Abstract

The increasing incidence of antibiotic resistance strains in Aeromonas hydrophila is due to extensive antimicrobial usage by human and fish farms for treatment and disease prevention. Multiple antibiotic resistance phenotypes among bacteria have been shown to be attributed to integrons. Forty strains of A. hydrophila isolated from freshwater fish were investigated for antibiotic sensitivity and plasmid profiling. Ten antibiotics were used, namely penicillin G, cephalotin, florfenicol, streptomycin, kanamycin, erythromycin, ampicillin, gentamicin, oxytetracycline and tetracycline. Polymerase chain reaction was carried out to detect integrase genes Int1, Int2 and Int3, gene cassette array, integron-associated aadA, sul1 and qac1 genes, streptomycin resistance genes strA-strB, β-lactamase resistance genes blaTEM and blaSHV, and tetracycline resistance genes tetA-E and tetM. As a result, A. hydrophila was sensitive to erythromycin, florfenicol, kanamycin and oxytetracycline, while the bacteria were resistant to cephalotin, gentamycin and penicillin G. In this present study, 12 out of 40 isolates contain plasmid size ranging from 6 to 23 kb. The intl1 gene was detected in 50% of A. hydrophila strains, but no isolates contain intl2 and intl3. No gene cassette was detected from all the A. hydrophila isolates. Different tetracycline resistance genes and aadA genes were detected. The detection of antibiotic resistance genes in A. hydrophila has public health and environmental concern.