Dataset Information

Concordance of disk diffusion, broth microdilution, and whole-genome sequencing for determination of in vitro antimicrobial susceptibility of Mannheimia haemolytica.

ABSTRACT: BACKGROUND:Extensive drug resistance (XDR) is an emerging concern with Mannheimia haemolytica, and a variety of testing methods are available for characterizing in vitro antimicrobial susceptibility. OBJECTIVES:To compare the concordance among disk diffusion, broth microdilution, and whole genome sequencing (WGS) for susceptibility testing of M. haemolytica before and after mass treatment using tulathromycin. ANIMALS:Forty-eight M. haemolytica isolates collected from high-risk beef stocker calves before and after mass treatment (metaphylaxis) using tulathromycin (Draxxin, Zoetis, Parsippany, NJ) given at the label dosage of 2.5 mg/kg body weight SC in the neck. METHODS:In vitro antimicrobial susceptibility was determined for all 48 isolates using disk diffusion, broth microdilution, and WGS. Concordance was calculated between pairs of susceptibility testing methods as follows: number of isolates classified identically by the 2 testing methods for each timepoint, divided by the number of isolates tested at that timepoint. Discordance was calculated as follows: number of isolates classified differently by the 2 testing methods for each timepoint, divided by the number of isolates tested at that timepoint. RESULTS:Concordance between testing methods ranged from 42.3% to 100%, depending on antimicrobial evaluated, timing of sample collection, and testing method used. Very major errors were identified in up to 7.7% of classifications whereas minor errors were seen in up to 50% of classifications depending on antimicrobial evaluated, timing of sample collection, and testing method used. CONCLUSIONS AND CLINICAL IMPORTANCE:Our results show that discrepancies in the results of different susceptibility testing methods occur and suggest a need for greater harmonization of susceptibility testing methods.

SUBMITTER: Snyder ER

PROVIDER: S-EPMC7517867 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature

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Concordance of disk diffusion, broth microdilution, and whole-genome sequencing for determination of in vitro antimicrobial susceptibility of Mannheimia haemolytica.

Snyder Emily R ER Savitske Bridget J BJ Credille Brent C BC

Journal of veterinary internal medicine 20200907 5

<h4>Background</h4>Extensive drug resistance (XDR) is an emerging concern with Mannheimia haemolytica, and a variety of testing methods are available for characterizing in vitro antimicrobial susceptibility.<h4>Objectives</h4>To compare the concordance among disk diffusion, broth microdilution, and whole genome sequencing (WGS) for susceptibility testing of M. haemolytica before and after mass treatment using tulathromycin.<h4>Animals</h4>Forty-eight M. haemolytica isolates collected from high-r ...[more]

PMID: 32893911

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Project description:Delafloxacin, a recently approved anionic fluoroquinolone, was tested within an international resistance surveillance program. The in vitro susceptibilities of 7,914 indicated pathogens causing acute bacterial skin and skin structure infections (ABSSSI) were determined using Clinical and Laboratory Standards Institute (CLSI) broth microdilution MIC testing methods. The U.S. Food and Drug Administration (FDA) susceptibility testing breakpoints and quality control ranges for routine broth microdilution and disk diffusion methods were confirmed. The delafloxacin MIC50/90 (% susceptibility) results were as follows: Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA), 0.008/0.25 ?g/ml (92.8%); Staphylococcus lugdunensis, 0.016/0.03 ?g/ml (99.3%); Streptococcus pyogenes, 0.016/0.03 ?g/ml (100.0%); Streptococcus anginosus group, 0.008/0.016 ?g/ml (100.0%); Enterococcus faecalis, 0.12/1 ?g/ml (66.2%); and Enterobacteriaceae, 0.12/4 ?g/ml (69.5%). The FDA clinical breakpoints were used to assess intermethod test agreement between delafloxacin MIC and disk diffusion methods for the indicated pathogens. The intermethod susceptibility test categorical agreement for delafloxacin was acceptable, with only 0.4% very major, false-susceptible errors among S. aureus strains. Across all FDA-indicated species, the selected breakpoints produced only 0.0 to 1.7% rates of serious (very major and major errors) intermethod error. Quality control ranges for these standardized delafloxacin susceptibility test methods were calculated from three multilaboratory (12 total sites) studies for six control organisms. In conclusion, the application of FDA MIC breakpoints for delafloxacin against contemporary (2014 to 2016) isolates of ABSSSI pathogens provides additional support for the use of delafloxacin in the treatment of adults with ABSSSI. Delafloxacin MIC and disk diffusion susceptibility testing methods have been standardized for clinical application, achieving high intermethod categorical agreement.

Dataset Information

Concordance of disk diffusion, broth microdilution, and whole-genome sequencing for determination of in vitro antimicrobial susceptibility of Mannheimia haemolytica.

Publications

Concordance of disk diffusion, broth microdilution, and whole-genome sequencing for determination of in vitro antimicrobial susceptibility of Mannheimia haemolytica.

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