Genetic diversity and characterization of potentially pathogenic Escherichia coli isolated from artisanal cheese in Venezuela

Abstract

Introduction: Artisanal raw milk cheese can be an important source of bacteria potentially harmful to humans, such as pathogenic Escherichia coli. The objective of this study was to determine the genetic diversity, pathogenicity, and antimicrobial resistance of 45 E. coli strains isolated from artisanal raw milk cheese in Venezuela.

Methods: These strains were isolated according to the procedures established by the Venezuelan Commission of Industrial Standards (COVENIN) and identified by conventional methods. Antimicrobial resistance was determined by the disk diffusion method, while phylogenetic grouping and detection of 6 virulence genes (fimH, kpsMT II, papAH, PAI, fyuA and usp) were performed by PCR amplification. Strain typing was performed by Rep-PCR.

Results: Of the 45 isolates, 73.3% were susceptible, while 26.7% were resistant to at least one of the tested antibiotics. Phylogenetic grouping revealed a relatively homogeneous distribution. Phylogenetic group A dominated in 82.2% of the strains followed by B1 and D (8.9% each). Three major virulence factors, fimH, fyuA, and kpsMTII, were genetically encoded in most strains. Rep-PCR typing of E. coli strains revealed a heterogeneous population structure.

Conclusions: E. coli isolated from artisanal dairy products share characteristics and virulence genes with extraintestinal pathogenic E. coli (ExPEC) strains from animals and humans, which represents a public health risk. Thus, it is necessary to increase hygienic and sanitary controls, especially those involved in the production stages, and emphasize the epidemiological surveillance of potentially pathogenic bacterial strains present in unpasteurized artisanal cheese marketed in the city of Mérida, Venezuela.