[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"$fxLN3MUwXCdr5RPjwZYIDpOj8CHyjOmngWTgoKXPtZbg":3,"$f_UUlESVYzkTAIvMOlNsIt9i-owhr-mSU5LQ-AyO3-Jo":36,"$f3Ft0rKFJHppdzE-vuveecxx1BUcg9iOlMLtyzf_MJDg":118,"$fucxFBm2ZjZfGSdmdRaSNGBI_F0jJme4f0GTvzUhQfL8":183},[4,8,12,16,20,24,28,32],{"title":5,"slug":6,"path":7},"About Microbeonline.com","about-microbeonline-com","\u002Fabout-microbeonline-com\u002F",{"title":9,"slug":10,"path":11},"About Me","about-me","\u002Fabout-microbeonline-com\u002Fabout-me\u002F",{"title":13,"slug":14,"path":15},"Advertise with Us","advertise-us","\u002Fadvertise-us\u002F",{"title":17,"slug":18,"path":19},"Privacy Policy","privacy-policy","\u002Fprivacy-policy\u002F",{"title":21,"slug":22,"path":23},"Authors","authors","\u002Fauthors\u002F",{"title":25,"slug":26,"path":27},"Microbes","microbes","\u002Fmicrobes\u002F",{"title":29,"slug":30,"path":31},"Books","recommended-books","\u002Frecommended-books\u002F",{"title":33,"slug":34,"path":35},"Tags","tags","\u002Ftags\u002F",{"type":37,"data":38},"blog",{"slug":39,"title":40,"description":41,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":44,"lastUpdatedDate":44,"draft":45,"category":46,"image":42,"body":47,"faq":48,"commentsClosed":45,"tags":64,"related":66,"comments":114},"chemiluminescence-immunoassay-clia-principle-procedure-interpretation","Chemiluminescence Immunoassay (CLIA): Principle, Procedure, and Interpretation","\u003Cp>How chemiluminescence immunoassay (CLIA) works, how it differs from ELISA and RIA, and how to read the result, including the cutoff index and why CLIA is more sensitive.\u003C\u002Fp>",null,"Acharya Tankeshwar","2026-08-31",false,"immunology","A serology lab that once ran an ELISA plate for hepatitis B surface antigen now gets the same result from an automated analyzer in under an hour, with a wider measuring range and no plate to wash. The method behind that shift is chemiluminescence, and understanding how it reports a result is what lets you trust the number it prints.\n\n## What a chemiluminescence immunoassay measures\n\nA chemiluminescence immunoassay is an immunoassay that detects an antigen or antibody using a label that emits light through a chemical reaction, rather than producing a color (as in [ELISA](https:\u002F\u002Fmicrobeonline.com\u002Felisa-principle-types-and-applications\u002F)) or radioactivity (as in [radioimmunoassay](https:\u002F\u002Fmicrobeonline.com\u002Fradioimmunoassay-principle-use-limitation\u002F)). The antibody-antigen binding step is the same idea used across immunoassays. What differs is the signal: the bound label triggers a chemical reaction that releases photons, and a luminometer measures the light emitted. The amount of light is proportional to the amount of analyte in the sample.\n\nBecause light emission can be measured over a very wide range and against almost no background, chemiluminescence gives the method its two defining strengths: high sensitivity and a broad dynamic range.\n\n## Why CLIA was developed: the problem it solves\n\nChemiluminescence immunoassay was developed to keep the sensitivity of radioimmunoassay while removing its central drawback. Radioimmunoassay is highly sensitive, but it uses radioactive labels, which require licensing, shielding, radioactive-waste disposal, and reagents with a short usable life. CLIA reaches comparable or better sensitivity using a chemiluminescent label, so it removes the radioactive hazard entirely. For that reason CLIA and related non-radioactive methods have largely replaced RIA in routine diagnostic laboratories. The full principle and limitations of the older method are on the radioimmunoassay page.\n\nAgainst ELISA, the gain is different. ELISA produces a color measured by absorbance, which works well but has a narrower measuring range and generally lower sensitivity than light-based detection. CLIA's light signal can be detected at very low analyte concentrations and across several orders of magnitude, which is why modern automated serology platforms moved from colorimetric ELISA readouts toward chemiluminescent ones.\n\n## How the light is produced: the detection chemistry\n\nThe defining step is how the label generates light. Two broad designs are in common use.\n\n1. **In a direct chemiluminescent label design**, the label itself (for example, an acridinium ester) is attached to the antibody. When a trigger reagent is added, the label undergoes a chemical reaction and emits a flash of light directly. The signal is read immediately.\n2. **In an enzyme-triggered design**, an enzyme label (for example, alkaline phosphatase or horseradish peroxidase) acts on a chemiluminescent substrate to produce light. This is the same enzyme-label idea used in ELISA, but the substrate produces light instead of color. When the enzyme is the same as in ELISA but the readout is light, the method is sometimes called a chemiluminescent enzyme immunoassay.\n\nA related variant, electrochemiluminescence immunoassay (ECLIA), generates light electrically at an electrode surface from a ruthenium label. It is widely used on large automated analyzers and follows the same interpretive logic as CLIA.\n\nIn every case, the sequence is the same: bind, wash away the unbound label, add the trigger, and measure the emitted light in relative light units (RLU).