[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"$fxLN3MUwXCdr5RPjwZYIDpOj8CHyjOmngWTgoKXPtZbg":3,"$f_CW4Zo7p2wy-c-pC74B_-BUY-IIitwLCscXDszxHQHU":36,"$f3Ft0rKFJHppdzE-vuveecxx1BUcg9iOlMLtyzf_MJDg":156,"$fucxFBm2ZjZfGSdmdRaSNGBI_F0jJme4f0GTvzUhQfL8":221},[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":44,"draft":45,"category":46,"image":42,"body":47,"faq":48,"commentsClosed":45,"tags":70,"related":72,"comments":152},"esbl-detection-and-confirmation","ESBL Detection: Screening, the Combined-Disk Confirmatory Test, and the AmpC Trap","How the lab detects an extended-spectrum beta-lactamase: the screening cutoffs, the CLSI combined-disk confirmatory test and its ≥5 mm rule, the control strains, and why a co-produced AmpC can hide an ESBL from a routine plate.",null,"Nisha Rijal","2026-08-01",false,"bacteriology","A woman is admitted with a febrile urinary tract infection. The lab reports her *E. coli* as resistant to ceftriaxone, and the team switches to a carbapenem. It works. Three beds down, an identical *E. coli* UTI is reported as susceptible to ceftriaxone, so it is prescribed. The patient does not improve. The difference was not the organism. It was whether the lab looked past the routine result and asked one more question: is this cephalosporin resistance being caused by an extended-spectrum beta-lactamase? That question, and the simple plate test that answers it, is what this article is about.\n\n## What an ESBL is\n\nAn extended-spectrum beta-lactamase (ESBL) is an enzyme, produced mainly by Gram-negative bacteria of the family Enterobacterales (especially *Escherichia coli* and *Klebsiella pneumoniae*), that hydrolyzes the oxyimino-cephalosporins (cefotaxime, ceftazidime, ceftriaxone) and the monobactam aztreonam, and is inhibited by clavulanic acid. Two features define it, and both matter for detection: it defeats third-generation cephalosporins, and clavulanic acid restores their activity.\n\nAn ESBL does *not* effectively hydrolyze cephamycins (such as cefoxitin) or carbapenems. Most ESBLs are Ambler Class A, Bush-Jacoby group 2be; a less common subset are OXA-type (Class D). The full framework is covered in the [beta-lactamase classification article](\u002Fbetalactamase-classification\u002F).\n\n## Why ESBLs matter clinically\n\nESBL genes are [plasmid-mediated](https:\u002F\u002Fmicrobeonline.com\u002Fplasmids-properties-types-uses\u002F), which drives both their spread and their danger. The same plasmid that carries the ESBL gene frequently carries resistance genes for other drug classes, aminoglycosides and fluoroquinolones among them. So an ESBL-producing organism often defeats not just the first-choice cephalosporin but the expected fallback as well, which is why ESBL infections escalate from routine to carbapenem-requiring so readily.\n\nESBL producers cause UTIs, bloodstream infections, pneumonia, and healthcare-associated infections, and they spread by contact with infected fluids, contaminated hands, or contaminated equipment such as catheters. This is why the detection question is not academic: a missed ESBL means a patient may receive a cephalosporin that will fail.\n\n## The two-step logic: screen, then confirm\n\nESBL detection is a **screen-then-confirm** sequence, and understanding *why* it has two steps is half the learning. Screening is sensitive but not specific: it flags anything suspicious. Confirmation is specific: it proves the suspicious result is actually due to an ESBL and not something else. A screen-positive isolate is a question; a confirm-positive isolate is an answer.\n\n**Step 1: Screening.** Using standard disk diffusion, reduced zone sizes around an indicator cephalosporin flag possible ESBL production. With cefotaxime, a zone of ≤27 mm is suspicious; with ceftazidime, ≤22 mm. Because no single cephalosporin catches every ESBL, testing more than one indicator drug increases sensitivity. A suspicious screen does not diagnose an ESBL; it triggers confirmation.\n\n**Step 2: Confirmation, the combined-disk test.** This is the core method. The principle is elegant: if resistance is caused by an ESBL, then adding clavulanic acid (which inhibits the ESBL) should restore the cephalosporin's activity, and the inhibition zone should grow. The test compares each cephalosporin alone against the same cephalosporin plus clavulanate:\n\n- Cefotaxime (30 µg) vs. cefotaxime-clavulanate (30\u002F10 µg)\n- Ceftazidime (30 µg) vs. ceftazidime-clavulanate (30\u002F10 µg)\n\n\u003Cfigure>\n\u003Cimg src=\"https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002Fesbl-combined-disk-test.png\" alt=\"Two Mueller-Hinton agar plates compared side by side in the ESBL combined-disk test. The left plate has a cefotaxime disk surrounded by a small zone of inhibition, because the ESBL destroys the antibiotic. The right plate has a cefotaxime-clavulanate disk surrounded by a much larger zone, because clavulanate inhibits the ESBL and restores the antibiotic's activity. A zone increase of 5 millimeters or more with clavulanate confirms ESBL production.