Occurrence of vancomycin-intermediate-resistant Staphylococcus aureus in Japan.
The Clinical and Laboratory Standards Institute (CLSI) amended the criteria for vancomycin susceptibility and resistance of Staphylococcus aureus in 2006. The earlier criteria had established that S. aureus with minimum inhibitory concentrations (MICs) of vancomycin of < or =4 microg/ml, 8 to 16 microg/ml, and > or =32 microg/ml were vancomycin-susceptible, -intermediate-resistant and -resistant, respectively. The revised recommendation states that bacteria showing vancomycin MICs of < or =2 microg/ml, 4 to 8 microg/ml, and > or =16 microg/ml are -susceptible, -intermediate-resistant, and -resistant, respectively. We examined, based on these new criteria, the vancomycin susceptibility of methicillin-resistant S. aureus (MRSA) strains isolated in Japan from 1978 through 2005 at 17 general hospitals. The results showed that, among 2446 MRSA isolates tested, 8 were classified as intermediate-vancomycin-resistant (VISA). Re-examination of vancomycin susceptibility in these 8 strains in 2006 revealed that 6 strains showed a vancomycin MIC of 4 microg/ml, as tested by the agar dilution method, broth dilution methods, and E-test; the 2 other strains had lost the vancomycin resistance. Pulsed-field gel electrophoresis (PFGE) of the chromosomal DNA of these strains exhibited five unique profiles; 2 strains isolated from the same hospital were identical. These results revealed that at least five different types of VISA strains could be identified in Japan so far according to the new CLSI criteria. All these VISA strains had type II staphylococcal cassette chromosome, mec. This study revealed, for the first time in Japan, the presence of intermediate vancomycin-resistant MRSA in this country.
Hanaki
Hideaki
H
Kitasato Research Center for Anti-infection Drugs, The Kitasato Institute, 5-9-1 Shirokane, Minato-ku, Tokyo, 108-0072, Japan. hanaki@lisci.kitasato-u.ac.jp
Hososaka
Yasuko
Y
Yanagisawa
Chie
C
Otsuka
Yoshihito
Y
Nagasawa
Zenzo
Z
Nakae
Taiji
T
Sunakawa
Keisuke
K
D016172:DNA Fingerprinting; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D006801:Humans; D007564:Japan; D016106:Methicillin Resistance / Q000187:drug effects* / Q000276:immunology*; D008826:Microbial Sensitivity Tests; D012016:Reference Values; D013211:Staphylococcus aureus / Q000145:classification* / Q000187:drug effects* / Q000235:genetics; D009626:Terminology as Topic; D014640:Vancomycin / Q000494:pharmacology*; D020713:Vancomycin Resistance / Q000235:genetics*
D014640:Vancomycin