\n\n## CLIA versus ELISA\n\n| Feature | ELISA | CLIA |\n| --- | --- | --- |\n| Signal produced | Color (chromogenic product) | Light (photons from a chemical reaction) |\n| Detector | Spectrophotometer \u002F plate reader (absorbance) | Luminometer (relative light units) |\n| Label | Enzyme (e.g., HRP, alkaline phosphatase) acting on a chromogenic substrate | Direct chemiluminescent label (e.g., acridinium ester) or enzyme acting on a chemiluminescent substrate |\n| Sensitivity | Good | Higher; light is detectable at very low analyte levels |\n| Dynamic range | Narrower | Wider, spanning several orders of magnitude |\n| Solid phase | Usually microtiter plate wells | Often magnetic microparticles on automated analyzers |\n| Automation | Can be manual or automated | Typically fully automated, closed-system |\n| Speed | Slower (plate incubation and washing) | Faster, hands-off on analyzers |\n| Cost and setup | Lower capital cost | Higher; analyzer and often proprietary reagents |\n| Typical readout | Absorbance converted to concentration or cutoff | RLU converted to concentration or signal-to-cutoff ratio |\n\nBoth methods rely on the same antibody-antigen binding step; the difference is entirely in how the bound label is detected. That single change, from measuring color to measuring light, is what gives CLIA its higher sensitivity and wider measuring range, and it is why automated serology platforms have largely moved from colorimetric ELISA readouts to chemiluminescent ones.\n\n## Procedure and formats\n\n\u003Cfigure>\n\u003Cimg src=\"https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002Fclia-principle.jpg\" alt=\"Working Principle of CLIA\" width=\"4917\" height=\"1698\" draggable=\"false\" contenteditable=\"false\">\u003Cfigcaption>Figure: Working Principle of CLIA\u003C\u002Ffigcaption>\n\u003C\u002Ffigure>\n\nCLIA can be run in the same formats as other immunoassays, and the format determines how the RLU relates to the analyte.\n\n1. **In a sandwich (two-site) format**, used for larger antigens, the analyte is captured between a solid-phase antibody and a labeled antibody. More analyte means more label retained, so more light. The signal is directly proportional to the analyte concentration.\n2. **In a competitive format,** used for small analytes, labeled and unlabeled analyte compete for a limited amount of antibody. More analyte in the sample means less labeled analyte bound, so less light. The signal is inversely proportional to the analyte concentration. This inversion is a common source of misreading and is addressed in the interpretation section.\n\nOn automated analyzers, magnetic microparticles usually serve as the solid phase, which speeds up the binding and washing steps and is part of why CLIA platforms are fast and hands-off.\n\n## Interpretation\n\n**From RLU to a result.** The luminometer reports relative light units. RLU on its own is not a result; it is converted to a concentration against a calibration curve, or, for qualitative tests, compared to a cutoff.\n\n**The cutoff index (S\u002FCO).** Many qualitative CLIA tests report a signal-to-cutoff ratio, often written S\u002FCO or COI (cutoff index). The instrument divides the sample's signal by the assay's cutoff value. An S\u002FCO at or above 1.0 is reactive (positive); below 1.0 is non-reactive (negative). Values close to 1.0 fall in a grey zone that many assays flag for repeat or confirmatory testing. Reading the S\u002FCO, not the raw RLU, is what a student needs to do at the bench.\n\n**Direction of the signal depends on the format.** In a sandwich assay, high light means high analyte. In a competitive assay, high light means low analyte. Reading a competitive result as if it were a sandwich result inverts the answer. Always know which format the assay uses before interpreting the number.\n\n**High-dose hook effect.** At very high analyte concentrations, a sandwich assay can paradoxically give a falsely low signal, because excess analyte saturates both the capture and the labeled antibody separately and prevents the sandwich from forming. This is the hook effect, and it is the CLIA counterpart of the prozone problem in agglutination and nephelometry. If a result looks implausibly low for a patient who is clearly positive on other grounds, dilution and retest is the check.\n\n**Reactive does not mean disease.** As with any serological screen, a reactive CLIA result reflects the presence of the target antigen or antibody, not a final diagnosis. Reactive screening results are confirmed according to the relevant testing algorithm before they are reported as positive.\n\n## Limitations\n\nCLIA requires a dedicated luminometer or automated analyzer, so it is more capital-intensive than a basic ELISA reader. The reagents and closed-system cartridges are often proprietary to the analyzer, which raises running cost and ties a lab to a platform.\n\nLike all immunoassays, it is subject to interference from heterophile antibodies, biotin (in some designs), and sample handling errors, and to the hook effect at extreme concentrations. It reports the presence of an analyte, not a clinical diagnosis, so screening-positive results still need confirmation.\n\n## How to remember\n\nAnchor CLIA on the signal, because the signal is the whole difference from its two neighbors:\n\n- **RIA emits radiation, ELISA emits color, CLIA emits light.** Same binding idea, three different signals. CLIA keeps RIA's sensitivity without the radioactivity, and beats ELISA's range because light beats color for detection.\n- **Read the S\u002FCO, not the RLU.** RLU is raw light; S\u002FCO is the answer. At or above 1.0 is reactive.\n- **Format flips the direction.** Sandwich: more light, more analyte. Competitive: more light, less analyte.