Recently, Vancomycin-resistant enterococci (VRE) have become important nosocomial pathogens in the world. In Japan, the VRE-infection was first reported in 1996. However, an epidemiological study on VRE has not been aggressively done in Japan. We conducted a survey study to explore the incidence and antimicrobial susceptibility of vancomycin-resistant enterococci isolated from fecal samples at 45 hospitals in the east area of Japan (Kanto, Koshinetsu, Tohoku, and Hokkaido) during June 1998 to March 1999.
The Enterococcosel agar containing vanocomycin (BBL) was used for screening VRE from fecal samples in each hospital. The suscceptibilities of the isolates to 8 antimicrobials were determined by the broth microdilution method and the definitions of resistance were based on current standards of the NCCLS standards. The VRE genotypes (vanA, vanB, vanC, and vanC_2/3) were confirmed by amplifying the respective genes by PCR. Eight hundred and ninety four strains of enterococci were tested by the microtiter plates hybridization method (WAKUNAGA SEIYAKU, Japan).
One thousand five hundred eighty three strains of enterococci were collected from 6, 914 patients in 45 hospitals. These strains included 72 (4.5%) strains Enterococcus faecalis, 33 (2.1%) strains Enterococcus faecium, 17 (1.1%) strains Enterococcus avium, 1, 040 (65.7%) strains Enterococcus gallinarum, 386 (24.4%) strains Enterococcus cassliflavus, and 35 (2.2%) strains Enterococcus flavescens.
These strains of vancomycin-resistant E. faecalis were isolated from 3 patients, two of these 3 strains had van A gene and other one had van B gene. Those 3 strains were in the Kanto area, and 2 of 3 strains were in Tokyo, Generally, though van A type VRE was highly resistaant to both vancomycin and teicoplanin. In our study, two strains of van A type E. faecalis were highly resistant to vancomycin (MICs>128μg/ml) and susceptible to teicoplanin with MICs 4μg/ml. Those two strains were different in susceptibilities of minocycline and ofloxacin, The result of the analysis of PFGE had also different patterns. VanB type E. fecalis was highly resistant to vancomycin and susceptible to teicoplanin (MICs 0.251μg/ml). For ampicillin and imipenem, 3 strains of E. faecalis were susceptible (MIC≤1μg/ml). One of 562 strains of E. gallinarum had vanB and vanC1 genes and was moderately resistant to vancomycin and susceptible to teicoplanin. All strains of E. casseliflavus and E. flavescens had vanC2/C3 gene only. All strains of E. faecium and E. avium did not detect van genes.
From this result, it was supposed that VRE were very rare in the east of Japan.