A randomized controlled trial of moxalactam versus clindamycin/tobramycin in the treatment of mixed anaerobic/aerobic infections.

Many infections are due to mixtures of facultative gram-negative bacilli and anaerobic bacteria. Moxalactam, a semisynthetic beta lactam antibiotic, is active against a wide range of anaerobic organisms, including most strains of Bacteroides fragilis, as well as many aerobic gram-negative bacilli. We performed a prospective, randomized controlled trial comparing moxalactam alone with the regimen of clindamycin and tobramycin for treatment of mixed aerobic/anaerobic infections. One hundred and six patients with presumed mixed infections were randomized to the study groups. The resultant groups were clinically and microbiologically comparable. The effectiveness of treatment was similar with both antibiotic regimens. Five of 25 patients tested in the moxalactam group had a prolongation of their prothrombin time and one of them developed clinically important bleeding. Two of the 23 patients tested in the clindamycin/tobramycin group had a prolonged prothrombin time with no bleeding. Decreases in hematocrit which could be "probably" or "possibly" related to antimicrobial use were seen in 6 of 48 moxalactam patients and none of 50 clindamycin/tobramycin patients (P = .03). Moxalactam, a potent antimicrobial for both anaerobic and aerobic organisms, demonstrated effectiveness in treating mixed anaerobic/aerobic infections similar to clindamycin/tobramycin but was associated with clinically important decreases in hematocrit.