\" width=\"2720\" height=\"1600\" draggable=\"false\" contenteditable=\"false\">\u003Cfigcaption>The ESBL combined-disk confirmatory test. Cefotaxime alone gives a small inhibition zone because the extended-spectrum beta-lactamase hydrolyzes the drug. Adding clavulanic acid, which inhibits the ESBL, restores the drug and enlarges the zone. An increase of 5 mm or more in the presence of clavulanate confirms the isolate is an ESBL producer. The same comparison is run with ceftazidime, and only one of the two drug pairs needs to show the 5 mm jump.\u003C\u002Ffigcaption>\n\u003C\u002Ffigure>\n\nBoth pairs are tested because some ESBLs hydrolyze one cephalosporin far more than the other. After 16 to 18 hours at 35 ± 2 °C in ambient air, measure all four zones.\n\n**The reading rule (the single most exam-relevant number):** a **≥5 mm increase** in zone diameter for *either* cephalosporin in the presence of clavulanate, compared with that cephalosporin alone, confirms ESBL production. Only one of the two drug pairs needs to show the ≥5 mm jump.\n\n**Controls (do not skip these)**\n\nEvery ESBL confirmatory run needs both controls, or the result is uninterpretable:\n\n- Positive control: *Klebsiella pneumoniae* ATCC 700603 (a known ESBL producer, should show the ≥5 mm increase).\n- Negative control: *Escherichia coli* ATCC 25922 (no ESBL, should show no significant increase).\n\n## The AmpC trap (why a real ESBL can read negative)\n\nClavulanic acid inhibits the ESBL, but it does *not* inhibit an AmpC enzyme. If an isolate co-produces both an ESBL and an AmpC, the AmpC keeps destroying the cephalosporin even after clavulanate has neutralized the ESBL, so the zone never grows by 5 mm and the confirmatory test reads falsely negative. In this situation, the ESBL is present but hidden.\n\nA useful clue appears on the routine susceptibility plate. If the isolate is resistant to cefoxitin (a cephamycin), it suggests the presence of AmpC because ESBLs alone do not cause cefoxitin resistance. When AmpC is suspected, the ESBL confirmatory test can be performed on media containing cloxacillin, which inhibits AmpC. Another option is to use cefepime, an AmpC-stable cephalosporin, with and without clavulanate to reveal the hidden ESBL. This is a good example of how one enzyme can mask another, making it difficult for a routine automated report to detect the ESBL correctly.\n\n**How this fits the workflow**\n\nAn ESBL result changes reporting. Historically, a confirmed ESBL prompted the lab to report all penicillins, cephalosporins, and aztreonam as resistant regardless of the individual zone sizes. Current CLSI guidance leans instead on using the revised cephalosporin breakpoints directly, but ESBL detection remains essential for infection control, for local resistance surveillance, and for the antibiogram that guides the next patient's empirical therapy.\n\n### How to Remember\n\n**The whole method in one image:** clavulanate is the ESBL's off-switch. Flip the switch (add clavulanate) and if the zone jumps open by 5 mm or more, an ESBL was doing the damage. If the zone does not budge, either there is no ESBL, or something clavulanate cannot switch off (an AmpC) is also in the room.\n\n**The ≥5 mm rule, made sticky:** picture the two disks side by side. The plain cephalosporin has a small clear zone (the enzyme is winning). Add clavulanate and the zone *breathes out* by at least a nail's width, about 5 mm. That breath is the ESBL confessing.\n\n**The AmpC trap in one line:** clavulanate silences the ESBL but not the AmpC, so a co-producer keeps the zone shut and the ESBL hides. If cefoxitin is also resistant, suspect the trap.\n\n### Key exam facts in one table\n\n| Question | Answer |\n| --- | --- |\n| What does an ESBL hydrolyze, and what spares it? | Hydrolyzes oxyimino-cephalosporins (cefotaxime, ceftazidime, ceftriaxone) and aztreonam; spared by cephamycins (cefoxitin) and carbapenems |\n| What inhibits an ESBL, and how is that used for detection? | Clavulanic acid; adding it restores cephalosporin activity, seen as a zone increase |\n| Which drugs are used in the combined-disk confirmatory test? | Cefotaxime and ceftazidime, each alone vs. with clavulanate |\n| What zone change confirms an ESBL? | A ≥5 mm increase for either cephalosporin when clavulanate is added |\n| Screening cutoff zones? | Cefotaxime ≤27 mm or ceftazidime ≤22 mm is suspicious |\n| Positive and negative control strains? | *K. pneumoniae* ATCC 700603 (positive); *E. coli* ATCC 25922 (negative) |\n| Why can a true ESBL test negative? | Co-produced AmpC is not inhibited by clavulanate and masks the ESBL |\n| What routine clue suggests a masking AmpC? | Resistance to cefoxitin (ESBLs alone spare cefoxitin) |\n| Most common Ambler class \u002F Bush-Jacoby group for ESBLs? | Class A \u002F group 2be |\n\n### Where Students Get Confused\n\n**\"An ESBL hydrolyzes everything, so nothing works.