Obligate Anaerobic Gram Negative Bacilli Flashcards
What are the basic characteristics of Bacteroides spp.?
- Obligate anaerobe
- Non-spore forming
What 3 species does the B.fragilis group consist of?
- B.fragilis
- B.thetaiotaomicron
- B.ovatus
What is the habitat of Bacteroides fragilis group?
NF of the mucosal orla cavity, URT and GIT
What is the spectrum of disease of Baceroides fragilis group?
- Endogenous; usually involves breach of mucosa
- Usually in infections below the diaphragm
- Abscesses (enclosed); cranium, periodontium. thorax, peritoneum, liver, female GT
- Can cause bacteremia, aspiration pneumonia, septic arthritis, chronic sinusitis, decubitus ulcers
What are the virulence factors of Bacteroides fragilis group?
- Capsules
- Endotoxin and succinic acid (inhibits phagocytosis)
- Enzymes mediating tissue damage
General characteristics of Bacteroides fragilis group?
- Saccharolytic
- Bile-resistant
- Non-pigmented
What does the Gram stain look like for Bacteroides fragilis group?
GNB or CB, pale staining pleomorphic (may look like safety pins)
What is B.fragilis group usually resistant to?
Kanamycin, colostin, vancomycin (KCV)
What is the habitat of B.ureolyticus?
NF of mucosa of GIT, URT and GUT
What is the spectrum of disease and virulence factors of B.ureolyticus?
Same as B.fragilis
What is an identifying colony morphology feature of B.ureolyticus?
May “pit” the agar or spread, may turn green when exposed to air
What does the Gram stain look like for B.ureolyticus?
Gram negative, tiny, pale staining, thin delicate rods w/rounded ends
Antimicrobial resistance to KV or C?
Susceptible to kanamycin and colistin.
Resistant to vancomycin
What distinguishes B.ureolyticus from B.fragilis?
B.fragilis:
- Does not reduce nitrate
- Indole + catalase variable
B.ureolyticus
- Reduces nitrate
- Urease pos
- Indole neg
- Catalse neg
What is the habitat of Prevotella spp.?
NF of URT (especially oral cavity), GIT and GUT
- Dental biofilms
Where do pigmented forms of Prevotella spp usually cause infection?
Head, neck, pleuropulmonary
What do Prevotells spp. look like on an anaerobic BA and LKV agar?
BA: Small, white, translucent/opaque, shiny.
Black pigmented - fluoresce brick red
LKV: Brown to black pigment
What does the Gram stain look like for Prevotella spp.?
GNB, in pairs or short chains
Prevotella spp. resistance to KV and C?
Resistant to vano and kana, colistin variable
Biochemical reactions for catalase and indole? (Prevotella spp.)
- Most catalase neg
- Most indole neg (P.intermedia is pos)
Habitat of Porphyromonas spp.?
NF of URT, GIT and GUT
Which pathogen is key in adult periodontitis?
Porphyromonas gingivalis
Porphyromonas spp Gram reaction?
GNCB
Asaccharolytic and pigmented
Porphyromonas spp. resistance to KV and C?
Sensitive to vanco, resistant to kana and colistin
