[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"$fxLN3MUwXCdr5RPjwZYIDpOj8CHyjOmngWTgoKXPtZbg":3,"$fIHhpmq5lhuPR9R0zBCwtd0Lpe8hgVG-apDe6Un59_eY":36,"$f3Ft0rKFJHppdzE-vuveecxx1BUcg9iOlMLtyzf_MJDg":159,"$fucxFBm2ZjZfGSdmdRaSNGBI_F0jJme4f0GTvzUhQfL8":224},[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":45,"draft":46,"category":47,"image":42,"body":48,"faq":49,"commentsClosed":46,"tags":50,"related":52,"comments":155},"stokes-disc-diffusion-method-principle-procedure-interpretation-results","Stokes Disc Diffusion Method: Why the Control Shares the Plate","Stokes disc diffusion runs a susceptible control strain on the same plate as the test isolate, so weak discs or off media distort both zones equally and the comparison still holds.",null,"Acharya Tankeshwar","2014-12-28","2026-07-29",false,"bacteriology","A rural laboratory receives a shipment of antibiotic discs that has spent three days in transit through the summer heat, with no guarantee the cold chain held. The discs may have lost potency, and there is no way to be sure. Running a standard [Kirby-Bauer technique](\u002Fantimicrobial-susceptibility-testing-procedure-modified-kirby-bauer-method\u002F) would compare each zone against a fixed millimeter chart that assumes the disc delivers its full stated potency. If the discs are weak, every isolate could read as falsely resistant, and the lab would never know.\n\nThe Stokes method solves exactly this problem. Instead of trusting the disc and comparing to a chart, it runs a known, fully susceptible control organism on the same plate as the patient's isolate, under the identical disc, medium, and incubation. If the disc has lost potency, the control's zone shrinks too, and the comparison stays valid because both zones moved together.\n\nThe test does not ask \"how big is the zone against a standard,\" it asks \"how does this isolate compare to a known susceptible strain that faced the same conditions.\" That single design choice is why Stokes remains in wide use wherever disc quality, media lots, or storage conditions cannot be tightly guaranteed.\n\n## Why This Matters\n\nKirby-Bauer is the more standardized method and the one most guidelines are written around, but it depends on every variable being tightly controlled: disc potency, agar depth, inoculum density, and incubation temperature all have to be within narrow limits, because the zone is read against a fixed breakpoint chart. When any of those cannot be guaranteed, the chart's assumptions break and the result becomes unreliable.\n\nStokes builds the control into the plate itself. Because the reference strain and the test strain sit on the same plate and face identical conditions, any drift in disc potency, media quality, incubation temperature, or atmosphere affects both equally. The comparison between the two zones stays meaningful even when the absolute zone sizes would not. This is why comparative disc diffusion based on the Stokes method has remained in wide use in the United Kingdom and in many resource-limited laboratories, where reliably storing and standardizing discs is not always possible. The trade-off is throughput: a Stokes plate tests one or two antibiotics against one isolate plus its control, where a Kirby-Bauer plate can carry many discs for a single isolate.\n\n## Principle\n\nThe Stokes method is a comparative disc diffusion technique. A known control organism of the same or a similar species as the test isolate is inoculated on the same plate as the test organism, and both are exposed to the same antimicrobial disc under identical technical conditions of medium, inoculum, incubation time, atmosphere, and temperature.\n\nBecause the control and test organisms grow adjacent to each other on one plate, the difference between their zone sizes can be measured directly. The control strain is a fully susceptible reference, so its zone represents what a susceptible organism looks like under that day's exact conditions. The test isolate is then classified by how its zone compares to the control's, rather than against a fixed millimeter value from a chart. Any variable that would distort a Kirby-Bauer reading, a weak disc, a thin plate, a warm incubator, distorts both zones equally and therefore cancels out of the comparison.\n\n## Conventional vs Modified Stokes: Which Strain Goes in the Middle\n\nThere are two layouts, and the difference is simply which organism occupies the center of the plate. This is a common point of confusion.\n\n|  | Conventional Stokes | Modified Stokes |\n| --- | --- | --- |\n| Center of plate | Test organism | Control organism |\n| Outer thirds | Control organism | Test organism |\n| Reading | Compare the central test zone to the outer control zones | Compare the outer test zones to the central control zone |\n\n![Stokes disc diffusion method](\u002Fblogs\u002FSchematic-diagram-showing-Stokes-disc-diffusion-method.jpg)Both give the same kind of comparison; only the physical arrangement differs. The layout described in the procedure below is the modified Stokes method (control in the center), which is the more commonly used version.