Growth Media

Growth Media

1. Agar Plates

   • Enriched Media
     • Contains specific nutrients required by bacterial pathogens to grow.
       • Sheep Blood Agar
         • Allows cultivation of fastidious organisms and shows hemolytic reactions
       • Chocolate Agar
         • Contains the same components as blood agar, but has been heated to 80C to lyse the RBCs, releasing X and V factor. For the growth of fastidious species, such as Neisseria and H. influenzae
       • Brain Heart Infusion Agar
         • Used for the cultivation of fastidious organisms including some fungi. Contains peptones, brain heart infusion, glucose, NaCl, and defibrinated sheep blood.
       • Mueller Hinton Agar
         • Contains beef extract, acid hydrosylate of casein, starch, and agar. A non-selective and non-differential medium that is used for antimicrobial susceptibility testing via the disk diffusion method.
   • Selective Media
     • Bordet-Gengou Agar
       • Potato-glycerol-based medium entiched with 15-20% defibrinated blood. Contains methicillin. Used for the isolation of Bordetella pertussis.
     • Buffered Charcoal Yeast Extract Agar
       • Contains yeast extract, charcoal, salts, l-cysteine HCl. ferric pyrophosphate, ACES buffer, and alpha-ketoglutarate. For the isolation of Legionella spp.
     • Columbia Colistin-Nalidixic Acid Agar
       • Columbia based agar with colistin, nalidixic acid, and 5% sheep blood. Prevents the growth of Gram-negative bacilli and selection for GPCs.
     • New York City Agar
       • Contains peptones, corn starch, phosphates, yeast autolysate, and antibiotics. Selects for Neisseria spp. as well as some mycoplasmas.
     • Modified Thayer-Martin Agar
       • Chocolate-based agar containing vancomycin, colistin, nystatin, and trimethoprim. Selects for Neisseria spp.
     • Strep Selective Agar
       • Contains crystal violet, colistin, trimethoprim-sulfamethoxazole, and 5% sheep blood. Selects for GAS and GBS.
     • Phenyl Ethyl Alcohol Agar
       • Inhibits the growth of Gram-negative organisms, selecting for Gram-positive cocci and anaerobic Gram-negative bacilli.
     • Thiosulfate-citrate-bile salts-sucrose Agar (TCBS)
       • Contains proteose peptone, yeast extract, bile, sodium citrate, sodium thiosulfate, sucrose, and bromthymol blue pH indicator.
     • Bird Seed Agar
       • Composed of glucose, seeds containing caffeic acid, potassium dihydrogen orthophosphate, and antibiotics. Inhibits most bacteria while allowing Cryptococcus spp. to grow and produce pigmentation. Brown-black colonies are positive for C. neoformans. Non-pigmented colonies include C. laurentii and Saccharomyces cerevisiae.
     • Lowenstein-Jensen Medium
       • Contains L-Asparagine, potato flour, monopotassium phosphate, magnesium sulfate, malachite green, egg suspension, and glycerol. Malachite green serves as an antimicrobial. Used for the cultivation of Mycobacterium spp., particularly M. tuberculosis.
   • Differential Media
     • Egg Yolk Agar
       • Differentiates between organisms that possess the enzymes lecithinase and lipase. Organisms that utilize lecithinase will produce a white opaque zone of precipitation around the colonies. Organisms that utilize lipase will produce colonies with an iridescent sheen on the surface.
     • ChromAgar
       • Contains peptones, NaCl, sodium deoxycholate, and chromogens. Used to differentiate between members of Enterobacteriaceae. Species of Salmonella produce pink to red colonies.
   • Selective and Differential Media
     • MacConkey Agar
       • Contains peptones, lactose, crystal violet, and bile salts. Neutral red is used as a pH indicator. Inhibits Gram positive organisms and allows for the growth and differentiation of lactose-fermenting Gram negative organisms. Lactose fermenters will form pink colonies.
         • MacConkey Sorbitol Agar: replaces lactose with sorbitol, which E. coli 0157:H7 cannot ferment.
     • Mannitol Salt Agar
       • Contains peptones, mannitol, phenol red indicator, and 7.5% NaCl. Used for the selection and differentiation of Staphylococcal species. S. aureus ferments mannitol, producing yellow colonies. Coagulase-negative Staph and Micrococcus spp. do not ferment mannitol and produce red colonies.
     • Eosin Methylene Blue Agar
       • Used for the selection and differentiation of enteric pathogens that ferment lactose. Contains peptones, lactose, and sucrose. Eosin and methylene blue act as indicators. Lactose fermenters will produce a green metallic sheen.
     • Hektoen Enteric Agar
       • Contains peptones, bile salts, lactose, sucrose, salicin, and ferric ammonium citrate. Bromthymol blue and acid fuchsin act as indicators. Used for the selection and differentiation of Salmonella and Shigella spp. from other Gram-negative enteric spp. Non-pathogenic spp. will produce salmon-colored colonies. Salmonella and Shigella produce green-black colored colonies.
     • Bile Esculin Agar
       • Contains peptones, bile salts, esculin, and ferric citrate. Allows for the selection and differentiation of Group D streptococci from Enterococci. GDS hydrolyzes esculin, resulting in dark-brown to black colonies
     • Xylose Lysine Deoxycholate Agar
       • Contains sodium deoxycholate, NaCl, xylose, lactose, sucrose, L-Lysine, phenol red indicator, and ferric ammonium citrate. Used for the selection and differentiation of Salmonella and Shigella spp. Salmonella can ferment xylose, producing a yellow color. Over time, the Salmonella colonies will turn pink, mimicking the Shigella colonies. The Salmonella colonies will metabolize thiosulfate to produce hydrogen sulfide, turning their centers black. Thus, Salmonella colonies will be pink with a black center and Shigella colonies will just be pink.
     • Simmons Citrate Agar
       • Media that is used to differentiate Gram-negative bacteria based on their ability to utilize citrate. Contains bromothymol blue as a pH indicator. A positive result turns the green media a blue color.

