Vol.57 No.1 January 2009

Prevalence of drug resistant gene and changes in susceptibility of methicillin-resistant Staphylococcus aureus strains isolated from 1990 to 2006 in Japan to antimicrobial agents

Takeshi Mikuniya, Yoshihisa Kato, Yuko Muto-Kobayashi, Yumiko Sanbongi, Atsuyuki Shimizu, Toru Hiraishi, Takashi Ida and Kazunori Maebashi

Applied Pharmacology Research Labs, Pharmaceutical Research Center, Meiji Seika Kaisha, Ltd., 760 Morooka, Kohoku-ku, Yokohama, Kanagawa, Japan

Abstract

We measured the MIC of arbekacin, vancomycin, teicoplanin and linezolid against 228 clinically isolated methicillin-resistant Staphylococcus aureus(MRSA), 47 isolates obtained from 1990 to 1993, 100 isolates from 1998 to 2001, and 81 isolates from 2005 to 2006 in Japan to determine susceptibility trends from 1990 to 2006. Anti-MRSA activity of all 4 agents was virtually constant during surveillance, and MIC₅₀ and MIC₉₀ against MRSA strains isolated in 2005 to 2006 were as follows: arbekacin, 0.5 μg/mL and 2 μg/mL; vancomycin, 1 μg/mL and 1 μg/mL; teicoplanin, 1 μg/mL and 2 μg/mL; linezolid, 2 μg/mL and 2 μg/mL. Of MRSA isolated in 2005 and 2006, 55.6% possessed aac (6')/aph (2") gene encoding for aminoglycoside acethyltransferase (6')/phosphotransferase (2"), with a slight increase since 2001. Reduced susceptibility to teicoplanin related single amino acid substitutions (I5N) in VraS.

Key word

methicillin-resistant Staphylococcus aureus, clinical isolate, surveillance, drug susceptibility

Received

October 3, 2008

Accepted

November 28, 2008

Jpn. J. Chemother. 57 (1): 37-40, 2009