Peer-Reviewed Journal Details
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Ngo, TPH,Smith, P,Bartie, KL,Thompson, KD,Verner-Jeffreys, DW,Hoare, R,Adams, A
2018
February
Journal Of Fish Diseases
Antimicrobial susceptibility of Flavobacterium psychrophilum isolates from the United Kingdom
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antimicrobial susceptibility broth microdilution disc diffusion epidemiological cut-off values Flavobacterium psychrophilum rainbow trout fry syndrome EPIDEMIOLOGIC CUTOFF VALUES ONCORHYNCHUS-MYKISS WALBAUM RAINBOW-TROUT FRY NORMALIZED RESISTANCE INTERPRETATION COLD-WATER DISEASE IN-VITRO INHIBITORY CONCENTRATION PSEUDOMONAS SP DIVERSITY BACTERIA
41
309
320
Routine application of antimicrobials is the current treatment of choice for rainbow trout fry syndrome (RTFS) or bacterial coldwater disease (BCWD) caused by Flavobacterium psychrophilum. In this study, the antimicrobial susceptibilities of 133 F.psychrophilum isolates, 118 of which were from the UK, were evaluated by broth microdilution and disc diffusion methods following VET04-A2 and VET03-A guidelines of Clinical and Laboratory Standards Institute (CLSI), respectively. Isolates were categorized as wild type (fully susceptible, WT) or non-wild type (NWT) using normalized resistance interpretation (NRI)-determined cut-off values (COWT). Broth microdilution testing showed that only 12% of UK isolates were WT to oxolinic acid (MIC COWT <= 0.25 mg/L) and 42% were WT for oxytetracycline (MIC COWT <= 0.25 mg/L). In contrast, all the isolates tested were WT (MIC COWT <= 2 mg/L) for florfenicol, the main antimicrobial for RTFS control in the UK. Disc diffusion-based COWT values were >= 51 mm for 10 mu g amoxicillin, >= 44 mm for 30 mu g florfenicol, >= 30 mm for 2 mu g oxolinic acid and >= 51 mm for 30 mu g oxytetracycline. There was a high categorical agreement between the classifications of the isolates by two testing methods for florfenicol (100%), oxytetracycline (93%) and oxolinic acid (99%).
10.1111/jfd.12730
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