[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"$fxLN3MUwXCdr5RPjwZYIDpOj8CHyjOmngWTgoKXPtZbg":3,"$fIHTmetqnbbl4jCQK6bOEsE0gnRaF8gbl4_5SdfIhw88":36,"$f3Ft0rKFJHppdzE-vuveecxx1BUcg9iOlMLtyzf_MJDg":278,"$fucxFBm2ZjZfGSdmdRaSNGBI_F0jJme4f0GTvzUhQfL8":342},[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":274},"brucellosis-etiology-pathogenesis-laboratory-diagnosis","Brucellosis (Brucella): The Intracellular Cause of Undulant Fever, and How It Is Diagnosed","\u003Cp>How \u003Cem>Brucella\u003C\u002Fem> causes brucellosis (undulant fever), why hiding inside macrophages makes it a chronic, relapsing infection that is slow to culture and a laboratory biohazard, and how it is diagnosed.\u003C\u002Fp>",null,"Acharya Tankeshwar","2013-10-27","2026-08-06",false,"bacteriology","A farmer in a rural area develops a fever that rises and falls in waves over several weeks, along with drenching night sweats, joint pains, and fatigue. He has been treated for malaria more than once with no improvement. He drinks fresh, unpasteurized milk from his own goats. The pattern of a relapsing fever that does not respond to antimalarials, in someone with animal or raw-dairy exposure, points to brucellosis.\n\nBrucellosis is one of the most common infections passed from animals to humans worldwide, yet it is easily missed because its wavering fever mimics malaria and many other illnesses. The organism behind it, *Brucella*, has a defining trick: it survives inside the body's own immune cells. This page is about how that intracellular life explains the whole disease, and how brucellosis is diagnosed.\n\n## Introduction\n\n*Brucella* is a small [Gram-negative coccobacillus](https:\u002F\u002Fmicrobeonline.com\u002Fgram-negative-cocci-coccobacilli-medical-significance-list-bacteria-diseases) and the cause of **brucellosis**, one of the world's most widespread zoonoses (diseases passed from animals to humans). Humans are an **accidental host**: the organism's natural home is livestock, and people are infected by contact with infected animals or their products, above all **unpasteurized dairy**.\n\nBrucellosis is known by many names that hint at its features and history: **undulant fever** (for the fever that rises and falls in waves), **Malta fever** and **Mediterranean fever** (for where it was first studied), and **Bang's disease**. It was first isolated by the British army doctor David Bruce, after whom the organism is named.\n\nTwo facts make brucellosis important and easy to miss. Its wavering fever closely mimics malaria and other febrile illnesses, so it is frequently misdiagnosed, especially in tropical regions. And the organism is a serious **laboratory biohazard**, one of the most common causes of laboratory-acquired infection, so a suspicion of brucellosis changes how the specimen must be handled (below).\n\n## **What Brucella looks like**\n\n![Brucella appearing as faintly staining ram-negative coccobacilli  - Brucellaappearing as faintly staining ram-negative coccobacilli](\u002Fblogs\u002FBrucella-gram-stain.png)Figure 1: *Brucella* appearing as faintly staining gram-negative coccobacilli\n\n*Brucella* is a small, non-motile, non-capsulated Gram-negative coccobacillus that often **stains faintly** (a weak, sometimes hard-to-see Gram-negative). It is:\n\n- **Strictly aerobic** (some species need added CO₂ to grow), **catalase-positive**, and **oxidase-positive**.\n- **Slow-growing** and **fastidious**, which is why culture takes weeks (below).\n- An **intracellular organism**, able to survive and multiply inside the host's macrophages.\n\n### **The species and their animal hosts**\n\n*Brucella* species are named by the animal they mainly infect, and the animal reservoir predicts the human risk. The four main human pathogens:\n\n- ***Brucella melitensis*** (goats and sheep): the **most pathogenic** and the commonest cause of human brucellosis.\n- ***Brucella abortus*** (cattle): causes abortion in cattle, hence the name.\n- ***Brucella suis*** (pigs).\n- ***Brucella canis*** (dogs).\n\nThe severity roughly follows the species: *B. melitensis* causes the most serious human disease, *B. abortus* generally milder.\n\n## **How people get brucellosis**\n\nHumans are infected in three main ways, each with a portal of entry:\n\n- **Ingestion:** eating undercooked meat or, most importantly, consuming **unpasteurized dairy** (milk, soft cheese). Entry is through the digestive tract. This is the commonest route in most settings.\n- **Direct contact:** the organism enters through skin cuts or mucous membranes during contact with infected animals or their tissues, an occupational risk for farmers, veterinarians, and slaughterhouse workers.\n- **Inhalation:** breathing in aerosols containing the organism, a risk in farms, slaughterhouses, and, notably, laboratories.\n\n**Person-to-person spread is rare**. The occupational and dietary pattern, farmers, abattoir and veterinary workers, and raw-dairy consumers, is the epidemiological signature of brucellosis.\n\n## **Virulence factors and how Brucella causes disease**\n\n*Brucella* has no exotoxins and a poorly understood set of virulence factors. Its power comes almost entirely from one strategy: **surviving inside the host's own cells**.\n\n**Survival inside macrophages (the key factor).** When *Brucella* is engulfed by macrophages, most bacteria would be destroyed. *Brucella* instead survives and multiplies inside them. This intracellular life is the master fact of the disease, and almost everything clinical follows from it:\n\n- Because the organism hides **inside cells**, [antibodies](https:\u002F\u002Fmicrobeonline.com\u002Fimmunoglobulin-structure\u002F) (which act outside cells) cannot easily reach it. This is why the infection persists and relapses, and why antibody tests confirm exposure but the organism is hard to clear.\n- Because macrophages carry it through the body, *Brucella* is delivered to the organs rich in these cells, the **lymph nodes, liver, spleen, and bone marrow** (the reticuloendothelial system).\n- Because it lives inside cells, treatment needs antibiotics that **penetrate cells** and must be given for a **long time and in combination**, or the infection relapses.\n\n**Endotoxin (LPS).** Its [lipopolysaccharide](https:\u002F\u002Fmicrobeonline.com\u002Flipopolysaccharide-lps-of-gram-negative-bacteria-characteristics-and-functions\u002F) is considered the main virulence factor in the classic sense, driving the fever and inflammation. There are no exotoxins.\n\n**Granuloma formation.** In the organs it seeds, the immune response to the intracellular organism forms **granulomas** (collections of immune cells, including epithelioid and giant cells), which can progress to abscesses. This granulomatous response is why brucellosis can cause chronic, localized disease in bone, liver, or spleen.