Bacteriologic and therapeutic considerations in intra-abdominal surgical infections

Treatment of anaerobic infection

Anaerobic bacteria are the predominant flora in the normal human skin and mucous membranes and are, therefore, a common cause of endogenous infections. Since anaerobic infections are generally polymicrobial, where anaerobes are mixed with aerobic organisms, therapy should provide coverage of both types of pathogens. The isolation of anaerobes requires appropriate methods of collection, transportation and cultivation of specimens. The lack of use of any of these methods can lead to inadequate recovery of anaerobes and inappropriate therapy. Treatment of anaerobic infection is complicated by the slow growth of these organisms and the growing resistance of anaerobic bacteria to antimicrobials. The primary role of antimicrobials is to limit the local and systemic spread of infection. Surgical drainage is of primary importance. This includes debriding of necrotic tissue, draining the pus, improving circulation, alleviating obstruction and increasing tissue oxygenation. The most effective antimicrobials against anaerobic organisms are metronidazole, the carbapenems (imipenem, meropenem and ertapenem), chloramphenicol, the combinations of a penicillin and a beta-lactamase inhibitor (ampicillin or ticarcillin plus clavulanate, amoxicillin plus sulbactam, and piperacillin plus tazobactam), tigecycline and clindamycin.

Identification of Bacteroides fragilisby a modified immuno polymerase chain reaction (mIPCR), using a specific monoclonal antibody

Bacteroides fragilis is the anaerobic species most commonly isolated from human clinical specimens, and is resistant to many antimicrobial agents. A monoclonal antibody, mAb4H8 (IgG3), reacting with a specific epitope in the lipopolysaccharide (LPS) isolated from most of the B. fragilis strains, was produced and employed with modified Immuno Polymerase Chain Reaction (mIPCR) for identification of B. fragilis with a detection limit of 10(4) cfu/mL bacterial suspension. A number of bacterial strains were examined, including B. fragilis, Bacteroides spp. other than B. fragilis and other genera. All the B. fragilis strains with the immunodominant (beta1,6-linked D-galactosyl chain) epitope were positive. None of the other strains showed the positive reaction. The results indicate that mIPCR assay with mAb4H8 has a high specificity and high sensitivity.