[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"$fxLN3MUwXCdr5RPjwZYIDpOj8CHyjOmngWTgoKXPtZbg":3,"$fPZn6kRyEI4Bew9eQeEiO-Qb3xLDNH4CcNmNv3BrU0P4":32,"$f3Ft0rKFJHppdzE-vuveecxx1BUcg9iOlMLtyzf_MJDg":145},[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":52,"related":54},"potato-dextrose-agar-pda-principle-composition-colony-characteristics","Potato Dextrose Agar (PDA): Composition, Preparation, Uses, and Fungal Colony Characteristics","Potato dextrose agar promotes sporulation in fungi that fail to produce conidia on richer media. Learn the composition, why potato infusion induces sporulation, typical colony characteristics of dermatophytes, and how PDA compares to Sabouraud agar.",null,"Nisha Rijal","2015-06-01","2026-07-13",false,"culture-media","A laboratory receives a skin scraping from a patient with a chronic nail infection. Culture on Sabouraud dextrose agar grows a slow-growing white mould after three weeks — but the hyphae are sterile: no conidia, no identifiable sporulation structure. A subculture onto potato dextrose agar produces rich sporulation after one week, revealing the characteristic pencil-shaped macroconidia and the red reverse pigment of *Trichophyton rubrum*.\n\nPotato dextrose agar was developed specifically for this purpose — stimulating sporulation in fungi that fail to produce identifying structures on nutritionally richer media. It is an essential supplementary medium in dermatophyte identification.\n\nPotato dextrose agar (PDA) is a general-purpose basal medium for identifying, cultivating and enumerating yeast and molds in foods and dairy products. It may also be used to cultivate yeasts and molds from clinical specimens. Since it stimulates sporulation and pigmentation, it also aids in cultivating and differentiating pathogenic and non-pathogenic fungi.\n\n![Fungal colony in PDA Source:Rachel Brown, University of Florida, Bugwood.org - Fungal colony in PDASource:Rachel Brown, University of Florida, Bugwood.org](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FFungal-colony-in-PDA-300x289.jpg)Figure: Fungal colony in PDA\\\nSource: Rachel Brown, University of Florida, Bugwood.org\n\nPDA is also useful for maintaining stock cultures of certain dermatophytes. Certain antibiotics or acids like chloramphenicol, tartaric acid and chlortetracycline can be added as selective agents.\n\nPotato dextrose agar with TA (tartaric acid) is recommended for the microbial examination of food and dairy products. Addition of chlortetracycline is recommended for the microbial enumeration of yeast and mold from cosmetics. Potato dextrose agar with chloramphenicol is recommended for the selective cultivation of fungi from mixed samples.\n\n## Principle\n\nPotato dextrose agar (PDA) contains dextrose as a carbohydrate source which serves as a growth stimulant and potato infusion provides a nutrient base for the luxuriant growth of most fungi. Agar is added as the solidifying agent. A specified amount of sterile tartaric acid (10%) may be incorporated to lower the pH of the medium to 3.5 so that bacterial growth is inhibited.\n\nCare should be taken not to reheat the acidified medium; heating in the acid state will hydrolyze the agar which can render the agar unable to solidify.\n\n## Composition of PDA\n\n\\*4.0gm of potato extract is equivalent to 200gm of potato infusion\n\n| Ingredients | Gm\u002FL |\n| --- | --- |\n| Dextrose | 20 g |\n| Potato extract | 4 g\\* |\n| Agar | 15 g |\n\nIf supplement added: tartaric acid – 1.4 gm (pH-3.5 +\u002F- 0.3 at 25°C)\n\nChloramphenicol   – 25 mg ( pH-5.6 +\u002F- 0.2 at 25°C)\n\nChlortetracycline    –  40 mg\n\n**Why potato infusion induces sporulation:** The potato infusion in PDA provides a nutritionally restricted environment — lower in amino acids and complex growth factors than [Sabouraud agar](https:\u002F\u002Fmicrobeonline.com\u002Fsabouraud-dextrose-agar-sda-principle-composition-uses-colony-morphology\u002F). Under nutritional stress, fungi are triggered to reproduce sexually or asexually, producing spores (conidia) as a survival mechanism. This is the reverse of what happens on rich media (blood agar, BHI), where organisms grow vegetatively without sporulating. The 2% dextrose provides sufficient carbon for sustained growth, while the restricted nitrogen from potato infusion creates the stress signal that triggers sporulation.