26. Anaerobic Bacteria Most Commonly Isolated from Infection Flashcards
Sensitivity of aerotolerant anaerobes to O2
> 5% O2
Anion that is lethal to strict anaerobes
Superoxide (SO) anion
Enzyme produced by facultative and aerobic bacteria that converts SO to H2O2 and O2
Superoxide dismutase (SOD)
SO –SOD–> H2O2 + O2
System lacking in strict anaerobes to use O2 as terminal electron acceptor
Cytochrome system
The means by which energy is produced by strict anaerobes
Fermentation
Microscopic characteristics of Peptostreptococcus
Gram-positive cocci in chains
The only genus of gram-positive anaerobic cocci involved in disease
Peptostreptococcus
Microscopic appearance of Veillonella
Gram-negative cocci
Microscopic appearance of Propionibacterium
Gram positive bacillus
Resembles Corynebacterium in morphology and arrangement
Propionibacterium
Acid produced by Propionibacterium
Propionic acid
Causative agent of acne vulgaris (pimples)
Propionibacterium acnes
Microscopic appearance of P. acnes
Gram-positive rod/bacillus
P. acnes is a common resident in the
Pilosebaceous glands of the human skin
P. acnes is highly susceptible to
β-lactam antimicrobial agents (Penicillin G)
Microscopic appearance of Actinomyces israelii
Gram-positive bacillus
Tends to form branches
Sometimes with beaded appearance
Oxygen requirements of A. israelii
Aerotolerant anaerobe
Drugs for A. israelii
Penicillin class
Disease caused by A. isralii
Lumpy jaw
Gram-positive anaerobic cocci in chains
Peptostreptococcus
Gram-positive, non-spore forming, anaerobic rod
Propionibacterium acnes
Gram-positive bacillus that may form branches or have a beaded appearance
Actinomyces israelii
Gram-positive, non-spore forming, anaerobic bacillus
Propionibacterium
Gram-negative anaerobic cocci
Veillonella
Appropriate specimens for anaerobic culture
- Blood
- Other normally sterile sites (pleural fluid)
- lung
- dental/sinus
- soft tissue
- female genital tract
- abdomen (aspirate, peritoneal fluid)
- bone
How to transport tissue specimens for anaerobic culture?
- Anaerobic pouch
- Anaerobic transport tube with medium
How to transport fluid or aspirated pus for anaerobic culture?
- express into anaerobic transport vials
- leave in syringe, discard needle and cover with sterile cap
How to transport swabs for anaerobic culture?
Must be collected in a sterile surgical field then placed in a special anaerobic swab device
Characteristics of primary media used for anaerobic culture
Non-selective
Selective
Differential
All primary media for anaerobic culture must be supplemented with
Vitamin K
Hemin
Substances in media that keep O2 levels low
Reducing agents
Anaerobic media that selects for gram-negative anaerobic bacilli
Laked kanamycin-vancomycin (KV) blood agar
Anaerobic media that is differential/selective for Bacteroides fragilis
Bacteroides bile esculin agar (BBE)
Selective/differential media or recognition of C. difficile
CCFA
Component in CCFA that inhibits gram-negative bacteria
Cycloserine
Component in CCFA that inhibits gram-positive and gram-negative organisms
Cefoxitin
Appearance of C. difficile in CCFA
C. difficile ferments fructose resulting in yellow colonies
PEA is selective for
Gram-positive cocci and bacilli
Nonselective and differential medium that allows detection of lecithinase and lipase
Egg Yolk Agar (EYA)
Result of lecithin breakdown in EYA
Opaque precipitate
Effect of lipase on EYA
Iridescent sheen on colony surface
Phase of bacterial growth that anaerobes are most sensitive to O2
Log/exponential phase
Temperature for incubation of anaerobic culture
35-37°C
Indicators used to validate anaerobic conditions
Methylene blue
Resazurin indicator
Incubation time for anaerobic rapid growers
24 hours
Incubation time if Actinomyces is suspected
> 7 days
Microscope used to look at tiny anaerobic colonies
Dissecting microscope
Anaerobes not inhibited by 20% bile
Bacteroides
Bilophilia
Percent of H2O2 used in the catalase test for anaerobes
15% H2O2
Antibiotic disks that may be used for presumptive identification of anaerobes
Kanamycin
Vancomycin
Colistin
Sensitivity to O2 of strict anaerobes