[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"$fxLN3MUwXCdr5RPjwZYIDpOj8CHyjOmngWTgoKXPtZbg":3,"$fXYIaEkVEjMJfciT9B5htfAQVSPp5dCVw5CaCBfTn2gE":36,"$f3Ft0rKFJHppdzE-vuveecxx1BUcg9iOlMLtyzf_MJDg":167,"$fucxFBm2ZjZfGSdmdRaSNGBI_F0jJme4f0GTvzUhQfL8":231},[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":59,"related":61,"comments":163},"lancefield-grouping-clinically-relevant-beta-hemolytic-streptococci","Lancefield Classification of Streptococci","Lancefield grouping of beta-hemolytic streptococci by C-carbohydrate antigen, covering Groups A, B, C, D, and F with key lab tests.",null,"Acharya Tankeshwar","2015-03-12","2026-08-02",false,"bacteriology","When a laboratory grows a beta-hemolytic streptococcus, the first question is which group it belongs to, because the group often predicts the disease and guides treatment. This page explains how streptococci are grouped and introduces the quick bench tests to identify each group.\n\nStreptococci are Gram-positive cocci either diplococci (lanceolate shaped; *S. pneumoniae*) or in chains. They are catalase-negative (an important test to differentiate streptococci from Staphylococci). These fastidious [gram-positive cocci](\u002Fgram-positive-cocci-of-medical-importance\u002F) may give either alpha or beta or gamma hemolysis when cultured on **blood agar.**\n\n> β-hemolytic streptococci produce hemolysins that lyse the sheep RBCs (poorly lyse human RBCs too), resulting in a clearing of the Blood Agar plate surrounding the colonies. More intense β-hemolysis is noted in areas where the medium has been “stabbed,” pushing some of the bacteria under the surface of the medium. The β-hemolysis in these areas is due to the combined action of both hemolysins of Streptococci (Streptolysin O and Streptolysin S). The surface β-hemolysis is largely due to streptolysin S (oxygen stable hemolysin), as Streptolysin O which is oxygen-labile does not show maximal activity on the surface of the agar.\n\n![ - Beta Hemolysis in Sheep Blood Agar.](\u002Fblogs\u002FIdentify-the-hemolysis-patten-shown-in-this-pic.jpg)Figure: Beta Hemolysis in Sheep Blood Agar.\n\nSerologic grouping of cell wall carbohydrates of Streptococci was classically been used to identify species of beta-hemolytic Streptococci, this grouping is known as  Lancefield grouping. Beta-hemolytic streptococci are arranged into twenty groups, A to V excluding I and J (that is, A through H and K through V). Rebecca Lancefield, a prominent American microbiologist, introduced the system. Of these twenty, only a few commonly infect humans, mainly groups A, B, C, D, F, and G, and this page focuses on those.\n\n![Streptococcus as seen in Scanning electron microscope (lancefield grouping) - Streptococcus as seen in scanning electron microscope](\u002Fblogs\u002Fstreptococci-300x223.jpg)Figure: Streptococcus as seen in scanning electron microscope\n\nThe basis of Lancefield grouping is the antigenic differences in C carbohydrates, a group-specific antigen.  C carbohydrate is located in the cell wall of streptococci\n\n> (Note: viridans streptococci and Streptococcus pneumoniae have no group-specific antigen).\n\nThe original Lancefield precipitin test is now rarely performed in clinical laboratories. Now, it has been replaced by either **latex agglutination** or coagglutination.\n\n## Group A Streptococci (GAS)\n\n*Streptococcus pyogenes,* is one of the most important human pathogens which causes Streptococcal sore throat, skin infections, and post-streptococcal sequelae such as rheumatic fever and post-streptococcal glomerulonephritis (PSGN). *S. pyogenes* is [inhibited by the antibiotic bacitracin,](\u002Fbacitracin-test-principle-procedure-expected-results-and-quality-control\u002F) an important diagnostic criterion.\n\n## Group B Streptococci\n\n*Streptococcus agalactiae* colonizes the genital tract of some women and can cause neonatal meningitis and sepsis. It can cause septic abortion and puerperal or gynecological sepsis and occasionally urinary tract infections. *S. agalactiae* gives [CAMP test](\u002Fcamp-test-principle-procedure-results\u002F) positive and can [hydrolyze the hippurate](\u002Fhippurate-hydrolysis-test-principle-procedure-uses-results\u002F).\n\n## Group C Streptococci\n\nGroup C beta-hemolytic streptococci currently include *S. dysgalactiae subsp. equisimilis* and other related strains under the same species or *S. equi* subspecies. *S. dysgalactiae subsp. equisimilis* has been recovered from pharyngitis and tonsillitis from patients with underlying diseases such as cardiopulmonary disease, diabetes, immunosuppression, HIV, etc.\n\n## Group D Streptococci\n\nIt includes enterococci (e.g., *Enterococcus faecalis* and *Enterococcus faecium*) and nonenterococci (*S. bovis*). Enterococci are members of the normal flora of the colon. They can cause urinary, biliary, and cardiovascular infections.