\n\n## Procedure\n\n### Preparing the inoculum\n\n1. Select at least three to five well-isolated colonies of the same morphological type from both the test and the control cultures. Touch the top of each colony with a loop and transfer the growth into a tube containing 4 to 5 mL of a suitable broth, such as tryptic soy broth.\n2. Incubate the broth cultures at 37°C until the turbidity reaches or exceeds that of a [0.5 McFarland standard](\u002Fpreparation-mcfarland-turbidity-standards\u002F)  (usually 2 to 6 hours).\n3. Adjust the turbidity of each actively growing broth culture with sterile saline or broth so it is optically comparable to a 0.5 McFarland standard. This corresponds to approximately 1 to 2 x 10⁸ CFU\u002FmL for *Escherichia coli* ATCC 25922. Use a photometric device, or visually compare each tube against the 0.5 McFarland standard using a card with a white background and contrasting black lines under adequate light.\n4. Within 15 minutes of adjusting the turbidity, dip a sterile cotton swab into each suspension, rotate it several times, and press it firmly against the inside wall of the tube above the fluid level to remove excess inoculum.\n\n### Inoculating and applying discs\n\n5. Divide a dried Mueller-Hinton agar plate into three sections in your mind: two outer thirds and a central third.\n6. Inoculate the control strain evenly across the central third of the plate (modified Stokes layout). Inoculate the test strain across the upper and lower thirds, leaving a gap of not more than 5 mm between the test and control areas on each side.\n7. Allow the inocula to dry for a few minutes with the lid on.\n8. Place each antimicrobial disc in the gap between the test and control areas, using sterile forceps, and press gently to ensure full contact with the agar. The disc sits at the boundary so that its zone extends into both the test and the control lawns.\n9. Within 30 minutes of applying the discs, incubate the plates aerobically at 35°C for 18 to 24 hours.\n\nNote: extremes in inoculum density must be avoided. Never use undiluted overnight broth cultures or other unstandardized inocula for streaking plates, as an inoculum that is too heavy or too light will distort the zones.\n\n## Interpretation of Results\n\nMeasure the radius of each zone of inhibition, from the edge of the disc to the edge of the zone, for both the test and the control. Then compare the test radius to the control radius.\n\n| Category | Criterion |\n| --- | --- |\n| Sensitive (S) | Test zone radius is equal to, wider than, or not more than 3 mm smaller than the control zone radius |\n| Intermediate (I) | Test zone radius is more than 2 mm, but smaller than the control by more than 3 mm |\n| Resistant (R) | No zone of inhibition, or test zone radius is 2 mm or less |\n\nThe logic is that a truly susceptible isolate should produce a zone close to the fully susceptible control's zone. A meaningfully smaller zone signals reduced susceptibility, and little or no zone signals resistance. Because the comparison is against the control on the same plate, the reading holds even if that day's discs or media were not perfectly standard.\n\n## Advantages of the Stokes Method\n\nThe strengths of Stokes all follow from having the control on the same plate:\n\n1. The control and test strains are read on the same plate, under identical conditions, so the comparison is direct.\n2. It is more reliable when disc quality cannot be guaranteed, because a weak disc shrinks the control zone too and is immediately obvious.\n3. Variation in environmental conditions such as temperature, incubation time, or atmosphere affects the control and test simultaneously, minimizing error.\n4. Errors from an inoculum that is too heavy or too light tend to show up in the control as well, flagging the problem rather than silently producing a wrong result.\n\n## How to Remember\n\nThe whole method collapses to one idea: **the control shares the plate, so every error is shared too.** If the disc is weak, the media is off, or the incubator drifts, the control zone changes right alongside the test zone, and the comparison survives. That is the entire reason Stokes exists.\n\nFor the two layouts: in **conventional** Stokes the **test** organism takes the **center**; in **modified** Stokes the **control** takes the center. A way to hold it: \"modified moves the control to the middle.\"\n\nOne sentence that captures it: Kirby-Bauer trusts the disc and reads against a chart; Stokes trusts nothing and reads against a control that faced the same day, which is why it holds up where standardization cannot be guaranteed.