infectious diseases
Mixed Anaerobic Infections
Pathophysiology of Mixed Anaerobic Infections
Mixed anaerobic infections can usually be characterized as follows: They tend to occur as localized collections of pus or abscesses. The reduced oxygen tension and low oxidation-reduction potential that prevail in avascular and necrotic tissues are critical for their survival. When bacteremia occurs, it usually does not lead to disseminated intravascular coagulation (DIC) and purpura. Overview of Clostridial Infections can lead to Some anaerobic bacteria possess distinct virulence factors. The virulence factors ofB. fragilisprobably account for its frequent isolation from clinical specimens despite its relative rarity in normal flora compared with otherBacteroidesspecies. This organism has a polysaccharide capsule that apparently stimulates abscess formation. An experimental model of intra-abdominal sepsis has shown thatB. fragilisalone can cause abscesses, whereas otherBacteroidesspecies require the synergistic effect of another organism. Another virulence factor, a potent endotoxin, is implicated in septic shock and DIC associated with severeFusobacteriumpharyngitis. Morbidity and mortality rates for anaerobic and mixed bacterial sepsis are as high as those for sepsis caused by a single aerobic organism. Anaerobic infections are often complicated by deep-seated tissue necrosis. The overall mortality rate for severe intra-abdominal sepsis and mixed anaerobic pneumonias tends to be high.B. fragilisbacteremia has a high mortality rate, especially in older adults and in patients with cancer. 