\"** No. ESBLs spare carbapenems and cephamycins. That is precisely why carbapenems are the reliable treatment and why cefoxitin susceptibility is a diagnostic clue.\n\n**\"A negative confirmatory test means no ESBL.\"** Not always. A co-produced AmpC can mask a real ESBL and give a false-negative. The cefoxitin clue and cloxacillin-containing media exist to catch exactly this.\n\n**\"Screening positive means the isolate is an ESBL producer.\"** No. Screening is sensitive, not specific. Many screen-positive isolates are not confirmed. The combined-disk test is what makes the call.\n\n**\"Any zone increase with clavulanate counts.\"** No. The threshold is a defined ≥5 mm increase, and it must be measured against the same cephalosporin tested alone, with valid controls on the plate.\n\n**\"ESBLs are Class A, full stop.\"** Mostly, but not entirely. The majority are Class A (group 2be); OXA-type ESBLs are Class D. The exception is worth knowing.\n\n### References\n\n1. Clinical and Laboratory Standards Institute (CLSI). *Performance Standards for Antimicrobial Susceptibility Testing.* M100, current edition. Wayne, PA: CLSI.\n2. Bush K, Jacoby GA. Updated functional classification of beta-lactamases. *Antimicrob Agents Chemother.* 2010;54(3):969-976. doi:10.1128\u002FAAC.01009-09\n3. Rawat D, Nair D. Extended-spectrum beta-lactamases in Gram-negative bacteria. *J Glob Infect Dis.* 2010;2(3):263-274. doi:10.4103\u002F0974-777X.68531\n4. Tille PM. *Bailey & Scott's Diagnostic Microbiology.* 15th ed. St. Louis: Elsevier; 2022.",[49,52,55,58,61,64,67],{"question":50,"answer":51},"\u003Cp>What is the confirmatory test for an ESBL?\u003C\u002Fp>","\u003Cp>The combined-disk test. Cefotaxime and ceftazidime are each tested alone and in combination with clavulanic acid. A zone diameter increase of 5 mm or more with clavulanate, for either cephalosporin, confirms ESBL production.\u003C\u002Fp>",{"question":53,"answer":54},"\u003Cp>Why is clavulanic acid used to detect ESBLs?\u003C\u002Fp>","\u003Cp>Clavulanic acid inhibits the ESBL enzyme. When it is added to a cephalosporin, the antibiotic's activity is restored and its inhibition zone enlarges. That enlargement is the visible proof that an ESBL was responsible for the resistance.\u003C\u002Fp>",{"question":56,"answer":57},"\u003Cp>Why can an ESBL-producing organism test negative on the confirmatory test?\u003C\u002Fp>","\u003Cp>If the isolate also produces an AmpC enzyme, clavulanic acid does not inhibit the AmpC, so the cephalosporin keeps being destroyed and the zone does not enlarge. The ESBL is present but masked. Resistance to cefoxitin is a clue that AmpC may be involved.\u003C\u002Fp>",{"question":59,"answer":60},"\u003Cp>What can ESBLs hydrolyze, and what can they not?\u003C\u002Fp>","\u003Cp>ESBLs hydrolyze oxyimino-cephalosporins (such as cefotaxime, ceftazidime, and ceftriaxone) and aztreonam. They cannot effectively hydrolyze cephamycins (such as cefoxitin) or carbapenems.\u003C\u002Fp>",{"question":62,"answer":63},"\u003Cp>Why does an ESBL-producing infection often fail more than one antibiotic class?\u003C\u002Fp>","\u003Cp>ESBL genes are usually plasmid-mediated, and the same plasmid frequently carries resistance genes for other classes such as aminoglycosides and fluoroquinolones. A single organism can therefore defeat both the first-choice drug and the expected backup.\u003C\u002Fp>",{"question":65,"answer":66},"\u003Cp>How does ESBL resistance spread between bacteria?\u003C\u002Fp>","\u003Cp>Because ESBL genes sit on plasmids, they transfer readily between bacteria of the same species and across genera, for example from \u003Cem>E. coli\u003C\u002Fem> to \u003Cem>Klebsiella\u003C\u002Fem> or \u003Cem>Pseudomonas\u003C\u002Fem>.\u003C\u002Fp>",{"question":68,"answer":69},"\u003Cp>Which control strains are used for the ESBL confirmatory test?\u003C\u002Fp>","\u003Cp>\u003Cem>Klebsiella pneumoniae\u003C\u002Fem> ATCC 700603 is the positive control and \u003Cem>Escherichia coli\u003C\u002Fem> ATCC 25922 is the negative control.