Anaerobic Bacteria Flashcards
Which bacteria are anaerobic gram positive bacilli
Actinomyces israelii, Bifidobacterium, Clostridium, Eubacterium, Lactobacillus, Mobiluncus, and Propionibacterium
Which bacteria are anaerobic gram positive cocci
Peptococcus niger and Peptostreptococcus
Which bacteria are anaerobic gram negative rods
Bacteroides, Bilophila, Fusobacterium, Porphyromonas, Prevotella
Which bacteria are anaerobic gram negative cocci
Veillonella
What are the different types of anaerobic bacteria?
- Facultative anaerobes: can grow aerobically and anaerobically
- Obligate anaerobe: require anaerobic conditions to grow
- Strict obligate anaerobe: cannot tolerate more than 0.5% oxygen
- Moderate obligate anaerobe: can tolerate 2-8% oxygen
- Aerotolerant anaerobes: grows poorly in ambient air (21% oxygen)
General body sites for anaerobic bacteria
Mucosal surfaces in GI tract, genitourinary tract, oral cavity, and upper respiratory tract; anaerobic bacteria can live in sites because facultatively anaerobic organisms use oxygen and outnumber these organisms
Exogenous vs endogenous diseases
Exogenous: from organisms, toxins, or spores from outside of the body, leading to disease; Ex: tetanus or botulism
Endogenous: caused by the host’s normal flora when someone is immunosuppressed, trauma, or malignancy
What are the most common anaerobic bacteria causing infections
Bacteroides fragilis group, pigmented Prevotella spp., Porphyromonas spp., Fusobacterium nucleatum, Clostridium perfringens, and anaerobic cocci
Which specimen are acceptable for anaerobic cultures?
Abscess aspirates, tissue/biopsy, suprapubic aspirate urine, blood/body fluids, protected brush bronchoscopy specimen, and anaerobic swabs (least desirable)
Which specimen are unacceptable for anaerobic cultures?
Material from superficial skin sites, voided or catheterized urine, expectorated sputum, throat/ nasopharyngeal swabs, bronchial washings, genital swabs, rectal swabs, and stool (unless it is for C. diff)
Anaerobic blood agar
nonselective media for growth of obligate and facultative anaerobic bacteria; Ex: CDC BAP, Brucella blood agar, enriched-brain-heart infusion blood agar, and Schaedler blood agar
Anaerobic phenylethyl alcohol blood agar (PEA)
inhibits facultative GNRs and supports growth of facultative GP and anaerobic bacteria
Bacteroides bile-esculin agar (BBE)
selective and differential agar that is used to isolate and identify Bacteroides fragilis group; it contains gentamicin (inhibits facultative organisms), bile (inhibits other anaerobes), and esculin (to identification of this group b/c it hydrolyzes esculin)
Cycloserine-cefoxitin-fructose agar (CCFA)
selective and differential agar for the isolation of Clostridium difficile; Cycloserine and cefoxitin are used to inhibit other organisms and C. difficile metabolizes proteins in the agar resulting is yellow colonies (agar is naturally pink)
Kanamycin-Vancomycin laked blood (KVLB) agar
selects for Bacteroides and Prevotella spp.; Kanamycin inhibits facultative GNRs and vancomycin inhibits GP; laked blood (hemolyzed blood) allows for certain Prevotella spp. to produce a brown/black pigment
Paromomycin-vancomycin laked blood (PVLB) agar
similar to KVLB except it has paromomycin instead of kanamycin; paromomycin will inhibit GNRs that are resistant to kanamycin
Thioglycollate broth (THIO)
nonselective where anaerobic bacteria grow towards the bottom of the broth and aerobic bacteria grow towards the top
What are the incubation requirements for anaerobic bacteria?
