Antimicrobial resistance and the prevalence of integron in Aeromonas hydrophila from hemorrhagic diseased Pangasius catfish of the Mekong Delta

Antimicrobial resistance from bacterial pathogens is becoming a health concern in many countries. The purpose of this investigation was to assess antimicrobial resistance and find out the prevalence of class 1 integrons from A. hydrophila that led to hemorrhagic disease in intensively farmed Tra catfish in the Mekong Delta, Vietnam. The research showed that a total of 74 isolates were isolated and identified as A. hydrophila by the API 20E kit and using the amplification products of the aerolysin gene for confirmation. The susceptibility of all isolates was tested against fifteen antimicrobial agents using the disk diffusion method. Our study indicated that most strains were resistant to the following antibiotics: trimethoprimsulfamethoxazole, ampicillin, cefalexin, tetracycline, amoxicillin, chloramphenicol, florfenicol, neomycin, and gentamycin. In addition, the investigation also indicated that most A. hydrophila isolates displayed multiple antibiotic resistance phenotypes. The MAR (multiple antibiotic resistance) index was high, ranging from 0.40 to 0.66 for A. hydrophila isolates, which indicated that these isolates were exposed to high risk sources of contamination where antibiotics were commonly used. Among all isolates, 12.16% (9/74 isolates) of class 1 integrons were determined by polymerase chain reaction