Prevalence and Antibiotic susceptibility of Aeromonas hydrophila isolated from fresh water fishes

Abstract

Aeromonas hydrophila is a microorganism that is a part of the normal bacterial flora of many animals. As an opportune organism, it is a secondary biological agent that contributes to the occurrence of a fish disease and its deterioration. Frequently, its presence is an indication of bad zoohygiene and zootechnical conditions in fish reservoir. Aeromonas is almost always present in clinical isolates and may be unjustly accused for bad health of fish. The research was undertaken to determine the prevalence of Aeromonas hydrophila from some selected freshwater fishes and to test antibiotic susceptibility. In the present study, 5 different species of fishes were examined each with three replicates were collected from different fish market in Dhaka Metropolitan City. Samples were collected from three different organs such as muscle, gill and gut. Total Bacterial Count (TBC) and Total Aeromonas like colonies on NA and different Aeromonas Agar media were enumerated using serial dilution techniques. Bacterial isolates were characterized to confirm the presence of Aeromonas hydrophila using biochemical test and with comparison to reference strain (ATCC 7966). Further molecular method was used for the confirmation. The diffusion disk technique was used for testing antibiotic susceptibility. Among organs, the highest incidence was found in the gill (54.5%) and lowest (8.8%) in the muscle. On the other hand, the lowest Aeromonas count was found 2.83±0.40x102 in Anabas testudineus and the highest was 1.03±0.153x103 in Oreochromis mossambicus. On market basis highest Aeromonas count was found in Ananda Bazar (8.10±1.09x102 cfu/g) and lowest in Hatirpool Bazar (5.63±0.90x102 cfu/g) with no significant difference. The isolates were tested for their susceptibility to 14 different antibiotics including Gentamycin, Amikacin & Chloramphenicol; and Maximum susceptibility to Tetracycline whereas all of the isolate showed resistant to a common used antibiotic Amoxyciline. The obtained results point that antimicrobial susceptibility was more or less same regardless of the origin of the samples collected. All the selected fishes in this study contain Aeromonas hydrophila in their different organs.