\n\n## Procedure for Preparation of media\n\n1. Suspend 39 grams of dehydrated media (supplied by commercial suppliers) in 1000 ml of distilled water. Heat to boiling to dissolve the medium completely.\n2. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes. Mix well before dispensing.\n3. In specific work, when pH 3.5 is required, the medium should be acidified with sterile 10% tartaric acid. The amount of acid required for 100 ml. of sterile, cooled medium is approximately 1 ml. Do not heat the medium after the addition of the acid.\n4. To process the specimen, streak the specimen onto the medium with a sterile [inoculating loop](\u002Finoculating-loop-types-and-uses\u002F) to obtain isolated colonies.\n5. Incubate the plates at 25 – 30°C in an inverted position (agar side up) with increased humidity.\n6. Cultures should be examined weekly for fungal growth and held for 4 – 6  weeks before being reported as negative.\n\n## Result\n\nYeasts will grow as creamy to white colonies. Molds will grow as filamentous colonies of various colors.\n\n**Typical colony morphology of some fungi**\n\n| Fungi | Colony Characteristics |  |  |  |  |\n| --- | --- | --- | --- | --- | --- |\n|  | Texture | Surface color | Reverse color | Zonation | Sporulation |\n| A.candidus | Velvety thick | Creamish white | Slightly creamish | Radially furrowed on the reverse | Moderate |\n| A.niger | Velvety | White with typical black spores | Yellow | Heavily furrowed on the reverse | Heavy |\n| A.sulphureus | Velvety | Dirty white with yellow spores at the center | Orange to chocolate color | Slightly radially furrowed | Moderate |\n| A. versicolor | Floccose | White to orange-cream with green spores at the center | Bright orange | Heavily wrinkled on reverse | Moderate |\n| Penicillium corylophilum | Velvety | Dark green | Colorless to Creamish | With shallow centre and radially furrowed raised margin | Moderate |\n| P. expansum | Velvety | Dark green with clear exudates and distinct sterile white margin | Yellow | Radially furrowed | Heavy |\n| Penicillium spp | Powdery | Olivaceous green with sterile white margin | Orange to red, wrinkled | Radially furrowed | Heavy |\n| Fusarium oxysporum | Floccose | Magenta pink | Magenta-red turning violet | With concentric zones of dark and light reddish coloration | Poor |\n\nCount the number of colonies and consider the dilution factor (if the test sample was diluted) in determining the yeast and\u002For mold counts per gram or milliliter of material.\n\n## PDA vs Sabouraud Dextrose Agar (SDA)\n\n| Feature | PDA | SDA |\n| --- | --- | --- |\n| Nutrient base | Potato infusion + dextrose | Peptone + high dextrose (2–4%) |\n| pH | \\~5.6 (acidic) | 5.6 (acidic) |\n| Sporulation induction | **Excellent** — nutritional restriction triggers conidia | Moderate — some fungi sporulate well, others don't |\n| Dermatophyte pigment | **Better** — red\u002Fyellow reverse pigments more prominent on PDA | Less pronounced pigment |\n| General fungal growth | Good | Excellent — broader use |\n| Antibiotics added? | Can be acidified or antibiotics added for selective version | Chloramphenicol ± cycloheximide versions available |\n| Primary use | Dermatophyte identification; sporulation induction | General fungal isolation and primary culture |\n| Incubation temperature | 25–28°C | 25–28°C (dermatophytes); 35–37°C (pathogens) |\n\n**Practical rule:** Use SDA for primary isolation of all fungi. Subculture onto PDA when dermatophyte identification requires better sporulation or pigment development.\n\n## Key Exam Facts in One Table\n\n| Feature | Detail |\n| --- | --- |\n| Type | General-purpose fungal culture medium |\n| Key components | Potato infusion (starch, vitamins) + dextrose 2% + agar |\n| pH | \\~5.6 (acidic — inhibits most bacteria) |\n| Primary use | Dermatophyte identification; sporulation induction in poorly-sporulating fungi |\n| *T. rubrum* | Wine-red reverse pigment — characteristic on PDA |\n| *M. canis* | Lemon-yellow reverse — characteristic on PDA |\n| Sporulation mechanism | Nutritional restriction from potato infusion triggers conidial production |\n| vs SDA | SDA for general isolation; PDA for dermatophyte ID and sporulation |\n| Incubation | 25–28°C for 1–4 weeks |\n\n**References and further readings**\n\n1. Acharya T., Hare J. (2022) Sabouraud Agar and Other Fungal Growth Media. In: Gupta V.K., Tuohy M. (eds) Laboratory Protocols in Fungal Biology. Fungal Biology. Springer, Cham. [https:\u002F\u002Fdoi.org\u002F10.1007\u002F978-3-030-83749-5_2](https:\u002F\u002Flink.springer.com\u002Fbook\u002F10.1007\u002F978-3-030-83749-5)\n2. Larone DH. Larone's Medically Important Fungi: A Guide to Identification. 