\n\n*Note: By the mid-1980s, the enterococcal streptococci (Lancefield group D) had taken up residence in their own newly created Enterococcus genus and the “dairy” or “lactic” streptococci (Lancefield group N) were moved to new Lactococcus genus.*\n\n## Group F Beta Hemolytic streptococci\n\nOrganisms of this group have been called *S. milleri* in the British taxonomic scheme and anginosus (*S. anginosus*) group in the American taxonomic group.  Group F Beta-hemolytic streptococci are recognized as a cause of severe suppurative infections including cellulitis, deep-tissue abscesses, bacteremia, osteomyelitis, and endocarditis.\n\nOther groups (K to U): These contain streptococcal species of limited virulence that can cause infections in immunocompromised individuals.\n\n## Summary of Medically Important Streptococci\n\n| Species | Lancefield Group | Typical Hemolysis | Important Lab Characteristics |\n| --- | --- | --- | --- |\n| Streptococcus pyogenes | A | Beta | Bacitracin sensitive PYR Test positive |\n| S. agalactiae | B | Beta | Bacitracin resistant Hippurate utilized CAMP test positive |\n| Enterococcus faecalis | D | Alpha, Beta or None | Growth in 6.5% NaCl PYR Test positive |\n| S. bovis | D | Alpha or none | No growth in 6.5% NaCl |\n| S. pneumoniae | Not groupable | Alpha | Bile soluble Inhibited by optochin |\n| Viridans group | Not groupable | Alpha | Not bile soluble Not inhibited by optochin |\n\n## Where students actually get confused\n\n- ***S. pneumoniae* and viridans streptococci don't get a Lancefield letter, full stop.** They lack the C-carbohydrate antigen entirely. Don't try to assign them a group, the correct answer is \"not groupable,\" and that's exactly why optochin and bile solubility exist as a separate identification path.\n- **\"Group D\" is a historical convenience, not current taxonomy.** Enterococcus was reclassified out of genus Streptococcus into its own genus in the mid-1980s. Exam questions and older texts still group Enterococcus and *S. bovis* together as \"Group D\" for teaching purposes, but they're genetically distinct genera now, separated at the bench by salt tolerance.\n- **Group C and G aren't always bacitracin-resistant.** As covered in the Bacitracin Test article, occasional Group C and G isolates show susceptibility, which is exactly why PYR exists as the tie-breaker for confirming true GAS.\n\n## How to Remember\n\nThis page ties together the individual streptococcal identification tests. Each of those tests, bacitracin, CAMP, PYR, salt tolerance, bile solubility, and optochin, exists because serological grouping is not practical for a routine laboratory.\n\nThe summary table above pulls all of these tests together: GAS is bacitracin-sensitive and PYR-positive; GBS reverses both and adds CAMP-positive and hippurate-positive; Group D splits on salt tolerance alone; and S. pneumoniae and the viridans group are not groupable at all. Those two are told apart by bile solubility and optochin instead of serology, because they do not carry the C-carbohydrate antigen this whole system depends on.\n\n**References**\n\n1. Procop, G. W., et al. (2017). *Koneman's Color Atlas and Textbook of Diagnostic Microbiology* (7th ed.). Wolters Kluwer.\n2. Tille, P. M. (2022). *Bailey & Scott's Diagnostic Microbiology* (15th ed.). Elsevier.\n3. Şahan Yapicier, Ö., Sababoglu, E., Ozturk, D., Turutoglu, H., Pehlivanoglu, F., & Kaya, M. (2021). Lancefield classification and antimicrobial resistance of hemolytic streptococci isolated from bovine mastitis. *Veterinaria italiana*, *57*(1), 41–47. \u003Chttps:\u002F\u002Fdoi.org\u002F10.12834\u002FVetIt.1855.9879.3> \n4. Facklam, R. F., Martin, D. R., Lovgren, M., Johnson, D. R., Efstratiou, A., Thompson, T. A., Gowan, S., Kriz, P., Tyrrell, G. J., Kaplan, E., & Beall, B. (2002). Extension of the Lancefield classification for group A streptococci by addition of 22 new M protein gene sequence types from clinical isolates: emm103 to emm124. *Clinical infectious diseases : an official publication of the Infectious Diseases Society of America*, *34*(1), 28–38. \u003Chttps:\u002F\u002Fdoi.org\u002F10.1086\u002F324621>",[50,53,56],{"question":51,"answer":52},"Why don't Streptococcus pneumoniae and viridans streptococci get assigned a Lancefield group?","Lancefield grouping is based on the C-carbohydrate antigen in the cell wall, and S. pneumoniae and viridans streptococci don't carry this antigen at all. They are correctly described as not groupable, and are identified instead using optochin sensitivity and bile solubility rather than serological grouping.",{"question":54,"answer":55},"Is Enterococcus still classified as Group D Streptococcus?","Not taxonomically. Enterococcus was reclassified into its own genus in the mid-1980s, separate from Streptococcus. The term Group D is still used informally in teaching to refer