Chapt 22 Anaerobes Flashcards
Exogenous
Originating outside of an organism, as opposed to an endogenous factor
Facultative anaerobe
Does not require O2 for growth but will use O2 & grow better if it is present
Endogenous
Originating from within an organism
Obligate anaerobe
Can live & reproduce only in a strict anaerobic environment (0% O2)
Microaerophilic
Require environments containing concentrations of O2 lower than present in atmosphere (abt 20%)
Capnophilic
Require an increased concentration of CO2 usually between 5 & 10%
Fusiform
Spindle-shaped or tapered at each end
Aerotolerance testing
Test used to determine whether an isolate is a strict anaerobe or a facultative anaerobe
BBE agar
Selective/Differential agar to isolate & ID Bacteroides fragilis
Inhibitors: Gentamycin & bile salts
Indicators: Esculin hydrolyzed to esculetin (black)
Form black-brown colonies
CDC-ANA agar
Enriched media for isolation of obligate gram (-) & gram(+) anaerobes
Nutrients: 5% sheep blood, vitamin K&B, yeast extract
Incubated anaerobically
CDC-KVLB agar
Selective isolation of anaerobes Bacteroides & Prevotella
Nutrients: 5% sheep blood
Inhibitors: Kanamycin & Vancomycin
Kanamycin inhibits most facultative gram (-) rods (enterics) Vancomycin inhibits most gram (+) “laked”=hemolyzed
Incubated anaerobically
CDC-PEA agar
Selective media for isolation of obligate anaerobes
Nutrients: 5% sheep blood
Inhibitors: Phenylethanol inhibits most facultative gram (-) rods
Incubated anaerobically
Thioglycolate broth
Enriched broth used to support growth for most bacteria, including anaerobes & microaerophils, routinely used for wound & sterile body fluid cultures
Nutrients: Casein, soy broth, & glucose
Inhibitors: Thioglycolate, cystine, & sodium sulfite reduce O2
Boil to expel dissolved O2, cool/hold at room temp before use, obligate anaerobes grow only at bottom
Anaerobic chamber
Incubation system that provides an O2 free environment for inoculating media & incubating cultures
Chopped Meat broth
Enriched broth useful for the growth of obligative anaerobes
Nutrients: Glucose, heme, vitamin K, yeast extract, tissue proteins
Supports growth of fastidious obligative anaerobes, especially Clostridium
Tetanus
Disease that acts on the central nervous system & is characterized by muscular contractions
Botulism
Serious form of food poisoning caused by the ingestion of preformed botulinum toxin produced by Clostridium botulinum
Anaerobic cultures must be incubated for atleast?
24 hrs @ 35 degrees C
If O2 is absent indicator strip will turn?
White
If O2 is present indicator strip will turn?
Blue
Not appropriate to perform anaerobic cultures from which sites?
Skin, oral cavity, upper respiratory tract (throat, sputum), GI tract, genital tract, urine, & stool… because they are expected to be there
Good source for anaerobic cultures?
Deep wounds, normally sterile body fluids, abscesses, surgical procedures, invasive deep pulmonary procedures, & blood cultures
ID of obligate anaerobes: Level I
Isolation, morphology & aerotolerance testing
ID of obligate anaerobes: Level II
Antibiotic susceptibility disks & simple spot tests
ID of obligate anaerobes: Level III
Comprehensive biochemical testing
Bacteroides fragilis (group)
Most common obligative anaerobe, most biota in guts, Gram(-) rods, large non-pigmented colonies, most are beta-lactamase (+) (multiple resistance) “below the waist” infections, blackening of agar around colonies on BBE agar (others are inhibited) Colistin (R) Kanamycin (R) Vancomycin (R)
Fusobacterium
Thin, gram(-) rods, pointed, tapered ends, common “above the waist” pathogen (head/neck wounds) Colistin (S) Kanamycin (S) Vancomycin (R) will grow better on BBE agar, but no darkening of agar, usually susceptible to other antibiotics
Prevotella
Gram(-) rods/coccobacilli, pigemented (brown-black) & nonpigmented colonies, fluorescent under UV light, will NOT grow on BBE agar, associated with oro-facial infections, Colistin (V) Kanamycin (R) Vancomycin (R)
Porphyromonas
Gram(-) rods, pigmented (brown/tan) colonies, associated with dental infections & periodontal disease, Colistin (R) Kanamycin (R) Vancomycin (S)
Veillonella
Gram(-) cocci (like Neisseria, but obligate anaerobe)
Peptostreptococcus
Gram(+) cocci (tetrads/short chains) slow growers, most common gram(+) anaerobe Colistin (R) Kanamycin (V) Vancomycin (S)
Propionibacterium
Gram(+) rods/”diptheroid” shaped, most frequent anaerobic gram(+) bacillus, small white-yellow colonies, P. acnes associated with acne, Colistin (R) Kanamycin (S) Vancomycin (S)
Actinomyces
Filamentous, diptheroid, gram(+) rod, deep infections, sulfur granule formation & purulent discharge, associated with oral infections following dental procedures Colistin (R) Kanamycin ( ) Vancomycin (S)
Bifidobacterium dentium
Gram(+) diptheroid, periodontal infections Colistin (R) Kanamycin ( ) Vancomycin (S)
Eubacterium lentum
Gram(+) diptheroids Colistin (R) Kanamycin (S) Vancomycin (S)
Clostridium
Large, thick gram(+) rods, spore formers, common in soil, dust, water, & GI tract
Clostridium perfringens
“Boxcar” gram(+) rods (chains), subterminal spores observed from direct clinical specimens, double zone of beta-hemolysis on blood agars, Lecithinase(+) on Egg Yolk agar, Reverse CAMP(+) most frequent Clostridium isolate: deep wounds (gas gangrene), small bowel necrosis, food poisoning
Clostridium botulinum
Large, pleomorphic gram(+) rods, “club shaped” sub-terminal spores, Classic food poisoning from ingestion of preformed toxin in improperly prepared canned foods (flaccid paralysis), infants=no raw honey
Clostridium tetani
Gram(+) rods, terminal spores “drum stick” or “tennis racket” shapes, difficult to culture in vitro, associated with deep wound infections & the production of toxin mediated rigid paralysis
Clostridium difficile
Gram(+) rods, sub-terminal spores, Antibiotic Associated Diarrhea (AAD), antibiotics disrupt GI tract biota, treatment: discontinue antibiotic (new antibiotic Fidaxomicin) serological detected from toxins from stool specimens
