Phenotypic and Genotypic Identification of Vancomycin Resistant Enterococci from Different Sources

Abstract

Enterococci are reservoirs for transmission of the most clinically important antimicrobial resistances such as vancomycin resistance. Therefore, this work aimed to determine the occurrence of enterococci and their respective vancomycine resistance genes (vanA and vanB) from different sources. Two hundred and twenty-four samples from chickens, turkey, fish and human urine, as well as, two types of human food including milk (raw and milk from mastitic animals) and sausage were tested for isolation of Enterococcus species. The isolates were identified morphologically and biochemically using catalase test, sodium chloride tolerance and growth at pH 9.6 and 10-45˚C. The vancomycin resistance profile of the isolates was verified by both disc diffusion and agar dilution methods. The genotypic enterococcal identification at both genus and species levels and their vancomycine resistance genes were also ascertained using PCR amplification of the respective genes for 28 isolates. Enterococci isolation rate was 70% of the examined samples with a higher percentage of vancomycine resistance (53.5%) and the minimum inhibitory concentrations (MICs) ranged from 16 to 512 µg/mL. Molecular identification of 28 enterococcal isolates revealed the dominance of E. faecalis (42.8%) and clarified a higher proportion of vanA (78.5%) and vanB (67.8%) genes. In conclusion, administration of the antimicrobials mainly vancomycin may be considered as a pronounced stress factor in the veterinary and human practices. In addition, VRE can act as a reservoir for vancomycin resistance.