[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"$fxLN3MUwXCdr5RPjwZYIDpOj8CHyjOmngWTgoKXPtZbg":3,"$f8S-1VDnebch5WiwDSgwUE7lj_uEkAWGKRcGiwjR6swE":36,"$f3Ft0rKFJHppdzE-vuveecxx1BUcg9iOlMLtyzf_MJDg":234,"$fucxFBm2ZjZfGSdmdRaSNGBI_F0jJme4f0GTvzUhQfL8":299},[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},"Abbreviations","abbreviations","\u002Fabbreviations\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},"Utilization Tests for Bacterial Identification","utilization-tests","\u002Futilization-tests\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":74,"related":76,"comments":230},"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>",null,"Acharya Tankeshwar","2020-04-24","2026-08-19",false,"bacteriology","In the 14th century, a disease swept across Europe and killed roughly a third of its people in a few years. It was called the **Black Death**. The cause was a single bacterium, *Yersinia pestis*, carried by fleas living on rats. The same organism still causes plague today, in scattered outbreaks, and it can still kill within days if untreated.\n\nMost students will never grow this organism, because it is so dangerous that it is handled only in high-containment laboratories. But *Yersinia pestis* is worth understanding, both for what it did to human history and for how it works: how a fleabite becomes a swollen, painful lymph node, how the infection can move to the lungs and then spread person to person through the air, and why it kills so fast. This page is about the organism, the disease it causes, and how it is recognized.\n\n## Overview\n\n*Yersinia pestis* is a Gram-negative rod of the family [Enterobacteriaceae](https:\u002F\u002Fmicrobeonline.com\u002Fenterobacteriaceae\u002F), and it causes **plague**, one of the deadliest infections known. Plague is a **zoonosis**: it lives naturally in rodents and is carried to humans by fleas. It has caused at least three great pandemics in history, including the 14th-century Black Death, which killed about a third of the population of Europe.\n\nTwo routes make it dangerous in different ways. A fleabite causes **bubonic plague**, a painful swelling of the lymph nodes. If the infection reaches the lungs, it becomes **pneumonic plague**, which spreads from person to person through the air and is rapidly fatal. Because of this, *Y. pestis* is treated as a high-risk organism and a potential agent of bioterrorism.\n\n![Yersinia pestis, major features](\u002Fblogs\u002FYersinia-pestis.jpg)Figure: *Yersinia pestis*, major features\n\n## Virulence factors and how Yersinia pestis causes plague\n\n*Yersinia pestis* is unusually good at defeating the immune system, which is why plague moves so fast. A few key factors explain it.\n\n**F1 capsule.** The organism makes a protein capsule (the F1 antigen) that coats it and blocks phagocytosis, so white blood cells cannot easily engulf it. This capsule is produced mainly at body temperature (37°C), that is, once the organism is inside a human, not in the cooler flea. The F1 antigen is also the target of the rapid diagnostic tests described below.\n\n**Type III secretion system and Yops.** This is the central weapon. *Y. pestis* builds a molecular needle (a Type III secretion system) that injects a set of proteins called **Yops** directly into host immune cells. These proteins shut the cell down from the inside: they block phagocytosis, stop the cell from signaling for help, and can trigger the cell to die. In effect, the organism disarms the very cells sent to destroy it. This is why the early infection meets so little resistance.\n\n**Plasminogen activator (Pla).** At the fleabite site, this enzyme dissolves the barriers that would normally contain an infection, letting the organism spread from the skin into the lymphatics and then the blood. Pla is one reason a local fleabite can become a body-wide infection so quickly.\n\n**Temperature sensing.** *Y. pestis* behaves differently at flea temperature (around 25 to 27°C) and human body temperature (37°C). It switches on its main antihost defenses, including the F1 capsule, once it senses it is inside a warm-blooded host. The organism essentially arms itself on entry.\n\n**Putting it together**\n\nThe sequence explains the disease. A flea bites and deposits *Y. pestis* in the skin. **Pla lets it spread** from the bite to the nearest lymph nodes. There it **resists being killed**: the F1 capsule blocks phagocytosis, and the Type III system injects Yops that disable the immune cells that do reach it. The organism multiplies in the lymph node, which swells into the painful **bubo** of bubonic plague. From there it can enter the blood (septicemic plague) and seed the lungs (pneumonic plague). Because its defenses are so effective, the immune system is overwhelmed quickly, which is why untreated plague can kill within days.\n\n## What Yersinia pestis looks like\n\n**Staining.** On Gram stain, *Y. pestis* is a Gram-negative rod or coccobacillus, and it is **pleomorphic** (variable in shape). Its most famous feature appears with Wayson or Giemsa stain: **bipolar staining**, where the two ends take up more stain than the middle, giving a \"safety pin\" appearance. This is the classic teaching image for the organism. One honest caution, worth remembering: many bipolar-staining organisms exist, so a safety-pin appearance suggests *Y. pestis* but does not prove it.\n\n**Key biochemical features.** *Y. pestis* is catalase-positive and oxidase-negative (the family pattern). It ferments glucose, mannitol, and maltose with acid but no gas, and does not ferment lactose or sucrose. It is indole-negative, urease-negative, and citrate-negative.\n\n**The temperature quirk (high-yield).** Two temperature facts set *Y. pestis* apart:\n\n- Its optimum growth temperature is about **27°C**, cooler than most human pathogens, a reminder that its natural home is the flea, not the human.\n- It is **non-motile at both 25°C and 37°C**. This is a useful contrast with the other *Yersinia* species (*Y. enterocolitica* and *Y. pseudotuberculosis*), which are motile at 25°C but non-motile at 37°C. So among the *Yersinia*, only *Y. pestis* is non-motile at the cooler temperature.\n\n![ - Y. pestisidentification flowchart.Image source: Laboratory Response Network (LRN)](\u002Fblogs\u002FYersinia-pestis-identification-flow-chart.png)Figure: *Y. pestis* identification flowchart. Image source: Laboratory Response Network (LRN)\n\n## Clinical Disease and Manifestations\n\nTransmission\n\nHuman can be infected by plague through:\n\n1. **Bite of infected rat fleas** (human fleas may rarely serve as a vector).\n2. Direct unprotected contact with tissues or bodily fluids of an infected animal (rodents) or contaminated materials.