Abstract

GUILLEN, Leidys; MILLAN, Beatriz  and  ARAQUE, María. Molecular characterization of Escherichia coli strains isolated from homemade dairy foods produced in Mérida, Venezuela . Infect. [online]. 2014, vol.18, n.3, pp.100-108. ISSN 0123-9392.

Objective: To determine phylogenetic groups and clonal diversity of Escherichia coli strains isolated from several homemade dairy foods produced and marketed in Mérida, Venezuela. Materials and methods: Forty-five E. coli strains isolated from homemade dairy products (cream cheese, curd and cottage cheese) were analyzed. These strains were isolated according to procedures established by the Venezuelan Commission of Industrial Norms (COVENIN) and identification was carried out using conventional methods. Antimicrobial susceptibility was determined by the disk diffusion method and phenotypes with intermediate or resistant susceptibility were confirmed by minimum inhibitory concentration (MIC). Phylogenetic groups were identified by PCR amplification of chuA , yjaA genes and the TspE4.c2 DNA fragment, while molecular typing was carried out by Rep-PCR. Results: Of the 45 isolates, 33 (73.3%) were susceptible to all antibiotics tested while 11 (24.4%) were ampicillin-resistant. The phylogenetic group A was the most common (82.2%), followed by B1 and D (8.9%, respectively). The phylogroup B2 was not detected and Rep-PCR typing of E. coli strains showed a heterogeneous population structure. Conclusion: The molecular characterization of E. coli strains showed that they were clonally nonrelated and mostly distributed among phylogenetic groups that belong to low pathogenicity commensal strains. Detection of E. coli strains in dairy foods indicates a contamination of fecal origin, which could be associated with the presence of other enteric pathogens.

Keywords : Escherichia coli; Phylogenetic groups; Molecular characterization; Dairy products.

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