Prevalence Of Escherichia Coli O157:H7, Listeria Monocytogenes And Staphylococcus Aureus In Ready-To-Eat Fresh Milk And Fresh Milk Products Inmilk Markets In Accra

Abstract

The fresh milk industry in Ghana is a source of livelihood for a significant proportion of smallscale farming households in the country. However, lack of consumer food safety assurance of fresh milk and fresh milk products have limited business growth of this sector. Reports on lack of cooling infrastructure, unhygienic handling, inadequate processing and post-process contamination contributes to microbial spoilage in dairy products leading to loss of large volumes of milk in developing countries. This study therefore sought to assess the microbiological quality and hygiene of raw milk from assemblers and fresh milk products from five informal milk markets. This was accomplished by subjecting randomly sampled fresh milk and fresh milk products (22 brukina, 18 boiled milk, 15 raw milk, 8 nunu, 24 yoghurt, 17 raw wagashi and 13 fried wagashi) to standard cultural methods of microbial assessments. Products were tested for concentration of index and hygiene indicators including total coliforms, fecal coliforms, Escherichia coli and Staphylococci. Confirmation of suspected pathogens was done with biochemical tests, API 20E and Matrix-Assisted Laser Desorption/Ionization Time Of Flight (MADLI-TOF) mass spectrometry. Quantitative Polymerase Chain Reaction (qPCR) was done to confirm the prevalence of E. coli O157:H7, Listeria monocytogenes and Staphylococcus aureus in the ready-to-eat (RTE) dairy products tested. Mean counts were reported in Log cfu/g or Log cfu/ml using Microsoft Excel (2016). Significant differences between total coliforms, fecal coliforms, E. coli and Staphylococci counts was determined using Analysis of Variance (ANOVA) with a P value of <0.05 using IBM SPSS version 21. The study in general identified insufficient heat treatment used to pasteurize the dairy products, poor hygienic practices and possible post-process contamination as reasons for the poor University of Ghana http://ugspace.ug.edu.gh V microbiological quality of the samples tested. The quality of the raw milk had a direct effect on the quality of the final milk products. There was statistical similarity (P≤0.05) in the coliform content between raw milk (3.64± 2.56 Log cfu/ml) and boiled milk (3.61± 3.06 Log cfu/ml) which signified insufficient heat treatment used in processing the boiled milk. The study identified a general high prevalence of coliform contamination (67%), with raw wagashi having the highest coliform and Escherichia coli concentrations of 5.90± 3.79 Log cfu/g and 2.61± 2.65 Log cfu/g respectively. Fried wagashi emerged as the only product which was safe from coliform contamination. The staphylococci concentration of the products analyzed were within the acceptable (3.0 Log cfu/ml/g) limits. L. monocytogenes was not detected in any of the products analyzed using cultural methods. Results from qPCR indicated high prevalence of E. coli O157:H7 in boiled milk (66%), nunu (37%) and brukina (14%). Boiled milk had a 42.8% S. aureus prevalence and 11.11% prevalence of L. monocytogenes. The results from the viability tests suggests shortfalls in the processing of the RTE fresh milk products in the local milk markets. The presence of significant pathogens in the product has implications on food security with respect to food safety. Overall microbiological analysis conducted suggests a poor quality of RTE fresh milk products sold in the informal markets in Accra. This indicates an urgent need for intervention measures with highlights on effective pasteurization of raw milk and training of the various stakeholders in the dairy value chain on hygienic handling to prevent post-process contamination.