Bacteriology Exam 11 (Anaerobes Flashcards
What is an obligate anaerobe?
Requires 0% oxygen to grow
What is an obligate aerobe?
Requires 15-23% oxygen to grow
What is a facultative anaerobe?
Requires 0-23% oxygen (can grow with or without)
What is a capnophilic organism?
Requires 5-10% CO2
What is an aerotolerant organism?
Requires reduced oxygen
What is a microaerophilic organism?
Requires 5% oxygen
Where would obligate aerobes vs obligate anaerobes grow in a tube?
Obligate aerobes - top
Obligate anaerobes - bottom
Where would facultative anaerobes vs aerotolerant anaerobes grow?
Facultative - all throughout the tube, mostly at top
Aerotolerant - throughout the tube
Are endogenous or exogenous organisms more common cause of human disease?
Endogenous
Anaerobic environments should consist of what?
85% nitrogen
10% CO2
5% Hydrogen gas
0% oxygen
What are the clinical signs of anaerobic infection?
Pus producing
Infection near mucosal surface
Infection that persists despite aminoglycoside therapy
Foul odor
Large quantities of gas
Presence of sulfur granules
Infection secondary to human or animal bite
Unacceptable samples for anaerobe testing
Throat swabs
NP swabs
Most sputums
Mouth swabs
Feces
Midstream or catheterized urine
Exposed wounds
Acceptable samples for anaerobe testing
Aspirated body fluids
Tissue biopsy
Aspirated pus
Surgical samples
Eswabs
Sterile body site fluids
Suprapubic aspirates
What is an example of a medium to transport anaerobes in to the lab?
Cairy Blair medium
What are Eswabs stored in?
Amies liquid
How long do Eswabs maintain anaerobic conditions?
48 hours at room temp
What is PRAS?
Pre-reduced, anaerobically sterilized transport media
At what nm is fluorescence observed under UV light?
366 nm
What additional nutritional requirements are required for anaerobic plates?
Vitamin K
Hemin
Yeast extract
What are types of anaerobic plates?
CDC ANA/Brucella (non selective blood agar)
BBE (bacteroides bile esculin)
KVLB (Kanamycin and Vancomycin with Laked Sheep Blood)
PEA
CNA
Cooked meat broth
Thioglycolate broth
What is CDC ANA agar useful for?
Best for detection of anaerobic GPC
Useful for hemolysis detection
What is BBE agar useful for? What does it contain?
Contains gentamicin and bile to inhibit most aerobes and anaerobes
Helps to identify B. frag group and bile tolerant bacteroides spp.
What color will B. frag group turn on BBE agar?
Turns agar black
What is Brucella agar most useful for?
Best for GNR
What is KVLB agar most useful for? What does it contain?
Bacteroides and Prevotella spp., yeasts, and Kanamycin resistant GNR
Contains Kanamycin that inhibits most GNR
Contains Vancomycin that inhibits most GPO
Contains laked blood that facilitates Prevotella pigmentation (black/brown)
What is PEA agar most useful for?
Grows mostly gram positive organisms
Selective media to suppress Enterobacteriaceae
What is CCFA agar useful for? What does it look like?
Growth of C. diff with yellow ground glass colony morphology and horse stable odor
What do anaerobic containers contain? What is the purpose of each?
Catalyst (removes O2)
Desiccant (Removes condensation)
Anaerobic gas with H2, CO2, N
Indicator (Methylene blue or Resazurin)
If the indicator turns pink (Resazurin) or blue (Methylene blue) what does this mean?
This means oxidation has occurred and oxygen has gotten into the anaerobic conditions
If the indicator stays colorless, what does this mean?
This means the indicator was reduced and no oxygen is in the anaerobic conditions which is good
When can plates be examined if using anaerobic closed chambers? When can they be examined if using anaerobic jars or pouches?
Closed chambers - after 24 hours
Jars/bags - after 48 hours
How long are anaerobic cultures held for?
5-7 days
If an organism grows on CO2 plates and Aerobic plates, but not anaerobic plates, what is it?
Obligate aerobe
If an organism grows on CO2 plates only, but not anaerobic or aerobic plates, what is it?
Capnophile
If an organism grows on CO2 plates, aerobic, and anaerobic plates, what is it?
Facultative anaerobe
If an organism grows on anaerobic plates, but not CO2 or aerobic plates, what is it?
Obligate anaerobe
What rapid biochemical testing is typically done on Anaerobes?
Fluorescence under UV light
Catalase
Spot indole
Urease
Motility
Antimicrobial disks (Kanamycin, vancomycin, colistin disks)
SPS disks
What is Egg Yolk agar selective for?
C. perfringens
Positive vs negative lecithinase test
Positive: appearance of white, opaque, diffuse zone that extends into the medium surrounding the colonies
Negative: absence of that zone extending from the edge of the colony
Positive vs negative lipase test
Positive: appearance of an iridescent sheen
Negative: absence of an iridescent sheen
What anaerobes are gram positive and spore forming?
Clostridium sp.
Where are Clostridium species naturally found?
Soil
What is Clostridium species very close to and hard to tell apart from? what is the difference?
Bacillus sp.
Bacillus is aerobic
Clostridium is anaerobic
What Clostridium sp. have a terminal spore? (of interest)
C. tetani
What Clostridium sp. have a subterminal spore? (of interest)
C. botulinum
C. difficile
What spore forming organism that we discussed has a central spore, but is aerobic?
Bacillus
C. perfringens: Swarming? Double zone hemolysis? Fluorescence? Gram stain? Spore location? Motility? Lecithinase? Lipase? Urease?
Swarming: NO
Double zone hemolysis: YES
Fluorescence: NO
Gram stain: POS
Spore location: SUB TERMINAL
Motility: NO
Lecithinase: POS
Lipase: NEG
Urease: NEG
What organism has a double zone of hemolysis?
C. perfringens
What organism has a “box car” gram stain morphology?
C. perfringens
T/F: C. perfringens is CAMP POS
False; it is REVERSE CAMP POS
C. perfringen sens/resis to vancomycin and kanamycin
Sensitive to both
Disease associations with C. perfringens
Gas gangrene
Food poisoning
Necrotizing bowl diease –> Pig bel disease
What is Pig Bel disease?
Associated with C. perfringens –> complication of infection by the Type C strain, mistaken sometimes as the 24 hour bug
What organism is the positive Nagler test used for? What is it?
C perfringens, positive result is lecithinase activity after streaking plate with organism and reagent (C perfringens type A antitoxin)
What type of hemolysis does the reverse camp test display for C. perfringens?
Bow tie zone of hemolysis towards GBS