6th ed. ASM Press; 2018.\n3. Chander J. Textbook of Medical Mycology. 4th ed. Jaypee Brothers Medical Publishers; 2018.\n4. Murray PR, Rosenthal KS, Pfaller MA. Medical Microbiology. 9th ed. Elsevier; 2020.\n5. Forbes BA, Sahm DF, Weissfeld AS. Bailey & Scott's Diagnostic Microbiology. 14th ed. Elsevier; 2023.\n6. Koneman EW, Allen SD, Janda WM, Schreckenberger PC, Winn WC. Koneman's Color Atlas and Textbook of Diagnostic Microbiology. 6th ed. Lippincott Williams & Wilkins; 2006.",[46,49],{"question":47,"answer":48},"Why does potato dextrose agar induce better sporulation than Sabouraud dextrose agar in some fungi?","PDA provides a nutritionally restricted environment — the potato infusion is low in amino acids and complex growth factors compared to the peptone-rich Sabouraud agar. This nutritional restriction creates metabolic stress that triggers fungi to reproduce by sporulation as a survival mechanism. On richer media like blood agar or BHI, the same fungi grow lush vegetative mycelium without sporulating. The 2% dextrose in PDA provides sufficient carbon for sustained growth, while the restricted nitrogen from potato infusion delivers the stress signal. This is why PDA is the preferred medium for inducing sporulation in dermatophytes that fail to produce diagnostic conidia on standard media.",{"question":50,"answer":51},"What is the diagnostic significance of red\u002Fwine-coloured reverse pigment on PDA?","A characteristic red to wine-red reverse pigment on the underside of colonies on PDA is highly characteristic of Trichophyton rubrum — the most common cause of tinea pedis (athlete's foot), tinea unguium (onychomycosis), and tinea corporis worldwide. This red reverse pigment is more prominently expressed on PDA than on Sabouraud agar, making PDA subculture valuable for confirming T. rubrum identity when reverse pigment is absent or faint on primary isolation plates. In combination with the microscopic appearance (thin-walled pencil-shaped macroconidia and tear-drop microconidia) and clinical presentation, the red reverse on PDA is an important identification feature.",[53],"fungal-culture-media",[55,69,93,106,113],{"slug":56,"title":57,"description":58,"seoTitle":38,"seoDescription":38,"author":59,"createdDate":60,"lastUpdatedDate":41,"draft":42,"category":43,"image":38,"faq":61,"tags":68},"czapek-dox-agar-principle-composition-colony-characteristics","Czapek Dox Agar: Composition, Principle, and Colony Characteristics of Aspergillus and Penicillium","Czapek Dox agar is a synthetic medium with sucrose as the sole carbon source and nitrate as the sole nitrogen source — used for identification of Aspergillus, Penicillium, and other environmental fungi.","Sushmita Baniya","2022-06-11",[62,65],{"question":63,"answer":64},"What makes Czapek Dox agar different from Sabouraud dextrose agar for fungal identification?","Czapek Dox agar is a synthetic (chemically defined) medium with sucrose as the sole carbon source and sodium nitrate as the sole nitrogen source — providing minimal, standardised nutrition. Sabouraud dextrose agar contains peptone as a complex nitrogen source, supporting more luxuriant growth. On Czapek Dox, the nutritional restriction reveals phenotypic differences in colony texture, colour, and growth rate that are suppressed on richer media. This makes Czapek Dox particularly useful for taxonomic characterisation of Aspergillus and Penicillium species, where colony morphology on a defined medium is part of the formal species description. It is not used for primary isolation from clinical specimens as it does not support fastidious organisms.",{"question":66,"answer":67},"Which fungi are best identified on Czapek Dox agar?","Czapek Dox agar is primarily used for identification of Aspergillus and Penicillium species — both common environmental moulds that may cause opportunistic infections in immunocompromised patients. On Czapek Dox, Aspergillus fumigatus produces characteristic blue-grey to grey-green colonies, A. flavus produces yellow-green colonies with granular texture, and A. niger produces dense black colonies. Penicillium species produce characteristic blue-green