Prevalence and Characterization of Pathogenic Escherichia Coli in Selected Indigenous Dairy Product

Abstract

Diarrhoeagenic E. coli is a major health concern. It causes mortality and morbidity especially in children of age five years and below in countries that are developing. Research has revealed that out of the six categories of diarrhoeagenic E. coli, Enterohaemorragic E. coli (EHEC) and Enteropathogenic E. coli (EPEC) are the most widespread cause of diarrhea. This work identified the existence of some E. coli that causes diarrhea in informal dairy products from selected traditional open markets and streets of Greater Accra and characterized the survival of E. coli O157:H7 in Mueller Hinton broth and wagashi, a soft unripened indigenous cheese. A total of 85 local dairy products, specifically raw milk, boiled milk, brukina, nunu and wagashi were examined. These were purchased from cow rearing locations and markets within Accra. E. coli was detected by enrichment in Brain Heart Infusion broth followed by plating on MacConkey agar. E. coli O157:H7 was determined on Sorbitol MacConkey agar which appeared colorless. Survival of E. coli O157:H7 to sub-lethal stresses of low pH, high salt and heat was determined in broth and at multiple processing stages of traditional wagashi. Out of the 85 milk samples, 60 (70.6%) tested positive for E. coli. Prevalence of 6 categories of diarrhoeagenic E. coli was determined by Multiplex Polymerase Chain Reaction (mPCR) using standard primers for their virulence genes. The multiplex RT PCR assay also detected 45 samples that tested positive for diarrheaogenic E. coli. Out of the 45 positive samples, 14 samples (26.7 %) were positive for Enterohemorrhagic E. coli (EHEC), 3 (6.7 %) were positive for Enteroinvasive E. coli (EIEC), 2 (4.4 %) were positive for Enteropathogenic E. coli (EPEC), 3 (6.7 %) were positive for Enterotoxigenic E. coli (ETEC) and 4 (8.9 %) were positive for Enteroagreggasive E. coli (EAEC). The remaining 19 (42.2 %) samples contained a mixture of two or more diarrheaogenic E. coli virulence genes. The presence of diarrhoeagenic E. coli in informal diary suggests that the consumption of the informal dairy products tested in this study could be a public health risk. Since E. coli is an indicator of poor hygiene in foods the study recommends food hygiene training for stakeholders and development of hygienic standard operating procedures for use by all stakeholders in the informal milk value chain to prevent or reduce consumer exposure to diarrhoeagenic E. coli through consumption of informal dairy products.