\n\n## Key exam facts in one table\n\n| Feature | Detail |\n| --- | --- |\n| Method type | Comparative disc diffusion; control and test on the same plate |\n| Key difference from Kirby-Bauer | Test zone compared to an on-plate control strain, not to a fixed breakpoint chart |\n| Main use case | Labs where disc potency, media, or storage cannot be tightly standardized (widely used in the UK) |\n| Conventional layout | Test organism in the center, control on the outer thirds |\n| Modified layout | Control organism in the center, test on the outer thirds |\n| What is measured | Zone radius (disc edge to zone edge), for both test and control |\n| Sensitive (S) | Test radius equal to, wider than, or not more than 3 mm smaller than the control |\n| Intermediate (I) | Test radius more than 2 mm, but smaller than the control by more than 3 mm |\n| Resistant (R) | No zone, or test radius 2 mm or less |\n| Inoculum | 0.5 McFarland (about 1 to 2 x 10⁸ CFU\u002FmL for *E. coli* ATCC 25922) |\n| Incubation | 35°C, aerobic, 18 to 24 hours |\n| Medium | Mueller-Hinton agar |\n| Main trade-off | Lower throughput; one or two antibiotics per plate versus many on a Kirby-Bauer plate |\n\n## Where Students Get Confused\n\n**Stokes measures the radius, Kirby-Bauer measures the diameter.** This is the single most missed difference. In Kirby-Bauer you measure the full zone diameter (including the disc) and compare it to a chart. In Stokes you measure the radius, from the disc edge to the zone edge, on both the test and the control, and compare the two. Mixing up radius and diameter will make every Stokes reading wrong.\n\n**Conventional and modified Stokes are not different tests, only different layouts.** The confusion is over which organism sits in the middle. Conventional puts the test organism in the center with controls outside; modified puts the control in the center with the test outside. The comparison and the interpretation are identical; only the physical arrangement changes.\n\n**The control is a fully susceptible strain, not a resistant one.** The control exists to show what a susceptible zone looks like under that day's exact conditions. It is not there to represent resistance. If the control's own zone is unexpectedly small, that is a warning that the discs or media are faulty, not a normal result to read past.\n\n**A big test zone is not automatically \"sensitive\" in isolation.** The whole point is the comparison. You read the test zone against the control zone, not against your memory of a normal zone size. An isolate is sensitive because its zone is close to the control's, not because the zone looks large on its own.\n\n**Stokes does not give an MIC.** Like Kirby-Bauer, it produces a categorical result (S, I, or R). If an exact minimum inhibitory concentration is needed, that requires a broth or agar dilution method or an E-test.\n\n## References and further reading\n\n1. Gosden PE, Andrews JM, Bowker KE, Holt HA, MacGowan AP, Reeves DS, Sunderland J, Wise R. Comparison of the modified Stokes' method of susceptibility testing with results obtained using MIC methods and British Society of Antimicrobial Chemotherapy breakpoints. J Antimicrob Chemother. 1998;42(2):161-169. \u003Chttps:\u002F\u002Fdoi.org\u002F10.1093\u002Fjac\u002F42.2.161>\n2. Tille PM. Bailey and Scott's Diagnostic Microbiology. 15th ed. St. Louis: Elsevier; 2022.\n3. CLSI. M02, Performance Standards for Antimicrobial Disk Susceptibility Tests. Clinical and Laboratory Standards Institute; current edition.",[],[51],"antimicrobial-susceptibility-testing",[53,80,105,130],{"slug":54,"title":55,"description":56,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":57,"lastUpdatedDate":58,"draft":46,"category":59,"image":42,"faq":60,"tags":79},"antimicrobial-susceptibility-testing-procedure-modified-kirby-bauer-method","Modified Kirby-Bauer Disc Diffusion Method: Procedure, Reading Rules & Common Errors","\u003Cp>The full modified Kirby-Bauer procedure: inoculum prep, disc placement, and the three exceptions to standard zone reading that catch most students off guard, including the β-lactamase \"heaped edge\" rule.\u003C\u002Fp>","2013-08-27","2026-08-20","general-microbiology",[61,64,67,70,73,76],{"question":62,"answer":63},"Why does incubating above 35°C invalidate oxacillin\u002Fmethicillin results?","Temperatures above 35°C can cause a methicillin-resistant Staphylococcus aureus (MRSA) isolate to falsely appear oxacillin-susceptible, leading to a misleading report and potentially ineffective treatment if a β-lactam is prescribed.",{"question":65,"answer":66},"Why is a heaped-up zone edge reported as resistant even if the zone looks otherwise normal-sized?","In β-lactamase-producing staphylococci tested against penicillin, the enzyme degrades the drug right at the zone boundary, creating a heaped-up, sharply defined edge. CLSI guidance is to report this as resistant regardless of the overall zone diameter.",{"question":68,"answer":69},"Why does agar depth matter for disc diffusion accuracy?","CLSI specifies a uniform Mueller-Hinton agar depth of approximately 4 mm. Agar poured too thin lets antibiotic diffuse further than intended, producing falsely large zones; too thick restricts diffusion and produces falsely small ones.",{"question":71,"answer":72},"What's the difference between standard Kirby-Bauer and the Stokes method?","\u003Cp>Standard Kirby-Bauer relies on tightly standardizing inoculum density, agar depth, disc potency, and incubation temperature independently. The Stokes method instead runs a known control strain on the same plate as the test organism, comparing results directly rather than against a fixed chart, making it more forgiving of batch-to-batch variation.