Monitoring of the Pseudomonas aeruginosa sensitivity to antibiotics in France and spreading of betalactamine resistance mechanisms:: GERPB 1999 study

A prospective survey was carried out in october 1999 in 15 french teaching hospitals. Average susceptibility rates, determined by minimal inhibitory concentrations, for the 738 non-repetitive strains of R aeruginosa isolated were: ticarcillin, 58%, ticarcillin + clavulanic acid, 56%, piperacillin, 73%, piperacillin + tazobactam, 82%, ceftazidime, 76%, cefepime, 53%, cetpirome, 36%, aztreonam, 58%, imipenem, 81%, amikacin, 62%, tobramycine, 71% and, ciprofloxacin, 60%. Among the 75% serotypable strains, the most frequent serotypes were, O : 6 (15.3%), O : 11 (14.5%), O : 1 (10.4%), O : 3 (7.9%), O : 4 (6.1%) and O : 12 (6.1%). The serotype O : 12 was the most resistant to antibiotics. Forty-two percent of the strains were resistant or presented an intermediate susceptibility to ticarcillin. Mechanisms were as follow: 14.5% non enzymatic mechanism, 12.5% overproduction of the constitutive cephalosporinase, 7.1% transferable betalactamase and, 6.9% combination of these mechanisms. Among the 67 transferable betalactamases: 48 (71.6%) were PSE-1, 12 (19.4%) TEM-2 and 6 (7.5%) oxacillinases. One extended spectrum betalactamase was characterized, Among the cephalosporines tested, cefepime was less affected by the overproduction of constitutive cephalosporinase. Ceftazidime, remained the best cephalosporin except against the strains overexpressing the chromosomal type 1 beta-lactamase. Resistance to tobramycin was mainly due to enzymatic mechanisms with a high level of resistance. Decreased susceptibility was more frequent for amikacin than for tobramycin. This was probably related with non enzymatic mechanisms. (C) 2001 Editions scientifiques et medicales Elsevier SAS.