2. Broth

   • Thioglycollate Broth
     • Supports the growth of a wide range of organisms. Used to determine the oxygen requirements of an organism.
   • Todd Hewitt Broth
     • Contains peptones, heart infusion, NaCO3, NaCl, and Na2PO4. Used for the cultivation of Strep spp., pneumococci, and other fastidious organisms.
       • LIM Broth
         • Todd Hewitt broth with colistin and nalidixic acid. Used for the cultivation of GBS.

3. Slants

   • Triple Sugar Iron
     • Consists of peptones, 1.0% lactose, 1.0% sucrose, and 0.1% glucose. Also contains phenol red pH indicator and ferrous sulfate. Used for the detection of carbohydrate fermentation and the production of hydrogen sulfide gas. Carbohydrate utilizers will turn the agar yellow, peptone utilizers will turn the agar red, and the production of hydrogen sulfide gas will turn the butt black. Reactions on the slant indicate oxidation while reactions on the butt indicate fermentation.
   • Lysine Iron Agar
     • Contains lysine, peptones, glucose, ferric ammonium citrate, sodium thiosulfate, and bromocresol purple indicator. Used for the detection of lysine deamination and lysine decarboxylation. Lysine deamination produced a burgundy slant, while lysine decarboxylation will produce a purple butt. Also tests for H2S production, similar to TSI slants.

4. Transport Media

   • Viral Transport Media
     • Contains salts, proteins, antibiotics, and buffers. Preserves viruses while still allowing some pathogenic bacteria to grow. Can be used for the cultivation of mycoplasma, chlamydia, and ureaplasma.
   • Cary and Blair Medium
     • Contains salts, sodium thioglycolate, and calcium chloride. Used for stool specimens to preserve pathogens such as Salmonella, Shigella, and Campylobacter.
   • Regan-Lowe Medium
     • Charcoal agar with defibrinated horse blood. Used to preserve Bordatella spp. for culture.

Images and files in the map