Vol.53 No.3 March 2005

High-level aminoglycoside-resistant Enterococcus from blood specimens

Akiko Kanayama¹⁾, Yuko Takahashi¹⁾, Utsuki Uchino¹⁾, Miyuki Hasegawa¹⁾, Yumie Sato¹⁾, Intetsu Kobayashi¹⁾and Akihiro Kaneko²⁾

¹⁾Chemotherapy Division, Mitsubishi Kagaku Bio-Clinical Laboratories, Inc.,
3-30-1 Shimura, Itabashi-ku, Tokyo, Japan
²⁾Department of Oral Surgery, School of Medicine, Tokai University

Abstract

Enterococcus is a normal constituent of the intestinal bacterial flora in humans, which occasionally causes opportunistic infections and induces sepsis in case of serious infections. The combination of aminoglycosides with penicillins is generally known to be one of the regimens for bacteremia due to Enterococcus. The drug susceptibility of high-level aminoglycoside-resistant (HLAR) isolates which were detected in part of the Enterococcus isolates derived from blood specimens and the resistance genes were investigated in the present study.
One hundred and forty-nine isolates of Enterococcus (2.2%) were detected in 6,730 blood specimens taken between February 2001 and February 2002. The details are as follows: Enterococcus faecalis strains accounted for 94 (63.1%) followed by Enterococcus faecium strains at 41 (27.5%), and both organisms accounted for 90.6% of all organisms. A total of 54 HLAR strains (36.2%) were detected in 149 strains of Enterococcus and the resistance rate of E. faecium was low, 4.9%, as compared with that of E. faecalis (50.0%). There were differences between E. faecium and E. faecalis in the resistance rate. The aac (6') -aph (2") gene was detected in 49 of the 54 strains (90.7%) with PCR. In addition, the inactivation of gentamicin (GM) was investigated in the 5 isolates without resistant genes. As a result, these isolates inactivated GM. The MICs of penicillin G (PCG), vancomycin (VCM), teicoplanin (TEIC), linezolid (LZD), telithromycin (TEL) and gatifloxacin (GFLX) for 54 isolates of HLAR were determined. The strains resistant to PCG, TEL and GFLX were about 4 to 44%. In the present study there were no strains resistant to VCM, TEIC or LZD, which suggests that these antibiotics are usefully therapeutic drugs for the treatment of infections caused by HLAR strains.

Key word

Enterococcus spp., high-level resistance, aminoglycoside-modifying enzyme, gene analysis

Received

October 27, 2004

Accepted

January 5, 2005

Jpn. J. Chemother. 53 (3): 177-182, 2005