[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"$fxLN3MUwXCdr5RPjwZYIDpOj8CHyjOmngWTgoKXPtZbg":3,"$fnJWduJvIQ9RP6BSjRKeoYRBdAPJ9wpy88DIMfHGDJiA":36,"$f3Ft0rKFJHppdzE-vuveecxx1BUcg9iOlMLtyzf_MJDg":129,"$fucxFBm2ZjZfGSdmdRaSNGBI_F0jJme4f0GTvzUhQfL8":194},[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":68,"related":70,"comments":125},"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.",null,"Nisha Rijal","2026-08-02","2026-08-05",false,"bacteriology","AmpC beta-lactamases are one of the most commonly missed resistance mechanisms in routine susceptibility testing. An AmpC-producing bacterium may appear susceptible to a third-generation cephalosporin in the laboratory, but the same antibiotic can fail during treatment because AmpC production is inducible and may become fully expressed (derepressed) after antibiotic exposure.\n\nUnlike ESBLs, AmpC enzymes are not inhibited by clavulanic acid. As a result, the standard ESBL confirmatory test does not detect AmpC. Even more importantly, when AmpC and ESBL are produced together, AmpC can mask the ESBL and cause the test to appear falsely negative.\n\nDetecting AmpC is based on one key principle: what inhibits it and what does not. It is inhibited by boronic acid and cloxacillin, but not by clavulanic acid. This simple difference distinguishes AmpC from ESBL, forms the basis of all confirmatory tests, and is the source of much of the confusion.\n\n## What an AmpC enzyme is, and why it evades routine testing\n\nAmpC beta-lactamases are Ambler Class C, Bush-Jacoby Group 1 cephalosporinases. (The Ambler and Bush-Jacoby classification systems are explained in full in the [beta-lactamase classification article](\u002Fbetalactamase-classification\u002F)). They hydrolyze penicillins, cephamycins (such as cefoxitin), and first-, second-, and third-generation cephalosporins, and they resist beta-lactam\u002Fbeta-lactamase-inhibitor combinations. They remain susceptible to cefepime and to carbapenems.\n\nTwo features make AmpC a detection problem. First, many AmpC enzymes are **inducible**: baseline production is low, so the isolate can look susceptible, but exposure to a beta-lactam ramps up enzyme production and unmasks resistance during therapy. Second, AmpC is **not inhibited by clavulanic acid**, so it slips straight past the ESBL confirmatory test that relies on clavulanate synergy.\n\n### Chromosomal vs. plasmid-mediated AmpC\n\nKnowing which type you are dealing with changes the interpretation.\n\n**Chromosomal AmpC** is native to certain organisms, classically the group remembered by the mnemonic below (*Enterobacter, Citrobacter, Serratia*, and others). In these, AmpC is expected and typically inducible; the question is not \"is AmpC present\" but \"will it express on treatment.\"\n\n**Plasmid-mediated AmpC (pAmpC)** is acquired, and it appears in organisms that do not normally carry a chromosomal ampC, principally *Klebsiella pneumoniae*, *Escherichia coli*, *Proteus mirabilis*, and *Salmonella*. Because these species have no native AmpC, finding AmpC activity in them signals a transferable, plasmid-borne enzyme. Most phenotypic detection tests are validated specifically for pAmpC in these AmpC-lacking species.\n\n### Step 1: Screening with cefoxitin\n\nThe first step in detecting AmpC is to test susceptibility to **cefoxitin**, a cephamycin antibiotic. ESBL-producing bacteria usually remain susceptible to cefoxitin, whereas AmpC-producing bacteria can hydrolyze cefoxitin and become resistant. Therefore, **cefoxitin resistance is an early sign of possible AmpC production**.\n\n*Note that, unlike ESBL detection, there are no CLSI-approved interpretive criteria for AmpC. The cutoffs below are widely used, well-validated research and consensus criteria rather than formally standardized breakpoints.*\n\nIn the disk diffusion method, a **cefoxitin (30 µg) zone diameter of less than 18 mm** is considered a positive screening result and indicates that confirmatory testing should be performed. However, a positive screening test does not confirm AmpC. Other mechanisms, such as reduced porin permeability, can also decrease the cefoxitin zone size even when AmpC is not present. This is why a confirmatory test is always required.