Anaerobic Procedures :) Flashcards
Facultative anaerobes grow in what kind of environment?
aerobically and anaerobically
obligate anaerobes can only grow in ______ environment. ________ is toxic to them. What does it mean if they’re a strict obligate anaerobe?
only anaerobic; oxygen is toxic
if strict obligate, they cannot tolerate more than 0.5% oxygen
what are moderate obligate anaerobes and aerotolerant anaerobes?
moderate: can tolerate 2-8% oxygen
aerotolerant grow poorly in ambient air (21% oxygen)
what does it mean that anaerobic bacteria require a low redox potential? Does human tissue have high or low redox potentials?
LRP means the environment is more anaerobic than aerobic; most human tissue have high redox potential (aerobic environment)
what are three reducing agents frequently included in anaerobic media?
- thioglycollate
- cysteine
- dithiothreitol
what are the common body sites that anaerobic bacteria like to colonize, and how is this possible?
oral cavity, URT, intestinal tract, genitourinary tract, and skin due to facultative organisms use up the oxygen in the protected areas
what are the two disease types for anaerobic bacteria, and which is more common to cause infections?
exogenous – from outside the body (eg due to spores)
endogenous – due to host normal flora that it cannot keep in their normal habitat
- more common infections than exogenous
2/3 of human infections are caused by what 6 organisms?
B. fragilis, pigmented Prevotella spp., Porphyromonas spp, Fusibacterium nucleatum, C. perfringens, and anaerobic cocci
what are some appropriate anaerobic specimens?
abcess aspirates, tissue/biopsy material, special aerobic swabs, protected bronchitis brushes, suprapubic urine aspirate, and blood/normally sterile body fluids
what is a major inappropriate specimen for anaerobic cultures?
swabs due to only holding a little of material and their likelihood of exposure to oxygen
what is a PRAS medium? what three things does it consist of?
prereduced, anaerobically sterilized
consists of:
1. agar transport media
2. rezasurin: oxygen indicator
3. reducing substances
what kind of loops and needles are not appropriate to use for anaerobic bacteria?
nichrome
what some examples of anaerobic blood agar plates (anaBAP)?
CDC anaBAP, Brucella BAP, enriched BHI, and Schaedler blood agar
what does the BBE agar have in it that makes it selective and differential for B. fragilis?
Gentamicin: antimicrobial agent
Bile: most anaerobes are inhibited by bile
Esculin: hydrolysis of esculin
- B. fragilis
- Bilophila wadsworthia
- some Fusobacterium spp.
what is the CCFA agar selective and differential for? What do pos and neg results look like
Clostridium difficile
- cycloserine and cefoxitin are antimicrobials that inhibit many organisms
- neg: still pink media
- pos: media turns yellow with ground glass colonies
KVLB agar will grow what two organisms?
Bacteroides spp. and Prevotella spp.
what is a catalyst that will remove oxygen to create an anaerobic environment? What are two indicators, and what colors are they when there is oxygen present
palladium (turns hydrogen and oxygen to make water)
indicators:
1. methylene blue: blue
2. rezasurin: pink
what is the principle of anaerobic tolerance and how to perform?
streak for growth on BAP (or choc) and also on anaBAP (eg Brucella plate). Incubate both and compare if there is something growing on the anaerobic plate that isn’t on the aerobic one
conventional biochemical tube tests what kind of tubes containing what kind of medium supplied with glucose/nitrate/urea?
Thio or peptone yeast medium
what system uses substrate tests to detect enzymes in an organism? what uses panels of wells containing biochemical reactions for ID?
rapid enzymatic systems
micro biochemical test tube
what are the most commonly disks for anaerobic tests? what id the diameter to consider a resistant or susceptible result?
vancomycin, colistin, and kanamycin
inhibition of 10 mm or more = susceptible
10 mm or less is considered resistant
what test is used to ID gram positive cocci, and what do resistant and susceptible results look like?
sodium polyanethol sulfonate (SPS)
12 mm or more = susceptible
12 mm or less = resistant
bile tolerance is used to see if an organism can grow in ____% bile
20
what measures and measures metabolic end products and cellular fatty acids?
gas-liquid chromatography
lecithinase degrades _______ to form insoluble _________ by inoculating the test organism onto an ___ ____ ____. What spp is this test used to ID?
degrades lecithin to form insoluble diglycerides onto an egg yolk agar
- pos result: white opaque zone on agar
- used to ID Clostridium spp.
what test degrades glycerol into free fatty acids? What does a pos result look like?
lipase
- pos: pearly sheen on egg yolk agar
a series of quadrant plates are known as ________?
presumpto plates
what organism is identified by the reverse CAMP test, and how to do the test?
C. perfringens toxin works with the beta-hemolysis of GBS
- streak down a line of GBS and perpendicular but not touching it, streak a line of suspected C. perfingens, Arrow of hemolysis is pos result
stool/rectal swabs are only acceptable specimens if you’re looking for what organism?
C. difficile