\n3. Inhalation of contaminated **airborne droplets from cases of pneumonic plague**.\n\nPlague exists in two natural cycles:\n\n1. Domestic cycle: It occurs between humans, rat fleas, and rodents.\n2. Wild or sylvatic cycle: It occurs in nature among wild rodents, independent of human beings.\n\n**Human plague occurs in three clinical forms;**\n\n![](\u002FAsexual%20spores%20of%20H.capsulatum.png)**1. Bubonic plague**: It is the **most common** type, transmitted by the bite of infected vector fleas. Bubonic plague is characterized by high fever and painful inflammatory swellings of **axilla and groin lymph nodes** (i.e. the characteristics buboes). Bubonic plague does not usually spread directly from person to person, because the bacteria are largely contained in the buboes. But if untreated it can progress to bloodstream and lung infection, which is frequently fatal.\n\n> Regional lymph nodes appear as tense, tender swellings called buboes; the most common site being inguinal, but also be crural, axillary, cervical, or submaxillary, depending on the site of the bite. Children are most likely to present with cervical or axillary buboes.\n\n**2. Pneumonic plague:** Pneumonic plague occurs as a consequence of bacteremic spread associated with bubonic plague or can be acquired by the airborne route during close contact with other pneumonic plague victims. The incubation period is 1-3 days, and infected individuals showed fever, headache, and respiratory symptoms (productive cough or hemoptysis, dyspnea, and chest pain). Pneumonic plague is highly infectious and is also rapidly fatal.\n\n**3. Septicemic plague**: It mostly develops as a consequence of bubonic or pneumonic plague. Widespread infection of the blood vessels causes bleeding into the skin, which can turn black from tissue death (gangrene). This blackening is the origin of the name Black Death\n\n### Laboratory Diagnosis of Plague\n\n> *Y. pestis* is a high-risk select agent; any suspected culture must be handled in a BSL-3 laboratory and referred to a reference\u002Fpublic-health laboratory. If a laboratory unexpectedly grows it, work should stop and the isolate be referred.\n\n**Specimen**\n\nbubo aspirate, sputum, or blood depending on the form; Cary-Blair for transport.\n\n![Bipolar appearance of Yersinia pestis in Giemsa stain - Bipolar appearance ofYersinia pestisin Giemsa stain](\u002Fblogs\u002FDark-stained-bipolar-ends-of-Yersinia-pestis-can-clearly-be-seen-in-this-Wrights-stain.png)Figure: Bipolar appearance of *Yersinia pestis* in Giemsa stain\n\n**Direct microscopy**\n\nGram stain shows pleomorphic Gram-negative coccobacilli with a capsule; Wayson or Giemsa shows the bipolar safety-pin appearance.\n\n### Culture\n\n*Y. pestis* is not fastidious and grows on ordinary media (blood agar, MacConkey) but slowly and best at about 28°C. On blood agar the colonies are small and non-hemolytic, and after a couple of days develop a beaten or \"hammered copper\" surface, sometimes described as a fried-egg shape. In broth it forms clumps that cling to the side of the tube (a \"stalactite\" pattern). These appearances are characteristic but slow, which is one reason rapid antigen tests are now preferred.\n\n![ - Yersinia pestisgrowth on Blood Agar A. 48 hours, B. 72 hours, C. 96 hours, and D. 96 hours “fried egg”](\u002Fblogs\u002FYersinia-pestis-growth-in-Blood-Agar.jpg)Figure: *Yersinia pestis* growth on Blood Agar A. 48 hours, B. 72 hours, C. 96 hours, and D. 96 hours “fried egg”\n\n**Identification**\n\nIf an isolate is grown and confirmed in a reference laboratory, this is the biochemical pattern that identifies it. The combination that points to *Y. pestis* is a non-motile, urease-negative, indole-negative, non-lactose-fermenting Gram-negative rod with bipolar staining.\n\n| Characteristics | Yersinia pestis |\n| --- | --- |\n| Catalase test | Positive |\n| Oxidase test | Negative |\n| Nitrate reduction test | Positive |\n| Methyl-Red (MR) test | Positive |\n| Voges-Proskauer (VP) test | Negative |\n| Citrate utilization test | Negative |\n| Indole test | Negative |\n| H2S production test | No |\n| Urease test | Negative |\n| Oxidative-fermentative (OF) test | Fermentative |\n| TSI reactions | Alkaline\u002FAcid, No gas, No H2S |\n| Motility | Non-motile |\n| Phenyl Pyruvic acid (PPA) test | Negative |\n| Lysine decarboxylation test | Negative |\n| Arginine decarboxylation test | Negative |\n| Ornithine decarboxylation test | Negative |\n| ONPG | +\u002F-(strain variability) |\n| Sugar fermentation test |  |\n| Glucose | Yes |\n| Sucrose | No |\n| Lactose | No |\n| Mannitol | Yes |\n\n### Antigen detection\n\n**F1 antigen detection** is the practical rapid test. A rapid immunochromatographic test (a dipstick, similar in idea to a rapid COVID or malaria test) detects the F1 capsular antigen directly from a bubo aspirate or sputum in minutes, which is invaluable in the field where plague outbreaks occur. [ELISA](https:\u002F\u002Fmicrobeonline.com\u002Felisa-principle-types-and-applications\u002F) and immunofluorescence can also detect F1.\n\n### Serological techniques\n\nAntibodies against the **F1 antigen** can be detected by passive hemagglutination or [complement fixation test](\u002Fcomplement-fixation-test-principle-procedure-results\u002F) or ELISA. The use of paired sera and the presence of a four-fold rise in titer confirms the diagnosis. The presence of antibodies provides limited diagnostic value, as the diagnosis is retrospective but may help as an epidemiological marker.\n\n### Other methods\n\nRapid diagnostic tests, Immunofluorescence antibody test, [Real-time Polymerase Chain reaction (PCR)](\u002Freal-time-pcr-principles-and-applications\u002F) can be used to identify Yersinia isolates to species level. PCR is available targeting gene coding F1 antigen, pesticin gene, and the plasminogen activator gene.\n\n### Typing\n\nTyping and differentiation between strains of *Yersinia* species can be achieved using a range of molecular techniques eg multiple-locus variable-number tandem-repeat analysis, [pulsed-field gel electrophoresis (PFGE)](https:\u002F\u002Fmicrobeonline.com\u002Fpulsed-field-gel-electrophoresis-pfge\u002F), whole-genome sequencing (WGS), etc. Biotyping is done based on glycerol fermentation and nitrate reduction.\n\n## How to remember\n\n**Safety pin, two dark ends.** Picture a safety pin: metal at both ends, gap in the middle. That is the bipolar staining of *Y. pestis* on Giemsa or Wayson stain, two dark ends with a pale center.  But the safety-pin appearance does not confirm plague, as other organisms stain this way too. It points, it does not prove.\n\n**It runs cold.