\n\n### Step 2: Confirmation with an AmpC inhibitor\n\nConfirmation uses the defining property: AmpC is inhibited by boronic acid and by cloxacillin. Adding one of these should restore cefoxitin activity if AmpC is the cause.\n\n**Cefoxitin-cloxacillin double-disk test.** Cloxacillin inhibits AmpC. A cefoxitin-cloxacillin disk is compared against a plain cefoxitin disk. A zone diameter **≥4 mm larger** with cloxacillin than without confirms AmpC production. This is simple, cheap, and widely used in resource-limited labs.\n\n**Boronic acid disk test.** Boronic acid (phenylboronic acid) is a reversible AmpC inhibitor. Cefoxitin (or cefotetan) is tested alone and with boronic acid added; a **≥5 mm increase** in zone diameter with boronic acid confirms AmpC. Boronic acid also inhibits KPC carbapenemases, so this reagent reappears in carbapenemase work, a useful thing to remember rather than relearn.\n\n**AmpC disk test (Tris-EDTA).** A cefoxitin-susceptible *E. coli* ATCC 25922 lawn is plated. A disk impregnated with Tris-EDTA (which permeabilizes the test organism and releases its beta-lactamases) plus the test organism is placed at the edge of the cefoxitin zone. A flattening or indentation of the *E. coli* inhibition zone next to the disk indicates AmpC. This is sensitive and specific but needs the EDTA-disk reagent.\n\n### Step 3: Telling AmpC apart from ESBL\n\nThis is where AmpC and ESBL detection meet, and it is the highest-yield concept to master. Two enzymes, two inhibitors, and the pattern of which inhibitor works tells you which enzyme you have.\n\n| Feature | ESBL | AmpC |\n| --- | --- | --- |\n| Ambler class \u002F Bush-Jacoby group | A (mostly) \u002F 2be | C \u002F 1 |\n| Hydrolyzes cefoxitin (a cephamycin)? | No (spared) | Yes |\n| Inhibited by clavulanic acid? | Yes | No |\n| Inhibited by boronic acid or cloxacillin? | No | Yes |\n| Effect on carbapenems | Spared | Spared |\n\nThe clean logic: **clavulanate synergy means ESBL; boronic-acid or cloxacillin synergy means AmpC.** When an isolate is resistant to cefoxitin *and* fails the ESBL confirmatory test, suspect AmpC. When an isolate co-produces both, the AmpC masks the ESBL (clavulanate cannot restore the cephalosporin because the AmpC keeps destroying it), and the ESBL only becomes visible once the AmpC is neutralized, either on cloxacillin-containing media or by adding boronic acid to the ESBL test. This masking effect is a common reason a true ESBL is missed.\n\n\u003Cfigure>\n\u003Cimg src=\"https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002Fesbl-vs-ampc-discrimination-flow.png\" alt=\"Decision flowchart for telling an ESBL apart from an AmpC beta-lactamase. Starting from a cephalosporin-resistant isolate, the dividing question is whether cefoxitin is also resistant. If cefoxitin is spared and clavulanate restores the cephalosporin, the enzyme is an ESBL. If cefoxitin is hydrolyzed and boronic acid or cloxacillin restores it while clavulanate does not, the enzyme is an AmpC. When both inhibitors show synergy, the isolate co-produces both enzymes and the AmpC masks the ESBL until it is neutralized.\" width=\"2720\" height=\"1880\" draggable=\"false\" contenteditable=\"false\">\u003Cfigcaption>Telling ESBL and AmpC apart comes down to two questions: does the isolate hydrolyze cefoxitin, and which inhibitor restores the cephalosporin? An ESBL spares cefoxitin and is unmasked by clavulanate; an AmpC hydrolyzes cefoxitin and is unmasked by boronic acid or cloxacillin, not clavulanate. When both inhibitors show synergy, the isolate produces both enzymes, and the AmpC hides the ESBL until it is neutralized on cloxacillin-containing media or with added boronic acid.\u003C\u002Ffigcaption>\n\u003C\u002Ffigure>\n\n### Why it matters at the bedside\n\nAn unrecognized AmpC producer treated with a third-generation cephalosporin risks clinical failure, because the enzyme derepresses under selective pressure even when the initial report reads susceptible. The safe therapeutic choices against a confirmed AmpC producer are cefepime (a weak AmpC inducer and poor substrate) or a carbapenem. Detection also matters for infection control: a plasmid-mediated AmpC in *E. coli* or *Klebsiella* is transferable and warrants the same containment attention as any mobile resistance determinant. Detection feeds the antibiogram and antimicrobial stewardship decisions for the next patient.