Dataset Information

Evaluation of six commercial and in-house phenotypic tests for detection of AmpC β-lactamases: is routine detection possible?

ABSTRACT:

Background

Phenotypic characterization of the prevalent AmpC β-lactamases in clinical isolates is essential for making informed empirical decisions and critical for strengthening antimicrobial stewardship programmes. This study focused on assessing six assays, two in-house and four commercial phenotypic tests for detection of AmpC, to study the feasibility of making its detection a routine diagnostic microbiology laboratory activity.

Methods

A total of 116 non-duplicate Gram-negative bacteria that were resistant to third-generation cephalosporins and amoxicillin/clavulanic acid, and resistant or susceptible to piperacillin/tazobactam and carbapenems, were screened by cefoxitin discs for AmpC. These isolates were subjected to two in-house (AmpC Tris-EDTA and disc approximation) methods and four commercial tests: D69C AmpC Detection Set; D72C ESBL, AmpC & Carbapenemase Detection Set; combination disc test: ESBL + AmpC Screen Disc Kit; and AmpC MIC Test Strip for confirmation of AmpC production. Ten whole-genome-sequenced AmpC-confirmed Gram-negative isolates were used as positive controls and one as a negative control.

Results

The prevalence of AmpC β-lactamases was 16%. Escherichia coli was a major carrier of plasmid-mediated AmpC (26.5%), followed by Klebsiella pneumoniae (23.4%). Phenotypically, 61% of AmpCs were detected by Tris-EDTA (accuracy: 73.8%), 76% by disc approximation (accuracy: 89.2%), 75% by the D69C AmpC Detection Set (accuracy: 95.4%), 74% by the D72C AmpC, ESBL & Carbapenemase Detection Set (accuracy: 95.4%), 76% by the combination disc test (accuracy: 95.4%) and 63% by AmpC MIC Test Strip (accuracy: 87.7%). The sensitivity and specificity of D69C were 97.9% and 88.2%, respectively, and 95.9% and 93.8% for the combination disc test, while for the disc approximation test and D72C they were 93.9% and 75%, and 93.9% and 100%, respectively. Screening by cefoxitin screening was less sensitive (75%) and specific (25%). Disc approximation and the combination disc test detect AmpC in Enterobacterales and also Pseudomonas aeruginosa and Acinetobacter species.

Conclusions

We recommend the in-house disc approximation test and the commercial D69C, as well as the combination disc test, as excellent tools for detection of AmpC. The cefoxitin test overcalls AmpC and cannot be considered a good stand-alone test for AmpC detection.

SUBMITTER: Al Mamari AMK

PROVIDER: S-EPMC10475971 | biostudies-literature | 2023 Oct

REPOSITORIES: biostudies-literature

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Publications

Evaluation of six commercial and in-house phenotypic tests for detection of AmpC β-lactamases: is routine detection possible?

Al Mamari Azza Mohammed Khalifa AMK Al Jabri Zaaima Z Sami Hiba H Rizvi Syed Gauhar A SGA Chan Moon Fai MF Al Siyabi Turkiya T Al Muharrmi Zakariya Z Rizvi Meher M

JAC-antimicrobial resistance 20230904 5

<h4>Background</h4>Phenotypic characterization of the prevalent AmpC β-lactamases in clinical isolates is essential for making informed empirical decisions and critical for strengthening antimicrobial stewardship programmes. This study focused on assessing six assays, two in-house and four commercial phenotypic tests for detection of AmpC, to study the feasibility of making its detection a routine diagnostic microbiology laboratory activity.<h4>Methods</h4>A total of 116 non-duplicate Gram-negat ...[more]

PMID: 37670936

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Project description:ObjectivesThe objective of this study was to determine the occurrence of chromosomal and plasmid-mediated β-lactamases (AmpC) genes in a collection of Malaysian isolates of Enterobacter species. Several phenotypic tests for detection of AmpC production of Enterobacter spp. were evaluated and the agreements between tests were determined.MethodsAntimicrobial susceptibility profiles for 117 Enterobacter clinical isolates obtained from the Medical Microbiology Diagnostic Laboratory, University Malaya Medical Centre, Malaysia, from November 2012-February 2014 were determined in accordance to CLSI guidelines. AmpC genes were detected using a multiplex PCR assay targeting the MIR/ACT gene (closely related to chromosomal EBC family gene) and other plasmid-mediated genes, including DHA, MOX, CMY, ACC, and FOX. The AmpC β-lactamase production of the isolates was assessed using cefoxitin disk screening test, D69C AmpC detection set, cefoxitin-cloxacillin double disk synergy test (CC-DDS) and AmpC induction test.ResultsAmong the Enterobacter isolates in this study, 39.3% were resistant to cefotaxime and ceftriaxone and 23.9% were resistant to ceftazidime. Ten (8.5%) of the isolates were resistant to cefepime, and one isolate was resistant to meropenem. Chromosomal EBC family gene was amplified from 36 (47.4%) E. cloacae and three (25%) E. asburiae. A novel blaDHA type plasmid-mediated AmpC gene was identified for the first time from an E. cloacae isolate. AmpC β-lactamase production was detected in 99 (89.2%) of 111 potential AmpC β-lactamase producers (positive in cefoxitin disk screening) using D69C AmpC detection set. The detection rates were lower with CC-DDS (80.2%) and AmpC induction tests (50.5%). There was low agreement between the D69C AmpC detection set and the other two phenotypic tests. Of the 40 isolates with AmpC genes detected in this study, 87.5%, 77.5% and 50.0% of these isolates were positive by the D69C AmpC detection set, CC-DDS and AmpC induction tests, respectively.ConclusionsBesides MIR/ACT gene, a novel plasmid-mediated AmpC gene belonging to the DHA-type was identified in this study. Low agreement was noted between the D69C AmpC detection set and two other phenotypic tests for detection of AmpC production in Enterobacter spp. As plasmid-mediated genes may serve as the reservoir for the emergence of antibiotic resistance in a clinical setting, surveillance and infection control measures are necessary to limit the spread of these genes in the hospital.

Dataset Information

Evaluation of six commercial and in-house phenotypic tests for detection of AmpC β-lactamases: is routine detection possible?

Background

Methods

Results

Conclusions

Publications

Evaluation of six commercial and in-house phenotypic tests for detection of AmpC β-lactamases: is routine detection possible?

Similar Datasets

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