\u003C\u002Fp>",{"question":74,"answer":75},"Why are sulfonamide and co-trimoxazole zones read differently from other antibiotics?","Slight bacterial growth often occurs within the inhibition zone with these drugs even in susceptible isolates. This faint growth should be ignored when reading the zone edge.",{"question":77,"answer":78},"Can disc diffusion provide an exact MIC value?","\u003Cp>No. Disc diffusion only categorizes isolates as Susceptible, Intermediate, or Resistant. For an exact MIC value, methods like E-test or broth\u002Fagar dilution are needed.\u003C\u002Fp>",[51],{"slug":81,"title":82,"description":83,"seoTitle":84,"seoDescription":85,"author":43,"createdDate":86,"lastUpdatedDate":87,"draft":46,"category":47,"image":42,"faq":88,"tags":104},"preparation-mcfarland-turbidity-standards","McFarland Turbidity Standards: Preparation and Use in Susceptibility Testing","How McFarland turbidity standards are prepared, why the 0.5 standard (1.5 x 10^8 CFU\u002FmL) is the target for antimicrobial susceptibility testing, and how a wrong inoculum density gives false results.","McFarland Turbidity Standards: Preparation, Why 0.5 Matters for AST, and How to Match Inoculum","","2016-06-09","2026-08-24",[89,92,95,98,101],{"question":90,"answer":91},"\u003Cp>What is a McFarland turbidity standard?\u003C\u002Fp>","\u003Cp>It is a reference suspension of known turbidity used to estimate the density of a bacterial suspension without counting individual cells. It is made by mixing barium chloride and sulfuric acid to form a barium sulfate precipitate whose cloudiness corresponds to a known cell density.\u003C\u002Fp>",{"question":93,"answer":94},"\u003Cp>Why is the 0.5 McFarland standard used for susceptibility testing?\u003C\u002Fp>","\u003Cp>Disk diffusion susceptibility testing was standardized and validated using an inoculum equivalent to 0.5 McFarland, which is about 1.5 x 10^8 CFU\u002FmL. All the zone-diameter breakpoints assume this density, so using it is what makes the result valid and comparable between laboratories.\u003C\u002Fp>",{"question":96,"answer":97},"\u003Cp>What happens if the inoculum is too dense or too light?\u003C\u002Fp>","\u003Cp>If it is too dense, the zones of inhibition come out smaller than they should and a susceptible organism can be misread as resistant. If it is too light, the zones come out larger and a resistant organism can be misread as susceptible. Both errors can misdirect treatment.\u003C\u002Fp>",{"question":99,"answer":100},"\u003Cp>How is a bacterial suspension matched to the standard?\u003C\u002Fp>","\u003Cp>Hold the suspension and the 0.5 McFarland standard side by side against a white background with contrasting black lines in good light, and compare the turbidity. Dilute if too dense, add organisms if too light, then use the adjusted suspension within 15 minutes.\u003C\u002Fp>",{"question":102,"answer":103},"\u003Cp>What is the difference between a McFarland standard and a McFarland densitometer?\u003C\u002Fp>","\u003Cp>The standard is the reference suspension or target density. The densitometer is an instrument that measures a suspension's turbidity photometrically and reports it in McFarland units, removing the need to prepare and compare against chemical standards.\u003C\u002Fp>",[51],{"slug":106,"title":107,"description":108,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":109,"lastUpdatedDate":45,"draft":46,"category":47,"image":42,"faq":110,"tags":129},"e-test-epsilometer-test-principle-purpose-procedure-results-and-interpretations","E-Test (Epsilometer): Why It Beats a Plain Disc Test, Procedure & Reading Rules","E-test gives an exact MIC value, not just a Susceptible\u002FResistant call. Full procedure, strip placement, and the reading rules that trip up most students — plus how E-test strips are used to screen for ESBL.","2015-01-09",[111,114,117,120,123,126],{"question":112,"answer":113},"What's the difference between E-test and disc diffusion?","Disc diffusion gives only a category — Susceptible, Intermediate, or Resistant. E-test gives an exact MIC value in µg\u002FmL as well as the S\u002FI\u002FR category, which matters most for borderline or treatment-failure cases where the precise number changes the decision.",{"question":115,"answer":116},"Why does E-test use an exponential antibiotic gradient instead of a fixed concentration?","The continuous exponential gradient along the strip lets a single strip cover a wide range of concentrations, so the exact MIC can be read directly from where the inhibition ellipse intersects the scale, rather than testing one fixed concentration at a time.",{"question":118,"answer":119},"If the inhibition ellipse intersects at different points on either side of the strip, which value do you read?","Always read the greater (higher) value. This is a deliberately