Comparative Bacteriological Evaluation of Frozen and Salt Water Tilapia Fishes (Oreochromos niloticus and Oreochromos aureus) Sold in Port Harcourt, Rivers State Nigeria

Abstract

Fishes are highly perishable, and prone to vast variations in quality due to differences in species, feeding habits as well as the environmental and preservation factors. This study Compared the bacteriological quality of Frozen and Salt Water Tilapia Fishes (Oreochromos niloticus and Oreochromos aureus) sold in Port Harcourt, Nigeria. Total number of sixty (60) samples were evaluated. Frozen tilapia (36) and salt water tilapia fishes (24) were obtained from the three sampling markets using sterile bags which were properly labelled. The samples were transported to the Laboratory for analyses within 2 hours of collection in a thermos box containing ice pack and  standard microbiological procedures were employed in the bacteriological evaluations. Different parts of the fishes such as Intestine, gills and flesh of the samples were dissected and used for bacteriological analysis. Statistical analyses were carried out using ANOVA and All pairs tukey- kramer. Results obtained from the study showed that the highest number of total heterotrophic bacteria count was obtained from frozen fish gills which was 7.7 x 106±0.98 cfu/g while the least count of 4.7 x 106±0.67 cfu/g was from salt water tilapia fish flesh. Total coliform count ranged from 3.3 x104±0.91 cfu/g to 8.0 x104±0.44a cfu/g for salt water flesh and frozen fish intestine from different markets respectively. Listeria species count ranged from 1.3 x104± 0.30 cfu/g to 4.3 x104±0.57 cfu/g for salt water fish intestine and frozen fish flesh respectively. Total Salmonella count ranged from 1.0 x103±0 cfu/g to 6.2x103±1.30cfu/g for frozen fish flesh and salt water fish intestine. These values were above the WHO permissible limit. Mean values for all the microbial counts were significantly different at (P<0.05) in the two samples across the sampled markets comparatively, frozen fish has more bacteriological load than salt water fish, this may be attributed to the handling, hygiene storage of the respective fishes as well as storage conditions. Listeria species were identified as L. monocytogenes, L. graji, L. seeligeri, L. ivanovii, and L. welshmeri by genomic studies. While three species of Salmonella such as S. arizonae, S. gallinarum, S. typhi were isolated. Other bacterial isolates were identified as Vibrio spp, Bacillus spp Staphylococcus spp Shigella spp Pseudomonas spp. Enterobacter spp. E. coli, Micrococcus spp. Acinetobacter spp. Klebsiella spp. This study revealed that fish sold at different markets in Port Harcourt especially frozen fish, is highly contaminated with different kinds of bacterial pathogens which may constitute potential public health hazard due to the unhygienic nature of fish vendors which predisposes frozen fishes to contamination by pathogenic microorganisms. Therefore proper blanching and heating methods should be employed during preparations of fishes to avoid cross contamination and food intoxication/ poisoning before consumption. It is important that all hazard analysis critical control point be adhered to for good production processes.