A comparison of the mechanisms of decreased susceptibility of aztreonam-resistant and ceftazidime-resistant Enterobacteriaceae

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A comparison of the mechanisms of decreased susceptibility of aztreonam-resistant and ceftazidime-resistant Enterobacteriaceae. / Piddock, L J; Traynor, E A; Wise, R.

In: Journal of Antimicrobial Chemotherapy, Vol. 26, No. 6, 12.1990, p. 749-62.

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@article{a7c767ba0fcf4fd9be420b36f8696841,
title = "A comparison of the mechanisms of decreased susceptibility of aztreonam-resistant and ceftazidime-resistant Enterobacteriaceae",
abstract = "Twenty five strains of Enterobacteriaceae (five each of Enterobacter cloacae, Citrobacter freundii, Serratia marcescens, Morganella morganii and Providencia stuartii) were exposed to aztreonam and ceftazidime at 1/2 and 1 x MIC in liquid medium for 22 h, and also to 3, 5 and 10 x MIC and 16 mg/l of each agent in agar. Any putative mutant with an increase in the MIC of greater than or equal to 4 fold was examined for beta-lactamase expression and outer membrane protein profile. Mutants were selected on agar at approximately 10(7); however in liquid medium not all strains yielded mutants. Mutants lacking an outer membrane protein (OMP) with a molecular weight of 40,000 (+/- 5000) were selected with both agents, as were mutants expressing constitutive Richmond and Sykes Class 1 beta-lactamase. For the Ent. cloacae mutants increased beta-lactamase gave rise to MICs above the breakpoint of both agents, whereas with the other species ceftazidime susceptibility was more affected. Strains that were OMP- rarely had MICs above the breakpoint, unless there was also increased beta-lactamase expression, as in species such as M. morganii. Hence the major mechanism of resistance in these strains would appear to be beta-lactamase mediated rather than due to altered expression of outer membrane proteins.",
keywords = "Aztreonam, Bacterial Outer Membrane Proteins, Ceftazidime, Culture Media, Drug Resistance, Microbial, Electrophoresis, Polyacrylamide Gel, Enterobacteriaceae, Microbial Sensitivity Tests, Molecular Weight, Mutation, Phenotype, beta-Lactamases",
author = "Piddock, {L J} and Traynor, {E A} and R Wise",
year = "1990",
month = dec,
language = "English",
volume = "26",
pages = "749--62",
journal = "Journal of Antimicrobial Chemotherapy",
issn = "0305-7453",
publisher = "Oxford University Press",
number = "6",

}

RIS

TY - JOUR

T1 - A comparison of the mechanisms of decreased susceptibility of aztreonam-resistant and ceftazidime-resistant Enterobacteriaceae

AU - Piddock, L J

AU - Traynor, E A

AU - Wise, R

PY - 1990/12

Y1 - 1990/12

N2 - Twenty five strains of Enterobacteriaceae (five each of Enterobacter cloacae, Citrobacter freundii, Serratia marcescens, Morganella morganii and Providencia stuartii) were exposed to aztreonam and ceftazidime at 1/2 and 1 x MIC in liquid medium for 22 h, and also to 3, 5 and 10 x MIC and 16 mg/l of each agent in agar. Any putative mutant with an increase in the MIC of greater than or equal to 4 fold was examined for beta-lactamase expression and outer membrane protein profile. Mutants were selected on agar at approximately 10(7); however in liquid medium not all strains yielded mutants. Mutants lacking an outer membrane protein (OMP) with a molecular weight of 40,000 (+/- 5000) were selected with both agents, as were mutants expressing constitutive Richmond and Sykes Class 1 beta-lactamase. For the Ent. cloacae mutants increased beta-lactamase gave rise to MICs above the breakpoint of both agents, whereas with the other species ceftazidime susceptibility was more affected. Strains that were OMP- rarely had MICs above the breakpoint, unless there was also increased beta-lactamase expression, as in species such as M. morganii. Hence the major mechanism of resistance in these strains would appear to be beta-lactamase mediated rather than due to altered expression of outer membrane proteins.

AB - Twenty five strains of Enterobacteriaceae (five each of Enterobacter cloacae, Citrobacter freundii, Serratia marcescens, Morganella morganii and Providencia stuartii) were exposed to aztreonam and ceftazidime at 1/2 and 1 x MIC in liquid medium for 22 h, and also to 3, 5 and 10 x MIC and 16 mg/l of each agent in agar. Any putative mutant with an increase in the MIC of greater than or equal to 4 fold was examined for beta-lactamase expression and outer membrane protein profile. Mutants were selected on agar at approximately 10(7); however in liquid medium not all strains yielded mutants. Mutants lacking an outer membrane protein (OMP) with a molecular weight of 40,000 (+/- 5000) were selected with both agents, as were mutants expressing constitutive Richmond and Sykes Class 1 beta-lactamase. For the Ent. cloacae mutants increased beta-lactamase gave rise to MICs above the breakpoint of both agents, whereas with the other species ceftazidime susceptibility was more affected. Strains that were OMP- rarely had MICs above the breakpoint, unless there was also increased beta-lactamase expression, as in species such as M. morganii. Hence the major mechanism of resistance in these strains would appear to be beta-lactamase mediated rather than due to altered expression of outer membrane proteins.

KW - Aztreonam

KW - Bacterial Outer Membrane Proteins

KW - Ceftazidime

KW - Culture Media

KW - Drug Resistance, Microbial

KW - Electrophoresis, Polyacrylamide Gel

KW - Enterobacteriaceae

KW - Microbial Sensitivity Tests

KW - Molecular Weight

KW - Mutation

KW - Phenotype

KW - beta-Lactamases

M3 - Article

C2 - 2081717

VL - 26

SP - 749

EP - 762

JO - Journal of Antimicrobial Chemotherapy

JF - Journal of Antimicrobial Chemotherapy

SN - 0305-7453

IS - 6

ER -