[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"$fxLN3MUwXCdr5RPjwZYIDpOj8CHyjOmngWTgoKXPtZbg":3,"$f7iegclfEgNZqpQRmTla6XpNucWFzAucqJNrydoUQZ3o":32,"$f3Ft0rKFJHppdzE-vuveecxx1BUcg9iOlMLtyzf_MJDg":166},[4,8,12,16,20,24,28],{"title":5,"slug":6,"path":7},"About Microbeonline.com","about-microbeonline-com","\u002Fabout-microbeonline-com\u002F",{"title":9,"slug":10,"path":11},"About Me","about-me","\u002Fabout-microbeonline-com\u002Fabout-me\u002F",{"title":13,"slug":14,"path":15},"Advertise with Us","advertise-us","\u002Fadvertise-us\u002F",{"title":17,"slug":18,"path":19},"Privacy Policy","privacy-policy","\u002Fprivacy-policy\u002F",{"title":21,"slug":22,"path":23},"Abbreviations","abbreviations","\u002Fabbreviations\u002F",{"title":25,"slug":26,"path":27},"Microbes","microbes","\u002Fmicrobes\u002F",{"title":29,"slug":30,"path":31},"Books","recommended-books","\u002Frecommended-books\u002F",{"type":33,"data":34},"blog",{"slug":35,"title":36,"description":37,"seoTitle":38,"seoDescription":38,"author":39,"createdDate":40,"lastUpdatedDate":41,"draft":42,"category":43,"image":38,"body":44,"faq":45,"tags":61,"related":63},"phage-typing-method","Phage Typing Method: Principle, Procedure, Results","How phage typing uses a bacterium's pattern of susceptibility to a phage panel to trace outbreaks, and why a \"positive\" result means the phage won.",null,"Acharya Tankeshwar","2020-03-05","2026-07-06",false,"bacteriology","A hospital records several severe *Staphylococcus aureus* wound infections across different wards over a few weeks. Infection control needs an answer fast: is this one outbreak strain moving between patients, or several unrelated infections that happened to cluster in time?\n\nCulturing and identifying the species answers \"what is it,\" but every case is already known to be *S. aureus*. What's needed is a way to tell whether these particular isolates are the same strain. Phage typing answers exactly that question by exposing each isolate to the same standardized panel of phages and reading which ones cause lysis. Two isolates with the same lysis pattern, the same phage type, are far more likely to share a common source; two isolates with different patterns very likely don't.\n\nThis is the same logic still used today for *Salmonella* Typhimurium DT104 and *Salmonella* Enteritidis PT4 in foodborne outbreak investigations, and it's why the \"pattern,\" not any single result, is what phage typing is actually reporting.\n\nBacteriophages, also known as phages, are viruses that attack bacteria. For the full history and range of phage applications, see the [Bacteriophage Hub](https:\u002F\u002Fmicrobeonline.com\u002Fbacteriophage-discovery-detection-applications\u002F). Depending on the method of replication, phages can be broadly classified as virulent phages (replicate via the lytic pathway) and temperate phages (replicate via both lytic and lysogenic pathways).\n\nIn phage typing, a panel of lytic phages is inoculated on a lawn inoculum of the bacteria under investigation. Phages which are able to set up a lytic infection in that isolate produce a clear zone. As the ability to be infected (and lysed) by different phages varies between different strains of bacteria, the pattern of lysis forms the basis of phage typing.\n\nMicrobiologists are using phage typing for several decades to determine the relatedness of species and also for various epidemiological purposes (surveillance, outbreak investigations etc.)  This phenotypical method is being replaced by various molecular typing methods Phage-typing methods are gradually being superseded by genotypic techniques such as clustered regularly interspaced short palindromic repeats (CRISPR) typing, whole-genome sequencing etc.\n\n## Principle\n\nBacterial strains are grown on a suitable culture medium and then subjected to attack by a series of different known phages. Some phages will kill the bacteria and lyse their colony, which can be visualized and measured but others won’t be able to kill a given bacteria. Depending on which groups of phages can lyse or fail to lyse bacterial strain, the bacteria are given a number, also called phage-type.