\n\n**Putting it together**\n\nThe sequence explains the undulant fever. *Brucella* enters (usually via raw dairy), is taken up by macrophages, and **survives inside them** instead of being killed. The macrophages carry it into the blood (bacteremia, causing a fever spike) and seed the liver, spleen, lymph nodes, and bone marrow. The immune system brings the bacteremia down (fever falls), but organisms sheltering inside cells and granulomas survive and later re-enter the blood (fever rises again), producing the classic **wavering, relapsing \"undulant\" fever**. The same intracellular hiding is why the disease becomes chronic and why it is so hard to cure without prolonged, cell-penetrating combination therapy.\n\n## **Laboratory diagnosis**\n\n**First, a safety warning**\n\n*Brucella* is a **Hazard Group 3 organism** and one of the most common causes of **laboratory-acquired infection**, usually from inhaling aerosols or from accidental inoculation.\n\n**If brucellosis is suspected, the laboratory must be informed, and cultures must be handled in a [biosafety cabinet](https:\u002F\u002Fmicrobeonline.com\u002Fbiological-safety-cabinet-bsc-types-working-mechanism\u002F) with aerosol-generating steps minimized.**\n\n**The diagnostic challenge**\n\nBecause the organism hides inside cells and grows slowly, catching it is difficult, so diagnosis usually combines culture, serology, and sometimes [PCR](https:\u002F\u002Fmicrobeonline.com\u002Fpolymerase-chain-reaction-pcr-steps-types-applications).\n\n![Brucella colonies in blood agar - Brucellacolonies in blood agar](\u002Fblogs\u002FBrucella-in-Blood-agar-plate.png)Figure 2: *Brucella* colonies in Blood Agar\n\n**Culture (definitive, but slow).** *Brucella* can be grown from blood, bone marrow, or tissue. Two features matter:\n\n- It is **very slow-growing**, so blood cultures must be **held for up to 6 to 8 weeks** before being called negative, far longer than routine cultures. The laboratory must be told to hold them.\n- **Bone marrow culture** is more sensitive than blood, because that is where the organism concentrates. The classic **Castañeda biphasic medium** (solid and liquid in one bottle) was designed for it. *Brucella* grows on [blood agar](https:\u002F\u002Fmicrobeonline.com\u002Fblood-agar-composition-preparation-uses-and-types-of-hemolysis\u002F) and [chocolate agar](https:\u002F\u002Fmicrobeonline.com\u002Fchocolate-agar-composition-uses-colony-characteristics\u002F) but not MacConkey, as small, white, non-hemolytic colonies.\n\n![ - Brucellaidentification flow chart(mage source: Laboratory Response Network (LRN)](\u002Fblogs\u002FBrucella-identification-flow-chart.png)Figure: *Brucella* identification flow chart (Image source: Laboratory Response Network (LRN)\n\n**Serology (the practical mainstay).** Because culture is slow and hazardous, most diagnosis is serological. The [**\u003Cu>Rose Bengal test\u003C\u002Fu>**](https:\u002F\u002Fmicrobeonline.com\u002Frose-bengal-plate-test-rbt-brucella-principle-procedure-limitation\u002F) is the most widely used **screening** test, a rapid slide agglutination that is quick and simple; its procedure and limitations are on its own page. A positive screen is followed by a quantitative agglutination test, complement fixation, or ELISA. The antibody pattern helps stage the illness:\n\n- **IgM** rises first (within 1 to 2 weeks), then **IgG** rises as the disease continues.\n- In **chronic brucellosis**, IgG persists while IgM has disappeared, so a high IgG with absent IgM suggests long-standing infection.\n\n**PCR** detects *Brucella* DNA in blood or tissue and is faster and safer than culture where available.\n\n## **Treatment**\n\nTreatment of brucellosis follows directly from the organism's intracellular life, and the *principle* is the high-yield part. Because *Brucella* hides inside cells, treatment must use antibiotics that **penetrate cells**, must **combine two drugs** (single drugs relapse), and must be given for a **prolonged course** (weeks, not days). The classic combination uses **doxycycline plus an aminoglycoside (or rifampicin)**. Using one drug, or too short a course, leads to relapse, which is the commonest treatment failure. Specific doses and durations are clinical decisions and are not covered here.\n\n## **Prevention**\n\nPreventing human brucellosis rests on food hygiene and occupational hygiene, because those are the two routes in:\n\n- **Pasteurize dairy.** The single most effective measure. All milk should be heat-treated, and raw milk and products made from it (soft cheese, ice cream) avoided.\n- **Cook meat thoroughly.**\n- **Occupational protection** for farmers, veterinarians, slaughterhouse workers, and laboratory staff (protective equipment, safe handling, informing the laboratory of suspected cases).\n- **Animal control:** vaccinating and testing livestock reduces the reservoir at source. There is **no routine human vaccine**.\n\nControlling brucellosis in animals is ultimately how human disease is reduced, since humans are only an accidental host.\n\n## **How to remember**\n\n**It lives inside your cells, and that explains everything.** *Brucella* survives inside macrophages. Hold that one fact and the whole disease follows: hiding from antibodies (so it relapses), riding macrophages to the liver, spleen, and marrow (where it seeds), needing cell-penetrating drugs in combination for weeks (or it relapses), and forming granulomas.\n\n**Undulant = up and down.** The fever of brucellosis rises and falls in waves (\"undulant\"). Each wave is a burst of organisms leaving their cellular hideouts into the blood; each fall is the immune system beating the wave back before the next escape. The name describes the mechanism.\n\n**Think dairy and animals, and malaria that won't respond.** A relapsing fever in someone with raw-milk or animal exposure, especially if \"malaria\" treatment has failed, should raise brucellosis. That clinical trigger is the exam and bench cue.\n\n**Tell the lab, and wait weeks.** Two lab facts: warn the laboratory (it's a Hazard Group 3 biohazard and a classic lab-acquired infection), and hold blood cultures for 6 to 8 weeks because it grows so slowly. Slow to grow, dangerous to handle.\n\n**Species by animal, melitensis worst.** The species are named by their animal host (*melitensis* goats\u002Fsheep, *abortus* cattle, *suis* pigs, *canis* dogs), and *B. melitensis* causes the most severe human disease.\n\n## **Key exam facts in one table**\n\n| **Fact** | **Detail** |\n| --- | --- |\n| Organism | *Brucella*, small Gram-negative coccobacillus (stains faintly) |\n| Disease | Brucellosis (undulant\u002FMalta\u002FMediterranean fever, Bang's disease) |\n| Zoonosis | Yes; humans are accidental hosts |\n| Main route | Unpasteurized dairy; also animal contact and aerosols |\n| Most pathogenic species | *Brucella melitensis* (goats\u002Fsheep) |\n| Other species | *B. abortus* (cattle), *B. suis* (pigs), *B. canis* (dogs) |\n| Key trait | Survives intracellularly in macrophages |\n| Organs seeded | Liver, spleen, lymph nodes, bone marrow (reticuloendothelial system) |\n| Fever pattern | Undulant (wavering, relapsing) |\n| Biosafety | Hazard Group 3; common laboratory-acquired infection |\n| Culture | Slow; hold blood cultures 6–8 weeks; bone marrow more sensitive; Castañeda biphasic medium |\n| Growth | Blood and chocolate agar, not MacConkey; some need CO₂ |\n| Screening serology | Rose Bengal test |\n| Antibody staging | IgM first, then IgG; chronic disease = IgG present, IgM absent |\n| Treatment principle | Combination therapy (e.g., doxycycline + aminoglycoside\u002Frifampicin), prolonged; single\u002Fshort courses relapse |\n| Prevention | Pasteurize dairy; occupational hygiene; no routine human vaccine |\n\n## **Where students get confused**\n\n**Why brucellosis relapses and is hard to cure.