ISSN:
1435-4373
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Successive transfer of three clinical isolates ofPseudomonas aeruginosa in liquid medium containing serial dilutions of several beta-lactam antibiotics was used to isolate resistant variants. The alpha-carboxy-penicillins (carbenicillin and ticarcillin), the acylureidopenicillins (piperacillin and azlocillin) and cephalosporins (moxalactam, cefoperazone, cefsulodin and ceftazidime) were used as the selective antibiotics. Resistant variants were isolated from two of the three strains (strains 27 and 45), using an inoculum size of 104–105 CFU/ml, which showed a mean 5 to 8-fold increase in MIC for most of the selected antibiotics. The 27-carbenicillin and 27-cefsulodin resistant variants showed beta-lactamase production similar to that of the parent. However, alterations were found in outer-membrane proteins and lipopolysaccharides. With azlocillin, moxalactam and ceftazidime as the selective antibiotics, resistant variants were isolated from strains 27 and 45 which showed a stable increased constitutive beta-lactamase production. From the third strain, 9150, the only variants isolated showed a two dilution-step increase in MIC to the antibiotics tested. The betalactamase production, outer-membrane proteins and lipopolysaccharides of these variants were similar to those of the parent.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02097185
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