Detection, Enumeration and Genotyping of E. coli, E. coli O157:H7 and Salmonella typhimurium from Raw Milk at selected farms in the Southern Region of Sarawak, Malaysia

Ernie Suhaiza, Radzi (2017) Detection, Enumeration and Genotyping of E. coli, E. coli O157:H7 and Salmonella typhimurium from Raw Milk at selected farms in the Southern Region of Sarawak, Malaysia. Masters thesis, Universiti Malaysia Sarawak.

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Abstract

Raw milk (unpasteurized milk) is known as a good medium for numerous infectious diseases and susceptible to contamination by many microorganisms including pathogenic microbes, which can cause food-borne illness and become threat to consumer’s health. However, demand for raw milk persisted and developed along with the public’s interest in minimally processed products. In this study, 200 raw milk samples were purchased from 6 selected dairy farms in Sarawak. Samples comprised of 100 raw goat milk and other 100 raw cow milk. Samples were examined for occurrence of E. coli, E. coli O157:H7 and Salmonella typhimurium using enumeration of MPN (most probable number) method and were screened for the presence of shiga toxins (stx) genes for E. coli O157:H7 and fliC genes for S. typhimurium. The prevalence of E. coli O157:H7 was 13% (n=26) for stx1 and/or stx2 with MPN value greater than 3.0 (>1100 MPN per mL). While the prevalence for S. typhimurium was 16% (n=32) for fliC gene with MPN more than 1100 per mL. These demonstrate genetic variability as the different strains would have variations in virulence and pathogenicity. Genotyping which consisted of BOX- and ERIC-PCR were performed to evaluate the relatedness of E. coli and S. typhimurium strains isolated. All isolates were related to their location so they were grouped in such a way that they were most related to each other from same sampling sites. Both genotyping methods given the equally high reliability with Simpson index of diversity for among E. coli isolates were 0.989 and 0.992 for BOX, 0.997 and 0.980 for ERIC-PCR for both cow and goat milk respectively. While S. typhimurium isolates were 0.985 and 0.999 for BOX, 0.900 and 0.872 for ERIC-PCR for both cow and goat milk respectively. Hence, these results demonstrate the presence of pathogenic E. coli O157:H7 and S. typhimurium in raw milk samples in the study area and revealed the potential risk of illness. However, raw milk is suggested to go through pasteurization process for hygiene and safety.

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