** *Y. pestis* prefers about 27°C, cooler than most human pathogens, because its real home is the flea, not you. And it is the one *Yersinia* that does not move even in the cold: non-motile at both 25°C and 37°C, while the others swim at 25°C.\n\n**The needle and the disguise.** Two virulence ideas anchor the pathogenesis: the F1 capsule is the disguise (it hides the organism from phagocytes), and the Type III secretion system is the needle (it injects Yops that shut down immune cells). Disguise plus needle is why plague meets so little resistance early.\n\n**Black Death, black skin.** In septicemic plague, bleeding into the skin and tissue death turn the skin black. That is where the name Black Death comes from.\n\n**Three forms, one progression.** Bubo (fleabite, lymph node) → blood (septicemic) → lungs (pneumonic, and now airborne and person-to-person). The disease moves outward from the bite, and only the lung form spreads between people through the air.\n\n## Key exam facts in one table\n\n| Fact | Detail |\n| --- | --- |\n| Organism \u002F family | *Yersinia pestis*, Gram-negative rod, family Enterobacteriaceae |\n| Disease | Plague (bubonic, pneumonic, septicemic) |\n| Transmission | Fleabite (rodent reservoir); airborne person-to-person in pneumonic plague |\n| Classic stain | Bipolar \"safety pin\" appearance (Wayson or Giemsa) |\n| Growth temperature | Optimum \\~27°C (cooler than most pathogens) |\n| Motility | Non-motile at both 25°C and 37°C (other *Yersinia* are motile at 25°C) |\n| Biochemical | Catalase +, oxidase −, urease −, indole −, citrate −; non-lactose fermenter |\n| TSI | Alkaline slant \u002F acid butt, no gas, no H₂S |\n| Key virulence factors | F1 capsule (antiphagocytic), Type III secretion + Yops (disable immune cells), Pla (spread) |\n| Rapid diagnosis | F1 antigen immunochromatographic test on bubo aspirate or sputum |\n| Confirmatory | Culture in reference lab; PCR (F1, pesticin, plasminogen activator genes) |\n| Biosafety | BSL-3 select agent; refer suspected isolates to a reference laboratory |\n| Most common form | Bubonic; bubo most often inguinal (cervical\u002Faxillary in children) |\n| Most fatal \u002F transmissible | Pneumonic plague (airborne, rapidly fatal) |\n\n## Where students get confused\n\n**Bipolar staining is not proof.** The safety-pin appearance is classic for *Y. pestis*, but other organisms stain the same way. It is a strong pointer that must be confirmed, not a diagnosis on its own. All *Y. pestis* may look bipolar, but not all bipolar cells are *Y. pestis*.\n\n**The temperature facts get mixed up.** Two separate points: the organism grows best at about 27°C, and it is non-motile at both temperatures. The contrast is with the other *Yersinia* species, which are motile at 25°C but not at 37°C. Only *Y. pestis* is non-motile in the cold.\n\n**Which forms spread between people.** Bubonic plague does not usually pass directly person to person; it comes from a fleabite. Only pneumonic plague spreads through the air between people. This distinction matters for outbreak control and is a common exam point.\n\n**F1 antigen has two roles.** F1 is both a virulence factor (the antiphagocytic capsule) and the target of the rapid diagnostic test.\n\n**\"Enterobacteriaceae\" but not a gut disease.** *Y. pestis* belongs to the same family as *E. coli* and *Salmonella*, and shares the family biochemistry (oxidase-negative, and so on), but it causes a flea-borne systemic disease, not gastroenteritis. Family membership is about shared biology, not shared disease. (The other two *Yersinia* species, *Y. enterocolitica* and *Y. pseudotuberculosis*, do cause gut infection.)\n\n**References**\n\n1. Tille, P. M. (2022). *Bailey & Scott's Diagnostic Microbiology* (15th ed.). Elsevier.\n2. Procop, G. W., et al. (2017). *Koneman's Color Atlas and Textbook of Diagnostic Microbiology* (7th ed.). Wolters Kluwer.\n3. World Health Organization. (2017). *Plague* (Fact sheet). World Health Organization.\n4. Perry, R. D., & Fetherston, J. D. (1997). Yersinia pestis: etiologic agent of plague. *Clinical Microbiology Reviews*, 10(1), 35–66. \u003Chttps:\u002F\u002Fdoi.org\u002F10.1128\u002FCMR.10.1.35>",[50,53,56,59,62,65,68,71],{"question":51,"answer":52},"\u003Cp>What disease does Yersinia pestis 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":54,"answer":55},"\u003Cp>Why is Yersinia pestis 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":57,"answer":58},"\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":60,"answer":61},"\u003Cp>Why does Yersinia pestis 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":63,"answer":64},"\u003Cp>Is Yersinia pestis 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":66,"answer":67},"\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":69,"answer":70},"\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":72,"answer":73},"\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>",[75],"enterobacteriaceae",[77,102,126,133,158,167,199],{"slug":75,"title":78,"description":79,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":80,"lastUpdatedDate":81,"draft":46,"category":47,"image":42,"faq":82,"tags":101},"Enterobacteriaceae: How to Identify and Tell Them Apart","A working guide to the Enterobacteriaceae: which genera matter, how lactose fermentation and biochemical tests separate them, and how to reason from a MacConkey plate to a genus.","2013-10-01","2026-08-18",[83,86,89,92,95,98],{"question":84,"answer":85},"\u003Cp>What is the single fastest test to know a Gram-negative rod belongs to the Enterobacteriaceae?\u003C\u002Fp>","\u003Cp>The oxidase test. Members of this family are oxidase-negative. If a Gram-negative rod is oxidase-positive, it is not in this family, and you should think of organisms such as \u003Cem>Pseudomonas\u003C\u002Fem> or \u003Cem>Vibrio\u003C\u002Fem> instead.\u003C\u002Fp>",{"question":87,"answer":88},"\u003Cp>Why are Salmonella and Shigella pale on MacConkey agar?\u003C\u002Fp>","\u003Cp>Because they do not ferment lactose. MacConkey agar turns pink only when an organism ferments lactose and lowers the pH. \u003Cem>Salmonella\u003C\u002Fem> and \u003Cem>Shigella\u003C\u002Fem> are non-lactose fermenters, so their colonies stay colorless. This is why a pale colony in a diarrheal stool is the one worth investigating.\u003C\u002Fp>",{"question":90,"answer":91},"\u003Cp>Is Enterobacteriaceae the same as Enterobacterales?\u003C\u002Fp>","\u003Cp>Not exactly. In 2016 the old family was reorganized into a larger order called Enterobacterales, and some genera were moved into separate families. In everyday clinical and exam use, the term Enterobacteriaceae is still used broadly for this whole group of enteric Gram-negative rods.\u003C\u002Fp>",{"question":93,"answer":94},"\u003Cp>What does IMViC stand for and why is it useful?