\n\n## How to Remember\n\n**The whole idea in one contrast:** two enzymes hide behind cephalosporin resistance, and the inhibitor that unmasks them tells them apart. Clavulanate opens the door on an ESBL. Boronic acid or cloxacillin opens the door on an AmpC. If cefoxitin is resistant, the door with the AmpC behind it is the one to try.\n\n**Which bugs carry chromosomal AmpC (classic mnemonic):** remember the classic chromosomal-AmpC organisms as a group: Enterobacter, Citrobacter (freundii), Serratia, Morganella, Providencia, and Hafnia. A common mnemonic is \"CHESPM,\" but the plainer point is that these species carry AmpC on the chromosome, so it is expected in them, and (for the acquired plasmid version) the AmpC-lacking hosts *E. coli*, *Klebsiella*, *Proteus*, *Salmonella*. The teaching point is the split: if AmpC turns up in the second group, it came in on a plasmid.\n\n**The inducibility image:** an inducible AmpC is a dimmer switch, not an on\u002Foff switch. On the plate under low light it looks susceptible. Give it a beta-lactam and it brightens (derepresses), which is why a susceptible report can still fail the patient.\n\n## Key exam facts in one table\n\n| Question | Answer |\n| --- | --- |\n| Ambler class and Bush-Jacoby group of AmpC? | Class C, Group 1 (cephalosporinases) |\n| Does AmpC hydrolyze cefoxitin? | Yes (unlike ESBL, which spares it) |\n| Which inhibitor blocks AmpC, and which does not? | Blocked by boronic acid and cloxacillin; not blocked by clavulanic acid |\n| Cefoxitin screening cutoff? | Zone <18 mm is a positive screen |\n| Cefoxitin-cloxacillin confirmatory criterion? | ≥4 mm zone increase with cloxacillin |\n| Boronic acid disk confirmatory criterion? | ≥5 mm zone increase with boronic acid |\n| Chromosomal AmpC organisms (classic)? | *Enterobacter*, *Citrobacter*, *Serratia*, and related |\n| Plasmid-mediated AmpC hosts (AmpC-lacking species)? | *E. coli*, *K. pneumoniae*, *P. mirabilis*, *Salmonella* |\n| Why can a susceptible AmpC report still fail? | Inducible enzyme derepresses under beta-lactam exposure |\n| Safe treatment choices against confirmed AmpC? | Cefepime or a carbapenem |\n| How does AmpC mask an ESBL? | Clavulanate cannot restore the cephalosporin because AmpC keeps hydrolyzing it |\n\n## Where Students Get Confused\n\n**\"AmpC and ESBL are detected the same way.\"** No, and this is the crux. ESBL is confirmed by clavulanate synergy; AmpC is confirmed by boronic-acid or cloxacillin synergy. Clavulanate does nothing to AmpC. Using the ESBL test alone will miss every AmpC.\n\n**\"A susceptible cephalosporin result rules out AmpC.\"** No. Inducible AmpC can read susceptible at baseline and derepress under therapy, causing failure. This is why detection, not just the routine MIC, matters for these organisms.\n\n**\"Cefoxitin resistance proves AmpC.\"** No, it screens for it. Porin loss can also reduce the cefoxitin zone. A positive screen must go to a confirmatory inhibitor test.\n\n**\"If the ESBL test is negative, there is no ESBL.\"** Not when AmpC is present. A co-produced AmpC masks the ESBL by continuing to hydrolyze the cephalosporin despite clavulanate. Neutralize the AmpC (cloxacillin media or added boronic acid) and the hidden ESBL appears.\n\n**\"Boronic acid is only an AmpC reagent.\"** It also inhibits KPC carbapenemases, which is why it reappears in carbapenemase detection. Same reagent, different context.\n\n### References\n\n1. Clinical and Laboratory Standards Institute (CLSI). *Performance Standards for Antimicrobial Susceptibility Testing.* M100, current edition. Wayne, PA: CLSI.\n2. Jacoby GA. AmpC beta-lactamases. *Clin Microbiol Rev.* 2009;22(1):161-182. doi:10.1128\u002FCMR.00036-08\n3. Black JA, Moland ES, Thomson KS. AmpC disk test for detection of plasmid-mediated AmpC beta-lactamases in Enterobacteriaceae lacking chromosomal AmpC beta-lactamases. *J Clin Microbiol.* 2005;43(7):3110-3113. doi:10.1128\u002FJCM.43.7.3110-3113.2005\n4. Coudron PE. Inhibitor-based methods for detection of plasmid-mediated AmpC beta-lactamases in *Klebsiella* spp., *Escherichia coli*, and *Proteus mirabilis*. *J Clin Microbiol.* 2005;43(8):4163-4167. doi:10.1128\u002FJCM.43.8.4163-4167.2005\n5. Tille PM. *Bailey & Scott's Diagnostic Microbiology.