Antibiotic resistance in bacteria isolated from the skin of trout in León Province, Spain

Antibiotic resistance among fish pathogens has become a major concern. Integrons play an important role in dissemination of antibiotics resistance genes among the different species of bacteria. This study was designed to determine the antibiotic susceptibility of 20 bacterial isolates were isolated from the skin of brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) collected from the rivers and fish farms in León Province, Spain and to detect class 1 and 2 integrons in these isolates by PCR to explore the role of these integrons in the antibiotic resistance. The investigated isolates included Pseudomonas fluorescens (P. fluorescens) (n=5), Aeromonas sobria (A. sobria) (n=3), Pantoea agglomerans (P. agglomerans) (n=3), Acinetobacter johnsonii (A. johnsonii) (n=2), Serratia fonticola (S. fonticola) (n=1), Staphylococcus equorum (S. equorum) (n=3), Yersinia kristensenii (Y. kristensenii) (n=2) and Xanthomonas retroflexus (X. retroflexus) (n=1). Antimicrobial susceptibility testing for the isolates revealed that they were sensitive to enrofloxacin (100%) and gentamicin (95%) while resistant to ampicillin (90%) and tetracycline (80%). PCR revealed that all the isolates didn’t harbor class 1 or 2 integrons. Therefore, the indiscriminate use of antibiotics must be restricted and more attention should be paid to biosecurity measures in aquaculture. Also, further studies are needed to assess role of integrons and other genetic elements in antimicrobial resistance in aquaculture.