\n\n## Key exam facts\n\n| Fact | Detail |\n| --- | --- |\n| Signal type | Light (photons) from a chemical reaction, measured in relative light units (RLU) |\n| Label examples | Acridinium ester (direct); enzyme + chemiluminescent substrate (enzyme-triggered); ruthenium (ECLIA) |\n| Detector | Luminometer |\n| Versus RIA | Same or better sensitivity, no radioactive hazard; CLIA largely replaced RIA |\n| Versus ELISA | Higher sensitivity and wider dynamic range; light versus color |\n| Sandwich format | Signal directly proportional to analyte (large analytes) |\n| Competitive format | Signal inversely proportional to analyte (small analytes) |\n| Qualitative readout | Signal-to-cutoff ratio (S\u002FCO or COI); ≥1.0 reactive |\n| Key false-low trap | High-dose hook effect (dilute and retest) |\n| Result meaning | Presence of analyte, not a diagnosis; confirm per algorithm |\n\n## Where students get confused\n\n**\"CLIA and ELISA are basically the same test.\"** They share the antibody-antigen binding step and can use the same enzyme labels, but the readout is different: ELISA measures color by absorbance, CLIA measures light by luminometer. That difference is why CLIA is more sensitive and has a wider measuring range, and it is the reason to build a separate page rather than fold CLIA into ELISA.\n\n**\"A higher RLU always means more of the analyte.\"** Only in a sandwich format. In a competitive format, higher light means less analyte. The format decides the direction, so identify it before reading the number.\n\n**\"The raw RLU is the result.\"** It is not. For qualitative tests the result is the signal-to-cutoff ratio (S\u002FCO), and for quantitative tests it is the concentration read off the calibration curve. RLU is the raw light signal before that conversion.\n\n**\"A very low signal rules out disease.\"** Not at extreme concentrations. The high-dose hook effect can drive a sandwich assay's signal falsely low when analyte is very high. If the low result does not fit the clinical picture, dilute and retest.\n\n**\"CLIA is a confirmatory test.\"** It is usually a screening or quantitative assay. A reactive screen is confirmed per the testing algorithm before being reported as positive.\n\n## References\n\n1. Tille PM. *Bailey & Scott's Diagnostic Microbiology.* 15th ed. St. Louis: Elsevier; 2022.\n2. Procop GW, et al. *Koneman's Color Atlas and Textbook of Diagnostic Microbiology.* 7th ed. Philadelphia: Wolters Kluwer; 2017.\n3. Leber AL, editor. *Clinical Microbiology Procedures Handbook.* 4th ed. Washington, DC: ASM Press; 2016. doi:10.1128\u002F9781683670438.CMPH",[49,52,55,58,61],{"question":50,"answer":51},"\u003Cp>What is the difference between CLIA and ELISA?\u003C\u002Fp>","\u003Cp>Both use antibody-antigen binding, but they report the result differently. ELISA produces a color that is measured by absorbance, while CLIA produces light that is measured by a luminometer. Because light can be detected at very low levels and across a wide range, CLIA is generally more sensitive than ELISA and has a broader measuring range, which is why many automated serology platforms use it.\u003C\u002Fp>",{"question":53,"answer":54},"\u003Cp>Is CLIA more sensitive than ELISA?\u003C\u002Fp>","\u003Cp>Yes, in general. Light-based detection can be measured at lower analyte concentrations and over a wider dynamic range than the color-based detection used in ELISA, so CLIA typically offers higher sensitivity.\u003C\u002Fp>",{"question":56,"answer":57},"\u003Cp>What does the S\u002FCO or cutoff index mean in a CLIA result?\u003C\u002Fp>","\u003Cp>The signal-to-cutoff ratio (S\u002FCO), sometimes called the cutoff index, is the sample's signal divided by the assay's cutoff value. A value at or above 1.0 is reactive (positive), and below 1.0 is non-reactive (negative). Values near 1.0 often fall in a grey zone that is repeated or confirmed.\u003C\u002Fp>",{"question":59,"answer":60},"\u003Cp>Why did CLIA replace radioimmunoassay (RIA) in many labs?\u003C\u002Fp>","\u003Cp>CLIA offers similar or better sensitivity than RIA but uses a light-emitting label instead of a radioactive one. This removes the need for radioactive licensing, shielding, and waste disposal, and the reagents last longer, so CLIA and related non-radioactive methods have largely replaced RIA in routine diagnostics.\u003C\u002Fp>",{"question":62,"answer":63},"\u003Cp>What is the hook effect in CLIA?\u003C\u002Fp>","\u003Cp>At very high analyte concentrations, a sandwich-format assay can give a falsely low result because the excess analyte prevents the antibody sandwich from forming properly. This is the high-dose hook effect. If a low result does not match the clinical picture, the sample is diluted and retested.\u003C\u002Fp>",[65],"immunoassays",[67,89],{"slug":68,"title":69,"description":70,"seoTitle":71,"seoDescription":72,"author":43,"createdDate":73,"lastUpdatedDate":74,"draft":45,"category":46,"image":42,"faq":75,"tags":88},"elisa-principle-types-and-applications","ELISA Test: Principle, Types (Direct, Indirect, Sandwich, Competitive), Procedure, and Uses","ELISA (Enzyme-Linked Immunosorbent Assay) is the most widely used immunoassay for detecting antibodies and antigens. Learn all four ELISA types: direct, indirect, sandwich, and competitive. Explore step-by-step procedures, clinical applications (such as HIV, HBsAg, and dengue), and guidance on choosing the right type for your needs.","ELISA: Compare Four Types, Procedure, Results, and Applications","Compare direct, indirect, sandwich, and competitive ELISA formats, then review their reagents, procedures, result interpretation, and diagnostic uses.","2012-04-10","2026-08-21",[76,79,82,85],{"question":77,"answer":78},"Why is the indirect ELISA format used for HIV antibody detection rather than the direct or sandwich format?","\u003Cp>Indirect ELISA is the correct format for detecting patient antibodies (serology) because it uses a known antigen coated on the plate to capture the unknown antibody from patient serum, and then detects the captured antibody using a secondary enzyme-labeled anti-human IgG antibody.