** Because *Brucella* hides inside macrophages, where antibodies cannot reach it and where many antibiotics do not penetrate. This is why it needs cell-penetrating drugs, in combination, for weeks, and why single or short courses fail.\n\n**It mimics malaria.** The wavering fever leads to repeated misdiagnosis as drug-resistant malaria, especially in the tropics. A relapsing fever with animal or raw-dairy exposure that does not respond to antimalarials should prompt thinking of brucellosis.\n\n**Cultures must be held for weeks.** *Brucella* grows so slowly that a routine culture discarded at the usual time will be falsely negative. The laboratory must be told to hold blood cultures for 6 to 8 weeks.\n\n**Tell the laboratory, it is a biohazard.** *Brucella* is one of the most common laboratory-acquired infections, from aerosols. A suspicion of brucellosis must be communicated so the lab handles it in a safety cabinet. Students often overlook that the diagnosis changes lab safety.\n\n**The species are named by animal host.** *melitensis* (goats\u002Fsheep), *abortus* (cattle), *suis* (pigs), *canis* (dogs). *B. melitensis* is the most virulent in humans.\n\n**Serology stages the illness.** IgM appears first; persistent IgG with absent IgM points to chronic disease. A single positive titer is interpreted with the clinical picture and exposure history.\n\n**References**\n\n1. Corbel, M. J. (1997). Brucellosis: an overview. *Emerging Infectious Diseases*, 3(2), 213–221. [\u003Cu>https:\u002F\u002Fdoi.org\u002F10.3201\u002Feid0302.970219\u003C\u002Fu>](https:\u002F\u002Fdoi.org\u002F10.3201\u002Feid0302.970219)\n2. Głowacka, P., Żakowska, D., Naylor, K., Niemcewicz, M., & Bielawska-Drózd, A. (2018). Brucella: virulence factors, pathogenesis and treatment. *Polish Journal of Microbiology*, 67(2), 151–161. [\u003Cu>https:\u002F\u002Fdoi.org\u002F10.21307\u002Fpjm-2018-029\u003C\u002Fu>](https:\u002F\u002Fdoi.org\u002F10.21307\u002Fpjm-2018-029)\n3. Hayoun, M. A., Muco, E., & Shorman, M. (2023). *Brucellosis*. In StatPearls. StatPearls Publishing. [\u003Cu>https:\u002F\u002Fwww.ncbi.nlm.nih.gov\u002Fbooks\u002FNBK441831\u002F\u003C\u002Fu>](https:\u002F\u002Fwww.ncbi.nlm.nih.gov\u002Fbooks\u002FNBK441831\u002F)\n4. Tille, P. M. (2022). *Bailey & Scott's Diagnostic Microbiology* (15th ed.). Elsevier.",[50,53,56,59,62,65,68,71],{"question":51,"answer":52},"\u003Cp>How do humans get brucellosis?\u003C\u002Fp>","\u003Cp>Most often by consuming unpasteurized dairy products (milk, soft cheese) from infected animals. It also spreads through contact with infected animals or their tissues (an occupational risk for farmers, veterinarians, and slaughterhouse workers) and by inhaling aerosols. Person-to-person spread is rare.\u003C\u002Fp>",{"question":54,"answer":55},"\u003Cp>Why is brucellosis called undulant fever?\u003C\u002Fp>","\u003Cp>Because the fever rises and falls in waves. Each wave reflects a burst of \u003Cem>Brucella\u003C\u002Fem> released from inside the host's cells into the blood; the fever falls as the immune system controls that wave, then rises again with the next release.\u003C\u002Fp>",{"question":57,"answer":58},"\u003Cp>Why is Brucella so hard to treat?\u003C\u002Fp>","\u003Cp>Because it survives inside the body's own cells (macrophages), where antibodies cannot reach it and many antibiotics do not penetrate well. Treatment therefore needs cell-penetrating antibiotics, given in combination and for a prolonged course; single or short courses lead to relapse.\u003C\u002Fp>",{"question":60,"answer":61},"\u003Cp>Why must Brucella blood cultures be kept for several weeks?\u003C\u002Fp>","\u003Cp>Because \u003Cem>Brucella\u003C\u002Fem> grows very slowly. A culture discarded at the usual time would be falsely negative, so blood cultures are held for up to 6 to 8 weeks, and the laboratory must be told to do so. Bone marrow culture is more sensitive than blood.\u003C\u002Fp>",{"question":63,"answer":64},"\u003Cp>What is the Rose Bengal test?\u003C\u002Fp>","\u003Cp>A rapid slide agglutination test that is the most widely used screening test for brucellosis. A positive result is then confirmed with a quantitative agglutination test, complement fixation, or ELISA.\u003C\u002Fp>",{"question":66,"answer":67},"\u003Cp>Which Brucella species causes the most severe disease?\u003C\u002Fp>","\u003Cp>\u003Cem>Brucella melitensis\u003C\u002Fem>, which mainly infects goats and sheep. The other human pathogens are \u003Cem>B. abortus\u003C\u002Fem> (cattle), \u003Cem>B. suis\u003C\u002Fem> (pigs), and \u003Cem>B. canis\u003C\u002Fem> (dogs).\u003C\u002Fp>",{"question":69,"answer":70},"\u003Cp>Why is Brucella dangerous in the laboratory?\u003C\u002Fp>","\u003Cp>It is a Hazard Group 3 organism and one of the most common causes of laboratory-acquired infection, mainly through inhaling aerosols. If brucellosis is suspected, the laboratory must be informed so specimens are handled in a biosafety cabinet.\u003C\u002Fp>",{"question":72,"answer":73},"\u003Cp>Why is brucellosis often mistaken for malaria?\u003C\u002Fp>","\u003Cp>Because its wavering, relapsing fever resembles malaria, and both occur in similar regions. A relapsing fever with animal or raw-dairy exposure that does not respond to antimalarial treatment should raise the possibility of brucellosis.\u003C\u002Fp>",[75],"gram-negative-cocci",[77,85,113,147,178,208,244,251],{"slug":78,"title":79,"description":80,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":81,"lastUpdatedDate":45,"draft":46,"category":47,"image":42,"faq":82,"tags":83},"gram-negative-cocci-coccobacilli-medical-significance-list-bacteria-diseases","Gram-Negative Cocci and Coccobacilli of Medical Significance: List, Diseases, and Lab Identification","\u003Cp>The medically important Gram-negative cocci include \u003Cem>Neisseria gonorrhoeae\u003C\u002Fem> (gonorrhoea, ophthalmia neonatorum), \u003Cem>N. meningitidis\u003C\u002Fem> (meningitis), and \u003Cem>Moraxella catarrhalis\u003C\u002Fem> (otitis media, COPD). This article covers all GN cocci and coccobacilli with diseases, key properties, and lab identification links.\u003C\u002Fp>","2016-04-11",[],[84,75],"bacterial-classification",{"slug":86,"title":87,"description":88,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":89,"lastUpdatedDate":90,"draft":46,"category":91,"image":42,"faq":92,"tags":111},"immunoglobulin-structure","Immunoglobulins (Antibodies): Structure and the Five Classes","\u003Cp>Antibody structure explained: heavy and light chains, Fab and Fc regions, variable and constant domains, the hinge, and how the five classes (IgG, IgM, IgA, IgE, IgD) differ. For micro and health-science students.