\u003C\u002Fp>","\u003Cp>IMViC stands for Indole, Methyl red, Voges-Proskauer, and Citrate. These four tests together separate the common genera. The classic contrast is \u003Cem>E. coli\u003C\u002Fem> (+ + − −) versus \u003Cem>Klebsiella\u003C\u002Fem> and \u003Cem>Enterobacter\u003C\u002Fem> (− − + +).\u003C\u002Fp>",{"question":96,"answer":97},"\u003Cp>Which Enterobacteriaceae are the main antibiotic-resistance concerns?\u003C\u002Fp>","\u003Cp>Three groups: organisms with inducible AmpC beta-lactamase (such as \u003Cem>Enterobacter\u003C\u002Fem>, \u003Cem>Serratia\u003C\u002Fem>, \u003Cem>Citrobacter freundii\u003C\u002Fem>, \u003Cem>Klebsiella aerogenes\u003C\u002Fem>), ESBL-producers (common in \u003Cem>E. coli\u003C\u002Fem> and \u003Cem>Klebsiella\u003C\u002Fem>), and carbapenem-resistant Enterobacteriaceae (CRE), where treatment options become very limited.\u003C\u002Fp>",{"question":99,"answer":100},"\u003Cp>What is the Vi antigen?\u003C\u002Fp>","\u003Cp>It is a special capsular antigen of \u003Cem>Salmonella\u003C\u002Fem> Typhi. \"Vi\" stands for virulence. It can cover the O antigen on fresh isolates, which is why an O-antigen agglutination test may read negative until the culture is heated.\u003C\u002Fp>",[75],{"slug":103,"title":104,"description":105,"seoTitle":106,"seoDescription":107,"author":43,"createdDate":108,"lastUpdatedDate":109,"draft":46,"category":110,"image":42,"faq":111,"tags":124},"elisa-principle-types-and-applications","ELISA Test: Principle, Types (Direct, Indirect, Sandwich, Competitive), Procedure, and Uses","ELISA (Enzyme-Linked Immunosorbent Assay) is the most widely used immunoassay for detecting antibodies and antigens. Learn all four ELISA types: direct, indirect, sandwich, and competitive. Explore step-by-step procedures, clinical applications (such as HIV, HBsAg, and dengue), and guidance on choosing the right type for your needs.","ELISA: Compare Four Types, Procedure, Results, and Applications","Compare direct, indirect, sandwich, and competitive ELISA formats, then review their reagents, procedures, result interpretation, and diagnostic uses.","2012-04-10","2026-07-29","immunology",[112,115,118,121],{"question":113,"answer":114},"Why is the indirect ELISA format used for HIV antibody detection rather than the direct or sandwich format?","Indirect ELISA is the correct format for detecting patient antibodies (serology) because it uses a known antigen coated on the plate to capture the unknown antibody from patient serum, and then detects the captured antibody using a secondary enzyme-labeled anti-human IgG antibody. For HIV screening, the plate wells are coated with HIV antigens (HIV-1 and HIV-2 proteins) — when patient serum contains anti-HIV antibodies, they bind to the plate-coated antigens. The enzyme-labeled anti-human IgG secondary antibody then binds to the captured human antibodies and generates the color signal. Direct ELISA would be inappropriate because the patient's own antibody cannot be enzyme-labeled — it is the unknown component being detected. Sandwich ELISA would be inappropriate because it detects antigens by capturing them between two antibodies, whereas HIV serology aims to detect the patient's antibody response. The indirect ELISA format has an additional advantage for clinical serology: the same enzyme-labeled anti-human IgG secondary antibody can be used for any antigen-antibody system, reducing the need to produce a separate enzyme-labeled antibody for every pathogen tested.",{"question":116,"answer":117},"What is the hook effect in sandwich ELISA and how can it cause a false negative?","The hook effect is a false negative that happens in sandwich ELISA when antigen is so abundant it saturates the capture and detector antibodies separately, so most antigen molecules bind only one antibody and the sandwich bridge never forms. The signal drops even though the sample is loaded with antigen. It is suspected when a patient with strong clinical features has an unexpectedly low or negative result (classically very active hepatitis B with high HBsAg, or tumor markers at very high levels). The fix is to dilute the sample and retest, which breaks the antigen excess and restores the sandwich. This is one of two opposite false negatives in ELISA; for how it contrasts with the window-period false negative in indirect ELISA, see \"Where Students Get Confused\" above.",{"question":119,"answer":120},"How do 3rd-generation and 4th-generation HIV ELISA kits differ, and what is the clinical significance?","Third-generation HIV ELISA kits detect anti-HIV IgG and IgM antibodies only, using an indirect or capture ELISA format. They cannot detect HIV p24 antigen. Their window period is approximately 22–28 days from infection to detection. Fourth-generation HIV combination ELISA kits simultaneously detect both anti-HIV antibodies (using the indirect ELISA component) AND HIV p24 antigen (using the sandwich ELISA component) in a single well. Because p24 antigen appears in blood 10–12 days after infection — well before antibodies develop — 4th-generation combo tests have a window period of approximately 15–20 days, reducing the false-negative window by approximately 7–10 days compared to 3rd-generation tests. This seemingly small reduction has significant public health implications: people tested during early acute HIV infection (when viral loads are highest and infectivity is greatest) are more likely to receive a true-positive result with 4th-generation testing, allowing earlier diagnosis, treatment initiation, and prevention of onward transmission. Current WHO and national guidelines in most countries recommend 4th-generation combo tests as the standard for HIV diagnosis wherever available.",{"question":122,"answer":123},"Does \"direct ELISA\" mean it detects antigen and \"indirect ELISA\" mean it detects antibody?","No, and this is a common misunderstanding. The words direct and indirect describe how the enzyme label reaches the target, not whether an antigen or an antibody is being detected. In direct ELISA the enzyme is attached to the primary antibody that binds the target. In indirect ELISA the enzyme is on a secondary antibody that binds the primary antibody, adding an amplification step. It is true that in clinical practice indirect ELISA is used mainly to detect patient antibodies (serology) and sandwich ELISA to detect patient antigens, but that is a matter of how each format is applied, not what the prefixes direct and indirect mean. To decide what a given ELISA detects, look at what is coated on the plate and what unknown is being captured from the