conservative rule — plates are never perfectly uniform, and erring toward the higher MIC avoids under-calling resistance.",{"question":121,"answer":122},"How is E-test used to screen for ESBL production?","Dual-ended combination strips carry the antibiotic alone on one end and the same antibiotic plus a β-lactamase inhibitor (such as clavulanic acid) on the other. A large drop in MIC on the inhibitor side compared to the antibiotic-alone side indicates ESBL production.",{"question":124,"answer":125},"Why is Mueller-Hinton agar used for E-test, and why does the depth matter?","Mueller-Hinton agar provides standardized, reproducible diffusion conditions with low inhibitor content. A uniform 4 mm depth is specified because agar depth directly affects how the antibiotic gradient diffuses, which affects the accuracy of the MIC reading.",{"question":127,"answer":128},"Is E-test used routinely on every isolate?","No — most labs reserve it for borderline, treatment-failure, or critical cases (such as confirming a borderline vancomycin MIC in MRSA) rather than running it as a routine first-line test, since disc diffusion is faster and cheaper for routine screening.",[51],{"slug":131,"title":132,"description":133,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":134,"lastUpdatedDate":87,"draft":46,"category":47,"image":42,"faq":135,"tags":154},"minimum-inhibitory-concentration-mic-broth-dilution-method-procedure-interpretation","Broth Dilution Method for MIC: Macrodilution vs Microdilution, Procedure & Troubleshooting","Step-by-step broth macrodilution and microdilution procedure for MIC determination: antibiotic stock prep, 0.5 McFarland standardization, reading results, and a troubleshooting guide for the errors that actually happen at the bench.","2013-11-15",[136,139,142,145,148,151],{"question":137,"answer":138},"What's the difference between broth macrodilution and microdilution?","\u003Cp>They follow the same principle (serial antibiotic dilutions inoculated with a standardized bacterial suspension) but macrodilution uses 1 mL per tube while microdilution uses 0.05–0.1 mL per well in a 96-well tray. Microdilution is far more common in routine clinical labs.\u003C\u002Fp>",{"question":140,"answer":141},"Why must the inoculum be standardized to a 0.5 McFarland standard?","The MIC result depends directly on how many bacteria you start with. Too light an inoculum reads a falsely low MIC; too heavy reads a falsely high one. The 0.5 McFarland standard ensures every test starts from a comparable, known bacterial density.",{"question":143,"answer":144},"Why are reference strains like E. coli ATCC 25922 run alongside patient isolates?","\u003Cp>They're quality-control checks. If a known reference strain's MIC falls outside its established CLSI range, it signals a problem with the test itself (inoculum, media, or technique) before patient results are trusted.\u003C\u002Fp>",{"question":146,"answer":147},"What happens if microdilution trays are stacked too high during incubation?","\u003Cp>Cultures at the center of a tall stack can incubate at a different temperature than intended, skewing growth and MIC readings, CLSI guidance caps stacking at four trays high.\u003C\u002Fp>",{"question":149,"answer":150},"Can broth dilution MIC testing be automated?","\u003Cp>Yes. Systems like Vitek 2, MicroScan Walkaway, and BD Phoenix automate broth microdilution and reading, and are widely used in clinical labs alongside or instead of manual testing.\u003C\u002Fp>",{"question":152,"answer":153},"Why might an MIC come back lower than clinically expected even with correct technique?","A few possibilities: the inoculum was too light, the cation-adjusted Mueller-Hinton broth's pH or calcium concentration is off, or there's a transcription\u002Freading error.",[51],{"enabled":156,"threads":157,"total":158},true,[],0,[160,166,173,180,186,191,197,202,208,211,218],{"slug":161,"name":43,"description":162,"image":163,"body":164,"postCount":165},"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.*",481,{"slug":167,"name":168,"description":169,"image":170,"body":171,"postCount":172},"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":174,"name":175,"description":176,"image":177,"body":178,"postCount":179},"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":181,"name":182,"description":176,"image":183,"body":184,"postCount":185},"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":187,"name":188,"description":176,"image":42,"body":189,"postCount":190},"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":192,"name":193,"description":194,"image":42,"body":195,"postCount":196},"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":198,"name":199,"description":200,"image":42,"body":42,"postCount":201},"guest-author","Guest Author","Guest Author \u002F Contributor",1,{"slug":203,"name":204,"description":176,"image":205,"body":206,"postCount":207},"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":209,"name":210,"description":200,"image":42,"body":42,"postCount":201},"dr-poonam-acharya","Dr. Poonam