\u003C\u002Fp>",[71],"antimicrobial-susceptibility-testing",[73,92,119,145],{"slug":74,"title":75,"description":76,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":77,"lastUpdatedDate":44,"draft":45,"category":46,"image":42,"faq":78,"tags":91},"betalactamase-classification","Beta-Lactamase Classification: Ambler vs. Bush-Jacoby, and Why an Enzyme Has Both","How the Ambler molecular classes (A through D) and Bush-Jacoby functional groups describe the same enzymes from two different angles, with the mapping most articles skip.","2021-05-26",[79,82,85,88],{"question":80,"answer":81},"Are the Ambler and Bush-Jacoby-Medeiros classification systems different enzymes or different views of the same ones?","They are two different views of the same enzymes. Ambler classifies by molecular structure, while Bush-Jacoby-Medeiros classifies by function, substrate and inhibitor profile. A single enzyme carries a label in both systems at once, for example AmpC is simultaneously Ambler Class C and Bush-Jacoby Group 1.",{"question":83,"answer":84},"Why doesn't clavulanic acid inhibit Ambler Class B enzymes?","Class B enzymes are metallo-beta-lactamases that require a zinc ion at the active site rather than serine. Clavulanic acid works against the serine-based classes (A, C, D) but has no effect on the zinc-dependent mechanism, which instead requires metal chelators like EDTA.",{"question":86,"answer":87},"\u003Cp>How many groups are in the Bush-Jacoby classification?\u003C\u002Fp>","\u003Cp>Three main functional groups with multiple subgroups. A fourth group originally existed but was merged because its enzyme properties overlapped with the other three.\u003C\u002Fp>",{"question":89,"answer":90},"\u003Cp>Which Ambler class contains the AmpC enzymes?\u003C\u002Fp>","\u003Cp>Ambler Class C, which corresponds to Bush-Jacoby Group 1, the cephalosporinases.\u003C\u002Fp>",[71],{"slug":93,"title":94,"description":95,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":96,"lastUpdatedDate":44,"draft":45,"category":97,"image":42,"faq":98,"tags":117},"plasmids-properties-types-uses","Plasmids: Properties, Types, and Functions","Plasmids: structure, types (R-plasmids, F-plasmid, virulence plasmids, Col plasmids), functions, and why they are the primary vehicle for antibiotic resistance spread worldwide. With clinical stories and comparison with the bacterial chromosome.","2019-10-13","general-microbiology",[99,102,105,108,111,114],{"question":100,"answer":101},"What is the difference between a plasmid and the bacterial chromosome?","Chromosome: essential genes, vertical inheritance only, replicates once per division. Plasmid: non-essential accessory genes (resistance, virulence), can transfer horizontally between species via conjugation\u002Ftransformation\u002Ftransduction, replicates independently.",{"question":103,"answer":104},"How do R-plasmids contribute to the antibiotic resistance crisis?","A single R-plasmid can carry resistance to 5+ antibiotic classes simultaneously and transfer between species via conjugation in under 30 minutes. ESBL and carbapenemase genes are predominantly plasmid-encoded — this is why resistance spreads faster than mutation alone could explain.",{"question":106,"answer":107},"What is the F plasmid and why is it historically important?","Prototype conjugative plasmid of E. coli. F+ donors transfer to F- recipients via sex pili. When integrated into the chromosome (Hfr strains), it transfers chromosomal DNA at high frequency — the basis of the first E. coli chromosome mapping experiments in the 1950s-60s.",{"question":109,"answer":110},"What are virulence plasmids and can removing them make bacteria harmless?","Carry toxin\u002Fadhesin\u002Finvasin genes essential for disease. B. anthracis requires BOTH pXO1 (toxin) and pXO2 (capsule) plasmids for full virulence; ETEC requires its enterotoxin plasmid. Not universal — many pathogens (M. tuberculosis, S. typhi) encode virulence chromosomally instead.",{"question":112,"answer":113},"What is plasmid copy number and why does it matter?","Average plasmid copies per cell. High-copy (15-200+): automatic maintenance, high protein yield — preferred for expression vectors. Low-copy (1-5): requires active partition systems — used when expressed protein is toxic at high levels.",{"question":115,"answer":116},"What is the relationship between plasmids, transposons, and integrons in resistance spread?","Integrons capture individual resistance gene cassettes. Transposons carry integrons and jump between chromosome\u002Fplasmid. Conjugative plasmids transfer transposons (with integrons, with genes) between cells and species. This three-level cascade explains the efficiency of resistance