sample.",[125],"immunoassays",{"slug":127,"title":128,"description":128,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":129,"lastUpdatedDate":130,"draft":46,"category":110,"image":42,"faq":131,"tags":132},"complement-fixation-test-principle-procedure-results","Complement Fixation Test: Principle, Procedure, Results","2015-05-05","2026-08-17",[],[125],{"slug":134,"title":135,"description":136,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":137,"lastUpdatedDate":138,"draft":46,"category":139,"image":42,"faq":140,"tags":156},"real-time-pcr-principles-and-applications","Real-time PCR (qPCR): Principles and Applications","Real-time PCR (qPCR) amplifies and quantifies DNA simultaneously using fluorescent probes. Learn SYBR Green vs TaqMan, Ct values, and clinical uses in viral load testing.","2019-12-26","2026-07-05","lab-equipment",[141,144,147,150,153],{"question":142,"answer":143},"What is the Ct value in real-time PCR and how is it interpreted?","The Ct value (cycle threshold) is the PCR cycle number at which the fluorescent signal from the reaction crosses a pre-set detection threshold. It is inversely proportional to the amount of starting template: a sample with high viral load reaches the threshold in fewer cycles (low Ct value), while a sample with low viral load requires more cycles (high Ct value). In HIV viral load monitoring, a Ct of approximately 20 corresponds to a high viral load, while a Ct above 34 indicates very low or undetectable levels. An important caveat: Ct values are not directly comparable between different assays, instruments, or laboratories.",{"question":145,"answer":146},"What is the difference between SYBR Green and TaqMan probes in real-time PCR?","SYBR Green is a fluorescent dye that binds to any double-stranded DNA and fluoresces — it is non-specific, detecting all amplification products including primer dimers and non-specific products. It is cheaper and simpler but requires melting curve analysis to confirm the correct product was amplified. TaqMan probes are sequence-specific — a labelled probe complementary to an internal target sequence is cleaved by Taq polymerase during extension, releasing a fluorescent reporter only when the correct sequence is amplified. TaqMan is more specific, suitable for multiplex detection, and is the standard for clinical diagnostic assays. SYBR Green is used in research settings where cost matters and melting curve verification is feasible.",{"question":148,"answer":149},"How does real-time PCR differ from conventional PCR?","In conventional PCR, amplification and detection are separate steps — the tube is opened after cycling and products are detected by gel electrophoresis. In real-time PCR, amplification and detection occur simultaneously in a closed tube — fluorescence is measured after each cycle as amplicon accumulates. The closed-tube design eliminates post-PCR handling and the carry-over contamination risk it creates. Real-time PCR is also quantitative, measuring the amount of starting template, while conventional PCR is qualitative (presence or absence only). Real-time PCR is faster because no gel electrophoresis step is required.",{"question":151,"answer":152},"What are the clinical applications of real-time PCR in microbiology?","Real-time PCR is used for viral load quantification — HIV, HCV, HBV, and CMV monitoring in transplant patients all rely on qPCR to measure virus copy numbers and guide treatment decisions. It is used for COVID-19 (SARS-CoV-2) detection, TB quantification, and diagnosis of infections where pathogen load correlates with disease severity or treatment response. It is also used for SNP detection, allelic discrimination, and — when combined with reverse transcription — for mRNA expression analysis and RNA virus detection.",{"question":154,"answer":155},"Why is real-time PCR preferred over conventional PCR in clinical diagnostic laboratories?","Real-time PCR is preferred for three reasons. First, the closed-tube format eliminates post-PCR amplicon manipulation, dramatically reducing the risk of carry-over contamination that causes false positives — a major problem in high-throughput diagnostic laboratories. Second, it is quantitative, providing viral load or copy number data that guides clinical decisions such as when to start or switch antiviral therapy. Third, it is faster — results are available in 1–3 hours compared to 4–6 hours for conventional PCR followed by gel electrophoresis.",[157],"pcr-techniques",{"slug":159,"title":160,"description":161,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":162,"lastUpdatedDate":163,"draft":46,"category":139,"image":42,"faq":164,"tags":165},"pulsed-field-gel-electrophoresis-pfge","Pulsed-Field Gel Electrophoresis (PFGE): Steps, Applications","Pulsed-field gel electrophoresis (PFGE) separates DNA fragments up to 10 Mb by switching the electric field between directions, forcing large molecules to reorient. Learn why pulsing works, the plug-based steps, and why PFGE was the gold standard for outbreak fingerprinting.","2019-09-16","2026-07-11",[],[166],"electrophoresis",{"slug":168,"title":169,"description":170,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":171,"lastUpdatedDate":172,"draft":46,"category":47,"image":42,"faq":173,"tags":198},"shigella-disease-properties-pathogenesis-and-laboratory-diagnosis","Shigella: Identification, Pathogenesis, and Bacillary Dysentery","How Shigella causes bacillary dysentery, how it spreads from cell to cell, and how the laboratory identifies it: non-lactose, non-motile, no H₂S, and how to differentiate it from Salmonella.","2013-05-18","2026-08-04",[174,177,180,183,186,189,192,195],{"question":175,"answer":176},"\u003Cp>Is Shigella motile or non-motile?\u003C\u002Fp>","\u003Cp>Non-motile. \u003Cem>Shigella\u003C\u002Fem> has no flagella, so it does not move and has no H antigen. This is one of the main features that separates it from \u003Cem>Salmonella\u003C\u002Fem>, which is motile.\u003C\u002Fp>",{"question":178,"answer":179},"\u003Cp>Does Shigella produce H₂S?\u003C\u002Fp>","\u003Cp>No. \u003Cem>Shigella\u003C\u002Fem> does not produce hydrogen sulfide, so it forms no black centers on selective media such as XLD agar. This is a key difference from \u003Cem>Salmonella\u003C\u002Fem>, which usually does produce H₂S.\u003C\u002Fp>",{"question":181,"answer":182},"\u003Cp>What are the TSI results for Shigella?\u003C\u002Fp>","\u003Cp>An alkaline slant over an acid butt (K\u002FA), with no gas and no H₂S. It ferments glucose but not lactose or sucrose. The absence of both gas and black color helps separate it from \u003Cem>Salmonella\u003C\u002Fem>.\u003C\u002Fp>",{"question":184,"answer":185},"\u003Cp>How do you tell Shigella from Salmonella?