Prevalence and Characteristics of Strains of Escherichia coli Isolated from Milk and Feces of Cows on Dairy Farms in Trinidad

Abstract

The prevalence, counts, and characteristics of Escherichia coli isolated from bulk milk, composite milk, and feces of dairy cows in eight milking centers were determined. The microbial quality of water used during milking was also investigated. Of a total of 175 bulk milk samples studied, 83 (47.4%) contained E. coli compared to only 14 (4.9%) of 287 composite milk samples and the difference was statistically significant (P ≤ 0.001; χ2). The ranges in mean counts of E. coli per milliliter of bulk milk and composite milk were 8.4 × 103 to 2.0 × 105 and 2.1 × 101 to 2.0 × 102, respectively. The prevalences and mean counts of E. coli and mean pH values for bulk milk from farms with and without subclinically mastitic cows were not significantly different (P ≥ 0.05; χ2). A total of 204 (65.2%) of 313 fecal samples of dairy cows were positive for E. coli. Of the samples of water used during milking collected from 171 dairy farms, 80 (46.8%) were free of coliforms while 59 (34.5%), 12 (7.0%), and 8 (4.7%) had ranges of coliform counts per 100 ml of 1 to 50, 51 to 100, and over 250, respectively. Twenty-six (27.7%) and 17 (18.5%) of 94 strains of E. coli isolated from bulk milk were enteropathogenic E. coli (EPEC) and verocytotoxigenic E. coli (VTEC) strains, respectively. Compared with 204 fecal strains of E. coli, 16 (7.8%) and 68 (35.6%) were EPEC and VTEC strains, respectively, and the differences were statistically significant (P ≤ 0.01; χ2). Similarly, the difference in prevalence of resistance to one or more of nine antimicrobial agents between bulk milk isolates (69.6%) and fecal isolates (25.9%) was statistically significant (P ≤ 0.001; χ2), and resistance to ampicillin was the most prevalent type of resistance for strains of E. coli from bulk milk isolates. It was concluded that the relatively high counts of toxigenic E. coli in bulk milk originating from dairy farms in Trinidad could pose a health risk to consumers. The poor microbial quality of water used on farms may be an important source of contamination of milk.

Occurrence and Characterization of Verocytotoxigenic Escherichia coli (VTEC) Strains from Dairy Farms in Trinidad

“…Adesiyun et al. (1997b) reported a prevalence of 18.5% for strains of VTEC in bulk milk compared with 3.6% in the present study.…”

“…The use of vero cell cytotoxicity assay determined 10.3% of 595 isolates to be positive for VT production. Amongst the verocytotoxigenic strains, 16.7% of isolates originated from cows’ faeces, a frequency slightly higher than the 14% reported for livestock (cattle, sheep, goats and sheep) in Trinidad by Adesiyun and Kaminjolo (1994), but considerably lower than the 36.6% frequency found in milk and faeces of dairy cows in the country (Adesiyun et al., 1997b). This variation in the frequency of VTEC strains could be time‐related, as the three studies were conducted at different times and they were cross‐sectional studies.…”

“…In a study on pre‐processed milk, 23.6% of the E. coli isolates were reported to be VT‐producing (Adesiyun, 1994). The fact that >35% of dairy farmers and their families consume raw milk (Adesiyun et al., 1997b) suggests that they may be exposed to VTEC strains with a potential to cause disease. In the current study, only one (1.8%) of 57 isolates from effluents was VTEC strain, which is a lower frequency than the 14.6% reported by Welch et al.…”

Fate ofEscherichia coliO157 : H7 in unpasteurized milk stored at 8 °C

“…1994 ; Ansay & Kaspar 1997). However, Adesiyun et al . (1997 ) found that 17 (18·5%) of 94 strains of E. coli isolated from bulk milk and 68 (35·6%) of 204 strains of E. coli isolated from faeces of dairy cows were VTEC strains.…”

Pre-processed bovine milk quality in Trinidad: Prevalence and characteristics of bacterial pathogens and occurrence of antimicrobial residues in milk from collection centres

“…The antimicrobial resistance of S. aureus and E. coli recovered from raw milk and milk products have been documented by others (Adesiyun, Webb, Romain, & Kaminjolo, 1997;Makovec & Ruegg, 2003;Pitkala, Haveri, Pyorala, & Myllys, 2004;Umoh, Adesiyun, & Gomwalk, 1990b) and it has also been reported that misuse or abuse of antimicrobial agents could result in resistant strains of bacteria in veterinary medicine (Washington, 1979).…”