Investigation of Prevalence of Vancomycin-resistant Enterococci and Genotypes of Glycopeptide Resistance Using Polymerase Chain Reaction

Hong, Ki Sook; Kang, Eun Suk; Lee, Mi Ae

Abstract

BACKGROUND: Enterococci are a leading cause of nosocomial infection and the emergence of resistant strain to various antibiotics including vancomycin is increasingly serious problems among enterococci. And the risk of spread of glycopeptide genes to other Gram-positive cocci makes the problems more serious. To evaluate the presence of vancomycin-resistant enterococci (VRE) in Ewha Womans University Hospital (EWUH), we screened hospitalized patients for fecal colonization and clinical isolates.
METHODS
We screened VRE in 574 stool specimens requested for routine cultures and 91 perirectal swabs or stool specimens from patients who reside in intensive care unit and hemato-oncologic ward in Mookdong and Tongdaemoon EWUH from December 1996 through April 1997. And 295 enterococcal species isolated from various clinical specimens were also included. To detect VRE, specimens were cultured in BHI agar medium including 6 g/mL of vancomycin and to determine the antibiotic susceptibility pattern, broth microdilution test using VITEK GPS-IZ, disk diffusion test and standard agar dilution test were performed. Multiplex PCR was done to determine the genotypes of VRE.
RESULTS
Nine enterococci (0.9%) were interpreted as VRE in standard agar dilution method. Two (0.3%) out of 665 were from stool speciemens for surveillence cuture and 7 (2.3%) out of 295 were from various clinical specimens for ordinary cultures including 5 E. casseliflavus, 2 E. gallinarum, 1 E. flavescens and 1 Enterococcus species. All isolates showed low-level resistance against vancomycin (8-16 g/mL) by standard agar dilution. But both disk diffusion method and VITEK system demonstrated difficulties in detecting low-level resistance. The genotypes of VRE were classified as van C-1 in 2 isolates and as van C-2 in 6 isolates except 1 isolates, which was unclassifiable in our study.
CONCLUSIONS
Even though VRE with high- or medium-level resistance against glycopeptide was not detected in EWUH from this period of investigation, the possibility of presence of VRE is impanding because several teaching hospitals already reported the presence of VRE in clinical isolates and fecal colonization. So continuous surveillence and strict infection control measures must be implemented to detect and prevent transmission of VRE infection.