\u003C\u002Fp>\u003Cp>\u003C\u002Fp>\u003Cp>For HIV screening, the plate wells are coated with HIV antigens (HIV-1 and HIV-2 proteins) when patient serum contains anti-HIV antibodies, they bind to the plate-coated antigens. The enzyme-labeled anti-human IgG secondary antibody then binds to the captured human antibodies and generates the color signal. \u003C\u002Fp>\u003Cp>\u003C\u002Fp>\u003Cp>Direct ELISA would be inappropriate because the patient's own antibody cannot be enzyme-labeled, it is the unknown component being detected. \u003C\u002Fp>\u003Cp>\u003C\u002Fp>\u003Cp>Sandwich ELISA would be inappropriate because it detects antigens by capturing them between two antibodies, whereas HIV serology aims to detect the patient's antibody response. \u003C\u002Fp>\u003Cp>\u003C\u002Fp>\u003Cp>The indirect ELISA format has an additional advantage for clinical serology: the same enzyme-labeled anti-human IgG secondary antibody can be used for any antigen-antibody system, reducing the need to produce a separate enzyme-labeled antibody for every pathogen tested.\u003C\u002Fp>",{"question":80,"answer":81},"What is the hook effect in sandwich ELISA and how can it cause a false negative?","The hook effect is a false negative that happens in sandwich ELISA when antigen is so abundant it saturates the capture and detector antibodies separately, so most antigen molecules bind only one antibody and the sandwich bridge never forms. The signal drops even though the sample is loaded with antigen. It is suspected when a patient with strong clinical features has an unexpectedly low or negative result (classically very active hepatitis B with high HBsAg, or tumor markers at very high levels). The fix is to dilute the sample and retest, which breaks the antigen excess and restores the sandwich. This is one of two opposite false negatives in ELISA; for how it contrasts with the window-period false negative in indirect ELISA, see \"Where Students Get Confused\" above.",{"question":83,"answer":84},"How do 3rd-generation and 4th-generation HIV ELISA kits differ, and what is the clinical significance?","Third-generation HIV ELISA kits detect anti-HIV IgG and IgM antibodies only, using an indirect or capture ELISA format. They cannot detect HIV p24 antigen. Their window period is approximately 22–28 days from infection to detection. Fourth-generation HIV combination ELISA kits simultaneously detect both anti-HIV antibodies (using the indirect ELISA component) AND HIV p24 antigen (using the sandwich ELISA component) in a single well. Because p24 antigen appears in blood 10–12 days after infection — well before antibodies develop — 4th-generation combo tests have a window period of approximately 15–20 days, reducing the false-negative window by approximately 7–10 days compared to 3rd-generation tests. This seemingly small reduction has significant public health implications: people tested during early acute HIV infection (when viral loads are highest and infectivity is greatest) are more likely to receive a true-positive result with 4th-generation testing, allowing earlier diagnosis, treatment initiation, and prevention of onward transmission. Current WHO and national guidelines in most countries recommend 4th-generation combo tests as the standard for HIV diagnosis wherever available.",{"question":86,"answer":87},"Does \"direct ELISA\" mean it detects antigen and \"indirect ELISA\" mean it detects antibody?","No, and this is a common misunderstanding. The words direct and indirect describe how the enzyme label reaches the target, not whether an antigen or an antibody is being detected. In direct ELISA the enzyme is attached to the primary antibody that binds the target. In indirect ELISA the enzyme is on a secondary antibody that binds the primary antibody, adding an amplification step. It is true that in clinical practice indirect ELISA is used mainly to detect patient antibodies (serology) and sandwich ELISA to detect patient antigens, but that is a matter of how each format is applied, not what the prefixes direct and indirect mean. To decide what a given ELISA detects, look at what is coated on the plate and what unknown is being captured from the sample.",[65],{"slug":90,"title":91,"description":92,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":93,"lastUpdatedDate":44,"draft":45,"category":46,"image":42,"faq":94,"tags":113},"radioimmunoassay-principle-use-limitation","Radioimmunoassay (RIA): The Competitive Principle (More Antigen, Less Signal)","How radioimmunoassay measures tiny amounts of antigen: labeled and unlabeled antigen compete for limited antibody, so the radioactive signal falls as the sample's antigen rises. Principle, procedure, RIA vs ELISA, and limitations.","2020-06-11",[95,98,101,104,107,110],{"question":96,"answer":97},"What is the principle of radioimmunoassay?","RIA is based on competition. A fixed, limited amount of antibody is offered both a fixed amount of radiolabeled antigen and the unknown unlabeled antigen from the sample. The two compete for the antibody, and the amount of labeled antigen that ends up bound is measured as radioactivity.",{"question":99,"answer":100},"Why does more antigen give a lower signal in RIA?","Because the patient's unlabeled antigen competes the labeled antigen away from the limited antibody sites. The more antigen in the