to both Enterococcus and Streptococcus bovis together, but they are genetically distinct genera, distinguished at the bench by the salt tolerance test.",{"question":57,"answer":58},"How many Lancefield groups are there, and which letters are excluded?","There are 20 described Lancefield groups, labeled A through V, excluding the letters I and J.",[60],"gram-positive-cocci",[62,77,108,131,148],{"slug":63,"title":64,"description":65,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":66,"lastUpdatedDate":67,"draft":46,"category":47,"image":42,"faq":68,"tags":75},"gram-positive-cocci-of-medical-importance","Gram Positive Cocci of Medical Importance","\u003Cp>Gram positive cocci by arrangement, clusters, chains, pairs, and tetrads, covering \u003Cem>Staphylococcus, Streptococcus, Enterococcus\u003C\u002Fem>, and \u003Cem>Micrococcus\u003C\u002Fem> with key identification tests\u003C\u002Fp>","2022-09-09","2026-08-21",[69,72],{"question":70,"answer":71},"What are the main genera of gram-positive cocci of medical importance?","\u003Cp>The most clinically significant genera are \u003Cem>Staphylococcus, Streptococcus,\u003C\u002Fem> and \u003Cem>Enterococcus\u003C\u002Fem>. \u003Cem>Micrococcus, Peptococcus,\u003C\u002Fem> and \u003Cem>Peptostreptococcus\u003C\u002Fem> are also gram-positive cocci but are rare pathogens, mostly normal flora.\u003C\u002Fp>",{"question":73,"answer":74},"How does cell arrangement (clusters, chains, pairs, tetrads) help identify gram-positive cocci?","\u003Cp>Arrangement under the microscope narrows identification before any biochemical test is run: clusters suggest \u003Cem>Staphylococcus\u003C\u002Fem>, chains suggest \u003Cem>Streptococcus\u003C\u002Fem>, pairs (diplococci) suggest \u003Cem>S. pneumoniae\u003C\u002Fem> or \u003Cem>Enterococcus\u003C\u002Fem>, and tetrads suggest \u003Cem>Micrococcus.\u003C\u002Fem> This is typically followed by the catalase test to confirm the genus-level call.\u003C\u002Fp>",[76,60],"bacterial-classification",{"slug":78,"title":79,"description":80,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":81,"lastUpdatedDate":82,"draft":46,"category":83,"image":42,"faq":84,"tags":106},"bacitracin-test-principle-procedure-expected-results-and-quality-control","Bacitracin Test: Principle, Procedure, Results","Bacitracin susceptibility test principle, procedure, and zone interpretation for presumptive identification of Streptococcus pyogenes (Group A Strep)","2013-05-17","2026-08-05","biochemical-tests",[85,88,91,94,97,100,103],{"question":86,"answer":87},"Does the bacitracin test need a minimum zone size to count as sensitive?","No. Unlike the optochin test, which uses zone-size cutoffs, the bacitracin test is a binary call: any visible zone of inhibition around the disk counts as sensitive, and no zone at all is resistant.",{"question":89,"answer":90},"\u003Cp>Can organisms other than \u003Cem>Streptococcus pyogenes\u003C\u002Fem> be bacitracin sensitive?\u003C\u002Fp>","Yes. Group C and G streptococci occasionally show susceptibility to the 0.04 IU bacitracin disk as well. When the result is ambiguous, a PYR test resolves it, S. pyogenes is the only beta-hemolytic streptococcus that gives a positive PYR reaction.",{"question":92,"answer":93},"Why does it matter which agar the bacitracin disk is placed on in a throat culture?","When bacitracin and optochin are both used in a combined respiratory culture workup, bacitracin should be placed on chocolate agar (where it also suppresses normal flora and improves detection of Haemophilus influenzae), while optochin goes on blood agar. Using the wrong medium for either disk can affect the reading.",{"question":95,"answer":96},"How does the bacitracin test identify Group A streptococci?","\u003Cp>Group A beta-hemolytic streptococci (\u003Cem>Streptococcus pyogenes\u003C\u002Fem>) are inhibited by the small amount of bacitracin in a 0.04 unit Taxo A disk, while most other beta-hemolytic streptococci are not. So any zone of inhibition around the disk is a presumptive identification of Group A strep, and no zone is resistant. The test is a binary call: any visible zone counts as sensitive, with no minimum size cutoff, which is different from the optochin test where zone size matters.\u003C\u002Fp>",{"question":98,"answer":99},"Why is the PYR test used alongside bacitracin?","\u003Cp>Because bacitracin susceptibility is not fully specific to Group A strep: Lancefield groups C and G streptococci occasionally show susceptibility too, which can cause a false-positive Group A call. PYR resolves it, since \u003Cem>Streptococcus pyogenes\u003C\u002Fem> is the only beta-hemolytic streptococcus that is PYR positive. A bacitracin-sensitive, PYR-positive beta-hemolytic streptococcus is a confident presumptive Group A strep.