Microbiological quality and safety of rastrineobola argntea(omena) solid in Kisumu town markets

Abstract

The Lake Victoria Rastrineobola argentea (omena) is today among the most important commercial fish species, ranking second to Nile perch, R. argentea is a relatively cheap source of animal protein. Sundried omena has also recently found use in the animal feed industries. The sun drying of omena is carried out at the fish landing sites along Lake Victoria; the fish is spread over fishing nets and left to dry for 6 to 8 hrs. During the drying process the fish is exposed to contamination from soil, animals and personnel processing the fish. This study was to investigate microbiological quality and safety of omena sold in retail markets in Kisumu town. The study design was based on random and repeated cross sectional sampling. The study was carried out in Kisumu town, targeting 6 markets; Oile, Jubilee, Kibuye, Kondele, Nyalenda and Manyatta. Total plate count (TPC), faecal coliform (FC) and presence or absence of Salmonella, Shigella and E. coli were used to assess the microbiological quality of the fish. Bacterial isolates were identified by biochemical and serological techniques. Antimicrobial susceptibility to ampicillin lOµg, tetracycline 30µg, cotrimoxazole 25µg, augumentin 30µg, gentamicin lOµg, kanamycin 30µg, cefuroxime 30µg, chloramphenicol 30µg, nalidixic acid 30µg and norfloxacin 10µg was performed using the disk diffusion method. In-vitro conjugation and plasmid finger printing experiments were carried out to determine transferable antimicrobial resistance and the type of plasmids involved in the enteric pathogens. A total of 60 fish samples were analyzed. The findings show that the products are of low microbial quality, TPC 7.34 ± 0.30 cfu/g and FC 4.13 ± 0.32 cfu/g at 95% confidence interval (CI). All the fish were found to be contaminated with E. coli, and in addition 6.67% of the products sampled tested positive for Salmonella. Shigella was absent in all samples analyzed. 26.53% of E. coli isolates tested were resistant to two or more antimicrobial agents tested, with the highest level of resistance detected against cotrimoxazole at 38.76%. The E. coli multiple antibiotic resistance (MAR) index was 0.084 indicating that the contamination was not originating from a high - risk source. A plasmid of approximately 5.6kb was commonly isolated from E. coli isolates that showed resistance to ampicillin. Plasmids isolated were not transferable by conjugation. The presence of Salmonella species and occurrence of MDR E. coli were identified as some of the possible health risks that may be associated with omena displayed for sale in Kisumu town markets. It is important that public health workers create awareness for the need to institute good hygiene practices (GHP) and hazard analysis critical control point (HACCP) as for the purpose of ensuring fish products are produced and sold under hygienic conditions