\n\n![ - Bacteriophage typing method (Image source: Ref-2)](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FPhage-typing-The-bacterial-sample-to-be-typed-is-plated-together-with-a-series-of.png)Figure: Bacteriophage typing method (Image source: Ref-2)\n\nPhage typing has been used for decades for subtyping of *Salmonella* Typhimurium to determine the epidemiological relation among isolates. The system distinguishes more than 300 definitive phage types (DT) of *Salmonella* Typhimurium based on their patterns of lysis to a unique collection of Salmonella phages e.g., S. Typhimurium DT104. Phage typing is also done for other species of Salmonella e.g. *Salmonella* Enteritidis PT4. Similarly, Staphylococci are typed to determine whether the isolates belonged to the more virulent phage types so that the appropriate infection control method could be instituted.\n\n**Salient features of phage typing methods**\n\n1. Phage typing is a rapid and low-cost approach for the epidemiological surveillance and outbreak investigation (identification of the source of infection).\n2. Phage-typing is the most widely recognized typing method for *Staphylococcus aureus* and is also still used widely for sub-dividing serotypes of *Pseudomonas aeruginosa* and *Salmonella \u002F Shigella* spp. Phage typing still remains as the gold standard method for epidemiological surveillance of *S*. Typhimurium.\n\n## Procedure\n\n1. Label each plate with the name\u002Fnumber of test bacterium.\n2. Place a sterile cotton swab in the bacterial suspension and remove the excess fluid by pressing and rotating the cotton against the inside of the tube above the fluid level.\n3. Streak the swab in three directions over the surface of the agar medium to obtain uniform growth. A final sweep is made around the rim of the agar. This is done to make a lawn culture of bacterium.\n4. Allow the plates to dry for five minutes.\n5. Divide the plate in four quarters (using a pencil, by drawing a line in the backside of the plate) and name each quarter with the name of the bacteriophage which you are going to inoculate in that region.\n6. Once the agar media has dried completely, spot-inoculate 10 µl phages (according to the labelling) by dropping just a tiny amount of the phage suspension from the [pipette tip](\u002Fpipette-tips-types-uses-and-criteria-to-choose-it\u002F).\n7. Repeat the above procedure with a fresh pipette tip and spot-inoculate this phage on its specifically labelled region.\n8. Allow the phage inocula to dry completely.\n9. Incubate at 37°C for 1-2 days (or 30°C if incubation is more than 2 days).\n\n![Bacteriophage typing method - Phage Typing Procedure (Image source: Ref-3)](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FBacteriophage-typing-method.jpg)Figure: Phage Typing Procedure (Image source: Ref-3)\n\n**Reporting**\n\nExamine the plates for evidence of lysis (a giant plaque) in the area where phage was inoculated and tabulate the results. Record positive for lysis (= sensitivity of a bacterial strain to a particular phage).\n\nThis is the same reading logic used in antibiotic susceptibility testing by disk diffusion: a clear zone means something killed the bacteria there, susceptibility to a phage in this case rather than to an antibiotic. It's also worth distinguishing this \"giant plaque\" from the discrete, countable plaques used in a [plaque assay](https:\u002F\u002Fmicrobeonline.com\u002Fphage-plaque-assay-principle-procedure-results\u002F). Here, a concentrated spot of phage either produces a zone of lysis or it doesn't; the result is qualitative (sensitive or resistant to that phage), not a count of individual plaques.\n\n### Limitations\n\n1. Phage typing requires different phages so phage typing is beyond the scope of local diagnostic laboratories. It is generally performed only at reference laboratories.\n2. Phage typing requires substantial technical expertise to perform. Careful control of environmental conditions and other variables is technically demanding.\n3. Maintenance of typing phages by the reference laboratory is time consuming and expensive approach.