\u003C\u002Fp>","2020-04-03","2026-08-08","immunology",[93,96,99,102,105,108],{"question":94,"answer":95},"\u003Cp>What is the basic structure of an antibody?\u003C\u002Fp>","\u003Cp>An antibody is a Y-shaped molecule made of two identical heavy chains and two identical light chains held together by disulfide bonds. The two arms (Fab regions) bind antigen; the stem (Fc region) carries out effector functions.\u003C\u002Fp>",{"question":97,"answer":98},"\u003Cp>What is the difference between the variable and constant regions?\u003C\u002Fp>","\u003Cp>The variable region, at the tips of the Fab arms, differs between antibodies and determines what antigen the antibody binds. The constant region is shared within a class and determines the antibody's class and function.\u003C\u002Fp>",{"question":100,"answer":101},"\u003Cp>What determines the class of an antibody?\u003C\u002Fp>","\u003Cp>The heavy chain constant region. There are five heavy chain types (γ, α, μ, ε, δ) giving the five classes IgG, IgA, IgM, IgE, and IgD. Light chains (kappa or lambda) do not determine class.\u003C\u002Fp>",{"question":103,"answer":104},"\u003Cp>What are CDRs?\u003C\u002Fp>","\u003Cp>Complementarity-determining regions are three short, highly variable loops within the variable region that actually contact the antigen. They are the most variable part of the antibody and determine its specificity.\u003C\u002Fp>",{"question":106,"answer":107},"\u003Cp>Which antibody classes have a hinge region?\u003C\u002Fp>","\u003Cp>IgG, IgA, and IgD have a hinge region that gives their arms flexibility. IgM and IgE lack a hinge but have an extra fourth constant domain instead.\u003C\u002Fp>",{"question":109,"answer":110},"\u003Cp>Why is IgM a pentamer?\u003C\u002Fp>","\u003Cp>Secreted IgM joins five units together with a J chain. This gives it ten binding sites, making it very effective at binding repetitive antigens and activating complement, which suits its role as the first antibody made in a response.\u003C\u002Fp>",[112],"antibody-mediated-immunity",{"slug":114,"title":115,"description":116,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":117,"lastUpdatedDate":118,"draft":46,"category":119,"image":42,"faq":120,"tags":145},"lipopolysaccharide-lps-of-gram-negative-bacteria-characteristics-and-functions","Lipopolysaccharide (LPS): Structure, Endotoxin, and How It Causes Septic Shock","Lipopolysaccharide (LPS): structure (Lipid A, core oligosaccharide, O-antigen), how endotoxin causes septic shock, the antibiotic paradox, Limulus test, O-antigen serotyping, and comparison with gram-positive LTA","2013-04-29","2026-08-17","general-microbiology",[121,124,127,130,133,136,139,142],{"question":122,"answer":123},"What is the difference between LPS, Lipid A, and endotoxin?","LPS = entire molecule (Lipid A + core oligosaccharide + O-antigen). Lipid A = the toxic anchor component embedded in the outer membrane, responsible for immune\u002Fpyrogenic effects. Endotoxin is essentially synonymous with LPS\u002FLipid A in modern usage.",{"question":125,"answer":126},"How does LPS cause septic shock?","LPS released from lysing bacteria binds LBP, transferred to CD14, presented to TLR4\u002FMD-2, triggering NF-κB signalling and massive cytokine release (TNF-α, IL-1β, IL-6, IL-8, NO). Result: fever, vasodilation\u002Fhypotension, vascular permeability, DIC, multi-organ failure.",{"question":128,"answer":129},"Why is LPS heat stable and why does this matter clinically?","LPS is a glycolipid that doesn't denature at sterilization temperatures. Autoclaving kills bacteria but does not inactivate LPS — pharmaceutical depyrogenation requires dry heat at 250°C or specific removal methods, not just sterilization.",{"question":131,"answer":132},"What is the Limulus Amebocyte Lysate (LAL) test?","Uses horseshoe crab amebocyte lysate, which clots\u002Fchanges colour in response to LPS. Globally mandated for testing IV pharmaceuticals, biologics, vaccines, and implantable devices for LPS contamination. Results reported in EU\u002FmL. Recombinant Factor C (rFC) is a sustainable alternative.",{"question":134,"answer":135},"What is the O-antigen and why is it used for serotyping?","The outermost, highly variable polysaccharide component of LPS. Variation between strains allows precise serotyping by agglutination (e.g. E. coli O157, Salmonella O:H typing, Widal test O-antigen detection).",{"question":137,"answer":138},"Why is treating gram-negative sepsis sometimes paradoxically dangerous?","Antibiotics killing bacteria release LPS simultaneously, triggering a massive cytokine storm that can acutely worsen haemodynamic status in the hours after treatment starts. This is not treatment failure — it requires intensified supportive care (vasopressors, fluids) alongside continued antibiotics.",{"question":140,"answer":141},"Can LPS be removed from pharmaceutical solutions?","Not by standard sterilization. Requires dry heat at 250°C (30+ min), ultrafiltration (10 kDa membranes), adsorption resins, or alkaline hydrolysis. Pharmaceutical manufacturing primarily prevents contamination using LPS-free Water for Injection rather than relying on removal.",{"question":143,"answer":144},"What is the difference between smooth and rough strain LPS?","Smooth (S) strains have complete LPS with full O-antigen — more resistant to complement\u002Fphagocytosis. Rough (R) strains lack O-antigen (truncated LPS) — generally less virulent but their exposed Lipid A is often a more potent TLR4 stimulant.",[146],"bacterial-structure-physiology",{"slug":148,"title":149,"description":150,"seoTitle":42,"seoDescription":42,"author":151,"createdDate":152,"lastUpdatedDate":153,"draft":46,"category":47,"image":42,"faq":154,"tags":176},"biological-safety-cabinet-bsc-types-working-mechanism","Biological Safety Cabinet Classes I, II, and III: Which Class for Which Organism","How Class I, II, and III biosafety cabinets differ in airflow and what each actually protects, which class is required at each biosafety level, the four Class II types explained, and why a laminar airflow cabinet must never be used for infectious work.","Nisha Rijal","2019-12-05","2026-07-23",[155,158,161,164,167,170,173],{"question":156,"answer":157},"When do I need a biosafety cabinet, and when is open-bench work okay?","BSL1 work does not require a cabinet; open-bench work with proper handwashing and PPE is acceptable. BSL2 work requires a Class II cabinet for aerosol-generating procedures; routine non-aerosol work can be done on the open bench. BSL3 and BSL4 work require a cabinet (Class II or III depending on the organism). The biosafety level of your laboratory and the risk group of the organism determine what you need.",{"question":159,"answer":160},"What is the difference between Class I, Class II, and Class III cabinets?","Class I protects the worker and environment but not the product (room air flows over the work). Class II protects the worker, environment, and product (inward airflow, downward laminar flow, HEPA exhaust) and is the standard for BSL2\u002F3 work. Class III provides maximum containment with a totally enclosed cabinet and is used for RG4 agents at BSL4. The more you need to protect, the higher