期刊
ANTIMICROBIAL AGENTS AND CHEMOTHERAPY
卷 56, 期 1, 页码 231-242出版社
AMER SOC MICROBIOLOGY
DOI: 10.1128/AAC.05252-11
关键词
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资金
- National Institute of Allergy and Infectious Diseases [R01AI079578]
- U.S. Department of Veterans Affairs
- Veterans Integrated Service Network 10 Geriatric Research, Education, and Clinical Center
- National Institutes of Health [R01AI072219, 2R01AI063517-06A1, T32 GM07250]
- Case Western Reserve University (CWRU)
The panoply of resistance mechanisms in Pseudomonas aeruginosa makes resistance suppression difficult. Defining optimal regimens is critical. Cefepime is a cephalosporin whose 3' side chain provides some stability against AmpC beta-lactamases. We examined the activity of cefepime against P. aeruginosa wild-type strain PAO1 and its isogenic AmpC stably derepressed mutant in our hollow-fiber infection model. Dose-ranging studies demonstrated complete failure with resistance emergence (both isolates). Inoculum range studies demonstrated ultimate failure for all inocula. Lower inocula failed last (10 days to 2 weeks). Addition of a beta-lactamase inhibitor suppressed resistance even with the stably derepressed isolate. Tobramycin combination studies demonstrated resistance suppression in both the wild-type and the stably derepressed isolates. Quantitating the RNA message by quantitative PCR demonstrated that tobramycin decreased the message relative to that in cefepime-alone experiments. Western blotting with AmpC-specific antibody for P. aeruginosa demonstrated decreased expression. We concluded that suppression of beta-lactamase expression by tobramycin (a protein synthesis inhibitor) was at least part of the mechanism behind resistance suppression. Monte Carlo simulation demonstrated that a regimen of 2 g of cefepime every 8 h plus 7 mg/kg of body weight of tobramycin daily would provide robust resistance suppression for Pseudomonas isolates with cefepime MIC values up to 8 mg/liter and tobramycin MIC values up to 1 mg/liter. For P. aeruginosa resistance suppression, combination therapy is critical.
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