Microbiology Notes By Sagar Aryal
Introduction Thayer-Martin Agar was developed in 1964 for the isolation of N. gonorrhoeae and N. meningitidis. A further modification of these early formulations was developed to improve the isolation of pathogenic Neisseria sp. from specimens, which contained large amounts of mixed microbial flora. Martin-Lewis Agar is the formulation made after modification which contains an increased … Read moreMartin Lewis Agar
Modified Thayer Martin Agar Thayer and Martin reported an improvement of the Chocolate Agar formulation that contained antimicrobics vancomycin, colistin and nystatin have been added to minimize overgrowth by contaminants, suppress the growth of saprophytic Neisseria sp., and enhance the growth of pathogenic Neisseria. Martin and Lester later added antibiotic trimethoprim to make the medium … Read moreModified Thayer Martin Agar
Yeast Extract Peptone Dextrose (YPD or YEPD) Agar Yeasts are unicellular eukaryotes and extensively studied model organism in molecular genetics. They are chemoorganotrophs as they utilize organic compounds as a source of energy. Yeast extract peptone dextrose (YPD or YEPD) Growth Agar is used for the maintenance and propagation of yeasts including S. cerevisiae in … Read moreYeast Extract Peptone Dextrose (YPD or YEPD) Agar
Heart Infusion Agar Fastidious organisms having exacting nutritional requirement can be cultivated on infusion media. Meat infusions were included in the first media used for the cultivation of bacteria. Huntoon prepared a medium using fresh beef heart and peptone which became known as Heart Infusion Agar. He demonstrated it could be used to support the … Read moreHeart Infusion Agar
Egg Yolk Agar Egg Yolk Agar, modified is based on the original formula for Egg Yolk Agar developed by McClung and Toabe for the isolation and differentiation of organisms based on Lecithinase and lipase production and proteolytic activity. Image Source: Noura El-Ahmady El-Naggar, DOI: 10.5897/AJMR11.346 Composition of Egg Yolk Agar Ingredients Gms/litre Casein enzymic hydrolysate 15.000 … Read moreEgg Yolk Agar
CHROMagar (Rambach Agar) The first chromogenic culture medium for detection of E. coli was invented and patented by Dr. A. Rambach in 1979. This technology is color-based differentiation method. It is based on soluble colorless molecules (called chromogens), composed of a substrate (targeting a specific enzymatic activity) and a chromophore. When the target organism’s enzyme … Read moreCHROMagar (Rambach Agar)
Endo Agar Endo Agar was developed by Endo to differentiate gram-negative bacteria on the basis of lactose fermentation while inhibiting gram-positive bacteria. Inhibition of the later was achieved without the use of bile salts as was traditionally used. Endo was successful in inhibiting gram-positive bacteria on his medium by the incorporation of sodium sulfite and … Read moreEndo Agar
Hektoen Enteric Agar Hektoen Enteric Agar is a selective and differential medium designed to isolate and differentiate members of the species Salmonella and Shigella from other Enterobacteriaceae. The medium was introduced in 1968 by Sylvia King and William I. Metzger. They formulated HE Agar medium while working at the Hektoen Institute in Chicago, to increase … Read moreHektoen Enteric Agar
Eosin Methylene Blue (EMB) Agar Eosin Methylene Blue (EMB) agar is a differential microbiological medium, which slightly inhibits the growth of Gram-positive bacteria and provides a color indicator distinguishing between organisms that ferment lactose (e.g., E. coli) and those that do not (e.g., Salmonella, Shigella). EMB agar was originally devised by Holt-Harris and Teague and further modified by Levine. It is thus … Read moreEosin Methylene Blue (EMB) Agar
Deoxycholate Citrate Agar (DCA) Deoxycholate Citrate Agar is a modification of Leifson formula and is recommended for the isolation of Salmonella and Shigella spp. This medium is similar to deoxycholate agar in comparison but is moderately more selective for enteric pathogens owing to increased concentrations of both citrate and deoxycholate salts. Sodium deoxycholate at pH … Read moreDeoxycholate Citrate Agar (DCA)