the class.",{"question":162,"answer":163},"Can I use a Class I cabinet for BSL2 work?","No. Using Class I for BSL2 (RG2 organisms) is a regulatory violation and a containment failure. Class II is required for BSL2 because RG2 organisms need product protection that Class I does not provide. Cost or equipment availability does not override this requirement.",{"question":165,"answer":166},"What is the difference between Type A2, Type B1, and Type B2 cabinets?","Type A2 recirculates 70% of air within the cabinet and exhausts 30% to the room; it is the workhorse for most BSL2\u002F3 work. Type B1 recirculates 30% and exhausts 70% to a hard duct; it is used when volatile chemicals or greater containment is needed. Type B2 exhausts 100% to a hard duct; it provides maximum containment but uses more energy. For most BSL2\u002F3 work, Type A2 is sufficient and is the standard choice.",{"question":168,"answer":169},"How often does a biosafety cabinet need to be certified?","Most regulations require annual recertification (some require every 6 months for heavily used cabinets). Certification verifies that the cabinet's airflow, HEPA filter integrity, and containment function are still adequate. Using a cabinet that hasn't been recently certified is a containment failure. Know the certification date before you work.",{"question":171,"answer":172},"What is the difference between a biosafety cabinet and a laminar airflow cabinet?","A BSC protects the worker from biohazards with inward airflow drawing aerosols away from the worker. A laminar airflow cabinet protects the product from contamination with outward airflow that pushes air toward the worker. Never use a laminar airflow cabinet for pathogenic work. For the full comparison, see Laminar Airflow Cabinet: Types and Working Principle.",{"question":174,"answer":175},"Is a Class II cabinet enough for all BSL3 work?","Class II is acceptable for most BSL3 organisms, but some highly hazardous RG3 agents may require Class III depending on institutional policy and the specific organism. Check your lab's SOPs and your biosafety officer's recommendations for agents on the borderline between Class II and Class III.",[177],"biosafety-levels",{"slug":179,"title":180,"description":181,"seoTitle":182,"seoDescription":183,"author":43,"createdDate":184,"lastUpdatedDate":185,"draft":46,"category":186,"image":42,"faq":187,"tags":206},"polymerase-chain-reaction-pcr-steps-types-applications","Polymerase Chain Reaction (PCR): Steps, Types, and Applications","PCR amplifies DNA exponentially in three steps: denaturation, annealing, and extension. Learn the components, steps, types: nested, multiplex, real-time, RT-PCR and clinical applications in diagnostic microbiology.","PCR: Steps, Reagents, Result Interpretation, and Applications","Review PCR reagents and the denaturation, annealing, and extension cycle, then compare major PCR variants, controls, interpretation, and applications.","2016-07-07","2026-08-15","lab-equipment",[188,191,194,197,200,203],{"question":189,"answer":190},"What is polymerase chain reaction (PCR) and what does it do?","\u003Cp>Polymerase chain reaction (PCR) is an in vitro molecular technique that amplifies a specific DNA or RNA sequence exponentially, producing up to 10 million copies from a single starting template within a few hours. It works by repeatedly cycling through three temperature-controlled steps (denaturation, annealing, and extension), using a heat-stable DNA polymerase (Taq polymerase) and short synthetic primers that define the target sequence. In clinical microbiology, PCR directly detects a pathogen's nucleic acid in a patient specimen, regardless of whether the organism is alive, cultivable, or present in small quantities.\u003C\u002Fp>",{"question":192,"answer":193},"What are the three steps of PCR and what temperature is used for each?","\u003Cp>PCR has three steps that repeat in each cycle. Denaturation occurs at 94–96°C, heat breaks the hydrogen bonds between the two DNA strands, separating them into single-stranded templates. Annealing occurs at 45–65°C, the temperature is lowered so primers can bind to their complementary sequences on each strand. Extension occurs at 72°C, Taq polymerase synthesizes a new complementary DNA strand starting from each primer. After 30–40 cycles, the target sequence is amplified by a factor of approximately 10 million.\u003C\u002Fp>",{"question":195,"answer":196},"What is Taq polymerase and why is it used in PCR?","\u003Cp>Taq polymerase is a thermostable DNA polymerase originally isolated from Thermus aquaticus, a bacterium that lives in boiling hot springs. Its defining property is heat stability, it remains active at 72°C and survives the 94°C denaturation step without being destroyed. This allows automated PCR cycling without adding fresh enzyme after every cycle. Without a heat-stable polymerase, PCR as an automated process would not be possible.\u003C\u002Fp>",{"question":198,"answer":199},"What is the difference between RT-PCR and real-time PCR?","\u003Cp>These two terms describe different aspects of PCR and are frequently confused. RT-PCR (reverse transcriptase PCR) refers to the template type: it adds a reverse transcription step that converts RNA into complementary DNA before amplification, making it possible to detect RNA viruses such as HIV, hepatitis C, dengue, and SARS-CoV-2. Real-time PCR (quantitative PCR or qPCR) refers to the detection method: fluorescence is measured during each amplification cycle, allowing quantitation of the target. A test can be both simultaneously: the COVID-19 PCR test is technically RT-qPCR, using reverse transcriptase for the RNA template and real-time detection for quantitation.\u003C\u002Fp>",{"question":201,"answer":202},"When should nested PCR be used instead of standard PCR?","\u003Cp>Nested PCR should be used when the target organism is present in very low quantities, below the detection threshold of standard single-round PCR. It uses two successive PCR reactions with two primer sets: outer primers amplify a large fragment first, then inner (nested) primers amplify a smaller specific region within that product. The double amplification dramatically increases sensitivity. Clinical applications include detection of \u003Cem>Rickettsia\u003C\u002Fem> and \u003Cem>Bartonella\u003C\u002Fem> in blood, \u003Cem>M. tuberculosis\u003C\u002Fem> in paucibacillary samples, herpesviruses and enteroviruses in CSF, and \u003Cem>Leishmania\u003C\u002Fem> in tissue.\u003C\u002Fp>",{"question":204,"answer":205},"What are the advantages of PCR over culture in clinical microbiology?","\u003Cp>PCR offers four key advantages over culture. Speed: results in hours rather than days: TB culture takes 6–8 weeks; PCR confirms TB the same day. Sensitivity: detects as few as 1–10 DNA copies per reaction, far below the threshold for culture positivity. Specificity: primers target a defined sequence, identifying the exact organism or resistance gene rather than just confirming growth. Versatility: works on organisms that cannot be cultured (many viruses, some parasites), on degraded specimens (formalin-fixed tissue, dried blood), and on samples with mixed flora where culture is uninterpretable.