\n4. phage-types can change following lysogenic conversion, loss of prophages, or gain or loss of R plasmids, and this variability is coupled with the continuous need to maintain the typing set of bacteriophages in a viable state by regular serial passage. This instability is the same phenomenon covered in [Bacteriophage Structure and Life Cycle](https:\u002F\u002Fmicrobeonline.com\u002Fbacteriophage-structure-replication-use\u002F): a strain's phage type is not a fixed identity, it can shift if the strain gains or loses a prophage through lysogenic conversion, or gains or loses an R plasmid.\n\n## How to Remember\n\n- **Reading the result:** a clear zone always means something got killed there, whether the killer is a phage (phage typing) or an antibiotic (disk diffusion susceptibility testing). Positive for lysis = that isolate is sensitive to that particular phage.\n- **\"Giant plaque\" isn't a real plaque count:** phage typing asks a yes\u002Fno question per phage (did it lyse this isolate or not), while a plaque assay asks a how-many question (how many individual phage particles are in a sample). Same visual idea, zone of clearing, different job.\n- **Why a phage type isn't permanent:** think of a phage type as a fingerprint written on something that can still be edited. Gain or lose a prophage through lysogenic conversion, or gain or lose an R plasmid, and the same strain's phage type can shift.\n\n## Key exam facts in one table\n\n| Concept | Detail | Why it matters |\n| --- | --- | --- |\n| Principle | A strain's susceptibility pattern to a standardized panel of phages defines its phage type | Same underlying idea as antibiogram-based typing, just with phages instead of antibiotics as the discriminating agent |\n| Classic examples | *Salmonella* Typhimurium DT104; *Salmonella* Enteritidis PT4; *Staphylococcus aureus* phage types | DT104 and PT4 are still commonly tested names in food\u002Foutbreak microbiology questions |\n| Positive result | A clear zone (lysis) at a phage's spot = that isolate is sensitive to that phage | Mirrors disk diffusion susceptibility logic: clear zone = the challenger won |\n| Main limitations | Requires reference-lab expertise and phage maintenance; technically demanding; phage types can change over time | Explains why phage typing is largely restricted to reference laboratories, not routine diagnostic labs |\n| Why phage types shift | Lysogenic conversion, prophage loss, R plasmid gain or loss | Ties directly to the phage life cycle content covered in Structure and Life Cycle |\n| Current status | Being progressively replaced by CRISPR typing and whole-genome sequencing | A common \"which method is now preferred\" exam angle |\n\n## Where Students Get Confused\n\n- **Assuming phage typing counts plaques the way a plaque assay does.** It doesn't. Phage typing is a per-phage yes\u002Fno susceptibility call across a panel; a plaque assay is a quantitative titer. The \"giant plaque\" language in the reporting step describes a zone of confluent lysis from a concentrated spot, not an individually countable plaque.\n- **Treating phage type as a fixed, permanent strain identity.** It can change if the strain gains or loses a prophage or an R plasmid, which is exactly why molecular methods like whole-genome sequencing have largely superseded it for definitive strain identification.\n- **Assuming phage typing is still the routine, first-line method everywhere.** It remains historically important and is still used in some reference labs and for some organisms, but it has been progressively replaced by CRISPR typing and whole-genome sequencing for most epidemiological work.\n\n**References and further reading**\n\n1. Mohammed, M. Phage typing or CRISPR typing for epidemiological surveillance of Salmonella Typhimurium?. BMC Res Notes 10, 578 (2017). \u003Chttps:\u002F\u002Fdoi.org\u002F10.1186\u002Fs13104-017-2878-0>\n2. Van der Merwe, Ruben & Helden, Paul & Warren, R & Sampson, Samantha & Gey van Pittius, Nico. (2014). Phage-based detection of bacterial pathogens. The Analyst. 139. 10.1039\u002Fc4an00208c.