Media Flashcards
Types of Media
Supportive - supports the growth of most non-fastidious bacteria
Enrichment - contains added growth factors (blood, vitamins, yeast extract)
Selective - contains additives such as dyes, bile salts, alcohols, acids, or antibiotics to inhibit growth of certain bacteria (ex. gram pos)
Differential - formulated to provide distinct colonial appearances based on certain biochemical reactions (ex. lactose fermentation, H2S production, etc.)
Sheep blood agar (SBA)
Enrichment and differential media
For the isolation of most non-fastidious bacteria
Differentiation through hemolysis
Chocolate agar (CHOC)
Enrichment media
For the isolation of Haemophilus and Neisseria species
Contains X & V factors needed for growth
Columbia colistin-nalidixic acid agar (CNA)
Selective media
For the isolation of Gram positive organisms
Colistin and nalidixic acid suppress most Gram negatives
Phenylethyl alcohol agar (PEA)
Selective media
For the isolation of GPC and anaerobic GNR
Phenylethyl alcohol inhibits enteric GNR
Group A - selective strep agar (SSA)
Selective media
For the isolation of Group A strep from respiratory sources
Contains antibiotics to suppress normal throat flora
Group B strep will also grow on this media
Eosin methylene blue (EMB)
Selective and differential media
For the isolation of enteric GNR
Eosin and methylene blue inhibit Gram positives
Lactose fermenters grow green-black or purple
E. coli produces green metallic sheen
Non-lactose fermenters grow colorless
MacConkey agar (MAC)
Selective and differential media
For the isolation of enteric GNR
Bile salts and crystal violet inhibit most Gram positive growth
Lactose fermenters grow pink
Non-lactose fermenters grow colorless
Sorbitol MacConkey agar (SMAC)
Selective media
For the isolation of E. coli O157:H7
E. coli O157:H7 doesn’t ferment sorbitol and will grow colorless
Hektoen enteric agar (HE)
Selective and differential media
For the isolation of Salmonella and Shigella in stool
Bile salts, bromothymol blue, and acid fuchsin inhibit normal GI flora
Lactose fermenters (nonpathogens) grow orange to salmon pink
Non-lactose fermenters (pathogens) grow green to blue-green
H2S producing colonies grow black
Xylose lysin deoxycholate (XLD)
Selective and differential media
For the isolation of Salmonella and Shigella in stool
Deoxycholate inhibits many GNR and Gram positives
Grows four different types of colonies
Yellow (ex. E coli), yellow with black centers (ex. Proteus spp), colorless or red (ex. Shigella), and red with black centers (ex. Salmonella)
Salmonella-Shigella agar (SS)
Selective media
For the isolation of Salmonella and Shigella in stool
Brilliant green and bile salts inhibit other enterics
Salmonella and Shigella don’t ferment lactose so they grow colorless
Salmonella colonies will appear with black centers due to H2S production
Gram negative broth
Enrichment and selective media
Deoxycholate and citrate salts retard growth of Gram positives
Inoculated media gets sub-cultured onto selective differential agar after 6-8 hours and 18-24 hours incubation
Deoxycholate citrate agar
Selective media
For the isolation of Salmonella and Shigella
Inhibits other enterics
Campylobacter broth
Enrichment media
For the isolation of Campylobacter from stool
Sub-culture to Campy-selective agar after overnight incubation at 4 degrees Celsius