Epidemiological cutoff value analysis of 229 MICs from standard testing of Flavobacterium columnare isolates by four laboratories

Le résumé fourni par la source

Antimicrobial resistance is a major public health concern. Therefore, it is critical to have standard methods and criteria, called epidemiological cutoff values (ECVs, a.k.a. ECOFFs) to monitor for the development of resistance. To develop ECVs for the fish pathogen Flavobacterium columnare, we tested the susceptibility of 229 isolates using the standard broth dilution susceptibility testing method in the Clinical Laboratory and Standards Institute (CLSI) VET04-A2 guideline. Using the method, we determined the minimum inhibitory concentration (MIC) against 10 antibiotics: ampicillin, enrofloxacin, erythromycin, florfenicol, flumequine, gentamicin, ormetoprim/sulfadimethoxine, oxolinic acid, oxytetracycline, and trimethoprim/sulfamethoxazole. We analyzed frequency distributions for each antibiotic to estimate an ECV which separates the wild-type isolates without resistance from the non-wild-type isolates that have developed resistance using two statistical methods: ECOFFinder (Turnidge et al., 2006) and Normalized Resistance Interpretation (Kronvall, 2010). ECVs were estimated for ampicillin, enrofloxacin, erythromycin, florfenicol, flumequine, oxolinic acid, and oxytetracycline. The estimated ECVs showed that the isolates categorized similarly among the quinolones (enrofloxacin, flumequine, and oxolinic acid) as wild-type and non-wild-type. Therefore, laboratories could potentially use one of these compounds to monitor quinolone resistance. An ECV for the potentiated sulfonamides could not be estimated because the potentiators may be masking resistance to sulfonamide. Similarly, an ECV for gentamicin was not evaluated because there are currently no existing quality control ranges to verify the results. The CLSI Veterinary Antimicrobial Susceptibility Testing subcommittee is currently reviewing the data and the ECVs proposed from our analysis. If adopted, the ECVs will be included in the next revision of the VET04-supplement document.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.