Acharya",{"slug":212,"name":213,"description":214,"image":215,"body":216,"postCount":217},"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":219,"name":220,"description":221,"image":222,"body":223,"postCount":201},"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.",[225,232,238,243,248,253,257,261,265,270,274,278,282,287,292,296,300,304,309,314,318,322,326,331,335,339,343,347,352,357,361,365,369,374,378,382,386,390,394,398,402,406,410,414,418,422,426,430,435,439,443,447,451,455,459,463,467,471,475,479,483,487,491,495,499,503,507,511,514,518,521,524,527,530,533,536,539,542,545,548,551,554,557],{"slug":226,"name":227,"description":228,"image":229,"body":230,"postCount":231},"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":233,"name":234,"description":235,"image":42,"body":236,"postCount":237},"microscopy","Microscopy","Microscope types, components, and microscopy techniques","These are list of blog posts related to microscopy. ",12,{"slug":239,"name":240,"description":241,"image":42,"body":42,"postCount":242},"gram-positive-cocci","Gram-Positive Cocci","Staphylococcus, Streptococcus, Enterococcus, Micrococcus — organisms, diseases, and identification tests",11,{"slug":244,"name":245,"description":246,"image":42,"body":42,"postCount":247},"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":249,"name":250,"description":251,"image":42,"body":42,"postCount":252},"gram-positive-rods","Gram-Positive Rods","Bacillus, Clostridium, Listeria, Corynebacterium, Actinomyces and related organisms",8,{"slug":254,"name":255,"description":256,"image":42,"body":42,"postCount":242},"mycobacteria","Mycobacteria","Mycobacterium tuberculosis, leprosy, atypical mycobacteria, and acid-fast organism diagnosis",{"slug":258,"name":259,"description":260,"image":42,"body":42,"postCount":237},"anaerobic-bacteriology","Anaerobic Bacteriology","Anaerobic organisms, anaerobic culture methods, and anaerobic infection diagnosis",{"slug":262,"name":263,"description":264,"image":42,"body":42,"postCount":237},"enterobacteriaceae","Enterobacteriaceae","Identification, differentiation, and clinical significance of Enterobacteriaceae family members",{"slug":266,"name":267,"description":268,"image":42,"body":42,"postCount":269},"spirochetes","Spirochetes","Treponema, Leptospira, Borrelia and spirochetal infections",7,{"slug":271,"name":272,"description":273,"image":42,"body":42,"postCount":231},"food-microbiology","Food Microbiology","Food-borne pathogens, food safety, spoilage, and preservation",{"slug":51,"name":275,"description":276,"image":42,"body":42,"postCount":277},"Antimicrobial Susceptibility Testing","Methods for testing antibiotic susceptibility in clinical microbiology",21,{"slug":279,"name":280,"description":281,"image":42,"body":42,"postCount":231},"antimicrobials-moa-amr","Antimicrobials (MOA & AMR)","Mechanisms, detection, and clinical significance of antimicrobial resistance",{"slug":283,"name":284,"description":285,"image":42,"body":42,"postCount":286},"sterilization-disinfection","Sterilization and Disinfection","Methods of sterilization and disinfection in healthcare and laboratory settings",10,{"slug":288,"name":289,"description":290,"image":42,"body":42,"postCount":291},"specimen-collection-transport","Specimen Collection and Transport","Collection, handling, and transport of clinical specimens for microbiological testing",27,{"slug":293,"name":294,"description":295,"image":42,"body":42,"postCount":277},"bacterial-structure-physiology","Bacterial Structure and Physiology","Bacterial cell structure, growth, physiology, and environmental factors affecting growth",{"slug":297,"name":298,"description":42,"image":42,"body":299,"postCount":190},"horizontal-gene-transfer","Horizontal Gene Transfer","Articles related to **Horizontal Gene Transfer**",{"slug":301,"name":302,"description":42,"image":42,"body":303,"postCount":286},"chromatography","Chromatography","Information about chromatographic techniques.",{"slug":305,"name":306,"description":307,"image":42,"body":308,"postCount":269},"electrophoresis","Electrophoresis","Information about Electrophoresis Techniques ","Detailed information  about Electrophoresis Techniques ",{"slug":310,"name":311,"description":312,"image":42,"body":313,"postCount":190},"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":315,"name":316,"description":317,"image":42,"body":42,"postCount":190},"bacteriophage","Bacteriophage","Description about Bacteriophage.",{"slug":319,"name":320,"description":321,"image":42,"body":42,"postCount":190},"malaria","Malaria","It is the collections of articles regarding malarial disease. ",{"slug":323,"name":324,"description":325,"image":42,"body":42,"postCount":190},"anaerobic-culture-techniques","Anaerobic Culture Techniques","Posts related with Anaerobic Culture Techniques.",{"slug":327,"name":328,"description":329,"image":42,"body":42,"postCount":330},"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":332,"name":333,"description":334,"image":42,"body":42,"postCount":269},"biosafety-levels","Biosafety levels ","Articles related to Biosafety