Anaerobic environment: 80-90% Nitrogen gas, 5-10% hydrogen gas, and 5-10% CO2; hydrogen gas removed oxygen by forming water with it and CO2 helps capnophiles grow
Grow at 35-37C
Clostridium spp. characteristics
obligate anaerobic GPR, spore-forming, and mostly catalase negative
C. perfringens diseases
most frequently isolated species; can cause bacteremia, food poisoning, cellulitis, female genital tract infections, and myonecrosis (gas gangrene)
C. perfringens characteristics
Colonies: gray, yellow, circular, glossy with a double zone of B hemolysis
GS: boxcar GPR, singly or paired, with central to subterminal oval spores
Biochemicals: lecithinase +, reverse CAMP +, and Nagler +
C. difficile diseases
causes antibiotic-associated diarrhea and pseudomembranous colitis
Can be toxigenic (toxin A and B) or nontoxigenic; EIA tests can be done to see if either toxin is present
C. difficile characteristics
Colony: creamy yellow/gray/white; irregular, coarse, and fluoresces under UV light; smells like horse manure
GS: straight GPR in short chains with rare oval subterminal spores and free spores
Biochemicals: weakly mannitol +, esculin +
C. botulinum diseases
causes botulism by producing different types of botulinal neurotoxin, leading to flaccid paralysis; there are different categories of botulism: food-bourne, wound, and infant
C. botulinum characteristics
Colony: gray/white, irregular, usually B hemolytic
GS: GPR singly or in pairs with oval, subterminal spores causing swelling of cells
Can detect the toxins
C. tetani diseases
causes tetanus with the tetanospasmin toxin that binds to components of the neuroexocytotic apparatus, blocking inhibitory impulses to motor neurons (leads to spastic paralysis)
C. tetani characteristics
asaccharolytic, can form a film over the entire agar surface; narrow B zone
GS: drumstick appearance
C. septicum diseases
bacteremia associated with neoplasias, particularly colon and breast cancer, leukemia, and lymphoma
C. septicum characteristics
Colony: gray, translucent, swarm, and B hemolytic
GS: pleomorphic GPR that can produce long filaments and rare oval spores
Biochemicals: sucrose - and DNase +
Actinomyces spp diseases
causes actinomycosis: a chronic granulomatous infection that can result in abscess formation with draining sinuses (can be in brain, lower resp tract, and genital tract); the discharge frequently has sulfur granules (masses of bacteria), which is diagnostic
Actinomyces spp. characteristics
GS: beaded appearance from irregular staining
Colony: All microaerophilic except A. meyeri (obligate anaerobe) and slow growing; spiderlike or wooly when young and molar tooth or raspberry like when old
Catalase -, indole -, nonmotile, nitrate +
A. israelii: most common, esculin + & urea -
A. meyeri: esculin - & urea -
A. naeslundii: urea +
A. odontolyticus: pigmented
A. viscosus: catalase +
Propionibacterium spp. diseases
Can cause infections of the skin, conjunctiva, bone, joint, and CNS; associated with surgical procedures
Propionibacterium spp. characteristics
GS: pleomorphic rods with diphtheroid appearance
Both nitrate + esculin -, nonmotile, and urea -
P. acnes: aerotolerant, catalase +, indole +
P. propionicum: not aerotolerant, catalase -, indole -
Bifidobacterium spp. characteristics
Catalase -, indole -, nitrate -, esculin +, nonmotile, urea -, and variably aerotolerant
Eubacterium spp. characteristics
GS: can have branching
nitrate -, arginine stimulates growth, catalase -, indole -, nonmotile, urea -, and strictly anaerobic
Lactobacillus spp. characteristics
catalase -, indole -, nitrate -, nonmotile, urea -, lactic acid is a major product; most are facultatively anaerobic
Mobiluncus spp. characteristics
strictly anaerobic, catalase -, indole -, esculin -, motile, urea -
Key: motile while other non-spore forming GPR are all nonmotile
How are microaerophilic streptococcus spp. differentiated from anaerobic streptococcus
Metronidazole: microaerophilic are resistant and anaerobic are susceptible
Finegoldia magna (Peptostreptococcus previously) characteristics
SPS resistant, indole -, urease -, cells are > 0.6 um
Parvimonas micra (Peptostreptococcus previously) characteristics
SPS resistant, indole -, urease -, cells < 0.6 um
Peptoniphilus asaccharolyticus (Peptostreptococcus previously) characteristics
SPS resistant, indole +, urease -, cells < 0.6 um
Peptostreptococcus anaerobius
SPS susceptible, indole -, urease -, cells < 0.6 um
Peptococcus niger characteristics
black pigmented colonies and catalase +
Bacteroides spp. diseases
can cause abscesses, mainly intra-abdominal, perineal, and perirectal
B. fragilis group causes bacteremia
B. fragilis group general biochemicals
Resistant to vanc, kanamycin, and colistin
Grows in 20% bile, nitrate -, and urea -
Other Bacteroides spp. biochemicals
Resistant to vanc and kanamycin, but variable for colistin and growth in bile, nitrate -, urea -
How are the species within the Bacteroides fragilis group differentiated from each other?
B. fragilis: esculin +, catalase +, indole -, Arabinose -, salicin -
B. ovatus: esculin +, catalase +, indole +, arabinose +, salicin +
B. thetaiotaomicron: esculin +, catalase +, indole +, arabinose +, salicin -
B. vulgatus: esculin -, catalase -, indole -, arabinose +, salicin -
Fusobacterium spp. diseases
F. nucleatum: most frequently isolated; associated with Lemierre’s syndrome (necrobacillosis) and can cause severe peritonsillar abscesses that lead to neck infections, jugular vein thrombophlebitis, and bacteremia
Other spp. are associated with intra-abdominal infections
Fusobacterium spp. biochemicals
All spp.: Resistant to vanc. and susceptible to kanamycin and colistin, catalase -, nitrate -, urea -
F. mortiferum: grows in 20% bile, indole -
F. necrophorum: variable bile growth, indole +
F. nucleatum: no growth in bile, indole +
F. varium: grows in bile, indole variable
Veillonella spp. diseases and biochemicals
can cause head/neck, respiratory, and bite infections
Resistant to vanc. and susceptible to kanamycin and colistin, does not grow in bile, indole -, nitrate +, urea -
Only one that is nitrate + for GN anaerobes
Prevotella spp. diseases and biochemicals
commonly found in the oral cavity and are associated with genitourinary tract infections
Resistant to both vanc. and kanamycin but variable for colistin, does not grow in bile, catalase -, nitrate -, urea -
Porphyromonas spp. biochemicals
asaccharolytic, Resistant to kanamycin and colistin and susceptible to vanc., does not grow in bile, nitrate -, urea -
Only GN anaerobe that is susceptible to vancomycin
