Gram-Negative Anaerobic Rods Flashcards
A large group of bacteria that dominates the normal flora of the large intestine
Gram-negative anaerobic rods
The most important members of the group fall into which closely-related genera?
Rod-shaped or coccobacillary
Predominantly intestinal, tend to produce abdominal infections
Bacteroides
The most important species of the entire bacteroides group
Bacteroides fragilis
Predominantly oral; tend to produce infections of the head, neck, respiratory tract, bite wounds
Porphyromonas and Prevotella
Makes black pigment; colonies fluoresce red under UV light
Porphyromonas
Two less-important genera, not closely-related biologically to the first group or each other, but with similar biology are?
Fusobacterium and Veillonella
Slender rods with tapered ends; mostly oral.
Fusobacterium
Cocci, in oral flora
Veillonella
Often contain multiple species of both anaerobic and facultative bacteria. The latter facilitate growth of anaerobes by using up ambient oxygen
-Often spread from endogenous sources
Infections with anaerobes
Peridontal disease, abdominal abscesses, infections of the female reproductive tract, and pneumonia due to aspiration of oropharyngeal contents are examples of types of infections produced by
Gram-negative anaerobes
Brain abscesses may form by spread of organisms from sites of infection in the
URT
Occurs when the organisms spread to the bloodstream from the intestine or a focus of infection
Septicemia
One of the organisms most commonly isolated from blood cultures
B. Fragilis
Secretes an exotoxin which is a protease which cleaves E-cadherin, loosens epithelial zona adherens junctions between enterocytes, and causes cytoskeletal changes in them
B. Fragilis
B. fragilis has recently been identified as a cause of
Diarrhea
The frequency with which Bacteroides fragilis and Fusobacterium are isolated from infections is far out of proportion to their relative abundance in normal flora. This suggests that they must have
Virulence factors
Has an anti-phagocytic capsule which is intensely inflammatory
B. Fragilis
B. fragilis has an anti-phagocytic capsule which is intensely inflammatory - administration of purified capsular substance provokes formation of an
Abscess
Their LPS lacks lipid A and has no endotoxic activity where as other Gram-negative anaerobes do have endotoxic LPS
Bacteroides
Specimens are cultured on rich media; selective media contain either kanamycin/vancomycin or bile
Gram-negative anaerobes
To treat infection by Gram (-) anaerobes, we create an
Oxygenated environment
Not effective against anaerobes
Aminoglycosides