\u003C\u002Fp>","\u003Cp>Both are pale, non-lactose-fermenting colonies on MacConkey agar. \u003Cem>Shigella\u003C\u002Fem> is non-motile and H₂S-negative; \u003Cem>Salmonella\u003C\u002Fem> is motile and usually H₂S-positive with black centers on selective media.\u003C\u002Fp>",{"question":187,"answer":188},"\u003Cp>Which Shigella species causes the most severe disease?\u003C\u002Fp>","\u003Cp>\u003Cem>Shigella dysenteriae\u003C\u002Fem> type 1. It produces Shiga toxin and can cause hemolytic uremic syndrome. However, it is not the most common species; \u003Cem>S. sonnei\u003C\u002Fem> is the most commonly isolated but causes the mildest illness.\u003C\u002Fp>",{"question":190,"answer":191},"\u003Cp>Why does Shigella spread so easily?\u003C\u002Fp>","\u003Cp>Because its infectious dose is very low. As few as 10 to 200 organisms can cause disease, so it passes readily from person to person, especially where handwashing and sanitation are difficult.\u003C\u002Fp>",{"question":193,"answer":194},"\u003Cp>Why is SS agar not ideal for Shigella?\u003C\u002Fp>","\u003Cp>Despite its name (Salmonella-Shigella agar), SS agar inhibits many \u003Cem>Shigella\u003C\u002Fem> strains, so it can fail to grow them. Other media such as XLD or MacConkey are more reliable for isolating \u003Cem>Shigella\u003C\u002Fem>.\u003C\u002Fp>",{"question":196,"answer":197},"\u003Cp>What is the difference between bacillary and amoebic dysentery?\u003C\u002Fp>","\u003Cp>Bacillary dysentery is caused by bacteria, mainly \u003Cem>Shigella\u003C\u002Fem>; amoebic dysentery is caused by the parasite \u003Cem>Entamoeba histolytica\u003C\u002Fem>. They differ in stool findings and treatment, and are compared in a separate article.\u003C\u002Fp>",[75],{"slug":200,"title":201,"description":202,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":203,"lastUpdatedDate":172,"draft":46,"category":47,"image":42,"faq":204,"tags":229},"salmonella-disease-properties-pathogenesis-and-laboratory-diagnosis","Salmonella: Properties, Enteric Fever, and Laboratory Diagnosis","How Salmonella causes enteric fever and gastroenteritis, how it is identified in the laboratory (TSI, H₂S, the S. Typhi biochemical pattern), and why blood culture beats the Widal test for diagnosis.","2013-04-27",[205,208,211,214,217,220,223,226],{"question":206,"answer":207},"\u003Cp>Is Salmonella lactose fermenter or non-fermenter?\u003C\u002Fp>","\u003Cp>Non-fermenter. \u003Cem>Salmonella\u003C\u002Fem> does not ferment lactose, so it forms pale, colorless colonies on MacConkey agar. This separates it from \u003Cem>E. coli\u003C\u002Fem>, which ferments lactose and turns pink.\u003C\u002Fp>",{"question":209,"answer":210},"\u003Cp>Does Salmonella produce H₂S?\u003C\u002Fp>","\u003Cp>Most salmonellae produce H₂S, which shows as a black center on selective media such as SS agar and Hektoen enteric agar. \u003Cem>S.\u003C\u002Fem> Typhi produces only weak H₂S. \u003Cem>Shigella\u003C\u002Fem> does not produce H₂S at all, which helps separate the two.\u003C\u002Fp>",{"question":212,"answer":213},"\u003Cp>What are the TSI results for Salmonella Typhi?\u003C\u002Fp>","\u003Cp>Alkaline slant over acid butt (K\u002FA), with weak H₂S and no gas. It ferments glucose but not lactose or sucrose. The weak H₂S and absence of gas are the classic \u003Cem>S.\u003C\u002Fem> Typhi pattern.\u003C\u002Fp>",{"question":215,"answer":216},"\u003Cp>Why is blood culture used for typhoid instead of stool?\u003C\u002Fp>","\u003Cp>Because enteric fever is a systemic infection. The organism survives inside cells and circulates in the blood rather than staying in the gut, so blood culture detects it reliably while stool culture often does not, especially early. Bone marrow culture is even more sensitive.\u003C\u002Fp>",{"question":218,"answer":219},"\u003Cp>What is the difference between typhoidal and non-typhoidal Salmonella?\u003C\u002Fp>","\u003Cp>Typhoidal \u003Cem>Salmonella\u003C\u002Fem> (\u003Cem>S.\u003C\u002Fem> Typhi and \u003Cem>S.\u003C\u002Fem> Paratyphi) infect only humans and cause enteric fever, a systemic illness. Non-typhoidal \u003Cem>Salmonella\u003C\u002Fem> come from animals and food and usually cause self-limited diarrhea, though they can invade the blood in vulnerable people.\u003C\u002Fp>",{"question":221,"answer":222},"\u003Cp>Is the Widal test reliable for diagnosing typhoid?\u003C\u002Fp>","\u003Cp>Not on its own. It supports a diagnosis but is often falsely negative in real cases and falsely positive in malaria and other conditions. Culture is the definitive test.\u003C\u002Fp>",{"question":224,"answer":225},"\u003Cp>How do you tell Salmonella from Shigella in the laboratory?\u003C\u002Fp>","\u003Cp>Both are pale non-lactose fermenters on MacConkey. \u003Cem>Salmonella\u003C\u002Fem> is motile and produces H₂S (black colonies on selective media); \u003Cem>Shigella\u003C\u002Fem> is non-motile and does not produce H₂S.\u003C\u002Fp>",{"question":227,"answer":228},"\u003Cp>Which Salmonella infection is linked to osteomyelitis in sickle cell disease?\u003C\u002Fp>","\u003Cp>Non-typhoidal \u003Cem>Salmonella\u003C\u002Fem> is a classic cause of osteomyelitis in people with sickle cell disease.\u003C\u002Fp>",[75],{"enabled":231,"threads":232,"total":233},true,[],0,[235,241,248,255,261,266,272,277,283,286,293],{"slug":236,"name":43,"description":237,"image":238,"body":239,"postCount":240},"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.*",468,{"slug":242,"name":243,"description":244,"image":245,"body":246,"postCount":247},"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.",78,{"slug":249,"name":250,"description":251,"image":252,"body":253,"postCount":254},"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":256,"name":257,"description":251,"image":258,"body":259,"postCount":260},"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":262,"name":263,"description":251,"image":42,"body":264,"postCount":265},"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":267,"name":268,"description":269,"image":42,"body":270,"postCount":271},"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":273,"name":274,"description":275,"image":42,"body":42,"postCount":276},"guest-author","Guest Author","Guest Author \u002F Contributor",1,{"slug":278,"name":279,"description":251,"image":280,"body":281,"postCount":282},"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.",17,{"slug":284,"name":285,"description":275,"image":42,"body":42,"postCount":276},"dr-poonam-acharya","Dr. Poonam