\u003C\u002Fp>",{"question":101,"answer":102},"Why is there no zone-size cutoff in the bacitracin test?","Because the 0.04 unit differential disk gives a binary result: any visible zone of inhibition, however small, is read as sensitive, and no zone is resistant. This differs from the optochin test, which uses a measured cutoff (14 mm or greater around a 6 mm disk). Importing optochin's measurement logic into the bacitracin test is a common error; here the presence or absence of any zone is what matters.",{"question":104,"answer":105},"Why should bacitracin be read from a pure subculture rather than a primary plate?","Because reading straight off a primary culture plate is less reliable. Mixed flora and overcrowded colonies near the disk are the main causes of misreads. If a primary-plate result looks ambiguous, the correct next step is a purified subculture, not a second look at the same plate. A light inoculum can also produce a misleading zone, so confluent growth from a pure culture gives the most reliable reading.",[107],"susceptibility-based-id",{"slug":109,"title":110,"description":111,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":112,"lastUpdatedDate":113,"draft":46,"category":83,"image":42,"faq":114,"tags":130},"camp-test-principle-procedure-results","CAMP Test: Principle, Procedure, and Results","CAMP test principle, procedure, and result interpretation for identifying Streptococcus agalactiae (Group B Strep), including the arrowhead hemolysis mechanism","2013-11-08","2026-07-16",[115,118,121,124,127],{"question":116,"answer":117},"Does the CAMP test detect cyclic AMP?","No. Despite the name overlap, CAMP here is an eponym for Christie, Atkins, and Munch-Petersen, the researchers who first described the phenomenon in 1944. It has nothing to do with the cyclic AMP signaling molecule.",{"question":119,"answer":120},"Why does a negative CAMP test not fully rule out Streptococcus agalactiae?","The CAMP test has approximately 98% sensitivity for GBS, not 100%. A negative result on a strongly suspected isolate should prompt further testing, such as hippurate hydrolysis or latex agglutination, rather than an automatic exclusion.",{"question":122,"answer":123},"What is the difference between a standard positive CAMP test and a positive reverse CAMP test?","A standard positive CAMP test shows an arrowhead zone of enhanced, complete hemolysis where the two streaks meet, seen with S. agalactiae. A positive reverse CAMP test shows an arrow of inhibited hemolysis instead, seen with organisms like Clostridium perfringens and Listeria. Same arrow shape, opposite underlying biology.",{"question":125,"answer":126},"Why does neither organism alone produce the CAMP arrowhead?","Because the arrowhead is the product of two substances acting together. Staphylococcus aureus beta-hemolysin partially damages the red blood cells in the agar, and Group B Streptococcus produces CAMP factor, which on its own causes no visible hemolysis. Only where the two diffusing substances overlap does the partial damage get completed into full hemolysis, forming the arrowhead that points toward the staphylococcal streak. It is a synergy, so both organisms are required.",{"question":128,"answer":129},"How do you tell Group A from Group B streptococci if the CAMP test is ambiguous?","Use the PYR test. Some Group A streptococci can give a CAMP reaction that looks positive, especially if the plate is incubated in CO2 or anaerobically instead of ambient air. PYR resolves it: Streptococcus pyogenes (Group A) is PYR positive, while Streptococcus agalactiae (Group B) is PYR negative. Incubating the CAMP plate in ambient air, as the standard method requires, also prevents most of these false positives.",[],{"slug":132,"title":133,"description":134,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":135,"lastUpdatedDate":82,"draft":46,"category":83,"image":42,"faq":136,"tags":146},"hippurate-hydrolysis-test-principle-procedure-uses-results","Hippurate Hydrolysis Test: Principle, Procedure, Results","\u003Cp>Hippurate hydrolysis test principle, classical and rapid ninhydrin procedures, for identifying \u003Cem>Streptococcus agalactiae\u003C\u002Fem> and other organisms.\u003C\u002Fp>","2015-03-14",[137,140,143],{"question":138,"answer":139},"Why do the classical and rapid hippurate methods detect two different products from the same reaction?","Because hippurate is one molecule made of two parts joined by an amide bond: benzoic acid and the amino acid glycine. Hippuricase cuts that bond and releases both. The classical ferric chloride method detects the benzoic acid half over 48 hours, while the rapid ninhydrin method detects the glycine half in 2 hours, forming a blue-purple color. They look completely different but are two windows onto the same cleavage.",{"question":141,"answer":142},"A Group D streptococcus tests weakly hippurate positive by the rapid method. How do I tell whether it is actually Group B