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Korean J Clin Pathol. 1997 Oct;17(5):743-756. Korean. Original Article.
Lee SY , Pai CH .
Abstract

BACKGROUNDS : Infections due to vancomycin-resistant enterococci (VRE) have been reported with increasing frequency in many parts of the world. However, VRE infection is still very rare in Korea. To assess the potential risk of VRE infection in a hospital where such infection is rarely reported, we screened hospitalized patients for fecal colonization with VRE and performed a clinical and epidemiological investigation of VRE colonization. MATERIALS AND METHODS: We screened 405 stool specimens from in- and outpatients for the presence of enterococci using EnterococcoselTM agar (BBLR, USA). Dark-brown or black colonies were tested for enterococci and speciated, followed by confirmation for vancomycin resistance using brain-heart infusion agar containing vancomycin (6microgram/mL). Antimicrobial susceptibilities were determined by agar dilution, disk diffusion, and Vitek GPS-IZ. We also performed pulsed-field gel electrophoresis (PFGE) after SmaI digestion of DNA and polymerase chain reaction for detection of vanA, B and C. To define risk factors for colonization, we reviewed the medical records of patients colonized with VRE or vancomycin- susceptible enterococci (VSE). RESULTS: Twelve (4.1%) of 295 hospitalized patients were colonized with VRE. Six were identified as Enterococcus(E) faecium, 2 each as E. faecalis and E. gallinarum, and 1 each as E. casseliflavus and E. avium. In contrast, only one(0.9%) VRB (E. casseliflavus) was isolated from outpatients. Patients in the intensive careunit (5.4%) and patients whose stool specimens were submitted for Clostridium difficile toxin assay (6.8%) were colonized at higher rate than other inpatients (2.5%), but not at a statistically significant level. Three strains had high-level resistance to van comycin(minimum inhibitory concentration, MIC>256microgram/mL), and the others had low-level resistance (MIC8-16microgram/mL) by agar dilution. But disk diffusion method and Vitek system had problems in detecting some strains with low-level resistance. PFGE patterns of VRE were diverse, suggesting that VRE have been introduced from multiple sources. The vans gene was detected in 3 isolates and vanC gene was found in 9 isolates. Compared with the patients with VSE colonization, patients with VRE had a significantly longer hospital stay, had more frequent invasive procedures or therapeutic interventions such as ventilator, total parenteral nutrition and hemodialysis, showed renal insufficiency more frequently, and were more likely to have received ciprofloxacin or clindamycin therapy. CONCLUSIONS: Although the incidence of VRE infection remains low in Korea, the findings from this study indicate that VRE are not uncommon intestinal colonizers among hospitalized patients. Strict infection control measures including screening for VRE, especially those from patients at risk, close surveillance, judicious use of antibiotics and patient isolation must be implemented to prevent infection and transmission of VRE.

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