High-risk clonal complexes CC2 and CC9 are widely distributed among Enterococcus faecalis hospital isolates recovered in Spain

INTRODUCTION. Our previously described multilocus sequence typing (MLST) scheme for Enterococcus faecalis has provided insight into the population structure and global epidemiology of this organism. Two high-risk complexes, CC2 and CC9, especially adapted to the hospital environment and widely distributed in Europe and America, were identified. The purpose of this study was to define the presence of CC2 and CC9 among E. faecalis strains isolated in Spain. METHODS. A total of 81 E. faecalis isolates recovered from several sources and geographic areas of Spain were characterized using MLST. Because of their clinical and epidemiological interest, strains were included from each of the vancomycin-resistant E. faecalis hospital outbreaks described in Spain. RESULTS. Among the isolates, CC2 and CC9 were detected in the hospital setting. Included in these CC were the vancomycin-resistant E. faecalis isolates causing hospital outbreaks in La Coruna, Palma de Mallorca and Valencia, as well as vancomycin-susceptible hospital isolates. The Index of Association (I-a), which measures linkage disequilibrium between alleles, revealed an epidemic population structure on a background of high recombination rates. CONCLUSIONS. High-risk complexes (CC2 and CC9) particularly adapted to the hospital environment were detected in Spain. Evolution of these CC in different areas depended on the local gene pool. Future infection control policies should be orientated to detect high-risk CC with the aim of predicting potential trends toward acquisition of specific resistance, such as to vancomycin.