Strep?","Two follow-up tests resolve it. Bile esculin separates them: Group D streptococci hydrolyze esculin, while Group B Strep does not. PYR is the other tiebreaker: enterococci are PYR positive, while Streptococcus agalactiae is PYR negative. A hippurate-positive, bile-esculin-negative, PYR-negative beta-hemolytic coccus fits Group B Strep.",{"question":144,"answer":145},"Why does switching from the classical to the rapid hippurate method change how often enterococci appear positive?","Because the rapid ninhydrin method is far more sensitive with enterococcal Group D strains than the classical method. A published evaluation found about 95 percent of enterococcal Group D strains positive by the rapid method versus about 9 percent by the classical method. So seeing more Group D positives on the rapid method is the method being accurate, not a contamination problem.",[147],"enzyme-tests",{"slug":149,"title":150,"description":151,"seoTitle":42,"seoDescription":42,"author":152,"createdDate":153,"lastUpdatedDate":154,"draft":46,"category":47,"image":42,"faq":155,"tags":162},"viridans-streptococci-pathogenesis-and-lab-diagnosis","Viridans Streptococci: Pathogenesis and Lab Diagnosis","\u003Cp>Viridans streptococci morphology, dental and endocarditis pathogenesis, and how optochin resistance and bile insolubility distinguish them from \u003Cem>S. pneumoniae.\u003C\u002Fem>\u003C\u002Fp>","Srijana Khanal","2022-05-29","2026-08-06",[156,159],{"question":157,"answer":158},"Why are viridans streptococci called \"viridans\"?","The name comes from the Latin \"viridis,\" meaning green, describing the green discoloration these organisms produce on blood agar due to alpha-hemolysis.",{"question":160,"answer":161},"Can viridans streptococci cause infective endocarditis in a healthy heart?","It's uncommon. Viridans streptococci typically cause subacute endocarditis in patients with pre-existing valve damage or prosthetic valves, where dextran helps them bind to fibrin-platelet aggregates on the damaged surface. This is why dental patients with known heart valve problems require antibiotic prophylaxis before procedures.",[60],{"enabled":164,"threads":165,"total":166},true,[],0,[168,174,181,188,194,199,205,210,215,218,225],{"slug":169,"name":43,"description":170,"image":171,"body":172,"postCount":173},"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.*",479,{"slug":175,"name":176,"description":177,"image":178,"body":179,"postCount":180},"ashma-shrestha","Ashma Shrestha","SEO Copywriter and Science Communicator\nKathmandu, Nepal","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Fashma-shrestha.png","Ashma Shrestha holds a Master of Science in Medical Microbiology from the Institute of Science and Technology (IOST), Tribhuvan University, Nepal, where she developed a strong foundation in virology, molecular biology, and diagnostic microbiology.\n\nShe now works as an SEO Copywriter at Resolution Digital, where she combines her scientific training with research-driven content strategy. She is certified in Google Analytics and Google Business Profile (GBP), and brings a data-informed approach to science communication writing content that is not only accurate but structured to reach and serve the students who need it most.\n\nAt microbeonline, Ashma contributes articles primarily in virology and molecular biology, areas she finds most compelling for their mechanistic depth and their growing clinical relevance. Her writing reflects the same standard the site is built on: factual rigor, clear explanation of the *why* behind microbiology concepts, and content that helps students move from memorization to genuine understanding.\n\nShe is passionate about making complex microbiological concepts accessible without sacrificing accuracy; a skill that sits at the intersection of her scientific training and her professional work in content and SEO.",78,{"slug":182,"name":183,"description":184,"image":185,"body":186,"postCount":187},"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":189,"name":190,"description":184,"image":191,"body":192,"postCount":193},"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":195,"name":196,"description":184,"image":42,"body":197,"postCount":198},"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":200,"name":201,"description":202,"image":42,"body":203,"postCount":204},"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":206,"name":207,"description":208,"image":42,"body":42,"postCount":209},"guest-author","Guest Author","Guest Author \u002F Contributor",1,{"slug":211,"name":152,"description":184,"image":212,"body":213,"postCount":214},"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":216,"name":217,"description":208,"image":42,"body":42,"postCount":209},"dr-poonam-acharya","Dr. Poonam