Affiliation:
1. Servicio de Microbiologı́a, Hospital Ramón y Cajal, Madrid 28034, Spain
Abstract
ABSTRACT
Despite the large number of in vitro mutations that increase resistance to extended-spectrum cephalosporins in TEM-type β-lactamases, only a small number occur in naturally occurring enzymes. In nature, and particularly in the hospital, bacteria that contain β-lactamases encounter simultaneous or consecutive selective pressure with different β-lactam molecules. All variants obtained by submitting an
Escherichia coli
strain that contains a
bla
TEM-1
gene to fluctuating challenge with both ceftazidime and amoxicillin contained only mutations previously detected in naturally occurring β-lactamases. Nevertheless, some variants obtained by ceftazidime challenge alone contained mutations never detected in naturally occurring TEM β-lactamases, suggesting that extended-spectrum TEM variants in hospital isolates result from fluctuating selective pressure with several β-lactams rather than selection with a single antibiotic.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Pharmacology (medical),Pharmacology
Cited by
52 articles.
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