\u003C\u002Fp>",[207],"pcr-techniques",{"slug":209,"title":210,"description":211,"seoTitle":212,"seoDescription":213,"author":43,"createdDate":214,"lastUpdatedDate":215,"draft":46,"category":216,"image":42,"faq":217,"tags":242},"blood-agar-composition-preparation-uses-and-types-of-hemolysis","Blood Agar: Composition, Preparation, and How to Read Hemolysis","Blood agar composition and preparation, how to tell alpha, beta, gamma, and alpha-prime hemolysis apart, and the double-zone target pattern, with a colony-appearance table for 20+ organisms and common modifications (chocolate, CNA, CVBA).","Blood Agar: Preparation, Hemolysis Patterns, and Identification Clues","Learn blood agar composition and preparation, distinguish alpha, beta, and gamma hemolysis, and use colony patterns to support bacterial identification.","2013-08-22","2026-08-14","culture-media",[218,221,224,227,230,233,236,239],{"question":219,"answer":220},"What is the difference between alpha and beta hemolysis?","\u003Cp>Alpha is partial lysis, green\u002Fbrown discoloration: \u003Cem>S. pneumoniae,\u003C\u002Fem> viridans streptococci. Beta is complete clear lysis: \u003Cem>S. pyogenes, S. agalactiae, S. aureus\u003C\u002Fem>. Gamma is no hemolysis: \u003Cem>Enterococcus, Klebsiella.\u003C\u002Fem>\u003C\u002Fp>",{"question":222,"answer":223},"Why is sheep blood used instead of human blood?","Consistent availability, no biohazard risk, reliable hemolysis patterns. Human blood may contain antibiotics or inhibitors and introduces infection risk.",{"question":225,"answer":226},"\u003Cp>Why does \u003Cem>S. pneumoniae\u003C\u002Fem> produce alpha not beta hemolysis?\u003C\u002Fp>","\u003Cp>The H₂O₂ produced by \u003Cem>S. pneumoniae\u003C\u002Fem> oxidizes hemoglobin to green products (verdohemoglobin), a partial degradation rather than true lysis. \u003Cem>S. pneumoniae\u003C\u002Fem> lacks the streptolysins O and S that produce the complete, clear lysis of beta hemolysis.\u003C\u002Fp>",{"question":228,"answer":229},"What does the size of the beta-hemolytic zone tell you?","\u003Cp>GAS (\u003Cem>S. pyogenes\u003C\u002Fem>): large zone 2-4× colony diameter. GBS (\u003Cem>S. agalactiae\u003C\u002Fem>): narrow zone barely beyond colony edge. Helps preliminary differentiation at 24 hours with CAMP test and bacitracin.\u003C\u002Fp>",{"question":231,"answer":232},"\u003Cp>What is the umbilicated colony appearance of \u003Cem>S. pneumoniae\u003C\u002Fem>?\u003C\u002Fp>","\u003Cp>Autolysin LytA causes central autolysis at 48-72 hours, raised ring with sunken center. Umbilicated appearance + alpha hemolysis = strong presumptive \u003Cem>S. pneumoniae.\u003C\u002Fem>\u003C\u002Fp>",{"question":234,"answer":235},"How does incubation atmosphere affect blood agar hemolysis?","\u003Cp>Streptolysin O is oxygen-labile, best seen in stab areas or anaerobically. Streptolysin S is oxygen-stable, visible aerobically on surface. Always stab blood agar.\u003C\u002Fp>",{"question":237,"answer":238},"\u003Cp>Why does \u003Cem>C. perfringens\u003C\u002Fem> produce double-zone hemolysis?\u003C\u002Fp>","\u003Cp>Theta-toxin: outer partial (alpha) zone. Alpha-toxin\u002Flecithinase: inner complete (beta) zone. Double-zone target pattern on anaerobic blood agar = strong presumptive \u003Cem>C. perfringens.\u003C\u002Fem>\u003C\u002Fp>",{"question":240,"answer":241},"Can blood agar be used for susceptibility testing?","\u003Cp>Yes. MH-F (Mueller-Hinton + 5% sheep blood) is CLSI-recommended for fastidious organisms: \u003Cem>S. pneumoniae, S. pyogenes, H. influenzae, N. gonorrhoeae.\u003C\u002Fem>\u003C\u002Fp>",[243],"bacterial-culture-media",{"slug":245,"title":246,"description":247,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":248,"lastUpdatedDate":215,"draft":46,"category":216,"image":42,"faq":249,"tags":250},"chocolate-agar-composition-uses-colony-characteristics","Chocolate Agar (CAP): Composition, Preparation, Uses, and Colony Morphology","\u003Cp>Chocolate agar is an enriched medium for isolating fastidious pathogens like \u003Cem>Haemophilus\u003C\u002Fem> and \u003Cem>Neisseria.\u003C\u002Fem> Learn its composition, preparation, CO₂ requirement, colony morphology, and key modifications like Thayer-Martin.\u003C\u002Fp>","2013-09-08",[],[243],{"slug":252,"title":253,"description":254,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":44,"lastUpdatedDate":255,"draft":46,"category":47,"image":42,"faq":256,"tags":272},"rose-bengal-plate-test-rbt-brucella-principle-procedure-limitation","Rose Bengal Test (RBT): How to Interpret It and When to Confirm","How to read and act on a Rose Bengal test for brucellosis: why the acidic pH matters, why a positive must be confirmed (especially in endemic areas), the prozone caveat, and where RBT fits in the brucellosis diagnostic algorithm.","2026-07-20",[257,260,263,266,269],{"question":258,"answer":259},"What does a positive Rose Bengal test mean?","It means the patient's serum contains anti-Brucella antibodies. This supports a diagnosis of brucellosis but does not confirm active infection on its own, because antibodies can also reflect past exposure or cross-reaction. A positive result should be confirmed by a quantitative test.",{"question":261,"answer":262},"Why is the Rose Bengal antigen kept at acidic pH?","The acidic pH (about 3.65) suppresses non-specific IgM agglutinins that would otherwise cause false positives, while preserving the reaction of specific anti-Brucella antibodies. The acidic buffer is what gives this simple slide test its specificity.",{"question":264,"answer":265},"Can a negative Rose Bengal test rule out brucellosis?","Not completely. In very early acute infection, antibodies may not have risen yet, and some chronic cases can be missed. If brucellosis is strongly suspected despite a negative RBT, a quantitative test should be performed.",{"question":267,"answer":268},"Why is Rose Bengal not recommended as a stand-alone screen in endemic areas?","Where brucellosis is common, many people carry antibodies from past exposure, so a positive RBT often reflects previous rather than active infection. Using it alone produces many false positives, so a confirmed or titrated approach is preferred.",{"question":270,"answer":271},"How is a positive Rose Bengal test confirmed?","With a quantitative method such as the standard agglutination test (SAT) for a titer, the complement fixation test (CFT), or an IgG-specific ELISA, before starting treatment.",[273],"immunoassays",{"enabled":275,"threads":276,"total":277},true,[],0,[279,285,292,299,305,310,316,321,327,330,336],{"slug":280,"name":43,"description":281,"image":282,"body":283,"postCount":284},"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":286,"name":287,"description":288,"image":289,"body":290,"postCount":291},"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":293,"name":294,"description":295,"image":296,"body":297,"postCount":298},"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":300,"name":301,"description":295,"image":302,"body":303,"postCount":304},"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":306,"name":307,"description":295,"image":42,"body":308,"postCount":309},"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":311,"name":312,"description":313,"image":42,"body":314,"postCount":315},"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":317,"name":318,"description":319,"image":42,"body":42,"postCount":320},"guest-author","Guest