* 15th ed. St. Louis: Elsevier; 2022.",[50,53,56,59,62,65],{"question":51,"answer":52},"\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":54,"answer":55},"\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":57,"answer":58},"\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":60,"answer":61},"\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":63,"answer":64},"\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":66,"answer":67},"\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>",[69],"antimicrobial-susceptibility-testing",[71,91,118],{"slug":72,"title":73,"description":74,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":75,"lastUpdatedDate":76,"draft":46,"category":47,"image":42,"faq":77,"tags":90},"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","2026-08-01",[78,81,84,87],{"question":79,"answer":80},"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":82,"answer":83},"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":85,"answer":86},"\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":88,"answer":89},"\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>",[69],{"slug":92,"title":93,"description":94,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":76,"lastUpdatedDate":76,"draft":46,"category":47,"image":42,"faq":95,"tags":117},"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.",[96,99,102,105,108,111,114],{"question":97,"answer":98},"\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":100,"answer":101},"\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":103,"answer":104},"\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":106,"answer":107},"\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":109,"answer":110},"\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":112,"answer":113},"\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":115,"answer":116},"\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>",[69],{"slug":119,"title":120,"description":120,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":121,"lastUpdatedDate":122,"draft":46,"category":47,"image":42,"faq":123,"tags":124},"phenotypic-methods-for-the-detection-of-carbapenemases","Phenotypic Methods for the Detection of Carbapenemases","2021-05-10","2026-07-05",[],[69],{"enabled":126,"threads":127,"total":128},true,[],0,[130,137,144,151,157,162,168,173,179,182,188],{"slug":131,"name":132,"description":133,"image":134,"body":135,"postCount":136},"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":138,"name":139,"description":140,"image":141,"body":142,"postCount":143},"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":145,"name":146,"description":147,"image":148,"body":149,"postCount":150},"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":152,"name":153,"description":147,"image":154,"body":155,"postCount":156},"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":158,"name":159,"description":147,"image":42,"body":160,"postCount":161},"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":163,"name":164,"description":165,"image":42,"body":166,"postCount":167},"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":169,"name":170,"description":171,"image":42,"body":42,"postCount":172},"guest-author","Guest Author","Guest Author \u002F Contributor",1,{"slug":174,"name":175,"description":147,"image":176,"body":177,"postCount":178},"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":180,"name":181,"description":171,"image":42,"body":42,"postCount":172},"dr-poonam-acharya","Dr. Poonam Acharya",{"slug":183,"name":43,"description":184,"image":185,"body":186,"postCount":187},"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":189,"name":190,"description":191,"image":192,"body":193,"postCount":172},"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.",[195,202,208,213,218,223,227,231,235,240,244,248,252,257,262,266,270,274,279,284,288,292,296,301,305,309,313,317,322,327,331,335,339,343,347,351,355,359,363,367,371,375,379,383,387,391,395,399,404,408,412,416,420,424,428,432,436,440,444,448,452,456,460,464,468,472,476,480,483,487],{"slug":196,"name":197,"description":198,"image":199,"body":200,"postCount":201},"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":203,"name":204,"description":205,"image":42,"body":206,"postCount":207},"microscopy","Microscopy","Microscope