Determination and transferability of plasmid‐mediated antibiotic resistance genes of the bacteria isolated from rainbow trout

Antibiotic resistance and the presence of resistance genes ( ARG s) were investigated in the bacteria isolated from rainbow trout ( Oncorhynchus mykiss ) from different trout farms located in Turkey. The most frequent types of antibiotic resistance were towards β‐lactams (cephalothin [70% of bacterial isolates], amoxicillin [63%], ampicillin [62%], ticarcillin [56%], aztreonam [51%]), macrolide [erythromycin, 68%] and sulphonamide [sulphamethoxazole, 51%]. Of bacterial isolates, 51% were multiple drug resistant ( MDR ), while 35% of the isolates were extensively drug resistant ( XDR ). None of isolates were pandrug resistant ( PDR ). The most common ARG s were amp C (36%) and sul1 (24%). The class 1 integron gene cassette was detected in 51% of the bacteria. There was a strong positive correlation between the antibiotic resistance rate and the presence of ARG s ( r 2  = .932). Gene encodes bla CTX ‐M1 , one of the extended spectrum beta‐lactamase enzymes, was first described in Aeromonas caviae, Photobacterium damselae, Pseudomonas luteola and Burkholderia cepacia . It was determined that 35% of the bacteria harboured at least one plasmid. Plasmid‐mediated ARG s were identified to be tetracyclines ( tet A, tet B, tet C, tet D), sulphonamides ( sul 1, sul 3) and β lactams ( amp C, bla pse ). Thus, results suggest that ARG contamination situation deliberates resistance to tetracycline, aminoglycoside, chloramphenicol and sulphonamide. Therefore, the presence and activity of ARG s in fish and in environmental bacteria may play an important role in the spread of resistance genes among bacteria by transposition or integron gene cassettes.