Levels",{"slug":336,"name":337,"description":338,"image":42,"body":42,"postCount":247},"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":340,"name":341,"description":342,"image":42,"body":42,"postCount":190},"pipette","Pipette","Posts related with Pipette. ",{"slug":344,"name":345,"description":346,"image":42,"body":42,"postCount":252},"bacteriology-mcqs","Bacteriology MCQs","This sections lists MCQs in Bacteriology.",{"slug":348,"name":349,"description":350,"image":42,"body":42,"postCount":351},"parasitology-mcqs","Parasitology MCQs","This section lists MCQs in Parasitology.",2,{"slug":353,"name":354,"description":355,"image":42,"body":42,"postCount":356},"virology-mcqs","Virology MCQs","This is the collections of Multiple Choice Questions in Virology.",4,{"slug":358,"name":359,"description":360,"image":42,"body":42,"postCount":247},"mcqs-in-microbiology","MCQs in Microbiology","This section lists the collections of Multiple Choice Questions in General Microbiology Topics. ",{"slug":362,"name":363,"description":364,"image":42,"body":42,"postCount":252},"immunology-mcqs","Immunology MCQs","In this section; we are posting collections of Multiple Choice Questions about Immunology. ",{"slug":366,"name":367,"description":368,"image":42,"body":42,"postCount":286},"microbial-curiosities","Microbial Curiosities","In this clusters, we are posting interesting and unique information about Microorganisms. ",{"slug":370,"name":371,"description":372,"image":42,"body":42,"postCount":373},"bacterial-culture-media","Bacterial Culture Media","Posts related to Bacterial Culture Media. ",23,{"slug":375,"name":376,"description":377,"image":42,"body":42,"postCount":190},"fungal-culture-media","Fungal Culture Media","Posts related to Fungal Culture Media.",{"slug":379,"name":380,"description":381,"image":42,"body":42,"postCount":247},"motility-test","Motility Test","This lists the procedure regarding various tests methods for bacterial motility.",{"slug":383,"name":384,"description":385,"image":42,"body":42,"postCount":286},"bacterial-enumeration","Bacterial enumeration","These posts are related to isolation and enumeration of bacteria. ",{"slug":387,"name":388,"description":389,"image":42,"body":42,"postCount":351},"gram-positive-coccobacillus","Gram-positive coccobacillus","List of Gram Positive Coccobacilli",{"slug":391,"name":392,"description":393,"image":42,"body":42,"postCount":356},"dimorphic-fungi","Dimorphic Fungi","This is about various dimorphic fungi. ",{"slug":395,"name":396,"description":397,"image":42,"body":42,"postCount":269},"bacterial-classification","Bacterial Classification","These posts are related with various approaches used for the classification of Bacteria. ",{"slug":399,"name":400,"description":401,"image":42,"body":42,"postCount":247},"immunofluorescence","Immunofluorescence ","Various Tests related to Immunofluorescence ",{"slug":403,"name":404,"description":405,"image":42,"body":42,"postCount":196},"antibody-mediated-immunity","Antibody-mediated Immunity","This clusters links the articles that are sharing insights about Antibody-mediated immunity. ",{"slug":407,"name":408,"description":409,"image":42,"body":42,"postCount":269},"hypersensitivity","Hypersensitivity","Articles related to Hypersensitivity.",{"slug":411,"name":412,"description":42,"image":42,"body":42,"postCount":413},"haemophilus","Haemophilus",3,{"slug":415,"name":416,"description":417,"image":42,"body":42,"postCount":356},"sexually-transmitted-infections-stis","Sexually transmitted infections (STIs)","This is the clusters of infections that are transmitted sexually. ",{"slug":419,"name":420,"description":421,"image":42,"body":42,"postCount":237},"adaptive-immunity","Adaptive Immunity","Blog posts related to B Cell Immunity and T Cell Immunity.",{"slug":423,"name":424,"description":425,"image":42,"body":42,"postCount":231},"fungal-diagnostics","Fungal Diagnostics","Various methods used for the Diagnosis of Fungal Infections. ",{"slug":427,"name":428,"description":429,"image":42,"body":42,"postCount":247},"laboratory-storage-and-preservation","Laboratory Storage and Preservation","Articles about Laboratory Storage of Antimicrobial Disk, Test organisms and Equipment used for this process. ",{"slug":431,"name":432,"description":433,"image":42,"body":434,"postCount":190},"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":436,"name":437,"description":438,"image":42,"body":42,"postCount":196},"laboratory-glassware","Laboratory Glassware","Posts about Laboratory Glassware. ",{"slug":440,"name":441,"description":442,"image":42,"body":42,"postCount":190},"helminths","Helminths","In this section, we are covering properties, life cycle, pathogenesis and laboratory diagnosis of Helminths\u002FHelminthic infestations. ",{"slug":444,"name":445,"description":446,"image":42,"body":42,"postCount":269},"protozoan-parasite","Protozoan Parasite","In this cluster, we are covering protozoan parasites. ",{"slug":448,"name":449,"description":450,"image":42,"body":42,"postCount":201},"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":452,"name":453,"description":454,"image":42,"body":42,"postCount":286},"bacterial-staining-technique","Bacterial