Resistance to antibiotics and heavy metals of Aeromonas hydrophila isolated from Nile tilapia (Oreochromis niloticus)

Abstract

The objective of this study was to evaluate resistance of Aeromonas hydrophila isolated from Nile tilapia to 14 antibiotics and 5 heavy metals. Two hundred and ninety samples of Nile tilapia were purchased from local market in Khon Kaen province and isolated for Aeromonas hydrophila. It was found that the 50 isolates of this bacteria (17.24%), then the bacterial isolates were tested for antibiotic resistance by disk diffusion method to antibiotics while heavy metals were tested by agar dilution method. The result showed that all the isolate samples were completely resistant to vancomycin, novobiocin and bacitracin but susceptible to gentamicin, kanamycin, neomycin, streptomycin, tetracycline and chloramphenicol. A low percentage of Aeromonas hydrophila isolates were resistant to nalidixic acid (10%), trimethoprim (4%), erythromycin (2%) and polymyxin B (2%). In the present study, resistance to heavy metals with ranged of concentrations of 50 – 1,600 μg mL–1 was as follows: mercury, 100%; zinc, 6% and arsenic, 4% and the isolates which were mercury resistance also showed resistance to vancomycin, novobiocin and bacitracin. Information of heavy metal and antibiotics resistant can be used to selected bacteria strain for cleaning up heavy metals from contaminated environment and for planning of antibiotics resistant surveillance.