Antimicrobial resistance profile of bacterial pathogens isolated from naturally infected fish in some lakes of Ethiopia

Abstract

Small scale fisheries play important role in providing food and livelihoods for households in Ethiopia. However, prevalence of bacterial fish infection and their antimicrobial resistance are increasing over the world accounting for the major limitations in fish productionas well asits consumption. A cross sectional study was carried out to identify bacterial pathogens isolated from naturally infectedNile tilapia (Oreochromis niloticus) and 20 were common carp (Cyprinus carpio)fish showing clinical signs of disease particularly hemorrhage and skin ulceration and to determine the antibiotic susceptibility of fish associated bacteria in Ethiopia. A total of 42 fish samples from two lakes (Hawassa and Ziway) were aseptically collected and bacteria were isolated from the kidney, liver and intestine. The isolates were identified by their morphological characteristics, biochemical tests and sequencing of 16S rRNA genes. Nine well known fish pathogens were identified from 49 positive samples at the lakes with prevalence rate of Aeromonasveronii(21.43%), Proteusmirabilis (19.05%), Edwardsiella tarda (16.67%), Shigella flexneri(11.9%), Stenotrophomonas maltophilia (11.9%), Aeromonas hydrophila (11.9 %),Pseudomonas putida (9.5%), Aeromonassobria (7.14%) and Pseudomonas hunanensis (7.14%).Of these pathogens, six (6) mostprevalent andknown potential pathogens (A. hydrophila, A. veronii, E. tarda, P. mirabilis, S. flexneri and S. maltophilia)were evaluated for antibiotic susceptibility by using Kirby Bauer disk diffusion assay. All the isolates tested were resistant to at least three (3) of the eight antibiotics evaluated. High levels of resistance were expressed by the majority (87.5%) of the pathogens against penicillin and vancomycin. The results indicate the presence of potential pathogens andmaximum levels of acquired antibiotic resistance in fish bacteria from the study area. Thus, theuse of antibiotic in fish farming in Ethiopia should be discouraged.It isalso advisable to cook fish properly before consumption, in order to kill bacterialpathogens that may be present.