HOCQUET D, ROUSSEL M, PLESIAT P, GESPA G; Interscience Conference on Antimicrobial Agents and Chemotherapy (42nd : 2002 : San Diego, Calif.).
Abstr Intersci Conf Antimicrob Agents Chemother Intersci Conf Antimicrob Agents Chemother. 2002 Sep 27-30; 42: abstract no. C2-1997.
Faculty of Medicine, Besancon, France
BACKGROUND: Bacteremias due to resistant P. aeruginosastrains are difficult to treat and often associated with poor clinical outcome. This study investigates the mechanisms responsible for resistance to beta-lactams (b L) and aminoglycosides (AGs) in invasive isolates. METHODS: 105 bacteremic isolates of P. aeruginosawere collected in 1999, in 6 French university-affiliated hospitals. MICs of 11 antipseudomonal antibiotics were determined by the macrodilution method in agar (NCCLS). beta-lactamases were identified by isoelectrofocusing and gene sequencing. AG-modifying enzymes were determined phenotypically by using the Schering-Plough Resistance Test Kit. Overproduction of efflux systems MexAB-OprM and MexXY-OprM was assessed by hybridizing membrane preparations with specific MexB, MexY, OprM antibodies, respectively. RESULTS: Susceptibility rates of the 105 isolates were as follows (NCCLS breakpoints): 75.7% ticarcillin, 93.5% piperacillin/tazobactam, 78.5% aztreonam, 81.3% ceftazidime, 65.4% cefepime, 82.2% imipenem; 51.4% gentamicin, 53.2% netilmicin, 75.7% tobramycin, 92.5% amikacin; 65.4% ciprofloxacin. Only 35.2% of the strains exhibited a wild-type susceptibility profile to b L and AGs. 35.3% of the resistant isolates were derepressed mutants for AmpC cephalosporinase, 17.6% harbored a secondary beta-lactamase, 38.2% produced one or several AG-modifying enzymes, 58.8% overexpressed MexXY, and 35.3% overexpressed MexAB. Interestingly, OprM production was found to be independent of that of MexAB, and only 5 out of the 24 MexAB overproducers showed a typical efflux resistance phenotype to b L. Non-enzymatic resistance to AGs was associated with MexXY upregulation in 66.7% of the bacteria, and due to an unknown mechanism in 29.3%. CONCLUSIONS: Frequently encountered in bacteremic, virulent strains of P. aeruginosa, efflux mechanisms are responsible for significant drug resistance mostly when associated with other mechanisms.
Publication Types:
Keywords:
- Anti-Bacterial Agents
- Ceftazidime
- Cephalosporinase
- Cephalosporins
- Imipenem
- Microbial Sensitivity Tests
- Penicillanic Acid
- Piperacillin
- Pseudomonas aeruginosa
- Ticarcillin
- beta-Lactamases
- beta-Lactams
- cefepime
- tazobactam
Other ID:
UI: 102267379
From Meeting Abstracts