sample, the less labeled antigen stays bound, so the bound radioactivity falls. The signal is inversely proportional to the antigen concentration.",{"question":102,"answer":103},"Which radioisotopes are used in RIA?","Most commonly iodine-125, and sometimes tritium (3H). The isotope labels the reagent antigen, and its radioactivity is measured with a gamma or scintillation counter.",{"question":105,"answer":106},"What is the difference between RIA and ELISA?","Both use the same competitive principle, but RIA uses a radioactive label read as radioactivity, while ELISA uses an enzyme label read as a color change. ELISA has replaced RIA in most routine laboratories because it avoids radiation hazard while giving comparable sensitivity.",{"question":108,"answer":109},"What is the difference between RIA and IRMA?","RIA is competitive and uses a labeled antigen, so the signal is inversely proportional to the antigen concentration. IRMA is non-competitive and uses a labeled antibody to sandwich the antigen, so its signal is directly proportional to the antigen concentration.",{"question":111,"answer":112},"Why has RIA been largely replaced?","Because of the hazards and inconvenience of radioactivity: safety precautions, licensing, radioactive waste disposal, and short reagent shelf life. ELISA and other non-radioactive assays match its performance without these problems.",[65],{"enabled":115,"threads":116,"total":117},true,[],0,[119,125,132,139,145,150,156,161,167,170,177],{"slug":120,"name":43,"description":121,"image":122,"body":123,"postCount":124},"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.*",489,{"slug":126,"name":127,"description":128,"image":129,"body":130,"postCount":131},"ashma-shrestha","Ashma Shrestha","SEO Copywriter and Science Communicator\nKathmandu, Nepal","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Fashma-shrestha.png","Ashma Shrestha holds a Master of Science in Medical Microbiology from the Institute of Science and Technology (IOST), Tribhuvan University, Nepal, where she developed a strong foundation in virology, molecular biology, and diagnostic microbiology.\n\nShe now works as an SEO Copywriter at Resolution Digital, where she combines her scientific training with research-driven content strategy. She is certified in Google Analytics and Google Business Profile (GBP), and brings a data-informed approach to science communication writing content that is not only accurate but structured to reach and serve the students who need it most.\n\nAt microbeonline, Ashma contributes articles primarily in virology and molecular biology, areas she finds most compelling for their mechanistic depth and their growing clinical relevance. Her writing reflects the same standard the site is built on: factual rigor, clear explanation of the *why* behind microbiology concepts, and content that helps students move from memorization to genuine understanding.\n\nShe is passionate about making complex microbiological concepts accessible without sacrificing accuracy; a skill that sits at the intersection of her scientific training and her professional work in content and SEO.",79,{"slug":133,"name":134,"description":135,"image":136,"body":137,"postCount":138},"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":140,"name":141,"description":135,"image":142,"body":143,"postCount":144},"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":146,"name":147,"description":135,"image":42,"body":148,"postCount":149},"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":151,"name":152,"description":153,"image":42,"body":154,"postCount":155},"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":157,"name":158,"description":159,"image":42,"body":42,"postCount":160},"guest-author","Guest Author","Guest Author \u002F Contributor",1,{"slug":162,"name":163,"description":135,"image":164,"body":165,"postCount":166},"srijana-khanal","Srijana Khanal","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Fsrijana-khanal-1.png","Srijana Khanal is a microbiology educator with nearly a decade of teaching experience, including her role as faculty in the Microbiology Department at National College, NIST. \n\nHer time in the classroom has given her a clear sense of where students struggle and what explanations actually work, a perspective that directly shapes how she writes.\n\nHer academic interests span Immunology, Genetics, Basic Sciences, and Research Methodology, and she brings the same rigor to her writing that she brought to teaching. Alongside academic writing, she has a passion for creative writing -- an instinct that shows in her ability to make dense scientific material readable without sacrificing accuracy.\n\nShe contributes to Microbeonline to extend her teaching reach beyond the classroom, helping medical and laboratory science students across the region build a stronger foundation in microbiology.",15,{"slug":168,"name":169,"description":159,"image":42,"body":42,"postCount":160},"dr-poonam-acharya","Dr. Poonam Acharya",{"slug":171,"name":172,"description":173,"image":174,"body":175,"postCount":176},"nisha-rijal","Nisha Rijal","Microbiologist and AMR Specialist Kathmandu, Nepal","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Fnisha-rijal-1.png","Nisha Rijal is a microbiologist with nearly 15 years of frontline diagnostic and surveillance experience at the National Public Health Laboratory (NPHL), national reference laboratory under the Department of Health Services, Nepal. She currently works as an AMR Support Officer at the World Health Organization (WHO), Nepal, where her work focuses on strengthening antimicrobial resistance surveillance systems and translating AMR data into actionable public health response.