Acharya",{"slug":287,"name":288,"description":289,"image":290,"body":291,"postCount":292},"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":294,"name":295,"description":296,"image":297,"body":298,"postCount":276},"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.",[300,307,313,318,323,328,332,336,339,344,348,353,357,362,367,371,375,379,383,387,391,395,399,403,407,411,415,419,424,429,433,437,441,445,449,453,457,461,465,469,473,477,481,485,489,493,497,501,506,510,514,518,522,526,530,534,538,542,546,550,554,558,562,566,570,574,578,582,585,589],{"slug":301,"name":302,"description":303,"image":304,"body":305,"postCount":306},"gram-negative-cocci","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":308,"name":309,"description":310,"image":42,"body":311,"postCount":312},"microscopy","Microscopy","Microscope types, components, and microscopy techniques","These are list of blog posts related to microscopy. ",12,{"slug":314,"name":315,"description":316,"image":42,"body":42,"postCount":317},"gram-positive-cocci","Gram-Positive Cocci","Staphylococcus, Streptococcus, Enterococcus, Micrococcus — organisms, diseases, and identification tests",11,{"slug":319,"name":320,"description":321,"image":42,"body":42,"postCount":322},"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":324,"name":325,"description":326,"image":42,"body":42,"postCount":327},"gram-positive-rods","Gram-Positive Rods","Bacillus, Clostridium, Listeria, Corynebacterium, Actinomyces and related organisms",8,{"slug":329,"name":330,"description":331,"image":42,"body":42,"postCount":317},"mycobacteria","Mycobacteria","Mycobacterium tuberculosis, leprosy, atypical mycobacteria, and acid-fast organism diagnosis",{"slug":333,"name":334,"description":335,"image":42,"body":42,"postCount":317},"anaerobic-bacteriology","Anaerobic Bacteriology","Anaerobic organisms, anaerobic culture methods, and anaerobic infection diagnosis",{"slug":75,"name":337,"description":338,"image":42,"body":42,"postCount":312},"Enterobacteriaceae","Identification, differentiation, and clinical significance of Enterobacteriaceae family members",{"slug":340,"name":341,"description":342,"image":42,"body":42,"postCount":343},"spirochetes","Spirochetes","Treponema, Leptospira, Borrelia and spirochetal infections",7,{"slug":345,"name":346,"description":347,"image":42,"body":42,"postCount":306},"food-microbiology","Food Microbiology","Food-borne pathogens, food safety, spoilage, and preservation",{"slug":349,"name":350,"description":351,"image":42,"body":42,"postCount":352},"antimicrobial-susceptibility-testing","Antimicrobial Susceptibility Testing","Methods for testing antibiotic susceptibility in clinical microbiology",21,{"slug":354,"name":355,"description":356,"image":42,"body":42,"postCount":327},"antimicrobials-moa-amr","Antimicrobials (MOA & AMR)","Mechanisms, detection, and clinical significance of antimicrobial resistance",{"slug":358,"name":359,"description":360,"image":42,"body":42,"postCount":361},"sterilization-disinfection","Sterilization and Disinfection","Methods of sterilization and disinfection in healthcare and laboratory settings",10,{"slug":363,"name":364,"description":365,"image":42,"body":42,"postCount":366},"specimen-collection-transport","Specimen Collection and Transport","Collection, handling, and transport of clinical specimens for microbiological testing",27,{"slug":368,"name":369,"description":370,"image":42,"body":42,"postCount":352},"bacterial-structure-physiology","Bacterial Structure and Physiology","Bacterial cell structure, growth, physiology, and environmental factors affecting growth",{"slug":372,"name":373,"description":42,"image":42,"body":374,"postCount":265},"horizontal-gene-transfer","Horizontal Gene Transfer","Articles related to **Horizontal Gene Transfer**",{"slug":376,"name":377,"description":42,"image":42,"body":378,"postCount":361},"chromatography","Chromatography","Information about chromatographic techniques.",{"slug":166,"name":380,"description":381,"image":42,"body":382,"postCount":343},"Electrophoresis","Information about Electrophoresis Techniques ","Detailed information  about Electrophoresis Techniques ",{"slug":157,"name":384,"description":385,"image":42,"body":386,"postCount":265},"PCR Techniques","Information about various types of Polymerase Chain Reaction Techniques ","More detailed information about various types of Polymerase Chain Reaction Techniques ",{"slug":388,"name":389,"description":390,"image":42,"body":42,"postCount":265},"bacteriophage","Bacteriophage","Description about Bacteriophage.",{"slug":392,"name":393,"description":394,"image":42,"body":42,"postCount":265},"malaria","Malaria","It is the collections of articles regarding malarial disease. ",{"slug":396,"name":397,"description":398,"image":42,"body":42,"postCount":265},"anaerobic-culture-techniques","Anaerobic Culture Techniques","Posts related with Anaerobic Culture Techniques.",{"slug":125,"name":400,"description":401,"image":42,"body":42,"postCount":402},"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":404,"name":405,"description":406,"image":42,"body":42,"postCount":343},"biosafety-levels","Biosafety levels ","Articles related to Biosafety Levels",{"slug":408,"name":409,"description":410,"image":42,"body":42,"postCount":322},"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":412,"name":413,"description":414,"image":42,"body":42,"postCount":265},"pipette","Pipette","Posts related with Pipette. ",{"slug":416,"name":417,"description":418,"image":42,"body":42,"postCount":327},"bacteriology-mcqs","Bacteriology MCQs","This sections lists MCQs in Bacteriology.",{"slug":420,"name":421,"description":422,"image":42,"body":42,"postCount":423},"parasitology-mcqs","Parasitology MCQs","This section lists MCQs in Parasitology.",2,{"slug":425,"name":426,"description":427,"image":42,"body":42,"postCount":428},"virology-mcqs","Virology MCQs","This is the collections of Multiple Choice Questions in Virology.",4,{"slug":430,"name":431,"description":432,"image":42,"body":42,"postCount":322},"mcqs-in-microbiology","MCQs in Microbiology","This section lists the collections of Multiple Choice Questions in General Microbiology Topics. ",{"slug":434,"name":435,"description":436,"image":42,"body":42,"postCount":327},"immunology-mcqs","Immunology MCQs","In this section; we are posting collections of Multiple Choice Questions about Immunology. ",{"slug":438,"name":439,"description":440,"image":42,"body":42,"postCount":271},"microbial-curiosities","Microbial Curiosities","In this clusters, we are posting interesting and unique information about Microorganisms. ",{"slug":442,"name":443,"description":444,"image":42,"body":42,"postCount":352},"bacterial-culture-media","Bacterial Culture Media","Posts related to Bacterial Culture Media. ",{"slug":446,"name":447,"description":448,"image":42,"body":42,"postCount":265},"fungal-culture-media","Fungal Culture Media","Posts related to Fungal Culture Media.",{"slug":450,"name":451,"description":452,"image":42,"body":42,"postCount":322},"motility-test","Motility