Clinical Features of VRE Infection, Microbiologic Characteristics and Genetic Relatedness of VRE Isolates from Six University Hospitals / 감염

BACKGROUND: In recent years, vancomycin-resistant enterococci (VRE) have become one of major nosocomial pathogens in Korea. VRE infection presents as an increasingly difficult clinical problem in the treatment and management. The purpose of this study was to determine the clinical features, microbiologic characteristics, and genetic relatedenss of clinical VRE isolates which were collected from six university hospitals, distributed nationwide in Korea. In addition, we aimed to elucidate the possibility of VRE dissemination between hospitals. METHODS: During one year (January, 1999 to January, 2000), 107 clinically suspected VRE isolates were collected from six university hospitals and were subjected to vancomycin resistance genotyping by vanA, vanB, vanC1 and vanC2 PCR. Those 70 isolates with vanA genotype were examined antimicrobial susceptibility by agar dilution method. Pulsed-field gel electrophoreis (PFGE) were used for discriminating the genetic relatedness of VRE isolates. Clinical characteristics of the 61 patients with vanA VRE infection were analyzed for the identification of risk factors for VRE infection. RESULTS: Out of 107 clinical VRE isolates from six hospitals, 70 isolates (65.4%) were vanA genotype VRE (67 E. faecium, 3 E. faecalis). Their MIC90 of vancomycin, teicoplanin and ampicillin were >512 microgram mL, 512 microgrammL and >512 microgrammL respectively. The prevalance of high-level resistance to gentamicin and streptomycin were 96.9% and 78.1%, respectively. Prolonged hospital stay, cerebro-vascular disease, use of third generation cephalosporins, use of Foley catheter and levin tube were associated with VRE infection. 64 vanA VRE (61 E. faecium, 3 E. faecalis) had unique PFGE pattern within each hospital and showed no evidence of VRE transmission between hospitals. CONCLUSION: This study demonstrated the most common vancomycin resistance genotype among clini-cal VRE isolates in Korea were vanA type VRE. vanA genotype VRE had unique PFGE pattern within each hospital and showed no evidence of inter-hospital transmission. This study suggested that maintaining HICPAC guidelines, restricted vancomycin usage and periodic surveillance in patients with high risk factors are important in preventing the emergence and spread of VRE infection within hospitals.

Molecular Epidemiologic Analysis of vanA-Containing Vancomycin-Resistant Enterococci / 대한진단검사의학회지

BACKGROUND: Vancomycin-resistant enterococci (VRE) have been increasingly isolated world-wide as a nosocomial pathogen. To target infection control, epidemiologic investigations of VRE should include analysis of the resistance gene in addition to typing of strains. We performed molec-ular characterization of the vanA resistance gene to evaluate the inter or intraconstitutional spread. METHODS: Twenty isolates of VanA VRE from the Centers for Disease Control and Prevention (CDC) and 17 from Ajou University Hospital (AUH) were investigated. Minimum inhibitory concen-trations of vancomycin, teicoplanin, and ampicillin were tested by the agar dilution method. Pulsed-field gel electrophoresis (PFGE) and long PCR-restriction fragment length polymorphism (long PCR-RFLP) were performed. The long PCR negative strains were typed by ORF1-, vanS-vanH-, vanX-, vanY-vanZ-, vanZ-, and IS1216-specific PCRs. Filter matings were performed by using rifampin-resistant, fusidic acid-resistant E. faecalis J H2-2 as the recipient. RESULTS: The PFGE from the VRE of the CDC showed 15 patterns including 4 clusters and PFGE from isolates of AUH revealed 6 patterns including 3 clusters. Tn1546 amplicons were detected in 18 of 20 (90%) CDC strains and 16 of 17 (94%) AUH strains. RFLP of Tn1546 amplicons revealed 5 different patterns in the VRE of the CDC strains, and 2 patterns in the VRE of the AUH strains. The mean transfer efficiency of the CDC and the AUH strains are 3.0 X 10(-8)and 4.9 X 10(-5)transconju-gant/ donor, respectively. CONCLUSIONS: Molecular typing of isolates from the CDC suggests the horizontal spread of vanA genes among genetically diverse strains. Analysis of the VRE from the AUH shows a mixed pattern with clonal dissemination of strains and horizontal transfer of vanA.