Staining Technique","Lists of various staining techniques that are used to stain bacteria. ",{"slug":456,"name":457,"description":458,"image":42,"body":42,"postCount":277},"enzyme-tests","Enzyme Tests","\u003Cp>Various Biochemical Test that are based on enzymatic activity of the microorganisms. \u003C\u002Fp>",{"slug":460,"name":461,"description":462,"image":42,"body":42,"postCount":242},"carbohydrate-utilization","Carbohydrate Utilization","\u003Cp>Various biochemical tests which are related to Carbohydrate fermentation or Utilization\u003C\u002Fp>",{"slug":464,"name":465,"description":466,"image":42,"body":42,"postCount":247},"susceptibility-based-id","Susceptibility-based ID","\u003Cp>These are susceptibility based identification test such as optochin sensitivity, bacitracin sensitivity etc. \u003C\u002Fp>",{"slug":468,"name":469,"description":470,"image":42,"body":42,"postCount":356},"microbial-metabolism","Microbial Metabolism","\u003Cp>Tests about Microbial Metabolism. \u003C\u002Fp>",{"slug":472,"name":473,"description":474,"image":42,"body":42,"postCount":252},"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":476,"name":477,"description":478,"image":42,"body":42,"postCount":413},"atypical-pneumonia","Atypical Pneumonia","\u003Cp>Organisms responsible for Atypical Pneumonia. \u003C\u002Fp>",{"slug":480,"name":481,"description":482,"image":42,"body":42,"postCount":247},"antigen","Antigen","\u003Cp>Various articles related to Antigens.\u003C\u002Fp>",{"slug":484,"name":485,"description":486,"image":42,"body":42,"postCount":269},"innate-immunity","Innate Immunity","\u003Cp>Articles related to Innate Immunity. \u003C\u002Fp>",{"slug":488,"name":489,"description":490,"image":42,"body":42,"postCount":356},"respiratory-tract-infection","Respiratory Tract Infection","\u003Cp>In this cluster, you can see various etiological agents that causes respiratory tract infection. \u003C\u002Fp>",{"slug":492,"name":493,"description":494,"image":42,"body":42,"postCount":247},"torch-infection","TORCH Infection","\u003Cp>In this section; you can find articles related with TOCH infection. \u003C\u002Fp>",{"slug":496,"name":497,"description":498,"image":42,"body":42,"postCount":252},"microbiology-for-beginners","Microbiology for Beginners","\u003Cp>These articles are very basic articles, which will share general concepts in Microbiology. \u003C\u002Fp>",{"slug":500,"name":501,"description":502,"image":42,"body":42,"postCount":190},"dna-replication","DNA Replication","\u003Cp>Articles related to DNA and Replication of DNA. \u003C\u002Fp>",{"slug":504,"name":505,"description":506,"image":42,"body":42,"postCount":269},"genetic-code","Genetic Code","\u003Cp>Articles related to Genetic Code.\u003C\u002Fp>",{"slug":508,"name":509,"description":510,"image":42,"body":42,"postCount":269},"molecular-technique","Molecular Technique","\u003Cp>Posts related to Molecular Techniques. \u003C\u002Fp>",{"slug":512,"name":513,"description":42,"image":42,"body":42,"postCount":201},"colorimetric-assay","Colorimetric Assay ",{"slug":515,"name":516,"description":517,"image":42,"body":42,"postCount":247},"pharmaceutical-microbiology","Pharmaceutical Microbiology","\u003Cp>Various articles related to Pharmaceutical Microbiology\u003C\u002Fp>",{"slug":519,"name":520,"description":42,"image":42,"body":42,"postCount":413},"blood-and-immune-cells","Blood and Immune Cells",{"slug":522,"name":523,"description":42,"image":42,"body":42,"postCount":247},"host-pathogen-interaction","Host Pathogen Interaction",{"slug":525,"name":526,"description":42,"image":42,"body":42,"postCount":356},"blood-culture","Blood Culture",{"slug":528,"name":529,"description":42,"image":42,"body":42,"postCount":356},"environmental-microbiology","Environmental microbiology ",{"slug":531,"name":532,"description":42,"image":42,"body":42,"postCount":190},"copromicroscopic-technique","Copromicroscopic Technique",{"slug":534,"name":535,"description":42,"image":42,"body":42,"postCount":413},"quality-control","Quality Control",{"slug":537,"name":538,"description":42,"image":42,"body":42,"postCount":356},"dermatophytes","Dermatophytes",{"slug":540,"name":541,"description":42,"image":42,"body":42,"postCount":413},"viral-hemorrhagic-fevers","Viral Hemorrhagic Fevers",{"slug":543,"name":544,"description":42,"image":42,"body":42,"postCount":356},"h2s-production","H2S Production",{"slug":546,"name":547,"description":42,"image":42,"body":42,"postCount":351},"water-quality-testing","Water Quality Testing",{"slug":549,"name":550,"description":42,"image":42,"body":42,"postCount":247},"virology-basics","Virology basics",{"slug":552,"name":553,"description":42,"image":42,"body":42,"postCount":356},"typing-methods","Typing Methods",{"slug":555,"name":556,"description":42,"image":42,"body":42,"postCount":413},"blotting-technique","Blotting Technique",{"slug":558,"name":559,"description":42,"image":42,"body":42,"postCount":356},"history-microbiology","History of Microbiology"]