Isolation and Identification of Escherichia coli and Its Resistance to Antibiotics and Disinfectants during Milk Collection in Dairy Farms
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Abstract:
To determine the state of Escherichia coli contamination, virulence genes harbored by E.coli isolates, and resistance of E.coli to antibiotics and disinfectants during the milk collection process in dairy farms, 655 samples were randomly collected from a dairy farm in Chengdu for the isolation and identification of E. coli strains. The virulence genes, drug resistance genes, and disinfectant resistance genes harbored by the isolates were detected, and highly virulent strains were screened for the measurement of susceptibility toward antibiotics and disinfectants. Results showed that a total of 249 E. coli strains were isolated, of which 123 were diarrheagenic. Enteroaggregative E. coli (EAEC) was the main diarrheagenic E. coli (DEC) in the dairy farm, accounting for 77.23% of all diarrheagenic strains. Sixteen strains from different sources, each carrying two to four virulence genes, were screened, among which 14 drug resistance genes and one disinfectant resistance gene were detected. Susceptibility testing revealed that resistance to bacitracin B was highest (100.00%), followed by penicillin (93.75%), rifampicin, and vancomycin (87.50%). The strains exhibited multidrug resistance (resistant to two to ten types of drugs). When testing was performed with eight selected common disinfectants, it was found that three disinfectants exerted significant bacteriostatic effects on the vast majority of E. coli strains in the dairy farm and could be recommended for use. Our findings indicate that the main DEC in the dairy farm was EAEC, and that certain strains exhibited resistance to antibiotics and disinfectants; these are issues worthy of attention.
