[In vivo combination effects of astromicin and beta-lactam antibiotics against Pseudomonas aeruginosa].

Astromicin (ASTM, Fortimicin) is a pseudodisaccharide aminoglycoside antibiotic. The ASTM exhibited excellent activity against Gram-positive and Gram-negative bacteria but was only weakly active against Pseudomonas aeruginosa. In vitro synergistical activities of ASTM combined with beta-lactam antibiotics have been reported against P. aeruginosa previously. In this paper, we investigated the in vivo combination efficacies of ASTM and beta-lactam antibiotics (latamoxef (LMOX), cefoperazone (CPZ), piperacillin (PIPC) and cefsulodin (CFS) against experimental infection with P. aeruginosa in both normal and immunosuppressed mice. In normal mice, the combination of ASTM with these beta-lactam antibiotics produced significantly greater protective effects than the single use of individual antibiotics against both strains of P. aeruginosa BMH No. 1 and E-2. In mice immunosuppressed with cyclophosphamide, the combination of ASTM with LMOX or CFS also exhibited synergistic protective effects against P. aeruginosa BMH No. 1, but PIPC and CPZ did not. From the above results, the combination therapy of ASTM with beta-lactam antibiotics appeared to be effective against experimental infections with P. aeruginosa in mice.