Aquaculture, by modern and technological methods, ensures effectual means for healthy fish production under “controllable” conditions.
However, fish have disease problems due to a lack of imbalance with microbiota or opportunistic pathogen in culture systems. In the present
study, we identified the opportunistic pathogens and some members of microbiota, which were obtained from our culture collection by
culturable methods and characterized biochemically in addition to molecular analysis. We identified the isolates by partial gene sequencing
and confirmed taxonomically in the bacterio.net database. The isolates were characterized based on antimicrobial susceptibilities by broth
microdilution method analysis, and the resistance gene determinants were screened by PCR analysis. A total of 14 species were identified with
high genetic similarity in the GenBank database. MIC results showed that bacteria have heterogeneous characteristics for the susceptibility
of an agent into the genus, and species have high MIC values for sulfamethoxazole, trimethoprim, and ampicillin comparing to other agents.
A total of 13 different resistance genes were determined in the bacteria, and some of them have multiple resistance genes up to five genes.