IN-VITRO ACTIVITY OF MEROPENEM AND 7 OTHE R BETA-LACTAM ANTIBIOTICS AGAINST K-PNEUMONIAE AND ENTEROBACTERIACEAE WITH EXTENDED-SPECTRUM BETA-LACTAMASES

Meropenem is a broad antibacterial spectrum carbapenem with a good act ivity on betalactam resistant Gram-negative bacilli. 120 non repetitiv e strains isolated from clinical samples from 1989 to 1992 were select ed : 60 K. pneumoniae, 7 E. coli, 2 E. aerogenes and 1 S. marcescens w ith extended spectrum betalactamases (23 CTX-1, 18 SHV-2, 5 SHV-3, 16 SHV-4, 4 SHV-5, 3 CTX-1+ SHV-4, 1 CAZ-1), 10 K. pneumoniae with broad spectrum TEM-1 enzyme, and 40 K. pneumoniae with only SHV- 1 chromosom al betalactamase. Determination of Minimal inhibitory concentrations ( MIC) was done by agar dilution method for meropenem and 7 other betala ctams (amoxicillin + clavulanic acid 2 mg/l, piperacillin + tazobactam 4 mg/l, cefoxitin, cefotetan, cefotaxime, ceftazidime, imipenem). All antibiotics except amoxicillin + clavulanic acid are active against s trains with constitutive penicillinase. For strains with TEM-1 penicil linase, cephamycins, third generation cephalosporins and carbapenems a re active. For strains with different extended spectrum betalactamases only cephamycins and carbapenems are efficious. There is no differenc e according to the period of isolation : 1989-90 or 1991-92. Meropenem has the best in vitro activity (MIC50 = 0,03 mg/l) for all strains in dependently of the nature of betalactamase.