Acharya",{"slug":219,"name":220,"description":221,"image":222,"body":223,"postCount":224},"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":226,"name":227,"description":228,"image":229,"body":230,"postCount":209},"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.",[232,239,245,249,254,259,263,267,271,276,280,285,289,294,299,303,307,311,316,321,325,329,333,338,342,346,350,354,359,364,368,372,376,381,385,389,393,397,401,404,408,412,416,420,424,428,432,436,441,445,449,453,457,461,464,468,471,475,479,483,487,491,495,499,503,507,511,515,518,522,525,528,531,534,537,540,543,546,549],{"slug":233,"name":234,"description":235,"image":236,"body":237,"postCount":238},"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":240,"name":241,"description":242,"image":42,"body":243,"postCount":244},"microscopy","Microscopy","Microscope types, components, and microscopy techniques","These are list of blog posts related to microscopy. ",12,{"slug":60,"name":246,"description":247,"image":42,"body":42,"postCount":248},"Gram-Positive Cocci","Staphylococcus, Streptococcus, Enterococcus, Micrococcus — organisms, diseases, and identification tests",11,{"slug":250,"name":251,"description":252,"image":42,"body":42,"postCount":253},"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":255,"name":256,"description":257,"image":42,"body":42,"postCount":258},"gram-positive-rods","Gram-Positive Rods","Bacillus, Clostridium, Listeria, Corynebacterium, Actinomyces and related organisms",8,{"slug":260,"name":261,"description":262,"image":42,"body":42,"postCount":248},"mycobacteria","Mycobacteria","Mycobacterium tuberculosis, leprosy, atypical mycobacteria, and acid-fast organism diagnosis",{"slug":264,"name":265,"description":266,"image":42,"body":42,"postCount":248},"anaerobic-bacteriology","Anaerobic Bacteriology","Anaerobic organisms, anaerobic culture methods, and anaerobic infection diagnosis",{"slug":268,"name":269,"description":270,"image":42,"body":42,"postCount":244},"enterobacteriaceae","Enterobacteriaceae","Identification, differentiation, and clinical significance of Enterobacteriaceae family members",{"slug":272,"name":273,"description":274,"image":42,"body":42,"postCount":275},"spirochetes","Spirochetes","Treponema, Leptospira, Borrelia and spirochetal infections",7,{"slug":277,"name":278,"description":279,"image":42,"body":42,"postCount":214},"food-microbiology","Food Microbiology","Food-borne pathogens, food safety, spoilage, and preservation",{"slug":281,"name":282,"description":283,"image":42,"body":42,"postCount":284},"antimicrobial-susceptibility-testing","Antimicrobial Susceptibility Testing","Methods for testing antibiotic susceptibility in clinical microbiology",21,{"slug":286,"name":287,"description":288,"image":42,"body":42,"postCount":204},"antimicrobials-moa-amr","Antimicrobials (MOA & AMR)","Mechanisms, detection, and clinical significance of antimicrobial resistance",{"slug":290,"name":291,"description":292,"image":42,"body":42,"postCount":293},"sterilization-disinfection","Sterilization and Disinfection","Methods of sterilization and disinfection in healthcare and laboratory settings",10,{"slug":295,"name":296,"description":297,"image":42,"body":42,"postCount":298},"specimen-collection-transport","Specimen Collection and Transport","Collection, handling, and transport of clinical specimens for microbiological testing",27,{"slug":300,"name":301,"description":302,"image":42,"body":42,"postCount":284},"bacterial-structure-physiology","Bacterial Structure and Physiology","Bacterial cell structure, growth, physiology, and environmental factors affecting growth",{"slug":304,"name":305,"description":42,"image":42,"body":306,"postCount":198},"horizontal-gene-transfer","Horizontal Gene Transfer","Articles related to **Horizontal Gene Transfer**",{"slug":308,"name":309,"description":42,"image":42,"body":310,"postCount":293},"chromatography","Chromatography","Information about chromatographic techniques.",{"slug":312,"name":313,"description":314,"image":42,"body":315,"postCount":275},"electrophoresis","Electrophoresis","Information about Electrophoresis Techniques ","Detailed information  about Electrophoresis Techniques ",{"slug":317,"name":318,"description":319,"image":42,"body":320,"postCount":198},"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":322,"name":323,"description":324,"image":42,"body":42,"postCount":198},"bacteriophage","Bacteriophage","Description about Bacteriophage.",{"slug":326,"name":327,"description":328,"image":42,"body":42,"postCount":198},"malaria","Malaria","It is the collections of articles regarding malarial disease. ",{"slug":330,"name":331,"description":332,"image":42,"body":42,"postCount":198},"anaerobic-culture-techniques","Anaerobic Culture Techniques","Posts related with Anaerobic Culture Techniques.",{"slug":334,"name":335,"description":336,"image":42,"body":42,"postCount":337},"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":339,"name":340,"description":341,"image":42,"body":42,"postCount":275},"biosafety-levels","Biosafety