Role of β-lactamase in in vivo development of ceftazidime resistance in experimental Pseudomonas aeruginosa endocarditis

A. S. Bayer, J. Peters, T. R. Parr, L. Chan, R. E. Hancock

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Two ceftazidime-resistant variants of Pseudomonas aeruginosa (PA-48, PA-60), obtained from cardiac vegetations of rabbits with endocarditis receiving ceftazidime therapy, were studied for mechanisms of resistance. Both resistant variants were stably derepressed for the type Id β-lactamase, which was ceftazidime inducible in the parental strain (PA-96) used to initially infect the rabbits. There was no evidence of ceftazidime bioinactivation by the resistant strains, and their outer membrane permeabilities were comparable to those of the parental strain. No alterations were observed in patterns of outer membrane proteins or membrane lipopolysaccharides in the resistant variants as compared with the parental strain. Penicillin-binding protein patterns of the resistant variants revealed the absence of penicillin-binding protein 4 in both, with acquisition of a new protein of higher apparent molecular weight in PA-60. Calculation of the rate of appearance of ceftazidime in the periplasm at sub-MICs suggested that slow enzymatic hydrolysis of the β-lactam, rather than nonhydrolytic trapping, was the major explanation for the induced resistance in vivo in strains PA-48 and PA-60.

Original languageEnglish
Pages (from-to)253-258
Number of pages6
JournalAntimicrobial Agents and Chemotherapy
Issue number2
Publication statusPublished - 1987

ASJC Scopus subject areas

  • Pharmacology
  • Pharmacology (medical)
  • Infectious Diseases

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