JAC Advance Access published online on January 28, 2003
Journal of Antimicrobial Chemotherapy, doi:10.1093/jac/dkg114
© 2003 by The British Society for Antimicrobial Chemotherapy
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Original article
1 Antibiotic Resistance
Monitoring & Reference Laboratory, Central Public Health
Laboratory,
61 Colindale Avenue, London NW9 5HT
* Corresponding author. E-mail: Dlivermore{at}phls.nhs.uk.
Received 23 July 2002
; revised 4 November 2002
; accepted 26 November 2002
MICs of piperacillin/tazobactam are conventionally
determined by varying the concentration of piperacillin in
the presence of a fixed 4 mg/L tazobactam. When tested in this way,
the MIC distribution for Klebsiella isolates with
extended-spectrum
Keywords: piperacillin/tazobactam, Klebsiella,
extended-spectrum Variable susceptibility to piperacillin/tazobactam
amongst Klebsiella spp. with extended-spectrum
-lactamases
2 Barts & The London School of Medicine & Dentistry,
Turner Street, London E1 2AD, UK
-lactamases (ESBLs)
is strongly bimodal, such that many producers are inhibited at 16 + 4
mg/L whilst others require MICs of 
512 + 4
mg/L. When, however, piperacillin/tazobactam was tested as a fixed
8:1 ratio, the MIC distribution became unimodal. If clavulanate
4 mg/L was combined with piperacillin, a unimodal MIC distribution
was seen for ESBL-producing Klebsiella spp. but
a bimodal distribution arose if the clavulanate concentration was
reduced to 0.25 mg/L. These data for alternative combinations suggested
that the bimodal MIC distribution seen for piperacillin + tazobactam
4 mg/L was a titration effect, not a reflection of some ESBLs being
resistant to tazobactam. Even within single strains, as defined
by serotype and DNA fingerprints, there was considerable variation
in susceptibility to piperacillin + tazobactam 4 mg/L,
with some representatives highly susceptible and others highly resistant.
Some of the more resistant representatives produced more of their ESBL,
or had a greater number of -lactamase
types, but these associations were not universal. Elevated resistance
to piperacillin + tazobactam was not associated with porin
change in any ESBL producer examined, but has been found by others.-lactamases
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  M Melzer, R Toner, S Lacey, E Bettany, and G Rait Biliary tract infection and bacteraemia: presentation, structural abnormalities, causative organisms and clinical outcomes Postgrad. Med. J., December 1, 2007; 83(986): 773 - 776. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. B. Kaneene, R. Miller, R. Sayah, Y. J. Johnson, D. Gilliland, and J. C. Gardiner Considerations When Using Discriminant Function Analysis of Antimicrobial Resistance Profiles To Identify Sources of Fecal Contamination of Surface Water in Michigan Appl. Envir. Microbiol., May 1, 2007; 73(9): 2878 - 2890. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Schmitt, E. Jacobs, and H. Schmidt Molecular characterization of extended-spectrum beta-lactamases in Enterobacteriaceae from patients of two hospitals in Saxony, Germany J. Med. Microbiol., February 1, 2007; 56(2): 241 - 249. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 O. Zimhony, I. Chmelnitsky, R. Bardenstein, S. Goland, O. Hammer Muntz, S. Navon Venezia, and Y. Carmeli Endocarditis Caused by Extended-Spectrum-{beta}-Lactamase-Producing Klebsiella pneumoniae: Emergence of Resistance to Ciprofloxacin and Piperacillin-Tazobactam during Treatment despite Initial Susceptibility. Antimicrob. Agents Chemother., September 1, 2006; 50(9): 3179 - 3182. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Bantar, E. Vesco, C. Heft, F. Salamone, M. Krayeski, H. Gomez, M. A. Coassolo, A. Fiorillo, D. Franco, C. Arango, et al. Replacement of Broad-Spectrum Cephalosporins by Piperacillin-Tazobactam: Impact on Sustained High Rates of Bacterial Resistance Antimicrob. Agents Chemother., February 1, 2004; 48(2): 392 - 395. [Abstract] [Full Text] [PDF]
|
|