Marine bacteria exposed to antibiotics in fish farms can acquire antimicrobial resistance by mobile
genetic elements and horizontal gene transfer. A total of 872 autochthonous marine bacterial strains
was isolated from samples collected from four different fish farms located at northern and southern Italian
Adriatic Sea. Resistance to only tetracycline (17%) and to trimethoprim–sulfadiazine (7%) were the
most frequent patterns obtained, while flumequine resistance has recorded in only 0.3% of the strains.
Comparing strains isolated from coastal areas and fish farms, a significant higher incidence (4% versus
10%) of multi-resistant strains in aquaculture centers was found. Significant differences in antibiotic
resistance incidence were also detected among the four fish farms due probably to different approaches
in farm management and the more or less frequent use of antibiotics. Antibiotic-resistant and multiresistant
strains isolated constitute an environmental reservoir directly involved in the seafood chain
and might represent a public health concern.
