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
Campylobacter blood agar (Campy BAP)
Enrichment and selective media
For the isolation of Campylobacter from stool
Modified Thayer-Martin (MTM)
Selective media
For the isolation of Neisseria spp
Contains vancomycin, colistin, nystatin, and trimethoprim to inhibit growth of other bacteria and fungi
Martin-Lewis
Selective media
For the isolation of Neisseria spp
Similar to Thayer-Martin but different antibiotics are used
Inhibits yeast better
New York City medium (NYC)
Selective media
For the isolation of genital mycoplasmas
Cystine-tellurite blood agar
Differential media
For the isolation of Corynebacterium diphtheriae
C. diphtheriae colonies will grow black
Loeffler medium
Enrichment media
For growth of Corynebacterium diphtheriae
Promotes development of metachromatic granules
Tindale agar
Selective and differential media
For the isolation of Corynebacterium diphtheriae
Corynebacterium spp produce gray to black colonies due to reduction of tellurite
C. diphtheriae colonies are surrounded by a brown halo
Bismuth sulfite agar
Selective media
For the isolation of Salmonella
Bismuth sulfite and brilliant green inhibit most others
S. typhi colonies are black surrounded by metallic sheen
Others are light green
Cefsulodin-irgasan-novobiocin agar (CIN)
Selective media
For the isolation of Yersinia enterocolitica, Aeromonas, and Plesiomonas shigelloides
Crystal violet inhibits most Gram negatives
Novobiocin inhibits GPC
Cefsulodin inhibits most Gram positives and Gram negatives
Y. enterocolitica ferments mannitol and appears as red “bulls-eye” colonies surrounds by colorless halo
Alkaline peptone water (APW)
Enrichment media
For the recovery of Vibrio species from stool
Alkaline pH suppresses commensals
Gets sub-cultured to TCBS
Thiosulfate citrate bile salts sucrose agar (TCBS)
Selective media
For the isolation of Vibrio
High pH inhibits most bacteria
V. cholerae ferments sucrose and produces yellow colonies
V. parahaemolyticus and V. vulnificus don’t ferment sucrose and usually produce blue-green colonies
Bordet-Gengou agar
Selective and enrichment media
For the isolation of Bordetella pertussis
Potato glycerol based medium enriched with blood
Contaminants inhibited by methicillin
“Cough plate”
Bordetella colonies resemble mercury droplets
Regan-Lowe agar
Selective media
For the isolation of Bordetella pertussis
Charcoal agar supplemented with horse blood, cephalexin, and amphotericin B
Buffered charcoal-yeast extract agar (BYCE)
Enrichment media
For the isolation of Legionella
Yeast extract and L-cysteine enhance growth of Legionella
Charcoal absorbs toxic compounds
Mannitol salt agar (MSA)
Selective and differential media
For the identification of S. aureus
Fermentation of mannitol results in yellow colonies
7.5% salt inhibits most organisms from growing
All staph can grow on MSA
Anaerobic blood agar (CDC)
Nonselective and enrichment media
For the growth of obligate and facultative anaerobes
Contains yeast extract, L-cysteine, and vitamin K
Bacteroides bile-esculin agar (BBE)
Selective and differential media
For the identification of Bacteroides fragilis
Bile salts and gentamicin act as inhibitors
B. fragilis grows black with dark halos due to esculin hydrolysis
Brucella agar
Enrichment media
For the growth of obligate and facultative anaerobes
Colistin-nalidixic acid blood agar (CNA)
Selective media
For the growth of obligate anaerobes and Gram positive facultative anaerobes
Cycloserine cefoxitin fructose egg yolk agar (CCFA)
Selective and differential media
For the growth of Clostridium difficile
Colonies grow yellow because of lactose fermentation
Have a chartreuse fluorescence
Egg-yolk agar (EYA)
Enrichment agar
For the determination of lecithinase and lipase production by clostridia and fusobacteria
Kanamycin-vancomycin laked blood agar (KVLB)
Selective media
For the isolation of anaerobic Gram negative rods (especially Bacteroides and Prevotella)
Thioglycolate broth (THIO)
All purpose media for the growth of most aerobes and anaerobes
Can be used as a backup method broth that detects organisms present in small numbers or anaerobes
Thioglycolate acts as a reducing agent
Aerobes grow at top, strict anaerobes at the bottom, and facultative anaerobes throughout