spread.",[118],"bacterial-structure-physiology",{"slug":120,"title":121,"description":122,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":123,"lastUpdatedDate":124,"draft":45,"category":46,"image":42,"faq":125,"tags":144},"ampc-beta-lactamase-detection","AmpC Beta-Lactamase Detection: Cefoxitin Screen, Inhibitor Confirmation, and Telling It Apart from an ESBL","How the lab detects an AmpC beta-lactamase: the cefoxitin screen, the cloxacillin and boronic acid confirmatory tests, chromosomal versus plasmid-mediated AmpC, and the inhibitor logic that separates AmpC from an ESBL.","2026-08-02","2026-08-05",[126,129,132,135,138,141],{"question":127,"answer":128},"\u003Cp>How is an AmpC beta-lactamase detected in the lab?\u003C\u002Fp>","\u003Cp>Detection begins with a cefoxitin screen: a cefoxitin zone under 18 mm is suspicious. Confirmation uses an AmpC inhibitor, either a cefoxitin-cloxacillin double-disk test (≥4 mm zone increase with cloxacillin) or a boronic acid disk test (≥5 mm increase with boronic acid). The AmpC disk test using Tris-EDTA is an alternative.\u003C\u002Fp>",{"question":130,"answer":131},"\u003Cp>How do you tell an AmpC apart from an ESBL?\u003C\u002Fp>","\u003Cp>By which inhibitor restores the cephalosporin. AmpC is inhibited by boronic acid and cloxacillin but not by clavulanic acid; an ESBL is the reverse. AmpC also hydrolyzes cefoxitin, whereas an ESBL spares it, so cefoxitin resistance points toward AmpC.\u003C\u002Fp>",{"question":133,"answer":134},"\u003Cp>Why is clavulanic acid not useful for detecting AmpC?\u003C\u002Fp>","\u003Cp>Clavulanic acid inhibits the serine ESBLs but does not inhibit AmpC enzymes. That is why the standard ESBL confirmatory test, which relies on clavulanate synergy, cannot detect an AmpC and can even be masked by one.\u003C\u002Fp>",{"question":136,"answer":137},"\u003Cp>What is the difference between chromosomal and plasmid-mediated AmpC?\u003C\u002Fp>","\u003Cp>Chromosomal AmpC is native to organisms such as \u003Cem>Enterobacter\u003C\u002Fem>, \u003Cem>Citrobacter\u003C\u002Fem>, and \u003Cem>Serratia\u003C\u002Fem>, where it is often inducible. Plasmid-mediated AmpC is acquired and appears in species that normally lack a chromosomal ampC, such as \u003Cem>E. coli\u003C\u002Fem>, \u003Cem>Klebsiella pneumoniae\u003C\u002Fem>, and \u003Cem>Proteus mirabilis\u003C\u002Fem>, where its presence signals a transferable enzyme.\u003C\u002Fp>",{"question":139,"answer":140},"\u003Cp>Why can an AmpC producer fail treatment despite a susceptible cephalosporin result?\u003C\u002Fp>","\u003Cp>Many AmpC enzymes are inducible. Baseline production is low, so the isolate can appear susceptible, but exposure to a beta-lactam increases enzyme production and unmasks resistance during therapy. Cefepime or a carbapenem is preferred for confirmed AmpC producers.\u003C\u002Fp>",{"question":142,"answer":143},"\u003Cp>Can an isolate produce both AmpC and ESBL?\u003C\u002Fp>","\u003Cp>Yes. When both are present, the AmpC masks the ESBL because clavulanic acid cannot restore the cephalosporin while the AmpC continues to hydrolyze it. Testing on cloxacillin-containing media or adding boronic acid neutralizes the AmpC and reveals the hidden ESBL.\u003C\u002Fp>",[71],{"slug":146,"title":147,"description":147,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":148,"lastUpdatedDate":149,"draft":45,"category":46,"image":42,"faq":150,"tags":151},"phenotypic-methods-for-the-detection-of-carbapenemases","Phenotypic Methods for the Detection of Carbapenemases","2021-05-10","2026-07-05",[],[71],{"enabled":153,"threads":154,"total":155},true,[],0,[157,164,171,178,184,189,195,200,206,209,215],{"slug":158,"name":159,"description":160,"image":161,"body":162,"postCount":163},"acharya-tankeshwar","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":165,"name":166,"description":167,"image":168,"body":169,"postCount":170},"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":172,"name":173,"description":174,"image":175,"body":176,"postCount":177},"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":179,"name":180,"description":174,"image":181,"body":182,"postCount":183},"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":185,"name":186,"description":174,"image":42,"body":187,"postCount":188},"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":190,"name":191,"description":192,"image":42,"body":193,"postCount":194},"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":196,"name":197,"description":198,"image":42,"body":42,"postCount":199},"guest-author","Guest Author","Guest Author \u002F