Phenotypic and genotypic antimicrobial resistance profiles of Flavobacterium psychrophilum and Flavobacterium branchiophilum isolated from rainbow trout (Oncorhynchus mykiss) in Slovenia

Pavlin, Katarina (author), Papić, Bojan (author), Zdovc, Irena (author), Knific, Tanja (author), Gruntar, Igor (author), Sitar, Rosvita (author), Žele-Vengušt, Diana (author), Seničar, Marija (author), Ocepek, Matjaž (author), Švara, Tanja (author)

Flavobacterium psychrophilum and Flavobacterium branchiophilum are important fish pathogens that cause considerable economic losses in freshwater aquaculture worldwide. Their antimicrobial resistance (AMR) profiles were evaluated using the latest Clinical and Laboratory Standards Institute broth microdilution method, which was adjusted for F. branchiophilum to achieve growth, and whole-genome sequencing (WGS). A total of 51 F. psychrophilum isolates and eight F. branchiophilum isolates from Slovenian farmed rainbow trout underwent phenotypic antimicrobial susceptibility testing. Overall, 86.3% of F. psychrophilum isolates were classified as non-wild-type (NWT) for oxytetracycline and enrofloxacin, and 90.2% of isolates were NWT for oxolinic acid. In contrast, all isolates tested were classified as wild-type (WT) for florfenicol and erythromycin. It was not possible to classify F. branchiophilum isolates as WT or NWT for the antimicrobials tested. A subset of F. psychrophilum (n = 7) and F. branchiophilum (n = 2) isolates was further characterised using WGS to investigate the mechanisms mediating antimicrobial resistance. In F. psychrophilum, the T83A or T83V substitution in GyrA was associated with reduced susceptibility to oxolinic acid. No other AMR genes or AMR-associated mutations were detected.

• Language: English
• Keywords: AMR profile, Flavobacterium branchiophilum, Flavobacterium psychrophilum, minimum inhibitory concentration, MIC, rainbow trout, Oncorhynchus mykiss, whole-genome sequencing, WGS
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: VF - Veterinary Faculty
• Publication status: Published
• Publication version: Version of Record
• Year: 2025
• Number of pages: 12 str.
• Numbering: Vol. 48, iss. 7, art. e14119
• PID: 20.500.12556/RUL-174756
• UDC: 636.09:616
• ISSN on article: 1365-2761
• DOI: 10.1111/jfd.14119
• COBISS.SI-ID: 230430979
• Publication date in RUL: 20.11.2025

Record is a part of a journal

• Title: Journal of fish diseases
• Shortened title: J. fish dis.
• Publisher: Wiley
• ISSN: 1365-2761
• COBISS.SI-ID: 515027481

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Projects

• Funder: ARIS - Slovenian Research and Innovation Agency
• Funding programme: Young researchers

• Funder: ARIS - Slovenian Research and Innovation Agency
• Project number: P4-0092
• Name: Zdravje živali, okolje in varna hrana