types, components, and microscopy techniques","These are list of blog posts related to microscopy. ",12,{"slug":209,"name":210,"description":211,"image":42,"body":42,"postCount":212},"gram-positive-cocci","Gram-Positive Cocci","Staphylococcus, Streptococcus, Enterococcus, Micrococcus — organisms, diseases, and identification tests",11,{"slug":214,"name":215,"description":216,"image":42,"body":42,"postCount":217},"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":219,"name":220,"description":221,"image":42,"body":42,"postCount":222},"gram-positive-rods","Gram-Positive Rods","Bacillus, Clostridium, Listeria, Corynebacterium, Actinomyces and related organisms",8,{"slug":224,"name":225,"description":226,"image":42,"body":42,"postCount":212},"mycobacteria","Mycobacteria","Mycobacterium tuberculosis, leprosy, atypical mycobacteria, and acid-fast organism diagnosis",{"slug":228,"name":229,"description":230,"image":42,"body":42,"postCount":212},"anaerobic-bacteriology","Anaerobic Bacteriology","Anaerobic organisms, anaerobic culture methods, and anaerobic infection diagnosis",{"slug":232,"name":233,"description":234,"image":42,"body":42,"postCount":207},"enterobacteriaceae","Enterobacteriaceae","Identification, differentiation, and clinical significance of Enterobacteriaceae family members",{"slug":236,"name":237,"description":238,"image":42,"body":42,"postCount":239},"spirochetes","Spirochetes","Treponema, Leptospira, Borrelia and spirochetal infections",7,{"slug":241,"name":242,"description":243,"image":42,"body":42,"postCount":201},"food-microbiology","Food Microbiology","Food-borne pathogens, food safety, spoilage, and preservation",{"slug":69,"name":245,"description":246,"image":42,"body":42,"postCount":247},"Antimicrobial Susceptibility Testing","Methods for testing antibiotic susceptibility in clinical microbiology",21,{"slug":249,"name":250,"description":251,"image":42,"body":42,"postCount":222},"antimicrobials-moa-amr","Antimicrobials (MOA & AMR)","Mechanisms, detection, and clinical significance of antimicrobial resistance",{"slug":253,"name":254,"description":255,"image":42,"body":42,"postCount":256},"sterilization-disinfection","Sterilization and Disinfection","Methods of sterilization and disinfection in healthcare and laboratory settings",10,{"slug":258,"name":259,"description":260,"image":42,"body":42,"postCount":261},"specimen-collection-transport","Specimen Collection and Transport","Collection, handling, and transport of clinical specimens for microbiological testing",27,{"slug":263,"name":264,"description":265,"image":42,"body":42,"postCount":247},"bacterial-structure-physiology","Bacterial Structure and Physiology","Bacterial cell structure, growth, physiology, and environmental factors affecting growth",{"slug":267,"name":268,"description":42,"image":42,"body":269,"postCount":161},"horizontal-gene-transfer","Horizontal Gene Transfer","Articles related to **Horizontal Gene Transfer**",{"slug":271,"name":272,"description":42,"image":42,"body":273,"postCount":256},"chromatography","Chromatography","Information about chromatographic techniques.",{"slug":275,"name":276,"description":277,"image":42,"body":278,"postCount":239},"electrophoresis","Electrophoresis","Information about Electrophoresis Techniques ","Detailed information  about Electrophoresis Techniques ",{"slug":280,"name":281,"description":282,"image":42,"body":283,"postCount":161},"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":285,"name":286,"description":287,"image":42,"body":42,"postCount":161},"bacteriophage","Bacteriophage","Description about Bacteriophage.",{"slug":289,"name":290,"description":291,"image":42,"body":42,"postCount":161},"malaria","Malaria","It is the collections of articles regarding malarial disease. ",{"slug":293,"name":294,"description":295,"image":42,"body":42,"postCount":161},"anaerobic-culture-techniques","Anaerobic Culture Techniques","Posts related with Anaerobic Culture Techniques.",{"slug":297,"name":298,"description":299,"image":42,"body":42,"postCount":300},"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":302,"name":303,"description":304,"image":42,"body":42,"postCount":239},"biosafety-levels","Biosafety levels ","Articles related to