Contributor",1,{"slug":201,"name":202,"description":174,"image":203,"body":204,"postCount":205},"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":207,"name":208,"description":198,"image":42,"body":42,"postCount":199},"dr-poonam-acharya","Dr. Poonam Acharya",{"slug":210,"name":43,"description":211,"image":212,"body":213,"postCount":214},"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":216,"name":217,"description":218,"image":219,"body":220,"postCount":199},"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.",[222,229,235,240,245,250,254,258,262,267,271,275,279,284,289,292,296,300,305,310,314,318,322,327,331,335,339,343,348,353,357,361,365,369,373,377,381,385,389,393,397,401,405,409,413,417,421,425,430,434,438,442,446,450,454,458,462,466,470,474,478,482,486,490,494,498,502,506,509,513],{"slug":223,"name":224,"description":225,"image":226,"body":227,"postCount":228},"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":230,"name":231,"description":232,"image":42,"body":233,"postCount":234},"microscopy","Microscopy","Microscope types, components, and microscopy techniques","These are list of blog posts related to microscopy. ",12,{"slug":236,"name":237,"description":238,"image":42,"body":42,"postCount":239},"gram-positive-cocci","Gram-Positive Cocci","Staphylococcus, Streptococcus, Enterococcus, Micrococcus — organisms, diseases, and identification tests",11,{"slug":241,"name":242,"description":243,"image":42,"body":42,"postCount":244},"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":246,"name":247,"description":248,"image":42,"body":42,"postCount":249},"gram-positive-rods","Gram-Positive Rods","Bacillus, Clostridium, Listeria, Corynebacterium, Actinomyces and related organisms",8,{"slug":251,"name":252,"description":253,"image":42,"body":42,"postCount":239},"mycobacteria","Mycobacteria","Mycobacterium tuberculosis, leprosy, atypical mycobacteria, and acid-fast organism diagnosis",{"slug":255,"name":256,"description":257,"image":42,"body":42,"postCount":239},"anaerobic-bacteriology","Anaerobic Bacteriology","Anaerobic organisms, anaerobic culture methods, and anaerobic infection diagnosis",{"slug":259,"name":260,"description":261,"image":42,"body":42,"postCount":234},"enterobacteriaceae","Enterobacteriaceae","Identification, differentiation, and clinical significance of Enterobacteriaceae family members",{"slug":263,"name":264,"description":265,"image":42,"body":42,"postCount":266},"spirochetes","Spirochetes","Treponema, Leptospira, Borrelia and spirochetal infections",7,{"slug":268,"name":269,"description":270,"image":42,"body":42,"postCount":228},"food-microbiology","Food Microbiology","Food-borne pathogens, food safety, spoilage, and preservation",{"slug":71,"name":272,"description":273,"image":42,"body":42,"postCount":274},"Antimicrobial Susceptibility Testing","Methods for testing antibiotic susceptibility in clinical microbiology",21,{"slug":276,"name":277,"description":278,"image":42,"body":42,"postCount":249},"antimicrobials-moa-amr","Antimicrobials (MOA & AMR)","Mechanisms, detection, and clinical significance of antimicrobial resistance",{"slug":280,"name":281,"description":282,"image":42,"body":42,"postCount":283},"sterilization-disinfection","Sterilization and Disinfection","Methods of sterilization and disinfection in healthcare and laboratory settings",10,{"slug":285,"name":286,"description":287,"image":42,"body":42,"postCount":288},"specimen-collection-transport","Specimen Collection and Transport","Collection, handling, and transport of clinical specimens for microbiological testing",27,{"slug":118,"name":290,"description":291,"image":42,"body":42,"postCount":274},"Bacterial Structure and Physiology","Bacterial cell structure, growth, physiology, and environmental factors affecting growth",{"slug":293,"name":294,"description":42,"image":42,"body":295,"postCount":188},"horizontal-gene-transfer","Horizontal Gene Transfer","Articles related to **Horizontal Gene Transfer**",{"slug":297,"name":298,"description":42,"image":42,"body":299,"postCount":283},"chromatography","Chromatography","Information about chromatographic techniques.",{"slug":301,"name":302,"description":303,"image":42,"body":304,"postCount":266},"electrophoresis","Electrophoresis","Information about Electrophoresis Techniques ","Detailed information  about Electrophoresis Techniques ",{"slug":306,"name":307,"description":308,"image":42,"body":309,"postCount":188},"pcr-techniques","PCR Techniques","Information about various types of Polymerase Chain Reaction Techniques ","More detailed information about various types of Polymerase Chain Reaction Techniques ",{"slug":311,"name":312,"description":313,"image":42,"body":42,"postCount":188},"bacteriophage","Bacteriophage","Description about