Genotypic diversity, antimicrobial resistance, and virulence factors of human isolates and probiotic cultures constituting two intraspecific groups of Enterococcus faecium isolates.

The intraspecific relationships among a collection of Enterococcus faecium isolates comprising probiotic cultures and human clinical isolates were investigated through the combined use of two high-resolution DNA-fingerprinting techniques. In addition, the incidences of antimicrobial resistance and virulence traits were investigated. A total of 128 E. faecium isolates from human clinical or nonclinical sources or used as probiotic cultures were subjected to fluorescent amplified fragment length polymorphism (FAFLP) fingerprinting and pulsed-field gel electrophoresis (PFGE) analysis of SmaI macrorestriction patterns. Susceptibilities to 16 antimicrobial agents were tested using broth microdilution, and the presence of the corresponding resistance genes was investigated using PCR. Multiplex PCR was used to detect the presence of the enterococcal virulence genes asa1, gelE, cylA, esp, and hyl. The results of the study showed that two intraspecific genomic groups (I and II) were obtained in FAFLP analysis. PFGE analysis demonstrated high variability within these two groups but also indicated that some probiotic cultures were indistinguishable and that a number of clinical isolates may be reisolations of commercial probiotic cultures. Compared to group II, which contained the majority of the probiotic isolates and fewer human clinical isolates, higher phenotypic and genotypic resistance frequencies were observed in group I. Two probiotic isolates were phenotypically resistant to erythromycin, one of which contained an erm(B) gene that was not transferable to enterococcal recipients. None of the probiotic E. faecium isolates demonstrated the presence of the tested virulence genes. The previously reported observation that E. faecium consists of two intraspecific genomic groups was further substantiated by FAFLP fingerprinting of 128 isolates. In combination with antimicrobial resistance and virulence testing, this grouping might represent an additional criterion in assessing the safety of new potential probiotic E. faecium isolates.

Development of a multiplex PCR for the detection of asa1, gelE, cylA, esp, and hyl genes in enterococci and survey for virulence determinants among European hospital isolates of Enterococcus faecium.

A multiplex PCR for the simultaneous detection of five virulence genes (asa1, gelE, cylA, esp, and hyl) in enterococci was developed. The presence of these genes was investigated in 153 clinical and 118 fecal Enterococcus faecium isolates from inpatients at an increased risk of developing infections (such as patients in intensive care units and hematology wards) from 13 hospitals in eight European countries. Of the 271 E. faecium isolates, 135 were vancomycin resistant E. faecium (VREF) isolates and 136 were vancomycin susceptible E. faecium (VSEF) isolates. Susceptibilities to ampicillin, gentamicin, streptomycin, vancomycin, teicoplanin, ramoplanin, quinupristin-dalfopristin, and linezolid were tested by the microdilution method. Overall, the prevalence of esp was significantly higher (P = 0.03) in clinical VREF isolates (92%) than in fecal VREF isolates (73%). In Italy, the prevalence of esp was significantly higher (P = 0.02) in VREF isolates (91%) than in VSEF isolates (68%), whereas in the United Kingdom, hyl was significantly more prevalent (P = 0.01) in VREF isolates (71%) than in VSEF isolates (29%). No significant differences were found for the other countries. Pulsed-field gel electrophoresis was used to check the clonality among the strains tested and showed the spread of two center-specific (esp-positive) VREF clones in Italy and one center-specific (hyl-positive) clone in the United Kingdom. These clones were resistant to ampicillin, gentamicin, and streptomycin. The multiplex PCR reported in this study is a convenient and rapid method for the simultaneous detection of the virulence genes asa1, gelE, cylA, esp, and hyl in enterococci. Molecular analysis showed the intrahospital spread of esp-positive VREF clones (in Italy) and hyl-positive VREF clones (in the United Kingdom); the role of hyl remains to be elucidated.