\n3. Kirchhelle Claas The forgotten typers: The rise and fall of Weimar bacteriophage-typing (1921–1935)0Notes Rec. \u003Chttp:\u002F\u002Fdoi.org\u002F10.1098\u002Frsnr.2019.0020>",[46,49,52,55,58],{"question":47,"answer":48},"What is phage typing used for?","Phage typing identifies and subtypes bacterial strains based on their pattern of susceptibility to a standardized panel of phages. It's used mainly for epidemiological surveillance and outbreak investigation, helping determine whether isolates from different cases share a common source.",{"question":50,"answer":51},"What does a positive phage typing result mean?","A positive result (a clear zone of lysis where a phage was spotted) means the bacterial isolate is sensitive to that particular phage. The overall pattern of positive and negative results across the full phage panel defines the isolate's phage type.",{"question":53,"answer":54},"Is a \"giant plaque\" in phage typing the same as a plaque in a plaque assay?","Not quite. The zone of lysis in phage typing comes from a concentrated spot of phage and gives a qualitative sensitive-or-resistant answer for that phage. A plaque assay instead counts individual, discrete plaques from a diluted sample to determine a quantitative phage titer.",{"question":56,"answer":57},"Why is phage typing mostly performed at reference laboratories rather than routine diagnostic labs?",": It requires maintaining a full panel of different phages in a viable state, careful control of technical variables, and substantial expertise, all of which are time-consuming and expensive to sustain outside specialized reference laboratories.",{"question":59,"answer":60},"Can a bacterial strain's phage type change over time?","Yes. Phage types can shift if a strain gains or loses a prophage through lysogenic conversion, or gains or loses an R plasmid, which is one reason phage typing has been progressively replaced by more stable molecular methods like whole-genome sequencing.",[62],"bacteriophage",[64,88,95,103,136],{"slug":65,"title":66,"description":67,"seoTitle":38,"seoDescription":38,"author":68,"createdDate":69,"lastUpdatedDate":41,"draft":42,"category":70,"image":38,"faq":71,"tags":87},"bacteriophage-discovery-detection-applications"," Bacteriophages: Discovery, Detection, and Applications in Modern Medicine","The history of bacteriophage discovery, how phages are detected in the environment, and why a century-old idea is now central to fighting antibiotic-resistant infections.","Guest Author","2022-05-21","general-microbiology",[72,75,78,81,84],{"question":73,"answer":74},"Who discovered bacteriophages, and when?","Frederick Twort first observed bacteriophage activity in England in 1915. Félix d'Herelle independently confirmed the discovery in France in 1917 and coined the term \"bacteriophage,\" and is often more strongly associated with the discovery because he pursued the research much further.",{"question":76,"answer":77},"Why did interest in bacteriophages decline after antibiotics were introduced?","Antibiotics worked broadly against many bacteria without needing to be matched to a specific host strain, making them faster and simpler to use than phages, which require a living, host-matched culture. Phage research and clinical use continued in Georgia and other former Soviet states even as interest declined in the West.",{"question":79,"answer":80},"What is the difference between a spot test and a plaque assay for detecting bacteriophages?","A spot test is a qualitative screen that shows whether an active phage is present against a given bacterial host, seen as a clear zone on a bacterial lawn. A plaque assay is a quantitative method using serial dilution and a double-layer agar overlay to determine the actual phage titer, the number of infectious particles present.",{"question":82,"answer":83},"Why has interest in bacteriophage therapy increased in recent years?","The rise of multidrug-resistant bacterial infections, where standard antibiotics fail, has renewed interest in phage therapy because phages can be matched with high specificity to resistant strains that no available antibiotic can treat.",{"question":85,"answer":86},"What are the main applications of bacteriophages besides therapy?","Bacteriophages are used in vaccine production, targeted drug delivery, as biomarker agents, for phage typing in disease diagnosis, for monitoring infections, and for decontaminating surfaces, in addition to their role in phage therapy for treating bacterial infections.",[62],{"slug":89,"title":90,"description":91,"seoTitle":38,"seoDescription":38,"author":39,"createdDate":92,"lastUpdatedDate":41,"draft":42,"category":70,"image":38,"faq":93,"tags":94},"bacteriophage-structure-replication-use","Bacteriophage