Bacteriological investigation of meat sold in Ojo, Lagos, Nigeria

Abstract

Meat (beef) is one of the most widely consumed food products which is remarkably known for its high protein content, vitamins and desirable taste. Meat is consumed by all and sundry. However, the intrinsic properties of meat make it highly susceptible to changes usually brought about by an array of physical, chemical and biochemical attributes. Several bacterial species have been implicated in the spoilage of meat and it provides a good source of nutrients. One kilogram of meat samples purchased from ten retail points in different markets namely Okoko, Ojo, Iyana-Iba, Igbo-Elerin, Ajangbadi, Ikotun, Obadore, Akesan, Alaba and Volkswagen markets were investigated for microorganisms by standard methods. The meat samples were obtained in duplicates and cultured on MacConkey agar, Mannitol salt agar and nutrient agar. They were divided into two batches, the first batch was stored at the refrigerated temperature (4 °C) while the second batch was at ambient temperature 27°C±2 °C for 24 hours. The meat samples were enumerated bacteriologically using blender method. Ten grams of each sample was blended and introduced into buffered peptone water, homogenized and pre-incubated for 1 h. Serial dilution was carried out and 0.1 ml of serially diluted samples inoculated into the agar. Various bacterial species were isolated, identified culturally, morphologically and biochemically. For ambient temperature stored meat, the total viable count ranged from 1.3 x 104 cfu/g to 2.3 x 106 while refrigerated samples had counts which ranged from 1.3 x 104 cfu/g to 7 x 105 cfu/g. In the unrefrigerated samples, total staphylococcal counts and total Enterobacteriaceae counts ranged from 1.3 x 103 cfu/g to 2.66 x 104 cfu/g and 1.2 x IO3 to 2.3 x 104 cfu/g respectively. Bacteria recovered include Staphylococcus aureus, Bacillus spp., Proteus spp., Micrococcus spp., Enterobacter spp., Leuconostoc spp., Klebsiella spp. and Pseudomonas spp., most of which are potentially spoilage bacteria as well as opportunistic pathogens. Several bacterial species isolated from refrigerated and unrefrigerated samples were similar, but the refrigerated meat appear to be safer as they had lower microbial load. Meat constitutes a risk factor which is minimized by careful handling, high personal hygiene and massive awareness campaign which may likely be heightened by consumption of raw or improperly cooked meat.