Author","Guest Author \u002F Contributor",1,{"slug":322,"name":323,"description":295,"image":324,"body":325,"postCount":326},"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":328,"name":329,"description":319,"image":42,"body":42,"postCount":320},"dr-poonam-acharya","Dr. Poonam Acharya",{"slug":331,"name":151,"description":332,"image":333,"body":334,"postCount":335},"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":337,"name":338,"description":339,"image":340,"body":341,"postCount":320},"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.",[343,349,355,360,365,370,374,378,382,387,391,396,400,405,410,413,417,421,426,430,434,438,442,446,449,453,457,461,466,471,475,479,483,486,490,494,498,502,506,509,513,516,520,524,528,532,536,540,545,549,553,557,561,565,569,573,577,581,585,589,593,597,601,605,609,613,617,621,624,628],{"slug":75,"name":344,"description":345,"image":346,"body":347,"postCount":348},"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":350,"name":351,"description":352,"image":42,"body":353,"postCount":354},"microscopy","Microscopy","Microscope types, components, and microscopy techniques","These are list of blog posts related to microscopy. ",12,{"slug":356,"name":357,"description":358,"image":42,"body":42,"postCount":359},"gram-positive-cocci","Gram-Positive Cocci","Staphylococcus, Streptococcus, Enterococcus, Micrococcus — organisms, diseases, and identification tests",11,{"slug":361,"name":362,"description":363,"image":42,"body":42,"postCount":364},"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":366,"name":367,"description":368,"image":42,"body":42,"postCount":369},"gram-positive-rods","Gram-Positive Rods","Bacillus, Clostridium, Listeria, Corynebacterium, Actinomyces and related organisms",8,{"slug":371,"name":372,"description":373,"image":42,"body":42,"postCount":359},"mycobacteria","Mycobacteria","Mycobacterium tuberculosis, leprosy, atypical mycobacteria, and acid-fast organism diagnosis",{"slug":375,"name":376,"description":377,"image":42,"body":42,"postCount":359},"anaerobic-bacteriology","Anaerobic Bacteriology","Anaerobic organisms, anaerobic culture methods, and anaerobic infection diagnosis",{"slug":379,"name":380,"description":381,"image":42,"body":42,"postCount":354},"enterobacteriaceae","Enterobacteriaceae","Identification, differentiation, and clinical significance of Enterobacteriaceae family members",{"slug":383,"name":384,"description":385,"image":42,"body":42,"postCount":386},"spirochetes","Spirochetes","Treponema, Leptospira, Borrelia and spirochetal infections",7,{"slug":388,"name":389,"description":390,"image":42,"body":42,"postCount":348},"food-microbiology","Food Microbiology","Food-borne pathogens, food safety, spoilage, and preservation",{"slug":392,"name":393,"description":394,"image":42,"body":42,"postCount":395},"antimicrobial-susceptibility-testing","Antimicrobial Susceptibility Testing","Methods for testing antibiotic susceptibility in clinical microbiology",21,{"slug":397,"name":398,"description":399,"image":42,"body":42,"postCount":369},"antimicrobials-moa-amr","Antimicrobials (MOA & AMR)","Mechanisms, detection, and clinical significance of antimicrobial resistance",{"slug":401,"name":402,"description":403,"image":42,"body":42,"postCount":404},"sterilization-disinfection","Sterilization and Disinfection","Methods of sterilization and disinfection in healthcare and laboratory settings",10,{"slug":406,"name":407,"description":408,"image":42,"body":42,"postCount":409},"specimen-collection-transport","Specimen Collection and Transport","Collection, handling, and transport of clinical specimens for microbiological testing",27,{"slug":146,"name":411,"description":412,"image":42,"body":42,"postCount":395},"Bacterial Structure and Physiology","Bacterial cell structure, growth, physiology, and environmental factors affecting growth",{"slug":414,"name":415,"description":42,"image":42,"body":416,"postCount":309},"horizontal-gene-transfer","Horizontal Gene Transfer","Articles related to **Horizontal Gene Transfer**",{"slug":418,"name":419,"description":42,"image":42,"body":420,"postCount":404},"chromatography","Chromatography","Information about chromatographic techniques.",{"slug":422,"name":423,"description":424,"image":42,"body":425,"postCount":386},"electrophoresis","Electrophoresis","Information about Electrophoresis Techniques ","Detailed information  about Electrophoresis Techniques ",{"slug":207,"name":427,"description":428,"image":42,"body":429,"postCount":309},"PCR Techniques","Information about various types of Polymerase Chain Reaction Techniques ","More detailed information about various types of Polymerase Chain Reaction Techniques ",{"slug":431,"name":432,"description":433,"image":42,"body":42,"postCount":309},"bacteriophage","Bacteriophage","Description about Bacteriophage.",{"slug":435,"name":436,"description":437,"image":42,"body":42,"postCount":309},"malaria","Malaria","It is the collections of articles regarding malarial disease. ",{"slug":439,"name":440,"description":441,"image":42,"body":42,"postCount":309},"anaerobic-culture-techniques","Anaerobic Culture Techniques","Posts related with Anaerobic Culture Techniques.",{"slug":273,"name":443,"description":444,"image":42,"body":42,"postCount":445},"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":177,"name":447,"description":448,"image":42,"body":42,"postCount":386},"Biosafety levels ","Articles related to Biosafety Levels",{"slug":450,"name":451,"description":452,"image":42,"body":42,"postCount":364},"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":454,"name":455,"description":456,"image":42,"body":42,"postCount":309},"pipette","Pipette","Posts related with Pipette. ",{"slug":458,"name":459,"description":460,"image":42,"body":42,"postCount":369},"bacteriology-mcqs","Bacteriology MCQs","This sections lists MCQs in Bacteriology.",{"slug":462,"name":463,"description":464,"image":42,"body":42,"postCount":465},"parasitology-mcqs","Parasitology MCQs","This section lists MCQs in Parasitology.",2,{"slug":467,"name":468,"description":469,"image":42,"body":42,"postCount":470},"virology-mcqs","Virology MCQs","This is the collections of Multiple Choice Questions in Virology.",4,{"slug":472,"name":473,"description":474,"image":42,"body":42,"postCount":364},"mcqs-in-microbiology","MCQs in Microbiology","This section lists the collections of Multiple Choice Questions in General Microbiology Topics. ",{"slug":476,"name":477,"description":478,"image":42,"body":42,"postCount":369},"immunology-mcqs","Immunology MCQs","In this section; we are posting collections of Multiple Choice Questions about Immunology. ",{"slug":480,"name":481,"description":482,"image":42,"body":42,"postCount":315},"microbial-curiosities","Microbial Curiosities","In this