Microbial studies on frozen shrimps processed in Ibadan and Lagos, Nigeria

Abstract

This study reports the microbial investigation on shrimps, a frozen seafood, processed at ten different processing plants in Ibadan and Lagos, Nigeria. Samples processed and unprocessed shrimps were collected and analyzed for the presence of microorganisms. Microbial loads were enumerated using microbiological media. A total of 120 isolates characterized as Bacillus sp.,Salmonella sp., Shigella sp., Enterobacter sp., Micrococcus sp., Escherichia coli,Flavobacterium sp., Staphylococcus auerus, Pseudomonas sp., Rhizopus sp.,Aspergillus flavis, Aspergillus formigatus, Mucor mucido, and Sacchromyces sp. were isolated from shrimps. No Vibrio sp. was isolated from any of the shrimp sample. Rhizopus sp., A. flavis, and M.  mucido were only found in unprocessed shrimp while Sacchromyces sp. and A. formigatus was found on processed shrimps only. Bacillus sp. were the most predominant species and most frequently isolated organism in this study, all the shrimps sampled haboured Bacillus sp. [20(16.7%)], followed by Salmonella sp. [18 (15.0%)], Shigella sp. [18 (15.0%)],Enterobacter sp. [13(10.8%)], Micrococcus sp. [13(10.8%)], E. coli [12(10.0%)],Flavobacterium sp. [5(4.2%)], S. auerus [5(4.2%)] and Pseudomonas sp.[1(0.8%)]. Rhizopus sp [8(6.7%)] was the most frequently implicated fungi in this study, followed by A. flavis [3(2.5%)], A. formigatus [1(0.8%)], M.r mucido[1(0.8%)], and Sacchromyces sp. [1(0.8%)]. The microbial loads at 24 and 48 h incubation showed that most of the shrimps exceed the FAO/WHO standard limit for food and water. At 24 and 48 h, processed shrimps gave total viable counts 70 - 440 and 100-1000 CFU/ml) coliform bacilli, 0 - 120 and 20 - 150 CFU/ml; Salmonella-Shigella (SS) counts, 0 - 120 and 0 - 700 CFU/ml and fungi count, 0 - 30 and 0 - 50 CFU/ml respectively, while unprocessed shrimps gave total viable counts, 390 - 1200 and 500 - 2000 CFU/ml; coliform bacilli, 120 - 350 and 380 - 1280 CFU/ml; SS counts, 80 - 1800 and 220 – 1850 CFU/ml and fungi count 70 - 260 and 120 - 600 CFU/ml respectively. The findings of this study indicates that none of the shrimps of the food processors and the water samples were within acceptable FAO/WHO/NAFDAC standards due to high colony counts, presence of indicator organisms /index of food quality - E. coli, Salmonella sp., Shigella sp., andS. auerus. This study suggests that most shrimps sold in the market may be sources of microbial food poison and intoxication hence, they are counter productive by being responsible for public health hazard and loss of revenue. Therefore, there is the need to improve on hygienic and sanitary practices in seafood processing plants and retail service outlets in order to obtain relatively safe processed seafood products for human consumption.   Key words: Microbial loads, index of food quality, microbiological quality, pathogens, shrimps.