Lab Practical Exam Review Flashcards
bacterial spores require temperatures above __ for destruction
100°C
bacterial vegetative cells are killed at temperatures of ___ to ___ in __ minutes
60°C, 70°C, 10
fungi can be killed at __ to __
50 to 60°C
fungal spores require __ to __ in __ minutes for destruction
70°, 80°, 10
- test for hemolysis of colonies
- primarily to distinguish staphylococci and streptococci
blood agar plates
- tests for staphylococci
- differential for S. aureus versus avirulent staphylococci
mannitol salt agar
- used for neisseria and haemophilus bacteria
- neisseria develop pink/purple coloration after oxidase test (addition of p-aminodimethylaniline oxalate)
- requires CO2
chocolate agar
- demonstrates presence of diptheroids (corynebacteria)
- tellurite ions diffuse into bacteria and reduce to tellurium metal which preceipitates
Mueller-Hinton tellurite agar
blood agar, mannitol salt agar, chocolate agar, mueller-hinton tellurite agar
plates for throat microbiota
- detects yeasts and molds
- yeasts will be glistening and pigmented or not
- molds will appear fuzzy or powdery
- requires 25°C first
sabouraud agar
blood agar, mannitol salt agar, sabouraud agar
plates for skin microbiota
- differential test to determine S. aureus
- converts fibrinogen to fibrin forming a clot
coagulase
- enzyme that degrades DNA; addition of toluidine blue makes pink halo
- differential for S. aureus
DNase
- golden colored colonies
- produces coagulase
- produces DNase
- beta hemolytic
S. aureus
resistant to novobiocin
S. saprophyticus
gram-positive cocci including pathogenic and generally non-pathogenic strains
streptococci
sole member of the Lancefield group A streptococci often referred to as GAS, or group A strep
- beta hemolysis
- susceptible to bacitracin
S. pyogenes
most common cause of life-threatening neonatal sepsis; S. agalactiae
group B streptococci (GBS)
- hemolysis
- bacitracin test
- CAMP test
tests to identify human streptococcal pathogens
bacitracin antibiotic susceptibility; GAS is susceptible
bacitracin test
GBS make a peptide that interacts beta hemolysins of S. aureus causing increased hemolysis
CAMP test (peptide)
- isolation of distinct colonies
- determine purity of culture
streak plate (4 quadrant streak or T-(3) streak)
- aseptic technique
- labeling
- ability to isolate individual colonies
steps for a streak plate
Enterococcus faecalis
Staphylococcus aureus
Bacillus cereus
gram-positive bacteria
Escherichia coli
Klebsiella aerogenes
Proteus vulgaris
Pseudomonas aeruginosa
Alcaligenes faecalis
gram-negative bacteria
primary stain; stains everything strongly in acid-fast stain
carbolfuchsin
counter-stain for acid fast staining (non-acid fast cells)
methylene blue
used for decolorization for acid-fast staining; removes stain from non acid-fast cells
acid alcohol
- Schaeffer-Fulton method
- uses primary stain malachite green to visualize cells
spore stain
stains cells weakly, steam forces stain into spores; spore retains stain while other bacterial cells lose it
malachite green
counterstain for spore stain
safranin
spores are resistant to __
decolorization
genus for spore stains
bacillus and clostridium
- selective for gram-negative enterics
- differential for coliforms
- uses lactose and neutral red pH indicator
MacConkey Agar
bacteria exhibit red/pink coloration on their surface on MacConkey Agar
lactose fermenters/coliforms
no change on MacConkey Agar; colonies appear uncolored or same color as medium
non-lactose fermenters/pathogens
bile salts and crystal violet; inhibit G+ growth
selective reasoning for MacConkey Agar
MacConkey Agar-
produces acid by-products from lactose fermentation, which turn the medium surrounding the colony red in the presence of neutral red indicator dye
E. coli
MacConkey Agar-
does not ferment lactose but does grow on the plate
P. aeruginosa
MacConkey Agar-
does not grow in the presence of bile salts and crystal violet, both of which inhibit the growth of gram-positive bacteria
S. epidermidis