Lab Finals Flashcards
3 intracellular nutrients present in chocolate agar
- hemoglobin
- hemin (X factor)
- nicotinamide adenine dinucleotide (NAD or V factor)
2 bases of blood agar and chocolate agar
- trypticase soy agar
- nutrient agar
Bacteria inhibited by phenylethyl alcohol (PEA) agar
Gram negative bacteria
Level of sodium chloride in mannitol salt agar (MSA)
7.5% sodium chloride
Bacteria that is able to grow on MSA
Staphylococcus sp. (+ salt-tolerant strains of Micrococcus and Enterococcus)
Carbohydrate in MSA
Mannitol
Indicator in MSA
Phenol red indicator
Color of colonies of mannitol fermenters in MSA
Yellow
Color of phenol red indicator at pH 8.4
Red
Color of phenol red indicator at pH 6.8
Yellow
Organisms that grow on Eosin Methylene Blue (EMB) agar
Gram negative bacteria
Organisms differentiated by EMB agar
Lactose fermenters (purple to green metallic sheen) from non-lactose fermenters (colorless)
2 dyes in EMB agar that inhibit gram positive bacteria
- eosin
- methylene blue
Carbohydrate in EMB agar
Lactose
Color of E. coli in EMB agar
Green metallic sheen
Organism with fish-eye appearance on EMB agar
Enterobacter aerogenes
Color of non-lactose fermenters in EMB agar
Colorless
Organism with green metallic sheen on EMB agar
E. coli
Organisms that grown on MacConkey (MAC) agar
Gram negative bacteria
Organisms differentiated by MAC agar
Lactose fermenters (pink to red) from non-lactose fermenters (colorless)
2 substances in MAC agar that inhibits gram positive bacteria
- Bile salts
- crystal violet
Carbohydrate source of MAC agar
Lactose
Organisms that grow on Hektoen Enteric Agar (HEA)
Stool pathogens
Organisms inhibited by HEA
Normal flora coliforms of the lower GI tract
2 inhibitors in HEA
Bile salts & citrate
3 carbohydrate sources in HEA
- lactose
- sucrose
- salicin
Indicator in HEA
Bromthymol blue indicator
pH ranges of bromthymol blue
- pH greater than 7.6: blue
- pH 6.0-7.6: green
- pH less than 6.0: yellow
H2S indicator in HEA
ferric ammonium citrate with Sodium thiosulfate
Color of colonies in HEA if they ferment 1-3 carbohydrates
Orange
Color of colonies in HEA is they are non-fermenters of carbohydrates
Green
Color of pathogens in HEA
Green colonies with or without black centers
Color of normal flora in HEA
Yellow colonies
Pathogen that produces yellow colonies in HEA due to sucrose fermentation
Yersinia enterocolitica
Organisms that grow in Xylose-Lysine Desoxycholate (XLD)
Stool pathogens
Inhibitor in XLD; inhibits gram positive bacteria, E. coli and inhibits swarming of Proteus
Desoxycholate and citrate
Indicator in XLD
Phenol red indicator
3 carbohydrates in XLD
- Xylose
- sucrose
- dextrose
Color of Salmonella on XLD
Red colonies with black centers
Color of Citrobacter and Proteus on XLD
Yellow colonies with black centers
Organism in XLD that produce red colonies with black centers
Salmonella
2 organisms that produce yellow colonies with black centers in XLD
- Proteus
- Citrobacter