Unusual increase of vancomycin-resistant Enterococcus faecium but not Enterococcus faecalis at a University Hospital in Taiwan

Background: Enterococcal infections at the Chang Gung Memorial Hospital, Taiwan, have increased significantly in recent years, accompanied by a significant growth of vancomycin resistance from < 1% to 3.8%. However, the significant increase in vancomycin resistance was only found in Enterococcus faecium (from 0.5% to 17.4%). Methods: A total of 172 patients infected with vancomycin-resistant enterococci (85 E. faecium and 87 E. faecalis) during 1998-2004 were retrospectively studied. Clinical and laboratory features were analyzed using Stata for Windows (version 8.2). Genotypes of the isolates were determined by infrequent-restriction-site polymerase chain reaction. Results: Multivariate analysis revealed that prior use of imipenem (odds ratio [OR], 30.1; 95% confidence interval [CI], 4.2-215.9) or clindamycin (OR, 6.5; 95% CI, 1.5-28.1), positive urine cultures (OR, 6.1; 95% CI, 2.1-17.8) and penicillin resistance (OR, 55.9; 95% CI, 18.5-168.3) were significantly associated with the infections caused by vancomycin-resistant E. faecium. Genotyping analysis demonstrated a predominant genotype in 71 (83.5%) of the E. faecium isolates, while diverse genotypes were found among the E. faecalis isolates. No apparent correlation between genotype and any specific ward was found. Up to the end of 2005, primary efforts to restrict imipenem usage and reinforce infection control measures have reduced by half the infections caused by vancomycin-resistant E. faecium. Conclusion: Multiple factors were associated with the unusual increase of vancomycin-resistant E. faecium infections in this hospital. Continuous monitoring of appropriate antimicrobial usage and stringent compliance to infection control measures are required to control the increase of such infections.