Selective decontamination of the digestive tract with oral aztreonam and temocillin.

Selective decontamination of the digestive tract by antimicrobial drugs with limited spectra of antibacterial activity has been reported to reduce the risk of superinfection and cross-infection in immunocompromised hosts by leaving the flora responsible for colonization resistance (largely anaerobic) intact. Aztreonam, a monobactam, and temocillin, a beta-lactam antibiotic, are possible candidates for use in selective decontamination of the digestive tract because of their specific activity against gram-negative bacteria. When these drugs were administered orally to mice, low dosages (0.016-1.13 mg per day) did not significantly affect colonization resistance. In volunteers, the indigenous flora either was not affected or was only minimally affected by orally administered aztreonam (20 mg and 100 mg every 8 hr). Intramuscular temocillin also was effective. However, in a small number of subjects inactivation (most likely enzymatic) of these antibiotics occurred in the bowel. Both drugs can be considered serious candidates for use in the selective decontamination of the digestive tract in granulocytopenic patients.