Studies on Microbiological, Proximate Mineral and Heavy Metal Composition of Freshwater Snails from Niger Delta Creek in Nigeria

Abstract

Microbial quality of freshwater snail samples from Itu creek, Niger Delta Nigeria was studied. The bacteria isolates were Proteus sp., Sreptococcus pyrogens, Shigella flexneri, Staphylococcus aureus, E. coli, Klebsiella aerogenes, Citrobacter, Bacillus subtilis, Bacillus cereus, Aeromonas sp., Micrococcus liteus, Streptococcus salivanus, Salmonella typhi, Vibrio parahaemolyticus, Vibrio sp. and Vibrio cholera. Proteus sp, Aeromonas sp. and Micrococcus liteus had the highest frequency of occurrence (10.25%). The fungi isolates were Aspergillus terreus, Cladosporium sp, Fusarium oxysporum, Cryptococcus sp, Aspergillus flavus, Aspergillus glaucus and Aspergillus niger in which A. niger, A. terreus and F. oxysporum had the highest occurrence (16.67%). The total heterotrophic count of the samples ranged from 4.0 x107 -1.42 x 108 cfu/g. The coliform levels were generally high and it ranged from 2.2-6.4 x 107 cfu/g in which the highest was recorded from P. canaliculata (A1). The Salmonella/Shigella counts ranged from 1.1-5.2 x 107 cfu/g in which the highest count was recorded from L. libycus (C1). The total Staphylococci count ranged from 1.7-3.5 x107 cfu/g in which A. fulica (D2) had the highest. The total vibrio counts ranged from 1.6-3.2 x 107 cfu/g. The fungi count ranged from 1.7-3.5 x 107 cfu/g. The total microbial counts obtained from this work were found to be higher than the specified standard limits (1x105 cfu/g) for bacteria and fungi and 1.x102 cfu/g for coliforms) by ICMSF (1982) and USFDA (1991). The crude protein content of the samples ranged from 28.87 d – 33.41a% in which the highest was obtained from A. fulica (D3). The Crude Fat, crude fiber and carbohydrate content ranged from 1.8-4.25% and 00.10-0.18%, respectively. The mineral elements such Na, Ca, K and P were detected in all the freshwater snail samples. The concentration of metal ranges of Zn, Fe, Mn, Mg, Pb, As and Cu in the samples were 78.6j -96.3a mg/kg, 15.7j -28.6a mg/kg, 58.6j -77.5a mg/kg, 0.258 j -0.297a mg/kg, 0.03 i -0.25a mg/kg, 0.04i -0.37a mg/kg and 12.6 j -16.3a mg/kg, respectively. It was observed that different metals were present in the samples at different levels but majority were found to be within the standard limits prescribed by EU and FAO. Freshwater snails from the creek in Niger Delta was found to be nutritionally richer but harbor pathogenic microorganism and heavy metals which can pose serious health hazard to consumers and they are not totally safe for human consumption.