Test","This lists the procedure regarding various tests methods for bacterial motility.",{"slug":454,"name":455,"description":456,"image":42,"body":42,"postCount":361},"bacterial-enumeration","Bacterial enumeration","These posts are related to isolation and enumeration of bacteria. ",{"slug":458,"name":459,"description":460,"image":42,"body":42,"postCount":423},"gram-positive-coccobacillus","Gram-positive coccobacillus","List of Gram Positive Coccobacilli",{"slug":462,"name":463,"description":464,"image":42,"body":42,"postCount":428},"dimorphic-fungi","Dimorphic Fungi","This is about various dimorphic fungi. ",{"slug":466,"name":467,"description":468,"image":42,"body":42,"postCount":343},"bacterial-classification","Bacterial Classification","These posts are related with various approaches used for the classification of Bacteria. ",{"slug":470,"name":471,"description":472,"image":42,"body":42,"postCount":322},"immunofluorescence","Immunofluorescence ","Various Tests related to Immunofluorescence ",{"slug":474,"name":475,"description":476,"image":42,"body":42,"postCount":271},"antibody-mediated-immunity","Antibody-mediated Immunity","This clusters links the articles that are sharing insights about Antibody-mediated immunity. ",{"slug":478,"name":479,"description":480,"image":42,"body":42,"postCount":343},"hypersensitivity","Hypersensitivity","Articles related to Hypersensitivity.",{"slug":482,"name":483,"description":42,"image":42,"body":42,"postCount":484},"haemophilus","Haemophilus",3,{"slug":486,"name":487,"description":488,"image":42,"body":42,"postCount":428},"sexually-transmitted-infections-stis","Sexually transmitted infections (STIs)","This is the clusters of infections that are transmitted sexually. ",{"slug":490,"name":491,"description":492,"image":42,"body":42,"postCount":312},"adaptive-immunity","Adaptive Immunity","Blog posts related to B Cell Immunity and T Cell Immunity.",{"slug":494,"name":495,"description":496,"image":42,"body":42,"postCount":306},"fungal-diagnostics","Fungal Diagnostics","Various methods used for the Diagnosis of Fungal Infections. ",{"slug":498,"name":499,"description":500,"image":42,"body":42,"postCount":322},"laboratory-storage-and-preservation","Laboratory Storage and Preservation","Articles about Laboratory Storage of Antimicrobial Disk, Test organisms and Equipment used for this process. ",{"slug":502,"name":503,"description":504,"image":42,"body":505,"postCount":265},"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":507,"name":508,"description":509,"image":42,"body":42,"postCount":327},"laboratory-glassware","Laboratory Glassware","Posts about Laboratory Glassware. ",{"slug":511,"name":512,"description":513,"image":42,"body":42,"postCount":265},"helminths","Helminths","In this section, we are covering properties, life cycle, pathogenesis and laboratory diagnosis of Helminths\u002FHelminthic infestations. ",{"slug":515,"name":516,"description":517,"image":42,"body":42,"postCount":265},"protozoan-parasite","Protozoan Parasite","In this cluster, we are covering protozoan parasites. ",{"slug":519,"name":520,"description":521,"image":42,"body":42,"postCount":276},"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":523,"name":524,"description":525,"image":42,"body":42,"postCount":361},"bacterial-staining-technique","Bacterial Staining Technique","Lists of various staining techniques that are used to stain bacteria. ",{"slug":527,"name":528,"description":529,"image":42,"body":42,"postCount":260},"enzyme-tests","Enzyme Tests","\u003Cp>Various Biochemical Test that are based on enzymatic activity of the microorganisms. \u003C\u002Fp>",{"slug":531,"name":532,"description":533,"image":42,"body":42,"postCount":317},"carbohydrate-utilization","Carbohydrate Utilization","\u003Cp>Various biochemical tests which are related to Carbohydrate fermentation or Utilization\u003C\u002Fp>",{"slug":535,"name":536,"description":537,"image":42,"body":42,"postCount":322},"susceptibility-based-id","Susceptibility-based ID","\u003Cp>These are susceptibility based identification test such as optochin sensitivity, bacitracin sensitivity etc. \u003C\u002Fp>",{"slug":539,"name":540,"description":541,"image":42,"body":42,"postCount":428},"microbial-metabolism","Microbial Metabolism","\u003Cp>Tests about Microbial Metabolism. \u003C\u002Fp>",{"slug":543,"name":544,"description":545,"image":42,"body":42,"postCount":327},"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":547,"name":548,"description":549,"image":42,"body":42,"postCount":484},"atypical-pneumonia","Atypical Pneumonia","\u003Cp>Organisms responsible for Atypical Pneumonia. \u003C\u002Fp>",{"slug":551,"name":552,"description":553,"image":42,"body":42,"postCount":322},"antigen","Antigen","\u003Cp>Various articles related to Antigens.\u003C\u002Fp>",{"slug":555,"name":556,"description":557,"image":42,"body":42,"postCount":343},"innate-immunity","Innate Immunity","\u003Cp>Articles related to Innate Immunity. \u003C\u002Fp>",{"slug":559,"name":560,"description":561,"image":42,"body":42,"postCount":428},"respiratory-tract-infection","Respiratory Tract Infection","\u003Cp>In this cluster, you can see various etiological agents that causes respiratory tract infection. \u003C\u002Fp>",{"slug":563,"name":564,"description":565,"image":42,"body":42,"postCount":322},"torch-infection","TORCH Infection","\u003Cp>In this section; you can find articles related with TOCH infection. \u003C\u002Fp>",{"slug":567,"name":568,"description":569,"image":42,"body":42,"postCount":343},"microbiology-for-beginners","Microbiology for Beginners","\u003Cp>These articles are very basic articles, which will share general concepts in Microbiology. \u003C\u002Fp>",{"slug":571,"name":572,"description":573,"image":42,"body":42,"postCount":265},"dna-replication","DNA Replication","\u003Cp>Articles related to DNA and Replication of DNA. \u003C\u002Fp>",{"slug":575,"name":576,"description":577,"image":42,"body":42,"postCount":343},"genetic-code","Genetic Code","\u003Cp>Articles related to Genetic Code.\u003C\u002Fp>",{"slug":579,"name":580,"description":581,"image":42,"body":42,"postCount":322},"molecular-technique","Molecular Technique","\u003Cp>Posts related to Molecular Techniques. \u003C\u002Fp>",{"slug":583,"name":584,"description":42,"image":42,"body":42,"postCount":276},"colorimetric-assay","Colorimetric Assay ",{"slug":586,"name":587,"description":588,"image":42,"body":42,"postCount":322},"pharmaceutical-microbiology","Pharmaceutical Microbiology","\u003Cp>Various articles related to Pharmaceutical Microbiology\u003C\u002Fp>",{"slug":590,"name":591,"description":42,"image":42,"body":42,"postCount":484},"blood-and-immune-cells","Blood and Immune Cells"]