levels ","Articles related to Biosafety Levels",{"slug":343,"name":344,"description":345,"image":42,"body":42,"postCount":253},"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":347,"name":348,"description":349,"image":42,"body":42,"postCount":198},"pipette","Pipette","Posts related with Pipette. ",{"slug":351,"name":352,"description":353,"image":42,"body":42,"postCount":258},"bacteriology-mcqs","Bacteriology MCQs","This sections lists MCQs in Bacteriology.",{"slug":355,"name":356,"description":357,"image":42,"body":42,"postCount":358},"parasitology-mcqs","Parasitology MCQs","This section lists MCQs in Parasitology.",2,{"slug":360,"name":361,"description":362,"image":42,"body":42,"postCount":363},"virology-mcqs","Virology MCQs","This is the collections of Multiple Choice Questions in Virology.",4,{"slug":365,"name":366,"description":367,"image":42,"body":42,"postCount":253},"mcqs-in-microbiology","MCQs in Microbiology","This section lists the collections of Multiple Choice Questions in General Microbiology Topics. ",{"slug":369,"name":370,"description":371,"image":42,"body":42,"postCount":258},"immunology-mcqs","Immunology MCQs","In this section; we are posting collections of Multiple Choice Questions about Immunology. ",{"slug":373,"name":374,"description":375,"image":42,"body":42,"postCount":204},"microbial-curiosities","Microbial Curiosities","In this clusters, we are posting interesting and unique information about Microorganisms. ",{"slug":377,"name":378,"description":379,"image":42,"body":42,"postCount":380},"bacterial-culture-media","Bacterial Culture Media","Posts related to Bacterial Culture Media. ",23,{"slug":382,"name":383,"description":384,"image":42,"body":42,"postCount":198},"fungal-culture-media","Fungal Culture Media","Posts related to Fungal Culture Media.",{"slug":386,"name":387,"description":388,"image":42,"body":42,"postCount":253},"motility-test","Motility Test","This lists the procedure regarding various tests methods for bacterial motility.",{"slug":390,"name":391,"description":392,"image":42,"body":42,"postCount":293},"bacterial-enumeration","Bacterial enumeration","These posts are related to isolation and enumeration of bacteria. ",{"slug":394,"name":395,"description":396,"image":42,"body":42,"postCount":358},"gram-positive-coccobacillus","Gram-positive coccobacillus","List of Gram Positive Coccobacilli",{"slug":398,"name":399,"description":400,"image":42,"body":42,"postCount":363},"dimorphic-fungi","Dimorphic Fungi","This is about various dimorphic fungi. ",{"slug":76,"name":402,"description":403,"image":42,"body":42,"postCount":275},"Bacterial Classification","These posts are related with various approaches used for the classification of Bacteria. ",{"slug":405,"name":406,"description":407,"image":42,"body":42,"postCount":253},"immunofluorescence","Immunofluorescence ","Various Tests related to Immunofluorescence ",{"slug":409,"name":410,"description":411,"image":42,"body":42,"postCount":204},"antibody-mediated-immunity","Antibody-mediated Immunity","This clusters links the articles that are sharing insights about Antibody-mediated immunity. ",{"slug":413,"name":414,"description":415,"image":42,"body":42,"postCount":275},"hypersensitivity","Hypersensitivity","Articles related to Hypersensitivity.",{"slug":417,"name":418,"description":42,"image":42,"body":42,"postCount":419},"haemophilus","Haemophilus",3,{"slug":421,"name":422,"description":423,"image":42,"body":42,"postCount":363},"sexually-transmitted-infections-stis","Sexually transmitted infections (STIs)","This is the clusters of infections that are transmitted sexually. ",{"slug":425,"name":426,"description":427,"image":42,"body":42,"postCount":244},"adaptive-immunity","Adaptive Immunity","Blog posts related to B Cell Immunity and T Cell Immunity.",{"slug":429,"name":430,"description":431,"image":42,"body":42,"postCount":238},"fungal-diagnostics","Fungal Diagnostics","Various methods used for the Diagnosis of Fungal Infections. ",{"slug":433,"name":434,"description":435,"image":42,"body":42,"postCount":253},"laboratory-storage-and-preservation","Laboratory Storage and Preservation","Articles about Laboratory Storage of Antimicrobial Disk, Test organisms and Equipment used for this process. ",{"slug":437,"name":438,"description":439,"image":42,"body":440,"postCount":198},"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":442,"name":443,"description":444,"image":42,"body":42,"postCount":204},"laboratory-glassware","Laboratory Glassware","Posts about Laboratory Glassware. ",{"slug":446,"name":447,"description":448,"image":42,"body":42,"postCount":198},"helminths","Helminths","In this section, we are covering properties, life cycle, pathogenesis and laboratory diagnosis of Helminths\u002FHelminthic