Biosafety Levels",{"slug":306,"name":307,"description":308,"image":42,"body":42,"postCount":217},"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":310,"name":311,"description":312,"image":42,"body":42,"postCount":161},"pipette","Pipette","Posts related with Pipette. ",{"slug":314,"name":315,"description":316,"image":42,"body":42,"postCount":222},"bacteriology-mcqs","Bacteriology MCQs","This sections lists MCQs in Bacteriology.",{"slug":318,"name":319,"description":320,"image":42,"body":42,"postCount":321},"parasitology-mcqs","Parasitology MCQs","This section lists MCQs in Parasitology.",2,{"slug":323,"name":324,"description":325,"image":42,"body":42,"postCount":326},"virology-mcqs","Virology MCQs","This is the collections of Multiple Choice Questions in Virology.",4,{"slug":328,"name":329,"description":330,"image":42,"body":42,"postCount":217},"mcqs-in-microbiology","MCQs in Microbiology","This section lists the collections of Multiple Choice Questions in General Microbiology Topics. ",{"slug":332,"name":333,"description":334,"image":42,"body":42,"postCount":222},"immunology-mcqs","Immunology MCQs","In this section; we are posting collections of Multiple Choice Questions about Immunology. ",{"slug":336,"name":337,"description":338,"image":42,"body":42,"postCount":167},"microbial-curiosities","Microbial Curiosities","In this clusters, we are posting interesting and unique information about Microorganisms. ",{"slug":340,"name":341,"description":342,"image":42,"body":42,"postCount":247},"bacterial-culture-media","Bacterial Culture Media","Posts related to Bacterial Culture Media. ",{"slug":344,"name":345,"description":346,"image":42,"body":42,"postCount":161},"fungal-culture-media","Fungal Culture Media","Posts related to Fungal Culture Media.",{"slug":348,"name":349,"description":350,"image":42,"body":42,"postCount":217},"motility-test","Motility Test","This lists the procedure regarding various tests methods for bacterial motility.",{"slug":352,"name":353,"description":354,"image":42,"body":42,"postCount":256},"bacterial-enumeration","Bacterial enumeration","These posts are related to isolation and enumeration of bacteria. ",{"slug":356,"name":357,"description":358,"image":42,"body":42,"postCount":321},"gram-positive-coccobacillus","Gram-positive coccobacillus","List of Gram Positive Coccobacilli",{"slug":360,"name":361,"description":362,"image":42,"body":42,"postCount":326},"dimorphic-fungi","Dimorphic Fungi","This is about various dimorphic fungi. ",{"slug":364,"name":365,"description":366,"image":42,"body":42,"postCount":239},"bacterial-classification","Bacterial Classification","These posts are related with various approaches used for the classification of Bacteria. ",{"slug":368,"name":369,"description":370,"image":42,"body":42,"postCount":217},"immunofluorescence","Immunofluorescence ","Various Tests related to Immunofluorescence ",{"slug":372,"name":373,"description":374,"image":42,"body":42,"postCount":167},"antibody-mediated-immunity","Antibody-mediated Immunity","This clusters links the articles that are sharing insights about Antibody-mediated immunity. ",{"slug":376,"name":377,"description":378,"image":42,"body":42,"postCount":239},"hypersensitivity","Hypersensitivity","Articles related to Hypersensitivity.",{"slug":380,"name":381,"description":42,"image":42,"body":42,"postCount":382},"haemophilus","Haemophilus",3,{"slug":384,"name":385,"description":386,"image":42,"body":42,"postCount":326},"sexually-transmitted-infections-stis","Sexually transmitted infections (STIs)","This is the clusters of infections that are transmitted sexually. ",{"slug":388,"name":389,"description":390,"image":42,"body":42,"postCount":207},"adaptive-immunity","Adaptive Immunity","Blog posts related to B Cell Immunity and T Cell Immunity.",{"slug":392,"name":393,"description":394,"image":42,"body":42,"postCount":201},"fungal-diagnostics","Fungal Diagnostics","Various methods used for the Diagnosis of Fungal Infections. ",{"slug":396,"name":397,"description":398,"image":42,"body":42,"postCount":217},"laboratory-storage-and-preservation","Laboratory Storage and Preservation","Articles about Laboratory Storage of Antimicrobial Disk, Test organisms and Equipment used for this