Antibiotic and Heavy Metal Resistance of Aeromonas spp. Isolated from Diseased Red Hybrid Tilapia (Oreochromis sp.)

Abstract

A total of 300 bacterial isolates of Aeromonas spp. were isolated from diseased Red Hybrid Tilapia, Oreochromis sp. All the bacterial isolates were tested for antibiotic susceptibility against 16 types of antibiotics by using disk diffusion method. The antibiotics tested in this study were nalidixic acid (30 µg/disk), oxolinic acid (2 µg/disk), compound sulphonamides (300 µg/disk), doxycycline (30 µg/disk), tetracycline (30 µg/disk), novobiocin (30 µg/disk), chloramphenicol (30 µg/disk), kanamycin (30 µg/disk), sulphamethoxazole (25 µg/disk), flumequine (30 µg/disk), erythromycin (15 µg/disk), ampicillin (10 µg/disk), spiramycin (100 µg/disk), oxytetracycline (30 µg/disk), amoxycillin (25 µg/disk) and fosfomycin (50 µg/disk). Heavy metal resistance pattern of the present bacterial isolates against mercury (Hg2+), chromium (Cr6+), copper (Cu2+) and Zinc (Zn2+) was also determined by using two fold agar dilution method. The results of the present study showed the percentage of antibiotic sensitivity of the present bacterial isolates ranged from 22.5% to 100% in which most of the present bacteria isolates were not sensitive to ampicillin. On the other hand, all the bacteria isolates were sensitive to nalidixic acid, flumequine and oxytetracycline. Overall, the total of sensitive case was reported as 75.5%, whereas antibiotic resistance and intermediate sensitive case was recorded as 19.0% and 5.5%, respectively. Multiple Antibiotic Resistance (MAR) value was recorded at 0.01. The MAR value indicated that the sampled fish were not highly exposed to the tested antibiotics. Low resistance activity of the present bacterial isolates to the tested heavy metals (Cr6+: 35.8%, Zn2+: 5.5%, Cu2+: 25% and Hg2+: 30%) revealed that low exposure of the tested heavy metals to the sampled fish.