Quiz 3 Flashcards
Risk Group 2 organisms handled in Selective/differential media lab
Proteus mirabilis and Proteus vulgaris
Proteus mirabilis characteristics
cream-colored smooth cultures, swarming
found in human intestines, water, soil
known to cause conjunctivitis, cellulitis, UTIs, pyelonephritis, respiratory infections
Proteus vulgaris characteristics
cream-colored smooth cultures
swarms but not as much as P. mirabilis
found in human intestines, water, soil
known to cause conjunctivitis, UTIs, and bloodstream and respiratory infections
Factors that make media selective
presence of toxic or inhibitory substances like salts, acid, base, chemical(crystal violet or methylene blue, antibiotics
purpose of selective Phenyl ethyl alcohol agar
isolate streptococci and staphylococci
selects for gram-positive
how does PEA agar select for gram-positive
phenyl ethyl alcohol inhibits DNA synthesis in gram-negative bacteria
what media can grow anaerobic gram-positive bacteria if 5% sheep’s blood is added?
phenyl ethyl alcohol agar
what does mannitol salt agar select for and how
selects for halotolerant species like Staphylococcus by high concentrations of salt
how does mannitol salt agar differentiate
on the basis of the ability to ferment mannitol
pathogenic species will ferment it and they will turn the pH indicator yellow
results of S. saprophyticus, S. epidermidis, and E. coli on MSA
S. saprophyticus turns yellow on this agar, S. epidermidis does not, E. coli does not grow
results of S. saprophyticus, S. epidermidis, and P. mirabilis on PEA agar
S. saprophyticus and S. epidermidis grow but P. mirabilis does not
for what and how does MacConkey agar select
isolate and differentiate the family Enterobacteriaceae
selects for gram-negative by inhibiting gram-positive cells with bile salts and crystal violet
how does MacConkey Agar differentiate
whether the organism can ferment lactose to acid
red indicates a lactose fermentor
results of E. coli DH5, P. vulgaris, and S. epidermidis on MacConkey Agar
Staphylococcus epidermidis cannot grow, Proteus vulgaris grows in a colorless colony, and Escherichia coli has a red color
Eosin Methylene Blue purpose and selectivity
isolate fecal coliforms
selects for gram-negative, pos. are inhibited by methylene blue
differentiation of EMB agar
eosin changes color based on fermentation of lactose and sucrose
green metallic sheen: coliforms present
pink: slow fermenters
colorless: non-fermenters
results of E. coli DH5, S. marcescens, and S. epidermidis on EMB agar
Staphylococcus epidermidis can’t grow
Serratia marcescens is pink
Escherichia coli DH5 is green
Hektoen agar purpose
isolate Shigella and Salmonella species from other enterics
Hektoen agar selects for what and how
selects for gram-negative
positive inhibited by bile salts
differentiation methods of HE agar
enterics other than Salmonella and Shigella will ferment lactose, sucrose, and salicin and produce yellow to pink colonies
Shigella, bacteria that ferment nothing, will have green/blue colonies
Salmonella, a species that reduces sodium thiosulfate to H2S, will produce black ppt
dyes used in HE agar
bromthymol blue and acid fuchsin indicate the fermentation of sugars
results of C. freundii, E. coli DH5, and S. epidermidis on HE agar
Staphylococcus epidermidis can’t grow
Citrobacter freundii turns blue/green
Escherichia coli DH5 turns yellow
Biosafety cabinet function
Recycle 70% of airflow through HEPA filters back into the workspace and 30% exhausted through more filters to prevent contamination by aerosols
Aspergillus niger group, hyphae type, and sexual/asexual spores
Deuteromycetes
Septate
No sexual spores
Conidia asexual spores
