Hospital dissemination of a clonal complex 17 vanB2-containing Enterococcus faecium

Sir, Since the first report in 1988, vancomycin-resistant enterococci (VRE) have emerged as an important cause of hospital-acquired infections, particularly in the United States. However, infections with VRE are still relatively uncommon in many European hospitals. The aim of this study was to characterize isolates from a prolonged outbreak of vancomycin-resistant and teicoplaninsusceptible (VanB phenotype) Enterococcus faecium that occurred in a Spanish hospital. Between January 2004 and July 2006, 107 E. faecium isolates were isolated from clinical samples in the Hospital General de Soria (HGS), Spain (estimated catchment population of 92 700): 30 were isolated in 2004, 44 in 2005 and 33 in 2006. Of these, 34 (31.8%) isolates from separate patients showed VanB phenotypes, for which the annual distribution was 23.2% (7 isolates) in 2004, 29.5% (13 isolates) in 2005 and 42.4% (14 isolates) in 2006. The remaining 73 E. faecium isolates were susceptible to both vancomycin and teicoplanin. From March 2004 to October 2005, only sporadic cases appeared; however, in November 2005 three cases were detected, peaking in March and April 2006 with five and four cases, respectively. Most VanB isolates were from males (58.8%), age . 65 years (84.4%), admitted to ICU (32.4%) and were isolated from wounds (35.3%) or the urinary tract (23.6%). Twenty-eight patients (82.4%) had predisposing underlying conditions, principally respiratory/cardiac diseases (27.3%), neurological diseases (27.3%), tumoral pathologies (27.3%) and urinary tract pathologies (21.2%). Thirty-two patients were treated with antibiotics within the month prior to infection; the most frequent agents were cephalosporins (47.1%) and vancomycin (23.5%). Statistical comparisons of demographic data, clinical characteristics, microbiological features and clinical outcomes of the 34 patients infected by VanB E. faecium with 50 patients infected by vancomycin-susceptible E. faecium showed that only previous treatment with cephalosporins and/or vancomycin was associated with the emergence of VanB E. faecium (P , 0.05). All 34 VanB isolates were also resistant to ampicillin (MICs . 8 mg/L), erythromycin (MICs . 4 mg/L) and levofloxacin (MICs . 2 mg/L), but were susceptible to high concentrations of gentamicin (MICs 4–8 mg/L). Seventeen of these isolates were randomly selected and subjected to further molecular and epidemiological studies. A vanB gene was detected by PCR in all 17 isolates, and sequencing confirmed that this was identical to the vanB2 allele. In addition, the intergenic region vanSB–vanYB, sequenced in four isolates, showed previously reported point mutations and a 5 bp deletion in vanB2. Amplification and posterior sequencing of vanXB–ORFC amplicons demonstrated genetic linkage of the vanB2 operon to a Tn5382-like element. The pbp5 gene was detected by PCR in the four isolates, but we did not find genetic linkage of pbp5 and the vanB2-containing Tn5382. This latter finding is in accordance with the high rate of ampicillin resistance (82.6%; 60/73 isolates) among our vancomycin-susceptible E. faecium isolates. The 17 VanB isolates harboured the enterococcal surface protein gene, esp, but not the hyl, gelE, cylA or asa1 virulence genes. By PFGE, the VanB2 isolates exhibited a genetic relatedness of 92–100%, and 12 were indistinguishable (Figure 1) indicating an outbreak strain. Five VanB isolates from other hospitals and one vancomycin-susceptible strain from HGS were used as controls,