powdery colonies with the brush-like conidiophore arrangement visible on LPCB mount. The standardised composition ensures reproducible colony morphology that matches published species descriptions used in formal identification.",[53],{"slug":70,"title":71,"description":72,"seoTitle":38,"seoDescription":38,"author":73,"createdDate":74,"lastUpdatedDate":41,"draft":42,"category":75,"image":38,"faq":76,"tags":92},"dermatophyte-test-medium-dtm-composition-preparation-and-uses","Dermatophyte Test Medium (DTM): Composition, Preparation, and the Pathogens It Can Miss","Why a clean, unchanged DTM tube after two weeks doesn't always mean no fungal infection, the color-change logic explained, and the one ingredient that can silently suppress a true pathogen along with the contaminants.","Acharya Tankeshwar","2021-01-30","mycology",[77,80,83,86,89],{"question":78,"answer":79},"What is Dermatophyte Test Medium (DTM) used for?","Screening for dermatophytes (ringworm-causing fungi) in samples like hair, skin scrapings, or nail clippings, using a color change from yellow to red\u002Fpink as the presumptive positive signal.",{"question":81,"answer":82},"Why does DTM turn red when dermatophytes grow?","Dermatophyte metabolism shifts the medium's pH alkaline, and the phenol red indicator turns pink at pH ≥ 8.2. Saprophytic fungi, by contrast, ferment sugars into acid and leave the medium yellow.",{"question":84,"answer":85},"Can DTM give a false negative result?","Yes. Cycloheximide, included to suppress saprophytic contaminants, can also suppress genuine pathogenic fungi that happen to be cycloheximide-sensitive, producing a \"no growth\" result indistinguishable from a true negative.",{"question":87,"answer":88},"Should DTM be used as the only fungal culture medium?","No. It should be paired with a cycloheximide-free medium whenever a broader fungal differential is clinically relevant, to avoid missing a cycloheximide-sensitive true pathogen.",{"question":90,"answer":91},"Why should DTM results be read within two weeks?","Because incubation beyond two weeks increases the risk of false positives, as slow-growing saprophytic fungi can eventually produce alkaline byproducts too.",[53],{"slug":94,"title":95,"description":96,"seoTitle":38,"seoDescription":38,"author":39,"createdDate":97,"lastUpdatedDate":41,"draft":42,"category":43,"image":38,"faq":98,"tags":105},"bird-seed-agar-principle-composition-uses","Bird Seed Agar (Niger Seed Agar): Composition, Uses, and Cryptococcus Identification","Bird seed agar selectively detects Cryptococcus neoformans by its brown-black melanin production from caffeic acid. Learn the principle, composition, colony appearance, and how it differentiates C. neoformans from other Cryptococcus species.","2018-10-31",[99,102],{"question":100,"answer":101},"How does bird seed agar identify Cryptococcus neoformans?","Bird seed agar (Niger seed\u002FStaib medium) contains caffeic acid derived from Guizotia abyssinica (Niger seeds). Cryptococcus neoformans possesses the enzyme laccase (phenol oxidase), which oxidises caffeic acid to melanin. This melanin deposits in the cell wall, producing distinctive brown-black colonies within 72 hours to 5 days at 30°C. Most other pathogenic yeasts — including all Candida species — lack laccase and remain white or cream coloured. The brown-black colony colour on bird seed agar is essentially diagnostic for Cryptococcus neoformans or C. gattii (both possess laccase) in the clinical laboratory.",{"question":103,"answer":104},"Can bird seed agar differentiate Cryptococcus neoformans from Cryptococcus gattii?","No — both C. neoformans and C. gattii produce laccase and give identical brown-black colonies on bird seed agar. They cannot be differentiated by this medium alone. Differentiation requires CanaVanine-Glycine-Bromothymol blue (CGB) agar: C. gattii grows on CGB agar and turns the medium blue (produces ammonia from glycine), while C. neoformans does not grow on CGB. This distinction matters clinically because C. gattii primarily infects immunocompetent hosts (unlike C. neoformans which predominantly causes disease in immunocompromised patients), affects different geographic areas, and may respond differently to antifungal therapy.",[53],{"slug":107,"title":108,"description":109,"seoTitle":38,"seoDescription":38,"author":39,"createdDate":110,"lastUpdatedDate":41,"draft":42,"category":43,"image":38,"faq":111,"tags":112},"sabouraud-dextrose-agar-sda-principle-composition-uses-colony-morphology","Sabouraud