\n\nHer research, published in peer-reviewed journals and cited over 220 times, spans some of the most clinically significant infectious disease challenges in Nepal and South Asia: antimicrobial resistance trends in *Vibrio cholerae* across an 11-year national surveillance dataset, sero-epidemiology of scrub typhus in patients with acute febrile illness, lower respiratory tract infections in HIV-positive patients, and gonococcal resistance surveillance. She was a contributor to Nepal's National Antimicrobial Resistance Containment Action Plan, a foundational policy document for AMR governance in Nepal. You can find list of [Nisha Rijal's article here in Google Scholar.](https:\u002F\u002Fscholar.google.com\u002Fcitations?user=N-Ruq54AAAAJ&hl=en)\n\nThis depth of experience is visible in her writing at Microbeonline. Her 53 published articles cover bacteriology, parasitology, mycology, immunology, and laboratory techniques, and are consistently among the most detailed and clinically grounded content on the site. She brings to every article the same standard that national reference laboratory work demands: methodological precision, awareness of real diagnostic constraints, and an understanding of what results actually mean for patient care in resource-limited settings.\n\nHer areas of particular expertise include antimicrobial susceptibility testing and resistance mechanism detection, quality assurance in clinical microbiology, and laboratory-based infectious disease surveillance.\n\n---\n\n*Nisha Rijal contributes to Microbeonline in a personal capacity. Her views and writing do not represent the positions of the World Health Organization or any other institution.*",54,{"slug":178,"name":179,"description":180,"image":181,"body":182,"postCount":160},"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.",[184,191,197,202,207,212,216,220,224,229,233,238,242,247,252,256,260,264,269,274,278,282,286,289,293,297,301,305,310,315,319,323,327,332,336,340,344,348,352,356,360,364,368,372,376,380,384,388,393,397,401,405,409,413,417,421,425,429,433,437,441,445,449,453,457,461,465,469,472,476,479,482,485,488,491,494,497,500,503,506,509,512,515],{"slug":185,"name":186,"description":187,"image":188,"body":189,"postCount":190},"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":192,"name":193,"description":194,"image":42,"body":195,"postCount":196},"microscopy","Microscopy","Microscope types, components, and microscopy techniques","These are list of blog posts related to microscopy. ",12,{"slug":198,"name":199,"description":200,"image":42,"body":42,"postCount":201},"gram-positive-cocci","Gram-Positive Cocci","Staphylococcus, Streptococcus, Enterococcus, Micrococcus — organisms, diseases, and identification tests",11,{"slug":203,"name":204,"description":205,"image":42,"body":42,"postCount":206},"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":208,"name":209,"description":210,"image":42,"body":42,"postCount":211},"gram-positive-rods","Gram-Positive Rods","Bacillus, Clostridium, Listeria, Corynebacterium, Actinomyces and related organisms",8,{"slug":213,"name":214,"description":215,"image":42,"body":42,"postCount":196},"mycobacteria","Mycobacteria","Mycobacterium tuberculosis, leprosy, atypical mycobacteria, and acid-fast organism diagnosis",{"slug":217,"name":218,"description":219,"image":42,"body":42,"postCount":196},"anaerobic-bacteriology","Anaerobic Bacteriology","Anaerobic organisms, anaerobic culture methods, and anaerobic infection diagnosis",{"slug":221,"name":222,"description":223,"image":42,"body":42,"postCount":196},"enterobacteriaceae","Enterobacteriaceae","Identification, differentiation, and clinical significance of Enterobacteriaceae family members",{"slug":225,"name":226,"description":227,"image":42,"body":42,"postCount":228},"spirochetes","Spirochetes","Treponema, Leptospira, Borrelia and spirochetal infections",7,{"slug":230,"name":231,"description":232,"image":42,"body":42,"postCount":190},"food-microbiology","Food Microbiology","Food-borne pathogens, food safety, spoilage, and preservation",{"slug":234,"name":235,"description":236,"image":42,"body":42,"postCount":237},"antimicrobial-susceptibility-testing","Antimicrobial Susceptibility Testing","Methods for testing antibiotic susceptibility in clinical microbiology",21,{"slug":239,"name":240,"description":241,"image":42,"body":42,"postCount":190},"antimicrobials-moa-amr","Antimicrobials (MOA & AMR)","Mechanisms, detection, and clinical significance of antimicrobial resistance",{"slug":243,"name":244,"description":245,"image":42,"body":42,"postCount":246},"sterilization-disinfection","Sterilization and Disinfection","Methods of sterilization and disinfection in healthcare and laboratory settings",10,{"slug":248,"name":249,"description":250,"image":42,"body":42,"postCount":251},"specimen-collection-transport","Specimen Collection and Transport","Collection, handling, and transport of clinical specimens for microbiological testing",27,{"slug":253,"name":254,"description":255,"image":42,"body":42,"postCount":237},"bacterial-structure-physiology","Bacterial Structure and Physiology","Bacterial cell structure, growth, physiology, and environmental factors affecting growth",{"slug":257,"name":258,"description":42,"image":42,"body":259,"postCount":149},"horizontal-gene-transfer","Horizontal Gene Transfer","Articles related to **Horizontal Gene Transfer**",{"slug":261,"name":262,"description":42,"image":42,"body":263,"postCount":246},"chromatography","Chromatography","Information about chromatographic