infestations. ",{"slug":450,"name":451,"description":452,"image":42,"body":42,"postCount":275},"protozoan-parasite","Protozoan Parasite","In this cluster, we are covering protozoan parasites. ",{"slug":454,"name":455,"description":456,"image":42,"body":42,"postCount":209},"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":458,"name":459,"description":460,"image":42,"body":42,"postCount":293},"bacterial-staining-technique","Bacterial Staining Technique","Lists of various staining techniques that are used to stain bacteria. ",{"slug":147,"name":462,"description":463,"image":42,"body":42,"postCount":284},"Enzyme Tests","\u003Cp>Various Biochemical Test that are based on enzymatic activity of the microorganisms. \u003C\u002Fp>",{"slug":465,"name":466,"description":467,"image":42,"body":42,"postCount":248},"carbohydrate-utilization","Carbohydrate Utilization","\u003Cp>Various biochemical tests which are related to Carbohydrate fermentation or Utilization\u003C\u002Fp>",{"slug":107,"name":469,"description":470,"image":42,"body":42,"postCount":253},"Susceptibility-based ID","\u003Cp>These are susceptibility based identification test such as optochin sensitivity, bacitracin sensitivity etc. \u003C\u002Fp>",{"slug":472,"name":473,"description":474,"image":42,"body":42,"postCount":363},"microbial-metabolism","Microbial Metabolism","\u003Cp>Tests about Microbial Metabolism. \u003C\u002Fp>",{"slug":476,"name":477,"description":478,"image":42,"body":42,"postCount":258},"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":480,"name":481,"description":482,"image":42,"body":42,"postCount":419},"atypical-pneumonia","Atypical Pneumonia","\u003Cp>Organisms responsible for Atypical Pneumonia. \u003C\u002Fp>",{"slug":484,"name":485,"description":486,"image":42,"body":42,"postCount":253},"antigen","Antigen","\u003Cp>Various articles related to Antigens.\u003C\u002Fp>",{"slug":488,"name":489,"description":490,"image":42,"body":42,"postCount":275},"innate-immunity","Innate Immunity","\u003Cp>Articles related to Innate Immunity. \u003C\u002Fp>",{"slug":492,"name":493,"description":494,"image":42,"body":42,"postCount":363},"respiratory-tract-infection","Respiratory Tract Infection","\u003Cp>In this cluster, you can see various etiological agents that causes respiratory tract infection. \u003C\u002Fp>",{"slug":496,"name":497,"description":498,"image":42,"body":42,"postCount":253},"torch-infection","TORCH Infection","\u003Cp>In this section; you can find articles related with TOCH infection. \u003C\u002Fp>",{"slug":500,"name":501,"description":502,"image":42,"body":42,"postCount":275},"microbiology-for-beginners","Microbiology for Beginners","\u003Cp>These articles are very basic articles, which will share general concepts in Microbiology. \u003C\u002Fp>",{"slug":504,"name":505,"description":506,"image":42,"body":42,"postCount":198},"dna-replication","DNA Replication","\u003Cp>Articles related to DNA and Replication of DNA. \u003C\u002Fp>",{"slug":508,"name":509,"description":510,"image":42,"body":42,"postCount":275},"genetic-code","Genetic Code","\u003Cp>Articles related to Genetic Code.\u003C\u002Fp>",{"slug":512,"name":513,"description":514,"image":42,"body":42,"postCount":253},"molecular-technique","Molecular Technique","\u003Cp>Posts related to Molecular Techniques. \u003C\u002Fp>",{"slug":516,"name":517,"description":42,"image":42,"body":42,"postCount":209},"colorimetric-assay","Colorimetric Assay ",{"slug":519,"name":520,"description":521,"image":42,"body":42,"postCount":253},"pharmaceutical-microbiology","Pharmaceutical Microbiology","\u003Cp>Various articles related to Pharmaceutical Microbiology\u003C\u002Fp>",{"slug":523,"name":524,"description":42,"image":42,"body":42,"postCount":419},"blood-and-immune-cells","Blood and Immune Cells",{"slug":526,"name":527,"description":42,"image":42,"body":42,"postCount":253},"host-pathogen-interaction","Host Pathogen Interaction",{"slug":529,"name":530,"description":42,"image":42,"body":42,"postCount":363},"blood-culture","Blood Culture",{"slug":532,"name":533,"description":42,"image":42,"body":42,"postCount":363},"environmental-microbiology","Environmental microbiology ",{"slug":535,"name":536,"description":42,"image":42,"body":42,"postCount":198},"copromicroscopic-technique","Copromicroscopic Technique",{"slug":538,"name":539,"description":42,"image":42,"body":42,"postCount":419},"quality-control","Quality Control",{"slug":541,"name":542,"description":42,"image":42,"body":42,"postCount":363},"dermatophytes","Dermatophytes",{"slug":544,"name":545,"description":42,"image":42,"body":42,"postCount":419},"viral-hemorrhagic-fevers","Viral Hemorrhagic Fevers",{"slug":547,"name":548,"description":42,"image":42,"body":42,"postCount":363},"h2s-production","H2S Production",{"slug":550,"name":551,"description":42,"image":42,"body":42,"postCount":358},"water-quality-testing","Water Quality Testing"]