An Investigation on Risk Factors Related to the Occurrence of Escherichia coli in Fluid Milk Marketed in Chittagong, Bangladesh

Background: Escherichia coli is one of the most important pathogens which could be transmitted by milk. The main aim of the present study was to assess risk factors related to the occurrence of E. coli in fluid milk marketed in Chittagong, Bangladesh. Methods: Totally, 169 milk samples were collected from different entry points in Chittagong, Bangladesh; and also, 17 samples were directly collected from a dairy farm. The milk samples were microbiologically analyzed for detection of E. coli. A questionnaire was designed and then administered by two trained veterinarians who interviewed milk vendors at time of milk collecting. The data were analyzed by Stata 11 (Stata Corp, College Station, Texas, USA). Results: E. coli was found in 18.3% and 11.8% milk samples obtained from markets and dairy farm, respectively. The results of univariable analysis showed that addition of water hyacinth leaves to milk had the strongest point estimate of effect Odds Ratio (OR 27.1) and high statistical significance (p=0.0007) despite wide 95% Confidence Intervals (CIs) of 2.8-1291.6. The final logistic regression model identified two variables as independent risk factors for the presence of E. coli in fluid milk including selling milk after 1-2 h of collection (OR 4.7, 95% CI 1.9-11.7), and also adding banana tree leaves into milk (OR 3.8, 95% CI 1.5-9.4). The final model identified washing milk vat/container everyday with tube well water (OR 0.1, 95% CI 0.05–0.3), as a protective factor. Conclusion: The two main factors with great influence on risk of E. coli in fluid milk marketed in Chittagong, Bangladesh consisted of selling milk after 1-2 h of collection and also adding banana tree leaves into milk. Educational awareness should be highlighted to inform consumers and farmers in this regard.