A Report of Vancomycin-susceptible, Teicoplanin-resistant Enterococcus faecalis ST6 in Malaysia

The ability to acquire antibiotic resistance and virulence has propelled Enterococcus faecalis to become a major nosocomial pathogen. In Malaysia, data on the antibiotic resistance determinants and virulence of Enterococcus circulating strains are still scarce. This study aimed to assess the genotype of an E. faecalis isolate initially identified as Streptococcus uberis, examine the antibiotic resistance genotypes, analyze the genetic variations within Tn1546 and investigate the presence of virulence genes. The E. faecalis isolate was genetically characterized using multilocus sequence typing (MLST). Minimum inhibitory concentrations to vancomycin and teicoplanin were determined. Antibiotic resistance and other virulence genes were amplified using nucleic acid polymerase chain reaction. Mapping of the Tn1546 transposon was performed and compared to the prototype sequences. The E. faecalis isolate was found to have a MLST profile corresponding to sequence type 6. The isolate was resistant to teicoplanin but susceptible to vancomycin. Its genome consisted the vanA and vanC1 genes. Novel genetic variations in the vanS, vanS-vanH intergenic region and vanY genes were present and six virulence genes were detected. The detection of the vanC1 gene, thought to be non-transferable, suggests the potential emergence of inter-species enterococcal vanC1 gene transfer. The peculiar antibiotics resistance phenotype of this E. faecalis isolate could be associated to the novel genetic variations found. This study highlights the presence of E. faecalis belonging to the high-risk clonal complex with multiple virulence factors in Malaysia.