Dextrose Agar (SDA): Composition, Principle, Uses, and Colony Morphology","Sabouraud Dextrose Agar (SDA) is the standard medium for fungal isolation. Learn its composition, how its acidic pH selects for fungi, colony morphology of dermatophytes and yeasts, cycloheximide modification, and clinical uses.","2015-07-05",[],[53],{"slug":114,"title":115,"description":116,"seoTitle":38,"seoDescription":38,"author":73,"createdDate":117,"lastUpdatedDate":118,"draft":42,"category":43,"image":38,"faq":119,"tags":144},"common-fungal-culture-media-uses","Common Fungal Culture Media and Their Uses in Clinical Mycology","A complete guide to fungal culture media — non-selective, selective, and differential media used in clinical mycology, with incubation temperatures, specimen types, cycloheximide sensitivity chart, and links to individual media articles.","2014-01-26","2026-07-18",[120,123,126,129,132,135,138,141],{"question":121,"answer":122},"Why must cycloheximide-containing media never be used alone?","Cycloheximide inhibits Cryptococcus neoformans, Aspergillus, Fusarium, and some Candida species. Always pair Mycosel or DTM with a cycloheximide-free medium.",{"question":124,"answer":125},"What is the difference between SDA and BHI for fungal isolation?","SDA (pH 5.6, high glucose): dermatophytes and subculture. BHI: richer, supports both mold and yeast phases of fastidious dimorphic fungi (Histoplasma, Blastomyces, Coccidioides) from primary specimens.",{"question":127,"answer":128},"How do you identify Candida species on CHROMagar?","C. albicans = green; C. tropicalis = blue-grey; C. krusei = pink flat spreading; C. glabrata = pink-mauve small. Different colored colonies immediately reveal mixed Candida infections.",{"question":130,"answer":131},"Why is Niger seed agar specific for Cryptococcus?","Cryptococcus produces laccase that oxidizes caffeic compounds to melanin = brown colonies. No other common clinical yeast produces laccase. Definitive Cryptococcus identification test.",{"question":133,"answer":134},"Why do fungi require longer incubation?","Fungi grow much slower — 1-4 weeks vs 18-48 hours for bacteria. Dimorphic fungi may take 2-4 weeks. Hold cultures minimum 4 weeks before reporting negative.",{"question":136,"answer":137},"What are the limitations of DTM?","False positives occur after 14 days as saprophytes eventually turn medium red. Positive = red color within 10-14 days. DTM is presumptive only — confirm by microscopy.",{"question":139,"answer":140},"What is the purpose of Tween 80 in cornmeal agar?","Reduces surface tension to enhance chlamydospore, pseudohyphae, and hyphae formation. C. albicans and C. dubliniensis produce terminal chlamydospores not seen in other Candida species.",{"question":142,"answer":143},"Which media for CSF with suspected Cryptococcus meningitis?","Niger seed agar + BHI or SABHI (non-selective). Never use cycloheximide media — Cryptococcus is sensitive. Perform India ink preparation in parallel.",[53],[146,152,159,163,167,171,176,181,185,189],{"slug":147,"name":73,"description":148,"image":149,"body":150,"postCount":151},"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":153,"name":154,"description":155,"image":156,"body":157,"postCount":158},"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":160,"name":59,"description":161,"image":38,"body":38,"postCount":162},"sushmita-baniya","Author \u002F Contributor",32,{"slug":164,"name":165,"description":161,"image":38,"body":38,"postCount":166},"samikshya-acharya","Samikshya Acharya",20,{"slug":168,"name":169,"description":161,"image":38,"body":38,"postCount":170},"alisha-tripathi","Alisha Tripathi",6,{"slug":172,"name":173,"description":174,"image":38,"body":38,"postCount":175},"aastha-shrestha","Aastha Shrestha"," Author \u002F Contributor",9,{"slug":177,"name":178,"description":179,"image":38,"body":38,"postCount":180},"guest-author","Guest Author","Guest Author \u002F Contributor",2,{"slug":182,"name":183,"description":161,"image":38,"body":38,"postCount":184},"srijana-khanal","Srijana Khanal",18,{"slug":186,"name":187,"description":179,"image":38,"body":38,"postCount":188},"dr-poonam-acharya","Dr. Poonam Acharya",1,{"slug":190,"name":39,"description":161,"image":38,"body":191,"postCount":192},"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]