Molecular analysis of antimicrobial resistance in gram-negative bacteria isolated from fish farms in Egypt.

As little is known about antimicrobial resistance genes in fish farms, this study was conducted to monitor the incidence and prevalence of a wide range of antimicrobial resistance genes in Gram-negative bacteria isolated from water samples taken from fish farms in the northern part of Egypt. Ninety-one out of two hundred seventy-four (33.2%) non-repetitive isolates of Gram-negative bacteria showed multidrug resistance phenotypes and harbored at least one antimicrobial resistance gene. PCR and DNA sequencing results showed that 72 (26.3%) isolates contain tetracycline resistance genes and 19 (6.9%) isolates were positive for class 1 integrons with 12 different gene cassettes. The beta-lactamase-encoding genes were identified in 14 (5.1%) isolates. The plasmid-mediated quinolone resistance genes, qnr and aac(6')-Ib-cr, were identified in 16 (5.8%) and 3 (1.1%) isolates, respectively. Finally, the florphenicol resistance gene, floR, was identified in four (1.5%) isolates. To the best of our knowledge, this is the first report for molecular characterization of antimicrobial resistance in Gram-negative bacteria isolated from fish farms in Africa.