Structure and Life Cycle: Lytic, Lysogenic, and Clinical Relevance","How bacteriophages are built and how they replicate, and why a dormant prophage can be the entire reason a bacterium turns pathogenic.","2020-06-22",[],[62],{"slug":96,"title":97,"description":98,"seoTitle":38,"seoDescription":38,"author":39,"createdDate":99,"lastUpdatedDate":41,"draft":42,"category":70,"image":100,"faq":101,"tags":102},"phage-plaque-assay-principle-procedure-results","Bacteriophage Plaque Assay: Principle, Procedure, Results","How the plaque assay counts infectious phage particles, why a \"plaque\" is the opposite of a bacterial colony, and where the dilution math trips students up.","2018-12-05","https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FBacteriophage-plaque-assay-1.jpg",[],[62],{"slug":104,"title":105,"description":106,"seoTitle":38,"seoDescription":38,"author":39,"createdDate":107,"lastUpdatedDate":41,"draft":42,"category":108,"image":38,"faq":109,"tags":134},"bacterial-genetics-mechanism-generalized-transduction","Generalized Transduction: Mechanism, Clinical Significance, and How It Spreads Antibiotic Resistance","How a packaging mistake inside a bacteriophage accidentally hands a random bacterial gene to a new host, the 1952 experiment that revealed it, and why it still matters for antibiotic resistance today.","2013-09-12","molecular-biology",[110,113,116,119,122,125,128,131],{"question":111,"answer":112},"What is generalized transduction?","Generalized transduction is the transfer of a random fragment of bacterial DNA from one bacterium to another, caused by a bacteriophage accidentally packaging host DNA instead of its own genome during the lytic cycle.",{"question":114,"answer":115},"Why is it called \"generalized\"?","Because the packaging error can occur anywhere along the host chromosome, virtually any gene, not a fixed, specific set, can potentially be transferred this way.",{"question":117,"answer":118},"Who discovered generalized transduction?","Norton Zinder and Joshua Lederberg discovered it in 1952 while studying Salmonella typhimurium, originally while looking for conjugation. They found that bacteriophage P22 could transfer genetic material even between bacteria physically separated by a filter.",{"question":120,"answer":121},"How is generalized transduction different from specialized transduction?","Generalized transduction happens during the lytic cycle from a random packaging mistake and can transfer any gene. Specialized transduction happens during the lysogenic cycle from an imprecise excision error and can only transfer genes located next to the phage's fixed integration site.",{"question":123,"answer":124},"Can generalized transduction spread antibiotic resistance?","Yes. It is a documented route for transferring antibiotic resistance genes, such as penicillinase genes, between Staphylococcus aureus strains, and continues to be studied as a mechanism of resistance spread in Salmonella and other genera.",{"question":126,"answer":127},"What is co-transduction?","Co-transduction is when two genes located close together on the bacterial chromosome are packaged into the same transducing phage particle and transferred together. The closer the genes, the higher their co-transduction frequency, a relationship historically used to map bacterial gene order.",{"question":129,"answer":130},"Can any bacteriophage cause generalized transduction?","Yes, both virulent and temperate phages can produce generalized transducing particles, since the packaging error is a lytic-cycle event and doesn't depend on the phage's ability to undergo lysogeny.",{"question":132,"answer":133},"Is the transducing phage particle infectious?","No. Since it contains only host DNA and no viral genome, it cannot replicate or initiate a normal infection; it can only deliver the host DNA it happens to be carrying.",[135,62],"horizontal-gene-transfer",{"slug":137,"title":138,"description":139,"seoTitle":38,"seoDescription":38,"author":39,"createdDate":107,"lastUpdatedDate":41,"draft":42,"category":108,"image":38,"faq":140,"tags":165},"bacterial-genetics-mechanism-specialized-transduction","Specialized Transduction: Mechanism, Steps, and How It Differs from Generalized Transduction","How a temperate