Journal article
Evaluation of the Haemophilus influenzae EUCAST and CLSI disc diffusion methods to recognize aminopenicillin and amoxicillin/clavulanate resistance
Journal of Antimicrobial Chemotherapy, Vol.75(9), pp.2594-2598
2020
Abstract
Objectives
Implementation of EUCAST susceptibility testing in an Australian hospital laboratory demonstrated higher rates of aminopenicillin and amoxicillin/clavulanate resistance in Haemophilus influenzae than previously recognized. This study aimed to better define the variability in the detection of β-lactam resistance based on EUCAST and CLSI disc diffusion (DD) methodology, by comparison with the recommended reference method, broth microdilution (BMD), and by concordance with genomic analysis.
Methods
A total of 100 random H. influenzae isolates were assessed for ampicillin and amoxicillin/clavulanate susceptibility by EUCAST and CLSI DD and BMD. WGS was used to analyse the ftsI gene of a subset of isolates with β-lactam resistance, other than that due to isolated β-lactamase production.
Results
Of the 100 isolates, 32 were categorized as either β-lactamase negative, ampicillin resistant (BLNAR) (n = 18) or β-lactamase positive, amoxicillin/clavulanate resistant (BLPACR) (n = 14) by EUCAST DD. All 18 EUCAST BLNAR isolates were genotypically confirmed by WGS. Five of 18 BLNAR isolates were concordant by CLSI DD, 12 by EUCAST BMD and 4 by CLSI BMD. Nine of 14 EUCAST BLPACR isolates were confirmed by WGS; the remaining 5 were 1 mm below the EUCAST DD breakpoint. Only one isolate was detected as BLPACR by CLSI DD. Group III mutations associated with high-level ampicillin resistance were identified in 10/32 isolates.
Conclusions
The EUCAST DD susceptibility method is more reliable than either CLSI or BMD for the detection of genotypically defined BLNAR resistance. However, accurate categorization of amoxicillin/clavulanate resistance remains problematic. Continuous and reproducible surveillance of resistance is needed; for this to be possible, robust susceptibility methods are required.
Details
- Title
- Evaluation of the Haemophilus influenzae EUCAST and CLSI disc diffusion methods to recognize aminopenicillin and amoxicillin/clavulanate resistance
- Authors/Creators
- T. Gottlieb (Author/Creator)G.W. Coombs (Author/Creator)J. Merlino (Author/Creator)T. Phan (Author/Creator)G.L. McKew (Author/Creator)S. Pang (Author/Creator)S.A. Fernando (Author/Creator)
- Publication Details
- Journal of Antimicrobial Chemotherapy, Vol.75(9), pp.2594-2598
- Publisher
- Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy
- Identifiers
- 991005544853907891
- Copyright
- © 2020 British Society for Antimicrobial Chemotherapy
- Murdoch Affiliation
- Antimicrobial Resistance and Infectious Disease Laboratory; School of Veterinary and Life Sciences
- Language
- English
- Resource Type
- Journal article
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- Citation topics
- 1 Clinical & Life Sciences
- 1.23 Antibiotics & Antimicrobials
- 1.23.347 Streptococcus Pneumoniae
- Web Of Science research areas
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- Microbiology
- Pharmacology & Pharmacy
- ESI research areas
- Pharmacology & Toxicology