bacterial Staining Technique","Lists of various staining techniques that are used to stain bacteria. ",{"slug":244,"name":541,"description":542,"image":42,"body":42,"postCount":364},"Enzyme Tests","\u003Cp>Various Biochemical Test that are based on enzymatic activity of the microorganisms. \u003C\u002Fp>",{"slug":544,"name":545,"description":546,"image":42,"body":42,"postCount":330},"carbohydrate-utilization","Carbohydrate Utilization","\u003Cp>Various biochemical tests which are related to Carbohydrate fermentation or Utilization\u003C\u002Fp>",{"slug":548,"name":549,"description":550,"image":42,"body":42,"postCount":335},"susceptibility-based-id","Susceptibility-based ID","\u003Cp>These are susceptibility based identification test such as optochin sensitivity, bacitracin sensitivity etc. \u003C\u002Fp>",{"slug":552,"name":553,"description":554,"image":42,"body":42,"postCount":442},"microbial-metabolism","Microbial Metabolism","\u003Cp>Tests about Microbial Metabolism. \u003C\u002Fp>",{"slug":556,"name":557,"description":558,"image":42,"body":42,"postCount":339},"substrate-utilization","Substrate Utilization","\u003Cp>The test in which a non-sugar carbon\u002Fnitrogen source is used or degraded (citrate, malonate, decarboxylases, indole, PAD).\u003C\u002Fp>",{"slug":560,"name":561,"description":562,"image":42,"body":42,"postCount":498},"atypical-pneumonia","Atypical Pneumonia","\u003Cp>Organisms responsible for Atypical Pneumonia. \u003C\u002Fp>",{"slug":564,"name":565,"description":566,"image":42,"body":42,"postCount":335},"antigen","Antigen","\u003Cp>Various articles related to Antigens.\u003C\u002Fp>",{"slug":568,"name":569,"description":570,"image":42,"body":42,"postCount":355},"innate-immunity","Innate Immunity","\u003Cp>Articles related to Innate Immunity. \u003C\u002Fp>",{"slug":572,"name":573,"description":574,"image":42,"body":42,"postCount":442},"respiratory-tract-infection","Respiratory Tract Infection","\u003Cp>In this cluster, you can see various etiological agents that causes respiratory tract infection. \u003C\u002Fp>",{"slug":576,"name":577,"description":578,"image":42,"body":42,"postCount":335},"torch-infection","TORCH Infection","\u003Cp>In this section; you can find articles related with TOCH infection. \u003C\u002Fp>",{"slug":580,"name":581,"description":582,"image":42,"body":42,"postCount":339},"microbiology-for-beginners","Microbiology for Beginners","\u003Cp>These articles are very basic articles, which will share general concepts in Microbiology. \u003C\u002Fp>",{"slug":584,"name":585,"description":586,"image":42,"body":42,"postCount":280},"dna-replication","DNA Replication","\u003Cp>Articles related to DNA and Replication of DNA. \u003C\u002Fp>",{"slug":588,"name":589,"description":590,"image":42,"body":42,"postCount":355},"genetic-code","Genetic Code","\u003Cp>Articles related to Genetic Code.\u003C\u002Fp>",{"slug":592,"name":593,"description":594,"image":42,"body":42,"postCount":355},"molecular-technique","Molecular Technique","\u003Cp>Posts related to Molecular Techniques. \u003C\u002Fp>",{"slug":596,"name":597,"description":42,"image":42,"body":42,"postCount":291},"colorimetric-assay","Colorimetric Assay ",{"slug":599,"name":600,"description":601,"image":42,"body":42,"postCount":335},"pharmaceutical-microbiology","Pharmaceutical Microbiology","\u003Cp>Various articles related to Pharmaceutical Microbiology\u003C\u002Fp>",{"slug":603,"name":604,"description":42,"image":42,"body":42,"postCount":498},"blood-and-immune-cells","Blood and Immune Cells",{"slug":606,"name":607,"description":42,"image":42,"body":42,"postCount":335},"host-pathogen-interaction","Host Pathogen Interaction",{"slug":609,"name":610,"description":42,"image":42,"body":42,"postCount":442},"blood-culture","Blood Culture",{"slug":612,"name":613,"description":42,"image":42,"body":42,"postCount":442},"environmental-microbiology","Environmental microbiology ",{"slug":615,"name":616,"description":42,"image":42,"body":42,"postCount":280},"copromicroscopic-technique","Copromicroscopic Technique",{"slug":618,"name":619,"description":42,"image":42,"body":42,"postCount":498},"quality-control","Quality Control",{"slug":621,"name":622,"description":42,"image":42,"body":42,"postCount":442},"dermatophytes","Dermatophytes",{"slug":624,"name":625,"description":42,"image":42,"body":42,"postCount":498},"viral-hemorrhagic-fevers","Viral Hemorrhagic Fevers",{"slug":627,"name":628,"description":42,"image":42,"body":42,"postCount":442},"h2s-production","H2S Production",{"slug":630,"name":631,"description":42,"image":42,"body":42,"postCount":437},"water-quality-testing","Water Quality Testing",{"slug":633,"name":634,"description":42,"image":42,"body":42,"postCount":335},"virology-basics","Virology basics",{"slug":636,"name":637,"description":42,"image":42,"body":42,"postCount":442},"typing-methods","Typing Methods",{"slug":639,"name":640,"description":42,"image":42,"body":42,"postCount":498},"blotting-technique","Blotting Technique",{"slug":642,"name":643,"description":42,"image":42,"body":42,"postCount":442},"history-microbiology","History of Microbiology"]