phage's imprecise exit from a bacterial chromosome hands off specific genes to a new host, the discovery that defined the phenomenon, and a full comparison with generalized transduction.",[141,144,147,150,153,156,159,162],{"question":142,"answer":143},"What is specialized transduction?","Specialized transduction is a process in which a temperate bacteriophage transfers only specific host genes, the ones located immediately adjacent to its chromosomal integration site, from one bacterium to another.",{"question":145,"answer":146},"Why is it called \"specialized\"?","Because the phage always integrates at the same fixed site on the chromosome, it can only ever pick up the specific genes next to that site, never a random gene from elsewhere in the genome, unlike generalized transduction.",{"question":148,"answer":149},"What causes specialized transduction to happen?","It happens when a lysogenized prophage excises itself imprecisely during induction, accidentally taking a piece of the adjacent bacterial chromosome along with it and leaving part of its own genome behind.",{"question":151,"answer":152},"How is specialized transduction different from generalized transduction?","Specialized transduction occurs during the lysogenic cycle and transfers only genes next to the phage's integration site. Generalized transduction occurs during the lytic cycle, from a random packaging error, and can transfer virtually any gene on the chromosome.",{"question":154,"answer":155},"Is specialized transduction the same as lysogenic conversion?","No. Specialized transduction transfers a previous host bacterium's genes to a new host. Lysogenic conversion is when the phage's own genome directly gives its host a new trait, as with diphtheria toxin, Shiga toxin, and erythrogenic toxin, without transferring any other bacterium's genes.",{"question":157,"answer":158},"Who discovered specialized transduction?","Morse, Esther Lederberg, and Joshua Lederberg described it in 1956, working with lambda phage and the gal operon in E. coli.",{"question":160,"answer":161},"Why does a specialized transducing phage sometimes need a \"helper\" phage?","Because the transducing phage's genome is defective, part of it was left behind during the faulty excision, it often cannot complete a full infectious cycle on its own and needs a normal, co-infecting helper phage to supply the missing functions.",{"question":163,"answer":164},"Is specialized transduction used in research today?","Yes. It is used deliberately to make precise, unmarked gene deletions in bacterial chromosomes, including in Mycobacterium tuberculosis research.",[135,62],[167,173,180,185,189,193,198,202,206,210],{"slug":168,"name":39,"description":169,"image":170,"body":171,"postCount":172},"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.*",433,{"slug":174,"name":175,"description":176,"image":177,"body":178,"postCount":179},"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.",81,{"slug":181,"name":182,"description":183,"image":38,"body":38,"postCount":184},"sushmita-baniya","Sushmita Baniya","Author \u002F Contributor",32,{"slug":186,"name":187,"description":183,"image":38,"body":38,"postCount":188},"samikshya-acharya","Samikshya Acharya",20,{"slug":190,"name":191,"description":183,"image":38,"body":38,"postCount":192},"alisha-tripathi","Alisha Tripathi",6,{"slug":194,"name":195,"description":196,"image":38,"body":38,"postCount":197},"aastha-shrestha","Aastha Shrestha"," Author \u002F Contributor",10,{"slug":199,"name":68,"description":200,"image":38,"body":38,"postCount":201},"guest-author","Guest Author \u002F Contributor",2,{"slug":203,"name":204,"description":183,"image":38,"body":38,"postCount":205},"srijana-khanal","Srijana Khanal",18,{"slug":207,"name":208,"description":200,"image":38,"body":38,"postCount":209},"dr-poonam-acharya","Dr. Poonam Acharya",1,{"slug":211,"name":212,"description":183,"image":38,"body":213,"postCount":214},"nisha-rijal","Nisha Rijal","**Nisha Rijal** is a microbiologist and quality assurance specialist. She served for nearly 12 years as a microbiologist at the National Public Health Laboratory (NPHL), Nepal's national reference laboratory, and continues to work as a consultant microbiologist in international public health organization. ",51]