Relation of Enterococcus faecalis and Enterococcus faecium isolates from foods and clinical specimens

Clinical Enterococcus faecalis (n=65) and Enterococcus faecium (n=12) blood isolates from three Swiss hospitals were characterized with testing for resistance to antimicrobial agents, pulsed-field gel electrophoresis (PFGE), and the occurrence of virulence factors. Phenotypic determination of resistance to antimicrobial agents resulted in 20% of E. faecalis isolates showing a triple resistance against chloramphenicol, tetracycline, erythromycin, and seven isolates (two E. faecalis and five E. faecium) exhibiting a multiresistance against five or more antimicrobials. One isolate each of E. faecalis and E. faecium showed vancomycin resistance. All isolates contained at least two of the nine tested virulence genes (agg, gelE, cyl, esp, efaAfs, efaAfm, cpd, cob, and ccf). Phylogenetic analysis of the PFGE profiles identified several small clusters within E. faecalis isolates, one of which included isolates of all three hospitals. Fifty-six (73%) isolates occurred as unique, patient-specific clones. Several PFGE types were associated with shared features in their resistance patterns, indicating spread between and within wards. Finally, enterococci from this study and previous isolates from cheeses were examined by PFGE typing. The comparison of PFGE profiles from human and food isolates resulted in clusters of genetically strong related strains, which suggests high similarities of the enterococcal community composition of these two environments. A possible spread of the enterococcal isolates through the food supply cannot be excluded.