techniques.",{"slug":265,"name":266,"description":267,"image":42,"body":268,"postCount":228},"electrophoresis","Electrophoresis","Information about Electrophoresis Techniques ","Detailed information  about Electrophoresis Techniques ",{"slug":270,"name":271,"description":272,"image":42,"body":273,"postCount":149},"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":275,"name":276,"description":277,"image":42,"body":42,"postCount":149},"bacteriophage","Bacteriophage","Description about Bacteriophage.",{"slug":279,"name":280,"description":281,"image":42,"body":42,"postCount":149},"malaria","Malaria","It is the collections of articles regarding malarial disease. ",{"slug":283,"name":284,"description":285,"image":42,"body":42,"postCount":149},"anaerobic-culture-techniques","Anaerobic Culture Techniques","Posts related with Anaerobic Culture Techniques.",{"slug":65,"name":287,"description":288,"image":42,"body":42,"postCount":144},"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.",{"slug":290,"name":291,"description":292,"image":42,"body":42,"postCount":228},"biosafety-levels","Biosafety levels ","Articles related to Biosafety Levels",{"slug":294,"name":295,"description":296,"image":42,"body":42,"postCount":206},"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":298,"name":299,"description":300,"image":42,"body":42,"postCount":149},"pipette","Pipette","Posts related with Pipette. ",{"slug":302,"name":303,"description":304,"image":42,"body":42,"postCount":228},"bacteriology-mcqs","Bacteriology MCQs","This sections lists MCQs in Bacteriology.",{"slug":306,"name":307,"description":308,"image":42,"body":42,"postCount":309},"parasitology-mcqs","Parasitology MCQs","This section lists MCQs in Parasitology.",2,{"slug":311,"name":312,"description":313,"image":42,"body":42,"postCount":314},"virology-mcqs","Virology MCQs","This is the collections of Multiple Choice Questions in Virology.",4,{"slug":316,"name":317,"description":318,"image":42,"body":42,"postCount":206},"mcqs-in-microbiology","MCQs in Microbiology","This section lists the collections of Multiple Choice Questions in General Microbiology Topics. ",{"slug":320,"name":321,"description":322,"image":42,"body":42,"postCount":228},"immunology-mcqs","Immunology MCQs","In this section; we are posting collections of Multiple Choice Questions about Immunology. ",{"slug":324,"name":325,"description":326,"image":42,"body":42,"postCount":246},"microbial-curiosities","Microbial Curiosities","In this clusters, we are posting interesting and unique information about Microorganisms. ",{"slug":328,"name":329,"description":330,"image":42,"body":42,"postCount":331},"bacterial-culture-media","Bacterial Culture Media","Posts related to Bacterial Culture Media. ",23,{"slug":333,"name":334,"description":335,"image":42,"body":42,"postCount":149},"fungal-culture-media","Fungal Culture Media","Posts related to Fungal Culture Media.",{"slug":337,"name":338,"description":339,"image":42,"body":42,"postCount":206},"motility-test","Motility Test","This lists the procedure regarding various tests methods for bacterial motility.",{"slug":341,"name":342,"description":343,"image":42,"body":42,"postCount":246},"bacterial-enumeration","Bacterial enumeration","These posts are related to isolation and enumeration of bacteria. ",{"slug":345,"name":346,"description":347,"image":42,"body":42,"postCount":309},"gram-positive-coccobacillus","Gram-positive coccobacillus","List of Gram Positive Coccobacilli",{"slug":349,"name":350,"description":351,"image":42,"body":42,"postCount":314},"dimorphic-fungi","Dimorphic Fungi","This is about various dimorphic fungi. ",{"slug":353,"name":354,"description":355,"image":42,"body":42,"postCount":228},"bacterial-classification","Bacterial Classification","These posts are related with various approaches used for the classification of Bacteria. ",{"slug":357,"name":358,"description":359,"image":42,"body":42,"postCount":206},"immunofluorescence","Immunofluorescence ","Various Tests related to Immunofluorescence ",{"slug":361,"name":362,"description":363,"image":42,"body":42,"postCount":155},"antibody-mediated-immunity","Antibody-mediated Immunity","This clusters links the articles that are sharing insights about Antibody-mediated immunity. ",{"slug":365,"name":366,"description":367,"image":42,"body":42,"postCount":228},"hypersensitivity","Hypersensitivity","Articles related to Hypersensitivity.",{"slug":369,"name":370,"description":42,"image":42,"body":42,"postCount":371},"haemophilus","Haemophilus",3,{"slug":373,"name":374,"description":375,"image":42,"body":42,"postCount":314},"sexually-transmitted-infections-stis","Sexually transmitted infections (STIs)","This is the clusters of infections that are transmitted sexually. ",{"slug":377,"name":378,"description":379,"image":42,"body":42,"postCount":196},"adaptive-immunity","Adaptive Immunity","Blog posts related to B Cell Immunity and T Cell Immunity.",{"slug":381,"name":382,"description":383,"image":42,"body":42,"postCount":190},"fungal-diagnostics","Fungal Diagnostics","Various methods used for the Diagnosis of Fungal Infections. ",{"slug":385,"name":386,"description":387,"image":42,"body":42,"postCount":206},"laboratory-storage-and-preservation","Laboratory Storage and Preservation","Articles about Laboratory Storage of Antimicrobial Disk, Test organisms and Equipment used for this process. ",{"slug":389,"name":390,"description":391,"image":42,"body":392,"postCount":149},"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":394,"name":395,"description":396,"image":42,"body":42,"postCount":155},"laboratory-glassware","Laboratory Glassware","Posts about Laboratory