Bacteriophage.",{"slug":315,"name":316,"description":317,"image":42,"body":42,"postCount":188},"malaria","Malaria","It is the collections of articles regarding malarial disease. ",{"slug":319,"name":320,"description":321,"image":42,"body":42,"postCount":188},"anaerobic-culture-techniques","Anaerobic Culture Techniques","Posts related with Anaerobic Culture Techniques.",{"slug":323,"name":324,"description":325,"image":42,"body":42,"postCount":326},"immunoassays","Immunoassays","You will get information about all the diagnostic tests that rely on the specific binding between an antigen and an antibody to detect or quantify a substance.",19,{"slug":328,"name":329,"description":330,"image":42,"body":42,"postCount":266},"biosafety-levels","Biosafety levels ","Articles related to Biosafety Levels",{"slug":332,"name":333,"description":334,"image":42,"body":42,"postCount":244},"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":336,"name":337,"description":338,"image":42,"body":42,"postCount":188},"pipette","Pipette","Posts related with Pipette. ",{"slug":340,"name":341,"description":342,"image":42,"body":42,"postCount":249},"bacteriology-mcqs","Bacteriology MCQs","This sections lists MCQs in Bacteriology.",{"slug":344,"name":345,"description":346,"image":42,"body":42,"postCount":347},"parasitology-mcqs","Parasitology MCQs","This section lists MCQs in Parasitology.",2,{"slug":349,"name":350,"description":351,"image":42,"body":42,"postCount":352},"virology-mcqs","Virology MCQs","This is the collections of Multiple Choice Questions in Virology.",4,{"slug":354,"name":355,"description":356,"image":42,"body":42,"postCount":244},"mcqs-in-microbiology","MCQs in Microbiology","This section lists the collections of Multiple Choice Questions in General Microbiology Topics. ",{"slug":358,"name":359,"description":360,"image":42,"body":42,"postCount":249},"immunology-mcqs","Immunology MCQs","In this section; we are posting collections of Multiple Choice Questions about Immunology. ",{"slug":362,"name":363,"description":364,"image":42,"body":42,"postCount":194},"microbial-curiosities","Microbial Curiosities","In this clusters, we are posting interesting and unique information about Microorganisms. ",{"slug":366,"name":367,"description":368,"image":42,"body":42,"postCount":274},"bacterial-culture-media","Bacterial Culture Media","Posts related to Bacterial Culture Media. ",{"slug":370,"name":371,"description":372,"image":42,"body":42,"postCount":188},"fungal-culture-media","Fungal Culture Media","Posts related to Fungal Culture Media.",{"slug":374,"name":375,"description":376,"image":42,"body":42,"postCount":244},"motility-test","Motility Test","This lists the procedure regarding various tests methods for bacterial motility.",{"slug":378,"name":379,"description":380,"image":42,"body":42,"postCount":283},"bacterial-enumeration","Bacterial enumeration","These posts are related to isolation and enumeration of bacteria. ",{"slug":382,"name":383,"description":384,"image":42,"body":42,"postCount":347},"gram-positive-coccobacillus","Gram-positive coccobacillus","List of Gram Positive Coccobacilli",{"slug":386,"name":387,"description":388,"image":42,"body":42,"postCount":352},"dimorphic-fungi","Dimorphic Fungi","This is about various dimorphic fungi. ",{"slug":390,"name":391,"description":392,"image":42,"body":42,"postCount":266},"bacterial-classification","Bacterial Classification","These posts are related with various approaches used for the classification of Bacteria. ",{"slug":394,"name":395,"description":396,"image":42,"body":42,"postCount":244},"immunofluorescence","Immunofluorescence ","Various Tests related to Immunofluorescence ",{"slug":398,"name":399,"description":400,"image":42,"body":42,"postCount":194},"antibody-mediated-immunity","Antibody-mediated Immunity","This clusters links the articles that are sharing insights about Antibody-mediated immunity. ",{"slug":402,"name":403,"description":404,"image":42,"body":42,"postCount":266},"hypersensitivity","Hypersensitivity","Articles related to Hypersensitivity.",{"slug":406,"name":407,"description":42,"image":42,"body":42,"postCount":408},"haemophilus","Haemophilus",3,{"slug":410,"name":411,"description":412,"image":42,"body":42,"postCount":352},"sexually-transmitted-infections-stis","Sexually transmitted infections (STIs)","This is the clusters of infections that are transmitted sexually. ",{"slug":414,"name":415,"description":416,"image":42,"body":42,"postCount":234},"adaptive-immunity","Adaptive Immunity","Blog posts related to B Cell Immunity and T Cell Immunity.",{"slug":418,"name":419,"description":420,"image":42,"body":42,"postCount":228},"fungal-diagnostics","Fungal