[Pseudomonas aeruginosa: acquired in vitro resistance to beta-lactams].
The development of resistance acquired in vitro to 5 semi-synthetic penicillins: carbenicillin, ticarcillin, azlocillin, mezlocillin, piperacillin and to 5 cephalosporins: cefotaxime, cefoperazone, moxalactam, cefsulodin and ceftazidime, was compared in 6 strains of Pseudomonas aeruginosa. The strains were selected on the basis of their phenotypic resistance: 3 were susceptible to all the betalactam antibiotics tested, 1 was resistant to carbenicillin and ticarcillin but remained susceptible to the others, 2 were susceptible to cefsulodin and ceftazidime but resistant to the others. The development of resistance was investigated by subsequent passages in liquid medium: up to 15 passages or up to an MIC of 4 096 mg/l for a penicillin or 512 mg/l for the cephalosporins. Irrespectively of the phenotypic resistance, for all cephalosorins the MIC became greater than or equal to 64 mg/l and very often greater than or equal to 512 mg/l after 1 to 3 passages. For the penicillin susceptible strains very high MICs were obtained more rapidly with azlocillin and piperacillin (1-2 passages) than with carbenicillin or ticarcillin (5-9 passages). These results are not in favour of a monotherapy with betalactam antibiotics, especially cephalosporins, in the treatment of Pseudomonas aeruginosa infections, but suggest the preferential use of carbenicillin and especially ticarcillin for sensitive isolates.
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002228:Carbenicillin / Q000494:pharmacology; D002441:Cefsulodin; D002442:Ceftazidime; D002511:Cephalosporins / Q000494:pharmacology; D010403:Penicillin Resistance; D011550:Pseudomonas aeruginosa / Q000187:drug effects*; D013982:Ticarcillin / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D002442:Ceftazidime; D013982:Ticarcillin; D002228:Carbenicillin; D002441:Cefsulodin
Pseudomonas aeruginosa: résistance acquise in vitro aux bêta-lactamines.