clusters, we are posting interesting and unique information about Microorganisms. ",{"slug":243,"name":484,"description":485,"image":42,"body":42,"postCount":395},"Bacterial Culture Media","Posts related to Bacterial Culture Media. ",{"slug":487,"name":488,"description":489,"image":42,"body":42,"postCount":309},"fungal-culture-media","Fungal Culture Media","Posts related to Fungal Culture Media.",{"slug":491,"name":492,"description":493,"image":42,"body":42,"postCount":364},"motility-test","Motility Test","This lists the procedure regarding various tests methods for bacterial motility.",{"slug":495,"name":496,"description":497,"image":42,"body":42,"postCount":404},"bacterial-enumeration","Bacterial enumeration","These posts are related to isolation and enumeration of bacteria. ",{"slug":499,"name":500,"description":501,"image":42,"body":42,"postCount":465},"gram-positive-coccobacillus","Gram-positive coccobacillus","List of Gram Positive Coccobacilli",{"slug":503,"name":504,"description":505,"image":42,"body":42,"postCount":470},"dimorphic-fungi","Dimorphic Fungi","This is about various dimorphic fungi. ",{"slug":84,"name":507,"description":508,"image":42,"body":42,"postCount":386},"Bacterial Classification","These posts are related with various approaches used for the classification of Bacteria. ",{"slug":510,"name":511,"description":512,"image":42,"body":42,"postCount":364},"immunofluorescence","Immunofluorescence ","Various Tests related to Immunofluorescence ",{"slug":112,"name":514,"description":515,"image":42,"body":42,"postCount":315},"Antibody-mediated Immunity","This clusters links the articles that are sharing insights about Antibody-mediated immunity. ",{"slug":517,"name":518,"description":519,"image":42,"body":42,"postCount":386},"hypersensitivity","Hypersensitivity","Articles related to Hypersensitivity.",{"slug":521,"name":522,"description":42,"image":42,"body":42,"postCount":523},"haemophilus","Haemophilus",3,{"slug":525,"name":526,"description":527,"image":42,"body":42,"postCount":470},"sexually-transmitted-infections-stis","Sexually transmitted infections (STIs)","This is the clusters of infections that are transmitted sexually. ",{"slug":529,"name":530,"description":531,"image":42,"body":42,"postCount":354},"adaptive-immunity","Adaptive Immunity","Blog posts related to B Cell Immunity and T Cell Immunity.",{"slug":533,"name":534,"description":535,"image":42,"body":42,"postCount":348},"fungal-diagnostics","Fungal Diagnostics","Various methods used for the Diagnosis of Fungal Infections. ",{"slug":537,"name":538,"description":539,"image":42,"body":42,"postCount":364},"laboratory-storage-and-preservation","Laboratory Storage and Preservation","Articles about Laboratory Storage of Antimicrobial Disk, Test organisms and Equipment used for this process. ",{"slug":541,"name":542,"description":543,"image":42,"body":544,"postCount":309},"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":546,"name":547,"description":548,"image":42,"body":42,"postCount":369},"laboratory-glassware","Laboratory Glassware","Posts about Laboratory Glassware. ",{"slug":550,"name":551,"description":552,"image":42,"body":42,"postCount":309},"helminths","Helminths","In this section, we are covering properties, life cycle, pathogenesis and laboratory diagnosis of Helminths\u002FHelminthic infestations. ",{"slug":554,"name":555,"description":556,"image":42,"body":42,"postCount":309},"protozoan-parasite","Protozoan Parasite","In this cluster, we are covering protozoan parasites. ",{"slug":558,"name":559,"description":560,"image":42,"body":42,"postCount":320},"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":562,"name":563,"description":564,"image":42,"body":42,"postCount":404},"bacterial-staining-technique","Bacterial Staining Technique","Lists of various staining techniques that are used to stain bacteria. ",{"slug":566,"name":567,"description":568,"image":42,"body":42,"postCount":304},"enzyme-tests","Enzyme Tests","\u003Cp>Various Biochemical Test that are based on enzymatic activity of the microorganisms. \u003C\u002Fp>",{"slug":570,"name":571,"description":572,"image":42,"body":42,"postCount":359},"carbohydrate-utilization","Carbohydrate Utilization","\u003Cp>Various biochemical tests which are related to Carbohydrate fermentation or Utilization\u003C\u002Fp>",{"slug":574,"name":575,"description":576,"image":42,"body":42,"postCount":364},"susceptibility-based-id","Susceptibility-based ID","\u003Cp>These are susceptibility based identification test such as optochin sensitivity, bacitracin sensitivity etc. \u003C\u002Fp>",{"slug":578,"name":579,"description":580,"image":42,"body":42,"postCount":470},"microbial-metabolism","Microbial Metabolism","\u003Cp>Tests about Microbial Metabolism. \u003C\u002Fp>",{"slug":582,"name":583,"description":584,"image":42,"body":42,"postCount":369},"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":586,"name":587,"description":588,"image":42,"body":42,"postCount":523},"atypical-pneumonia","Atypical Pneumonia","\u003Cp>Organisms responsible for Atypical Pneumonia. \u003C\u002Fp>",{"slug":590,"name":591,"description":592,"image":42,"body":42,"postCount":364},"antigen","Antigen","\u003Cp>Various articles related to Antigens.\u003C\u002Fp>",{"slug":594,"name":595,"description":596,"image":42,"body":42,"postCount":386},"innate-immunity","Innate Immunity","\u003Cp>Articles related to Innate Immunity. \u003C\u002Fp>",{"slug":598,"name":599,"description":600,"image":42,"body":42,"postCount":470},"respiratory-tract-infection","Respiratory Tract Infection","\u003Cp>In this cluster, you can see various etiological agents that causes respiratory tract infection. \u003C\u002Fp>",{"slug":602,"name":603,"description":604,"image":42,"body":42,"postCount":364},"torch-infection","TORCH Infection","\u003Cp>In this section; you can find articles related with TOCH infection. \u003C\u002Fp>",{"slug":606,"name":607,"description":608,"image":42,"body":42,"postCount":386},"microbiology-for-beginners","Microbiology for Beginners","\u003Cp>These articles are very basic articles, which will share general concepts in Microbiology. \u003C\u002Fp>",{"slug":610,"name":611,"description":612,"image":42,"body":42,"postCount":309},"dna-replication","DNA Replication","\u003Cp>Articles related to DNA and Replication of DNA. \u003C\u002Fp>",{"slug":614,"name":615,"description":616,"image":42,"body":42,"postCount":386},"genetic-code","Genetic Code","\u003Cp>Articles related to Genetic Code.\u003C\u002Fp>",{"slug":618,"name":619,"description":620,"image":42,"body":42,"postCount":364},"molecular-technique","Molecular Technique","\u003Cp>Posts related to Molecular Techniques. \u003C\u002Fp>",{"slug":622,"name":623,"description":42,"image":42,"body":42,"postCount":320},"colorimetric-assay","Colorimetric Assay ",{"slug":625,"name":626,"description":627,"image":42,"body":42,"postCount":364},"pharmaceutical-microbiology","Pharmaceutical Microbiology","\u003Cp>Various articles related to Pharmaceutical Microbiology\u003C\u002Fp>",{"slug":629,"name":630,"description":42,"image":42,"body":42,"postCount":523},"blood-and-immune-cells","Blood and Immune Cells"]