Diagnostics","Various methods used for the Diagnosis of Fungal Infections. ",{"slug":422,"name":423,"description":424,"image":42,"body":42,"postCount":244},"laboratory-storage-and-preservation","Laboratory Storage and Preservation","Articles about Laboratory Storage of Antimicrobial Disk, Test organisms and Equipment used for this process. ",{"slug":426,"name":427,"description":428,"image":42,"body":429,"postCount":188},"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":431,"name":432,"description":433,"image":42,"body":42,"postCount":249},"laboratory-glassware","Laboratory Glassware","Posts about Laboratory Glassware. ",{"slug":435,"name":436,"description":437,"image":42,"body":42,"postCount":188},"helminths","Helminths","In this section, we are covering properties, life cycle, pathogenesis and laboratory diagnosis of Helminths\u002FHelminthic infestations. ",{"slug":439,"name":440,"description":441,"image":42,"body":42,"postCount":188},"protozoan-parasite","Protozoan Parasite","In this cluster, we are covering protozoan parasites. ",{"slug":443,"name":444,"description":445,"image":42,"body":42,"postCount":199},"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":447,"name":448,"description":449,"image":42,"body":42,"postCount":283},"bacterial-staining-technique","Bacterial Staining Technique","Lists of various staining techniques that are used to stain bacteria. ",{"slug":451,"name":452,"description":453,"image":42,"body":42,"postCount":183},"enzyme-tests","Enzyme Tests","\u003Cp>Various Biochemical Test that are based on enzymatic activity of the microorganisms. \u003C\u002Fp>",{"slug":455,"name":456,"description":457,"image":42,"body":42,"postCount":239},"carbohydrate-utilization","Carbohydrate Utilization","\u003Cp>Various biochemical tests which are related to Carbohydrate fermentation or Utilization\u003C\u002Fp>",{"slug":459,"name":460,"description":461,"image":42,"body":42,"postCount":244},"susceptibility-based-id","Susceptibility-based ID","\u003Cp>These are susceptibility based identification test such as optochin sensitivity, bacitracin sensitivity etc. \u003C\u002Fp>",{"slug":463,"name":464,"description":465,"image":42,"body":42,"postCount":352},"microbial-metabolism","Microbial Metabolism","\u003Cp>Tests about Microbial Metabolism. \u003C\u002Fp>",{"slug":467,"name":468,"description":469,"image":42,"body":42,"postCount":249},"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":471,"name":472,"description":473,"image":42,"body":42,"postCount":408},"atypical-pneumonia","Atypical Pneumonia","\u003Cp>Organisms responsible for Atypical Pneumonia. \u003C\u002Fp>",{"slug":475,"name":476,"description":477,"image":42,"body":42,"postCount":244},"antigen","Antigen","\u003Cp>Various articles related to Antigens.\u003C\u002Fp>",{"slug":479,"name":480,"description":481,"image":42,"body":42,"postCount":266},"innate-immunity","Innate Immunity","\u003Cp>Articles related to Innate Immunity. \u003C\u002Fp>",{"slug":483,"name":484,"description":485,"image":42,"body":42,"postCount":352},"respiratory-tract-infection","Respiratory Tract Infection","\u003Cp>In this cluster, you can see various etiological agents that causes respiratory tract infection. \u003C\u002Fp>",{"slug":487,"name":488,"description":489,"image":42,"body":42,"postCount":244},"torch-infection","TORCH Infection","\u003Cp>In this section; you can find articles related with TOCH infection. \u003C\u002Fp>",{"slug":491,"name":492,"description":493,"image":42,"body":42,"postCount":266},"microbiology-for-beginners","Microbiology for Beginners","\u003Cp>These articles are very basic articles, which will share general concepts in Microbiology. \u003C\u002Fp>",{"slug":495,"name":496,"description":497,"image":42,"body":42,"postCount":188},"dna-replication","DNA Replication","\u003Cp>Articles related to DNA and Replication of DNA. \u003C\u002Fp>",{"slug":499,"name":500,"description":501,"image":42,"body":42,"postCount":266},"genetic-code","Genetic Code","\u003Cp>Articles related to Genetic Code.\u003C\u002Fp>",{"slug":503,"name":504,"description":505,"image":42,"body":42,"postCount":244},"molecular-technique","Molecular Technique","\u003Cp>Posts related to Molecular Techniques. \u003C\u002Fp>",{"slug":507,"name":508,"description":42,"image":42,"body":42,"postCount":199},"colorimetric-assay","Colorimetric Assay ",{"slug":510,"name":511,"description":512,"image":42,"body":42,"postCount":244},"pharmaceutical-microbiology","Pharmaceutical Microbiology","\u003Cp>Various articles related to Pharmaceutical Microbiology\u003C\u002Fp>",{"slug":514,"name":515,"description":42,"image":42,"body":42,"postCount":408},"blood-and-immune-cells","Blood and Immune Cells"]