process. ",{"slug":400,"name":401,"description":402,"image":42,"body":403,"postCount":161},"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":405,"name":406,"description":407,"image":42,"body":42,"postCount":222},"laboratory-glassware","Laboratory Glassware","Posts about Laboratory Glassware. ",{"slug":409,"name":410,"description":411,"image":42,"body":42,"postCount":161},"helminths","Helminths","In this section, we are covering properties, life cycle, pathogenesis and laboratory diagnosis of Helminths\u002FHelminthic infestations. ",{"slug":413,"name":414,"description":415,"image":42,"body":42,"postCount":161},"protozoan-parasite","Protozoan Parasite","In this cluster, we are covering protozoan parasites. ",{"slug":417,"name":418,"description":419,"image":42,"body":42,"postCount":172},"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":421,"name":422,"description":423,"image":42,"body":42,"postCount":256},"bacterial-staining-technique","Bacterial Staining Technique","Lists of various staining techniques that are used to stain bacteria. ",{"slug":425,"name":426,"description":427,"image":42,"body":42,"postCount":156},"enzyme-tests","Enzyme Tests","\u003Cp>Various Biochemical Test that are based on enzymatic activity of the microorganisms. \u003C\u002Fp>",{"slug":429,"name":430,"description":431,"image":42,"body":42,"postCount":212},"carbohydrate-utilization","Carbohydrate Utilization","\u003Cp>Various biochemical tests which are related to Carbohydrate fermentation or Utilization\u003C\u002Fp>",{"slug":433,"name":434,"description":435,"image":42,"body":42,"postCount":217},"susceptibility-based-id","Susceptibility-based ID","\u003Cp>These are susceptibility based identification test such as optochin sensitivity, bacitracin sensitivity etc. \u003C\u002Fp>",{"slug":437,"name":438,"description":439,"image":42,"body":42,"postCount":326},"microbial-metabolism","Microbial Metabolism","\u003Cp>Tests about Microbial Metabolism. \u003C\u002Fp>",{"slug":441,"name":442,"description":443,"image":42,"body":42,"postCount":222},"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":445,"name":446,"description":447,"image":42,"body":42,"postCount":382},"atypical-pneumonia","Atypical Pneumonia","\u003Cp>Organisms responsible for Atypical Pneumonia. \u003C\u002Fp>",{"slug":449,"name":450,"description":451,"image":42,"body":42,"postCount":217},"antigen","Antigen","\u003Cp>Various articles related to Antigens.\u003C\u002Fp>",{"slug":453,"name":454,"description":455,"image":42,"body":42,"postCount":239},"innate-immunity","Innate Immunity","\u003Cp>Articles related to Innate Immunity. \u003C\u002Fp>",{"slug":457,"name":458,"description":459,"image":42,"body":42,"postCount":326},"respiratory-tract-infection","Respiratory Tract Infection","\u003Cp>In this cluster, you can see various etiological agents that causes respiratory tract infection. \u003C\u002Fp>",{"slug":461,"name":462,"description":463,"image":42,"body":42,"postCount":217},"torch-infection","TORCH Infection","\u003Cp>In this section; you can find articles related with TOCH infection. \u003C\u002Fp>",{"slug":465,"name":466,"description":467,"image":42,"body":42,"postCount":239},"microbiology-for-beginners","Microbiology for Beginners","\u003Cp>These articles are very basic articles, which will share general concepts in Microbiology. \u003C\u002Fp>",{"slug":469,"name":470,"description":471,"image":42,"body":42,"postCount":161},"dna-replication","DNA Replication","\u003Cp>Articles related to DNA and Replication of DNA. \u003C\u002Fp>",{"slug":473,"name":474,"description":475,"image":42,"body":42,"postCount":239},"genetic-code","Genetic Code","\u003Cp>Articles related to Genetic Code.\u003C\u002Fp>",{"slug":477,"name":478,"description":479,"image":42,"body":42,"postCount":217},"molecular-technique","Molecular Technique","\u003Cp>Posts related to Molecular Techniques. \u003C\u002Fp>",{"slug":481,"name":482,"description":42,"image":42,"body":42,"postCount":172},"colorimetric-assay","Colorimetric Assay ",{"slug":484,"name":485,"description":486,"image":42,"body":42,"postCount":217},"pharmaceutical-microbiology","Pharmaceutical Microbiology","\u003Cp>Various articles related to Pharmaceutical Microbiology\u003C\u002Fp>",{"slug":488,"name":489,"description":42,"image":42,"body":42,"postCount":382},"blood-and-immune-cells","Blood and Immune Cells"]