Glassware. ",{"slug":398,"name":399,"description":400,"image":42,"body":42,"postCount":155},"helminths","Helminths","In this section, we are covering properties, life cycle, pathogenesis and laboratory diagnosis of Helminths\u002FHelminthic infestations. ",{"slug":402,"name":403,"description":404,"image":42,"body":42,"postCount":211},"protozoan-parasite","Protozoan Parasite","In this cluster, we are covering protozoan parasites. ",{"slug":406,"name":407,"description":408,"image":42,"body":42,"postCount":160},"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":410,"name":411,"description":412,"image":42,"body":42,"postCount":246},"bacterial-staining-technique","Bacterial Staining Technique","Lists of various staining techniques that are used to stain bacteria. ",{"slug":414,"name":415,"description":416,"image":42,"body":42,"postCount":237},"enzyme-tests","Enzyme Tests","\u003Cp>Various Biochemical Test that are based on enzymatic activity of the microorganisms. \u003C\u002Fp>",{"slug":418,"name":419,"description":420,"image":42,"body":42,"postCount":201},"carbohydrate-utilization","Carbohydrate Utilization","\u003Cp>Various biochemical tests which are related to Carbohydrate fermentation or Utilization\u003C\u002Fp>",{"slug":422,"name":423,"description":424,"image":42,"body":42,"postCount":206},"susceptibility-based-id","Susceptibility-based ID","\u003Cp>These are susceptibility based identification test such as optochin sensitivity, bacitracin sensitivity etc. \u003C\u002Fp>",{"slug":426,"name":427,"description":428,"image":42,"body":42,"postCount":314},"microbial-metabolism","Microbial Metabolism","\u003Cp>Tests about Microbial Metabolism. \u003C\u002Fp>",{"slug":430,"name":431,"description":432,"image":42,"body":42,"postCount":211},"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":434,"name":435,"description":436,"image":42,"body":42,"postCount":371},"atypical-pneumonia","Atypical Pneumonia","\u003Cp>Organisms responsible for Atypical Pneumonia. \u003C\u002Fp>",{"slug":438,"name":439,"description":440,"image":42,"body":42,"postCount":206},"antigen","Antigen","\u003Cp>Various articles related to Antigens.\u003C\u002Fp>",{"slug":442,"name":443,"description":444,"image":42,"body":42,"postCount":228},"innate-immunity","Innate Immunity","\u003Cp>Articles related to Innate Immunity. \u003C\u002Fp>",{"slug":446,"name":447,"description":448,"image":42,"body":42,"postCount":314},"respiratory-tract-infection","Respiratory Tract Infection","\u003Cp>In this cluster, you can see various etiological agents that causes respiratory tract infection. \u003C\u002Fp>",{"slug":450,"name":451,"description":452,"image":42,"body":42,"postCount":206},"torch-infection","TORCH Infection","\u003Cp>In this section; you can find articles related with TOCH infection. \u003C\u002Fp>",{"slug":454,"name":455,"description":456,"image":42,"body":42,"postCount":211},"microbiology-for-beginners","Microbiology for Beginners","\u003Cp>These articles are very basic articles, which will share general concepts in Microbiology. \u003C\u002Fp>",{"slug":458,"name":459,"description":460,"image":42,"body":42,"postCount":149},"dna-replication","DNA Replication","\u003Cp>Articles related to DNA and Replication of DNA. \u003C\u002Fp>",{"slug":462,"name":463,"description":464,"image":42,"body":42,"postCount":228},"genetic-code","Genetic Code","\u003Cp>Articles related to Genetic Code.\u003C\u002Fp>",{"slug":466,"name":467,"description":468,"image":42,"body":42,"postCount":228},"molecular-technique","Molecular Technique","\u003Cp>Posts related to Molecular Techniques. \u003C\u002Fp>",{"slug":470,"name":471,"description":42,"image":42,"body":42,"postCount":160},"colorimetric-assay","Colorimetric Assay ",{"slug":473,"name":474,"description":475,"image":42,"body":42,"postCount":206},"pharmaceutical-microbiology","Pharmaceutical Microbiology","\u003Cp>Various articles related to Pharmaceutical Microbiology\u003C\u002Fp>",{"slug":477,"name":478,"description":42,"image":42,"body":42,"postCount":371},"blood-and-immune-cells","Blood and Immune Cells",{"slug":480,"name":481,"description":42,"image":42,"body":42,"postCount":206},"host-pathogen-interaction","Host Pathogen Interaction",{"slug":483,"name":484,"description":42,"image":42,"body":42,"postCount":314},"blood-culture","Blood Culture",{"slug":486,"name":487,"description":42,"image":42,"body":42,"postCount":314},"environmental-microbiology","Environmental microbiology ",{"slug":489,"name":490,"description":42,"image":42,"body":42,"postCount":228},"copromicroscopic-technique","Copromicroscopic Technique",{"slug":492,"name":493,"description":42,"image":42,"body":42,"postCount":371},"quality-control","Quality Control",{"slug":495,"name":496,"description":42,"image":42,"body":42,"postCount":228},"dermatophytes","Dermatophytes",{"slug":498,"name":499,"description":42,"image":42,"body":42,"postCount":371},"viral-hemorrhagic-fevers","Viral Hemorrhagic Fevers",{"slug":501,"name":502,"description":42,"image":42,"body":42,"postCount":314},"h2s-production","H2S Production",{"slug":504,"name":505,"description":42,"image":42,"body":42,"postCount":309},"water-quality-testing","Water Quality Testing",{"slug":507,"name":508,"description":42,"image":42,"body":42,"postCount":206},"virology-basics","Virology basics",{"slug":510,"name":511,"description":42,"image":42,"body":42,"postCount":314},"typing-methods","Typing Methods",{"slug":513,"name":514,"description":42,"image":42,"body":42,"postCount":371},"blotting-technique","Blotting Technique",{"slug":516,"name":517,"description":42,"image":42,"body":42,"postCount":314},"history-microbiology","History of Microbiology"]