International dissemination of Escherichia coli strains with discrepant behaviour in phenotypic antimicrobial susceptibility tests

Creely, David; Zambardi, Gilles; Belkum, Alex van; Dunne, W. Michael; Peyret, M.; Gayral, J P; Shortridge, Dee; Shubert, C.

doi:10.1007/s10096-013-1837-5

Cited by 7 publications

(11 citation statements)

References 18 publications

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“…Previous work revealed that E. coli clinical isolate 907355 is resistant to piperacillin-tazobactam (TZP; MIC for the combination, >128 µg/ml piperacillin and 4 µg/ml tazobactam [expressed here as ≥128/4 µg/ml]) in BMD tests, yet susceptible (MIC, ≤16/4 µg/ml) by the AD method ( 24 , 25 ). To further investigate the nature of this discordant behavior, BMD assays were performed with two other β-lactam/β-lactamase inhibitor combinations, ampicillin-sulbactam (SAM) and amoxicillin-clavulanate (AMC).…”

Section: Resultsmentioning

confidence: 99%

“…We have identified a number of clinical E. coli isolates that exhibit discordant behavior and heterogeneous resistance in disk diffusion (DD), agar dilution (AD), and broth microdilution (BMD) antibiotic susceptibility testing (AST) assays ( 24 , 25 ). A PCR- and sequence-based screen for plasmid-borne β-lactamase genes revealed that many of the isolates harbored only bla TEM-1 .…”

Section: Introductionmentioning

confidence: 99%

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Extensive Gene Amplification as a Mechanism for Piperacillin-Tazobactam Resistance in Escherichia coli

Schechter

Creely

Garner

et al. 2018

mBio

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Although the TEM-1 β-lactamase (BlaTEM-1) hydrolyzes penicillins and narrow-spectrum cephalosporins, organisms expressing this enzyme are typically susceptible to β-lactam/β-lactamase inhibitor combinations such as piperacillin-tazobactam (TZP). However, our previous work led to the discovery of 28 clinical isolates of Escherichia coli resistant to TZP that contained only blaTEM-1. One of these isolates, E. coli 907355, was investigated further in this study. E. coli 907355 exhibited significantly higher β-lactamase activity and BlaTEM-1 protein levels when grown in the presence of subinhibitory concentrations of TZP. A corresponding TZP-dependent increase in blaTEM-1 copy number was also observed, with as many as 113 copies of the gene detected per cell. These results suggest that TZP treatment promotes an increase in blaTEM-1 gene dosage, allowing BlaTEM-1 to reach high enough levels to overcome inactivation by the available tazobactam in the culture. To better understand the nature of the blaTEM-1 copy number proliferation, whole-genome sequence (WGS) analysis was performed on E. coli 907355 in the absence and presence of TZP. The WGS data revealed that the blaTEM-1 gene is located in a 10-kb genomic resistance module (GRM) that contains multiple resistance genes and mobile genetic elements. The GRM was found to be tandemly repeated at least 5 times within a p1ESCUM/p1ECUMN-like plasmid when bacteria were grown in the presence of TZP.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Extensive Gene Amplification as a Mechanism for Piperacillin-Tazobactam Resistance in Escherichia coli

Schechter

Creely

Garner

et al. 2018

mBio

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“…However, certain drugs (especially combinations) are often problematic. Root causes for such differences are usually unknown, but clear differences between piperacillin-tazobactam (TZP) broth microdilution (BMD) and agar dilution (AD) results were observed for isolates of several species (2)(3)(4)(5). Although differences between BMD and AD have been observed for other species, the population analysis discussed here was limited to Escherichia coli.…”

mentioning

confidence: 99%

“…Although differences between BMD and AD have been observed for other species, the population analysis discussed here was limited to Escherichia coli. We recently demonstrated that this aberrant phenotype can be clonal in E. coli (5). In this study, isolates were tested by population analysis (PA) in order to determine whether heterogeneity of resistance expression was a factor in the category differences observed between BMD and AD for TZP.…”

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confidence: 99%

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Population Analysis of Escherichia coli Isolates with Discordant Resistance Levels by Piperacillin-Tazobactam Broth Microdilution and Agar Dilution Testing

Shubert

Slaughter

Creely

et al. 2014

Antimicrob Agents Chemother

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Population analysis was performed for 42 Escherichia coli isolates to determine whether heterogeneity of resistance was a factor in piperacillin-tazobactam category differences between agar dilution and broth microdilution. Of 20 isolates discordant between methods, 80% were heterogeneous. Of 22 isolates in agreement, 59% were homogeneous. Heterogeneity and homogeneity rates for those in agreement were significantly different from those that were discordant (P value, 0.010). Heterogeneity of resistance expression appears to be an important factor in category differences observed between broth microdilution and agar dilution for piperacillin-tazobactam. Interpretation of antimicrobial susceptibility tests can be subjective, even for established reference methods. Various in vitro methods to assess susceptibility have been developed, and conditions can vary widely during measurements. This diversity can cause differences in the metabolic status of bacterial cells and thus their reactivity to antibiotics, implying that results from different methods can vary per strain, as was recently seen in a multicenter study of Pseudomonas aeruginosa (1). Methodological differences can lead to very major errors (VMEs) (reference method resistant and comparator susceptible), which may lead to treatment failure. Major errors (MEs) (reference method susceptible and comparator resistant) can also occur and, although less serious therapeutically, can lead to disqualification of otherwise useful antimicrobials. The frequency of VMEs and MEs depends on the methods used and organism/antimicrobial combinations. However, certain drugs (especially combinations) are often problematic. Root causes for such differences are usually unknown, but clear differences between piperacillin-tazobactam (TZP) broth microdilution (BMD) and agar dilution (AD) results were observed for isolates of several species (2-5). Although differences between BMD and AD have been observed for other species, the population analysis discussed here was limited to Escherichia coli. We recently demonstrated that this aberrant phenotype can be clonal in E. coli (5). In this study, isolates were tested by population analysis (PA) in order to determine whether heterogeneity of resistance expression was a factor in the category differences observed between BMD and AD for TZP.A subset of 42 E. coli isolates was selected from a larger set of Enterobacteriaceae obtained for the purpose of studying TZP susceptibility (5). The isolates were obtained globally from as many geographically diverse locations as possible. Isolates in agreement as well as those in disagreement between BMD and AD were included. Strain characteristics are included in Table 1. BMD and AD TZP susceptibility testing was performed according to CLSI guidelines (6) and was done in triplicate. MICs were determined by examining the growth for each of the three replicates for each isolate and method. The lowest concentration that completely inhibited visible growth as detected by the unaided eye was recorded as t...

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Mechanisms and clinical relevance of bacterial heteroresistance

2019

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International dissemination of Escherichia coli strains with discrepant behaviour in phenotypic antimicrobial susceptibility tests

Cited by 7 publications

References 18 publications

Extensive Gene Amplification as a Mechanism for Piperacillin-Tazobactam Resistance in Escherichia coli

Extensive Gene Amplification as a Mechanism for Piperacillin-Tazobactam Resistance in Escherichia coli

Population Analysis of Escherichia coli Isolates with Discordant Resistance Levels by Piperacillin-Tazobactam Broth Microdilution and Agar Dilution Testing

Mechanisms and clinical relevance of bacterial heteroresistance

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