Previous Article | Next Article ![]()
Antimicrobial Agents and Chemotherapy, October 2000, p. 2759-2763, Vol. 44, No. 10
Institute of Medical Microbiology, University
of Zürich, CH-8028 Zürich,
Switzerland,1 and Department of
Bacteriology, National Institute of Infectious Diseases, Shinjuku-ku,
Tokyo 162-8640, Japan2
Received 29 November 1999/Returned for modification 28 March
2000/Accepted 16 July 2000
SHV extended-spectrum
0066-4804/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Contribution of Natural Amino Acid Substitutions in
SHV Extended-Spectrum
-Lactamases to Resistance against
Various
-Lactams
-lactamases (ESBLs) arise through single
amino acid substitutions in the parental enzyme, SHV-1. In order to
evaluate the effect of genetic dissimilarities around the structural
gene on MICs, we had previously devised an isogenic system of strains.
Here, we present an extended version of the system that now allows
assessment of all major types of SHV
-lactamases as well as of two
types of promoters of various strengths. Moreover, we devised a novel
vector, pCCR9, to eliminate interference of the selection marker. A
substitution within the signal sequence, I8F found in SHV-7, slightly
increased MICs, suggesting more efficient transfer of enzyme precursor
into the periplasmic space. We also noted that combination of G238S and
E240K yielded higher resistance than G238S alone. However, the
influence of the additional E240K change was more pronounced with
ceftazidime and aztreonam than with cefotaxime and ceftriaxone. The SHV
enzymes characterized by the single change, D179N, such as SHV-8,
turned out to be the weakest SHV ESBLs. Only resistance to ceftazidime
was moderately increased compared to SHV-1.
*
Corresponding author. Mailing address: Institute of
Medical Microbiology, University of Zürich, P.O. Box, CH-8028
Zürich, Switzerland. Phone: 41-1-634-26 48. Fax: 41-1-634-4906. E-mail: haechler{at}immv.unizh.ch.
This article has been cited by other articles:
| Clin. Vaccine Immunol. | Clin. Microbiol. Rev. |
|---|---|
| J. Clin. Microbiol. | ALL ASM JOURNALS |