Gram-negative rod bacteremia: microbiologic, immunologic, and therapeutic considerations.

During the last 2 decades, Gram-negative rod bacteremia has become the leading infectious disease problem in American hospitals. With improvements in conventional microbiologic techniques, bacteremic infection can be diagnosed reliably within 3 days using only three sets of cultures. Clinical management still requires aggressive, presumptive use of antimicrobials in patients with the most adverse host factors. In the latter group, the use of combinations of antibiotics that interact synergistically in vitro has improved clinical results. In bacteremia due to anaerobes, particularly Bacteroides species, drainage of infected sites is probably more important than specific drug therapy. Various host defects have been associated with Gram-negative bacteremia; the most common in the nonleukopenic patient is impaired opsonization. The evidence that endotoxins are involved in the pathophysiology of Gram-negative bacillemia is inferential. Nevertheless, both clinical and experimental evidence suggest that active or passive immunization with endotoxin components or antigens similar to Gram-negative polysaccharides may be protective.