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The Journal of the Japanese Society for Clinical Microbiology |
Biblioraphy Information
| ArticleTitle |
Influence of Cation Supplements on Detection of Methicillin Resistance in Staphylococcus aureus |
| Language |
J |
| AuthorList |
Tetsuo Yamaguchi1), Hiroyuki Tojo2), Katsumi Chiba3), Tetsuya Matsumoto1) |
| Affiliation |
1) Department of Microbiology, Tokyo Medical University, Tokyo, Japan
2) Microbiology group, Eiken Chemical Co., Ltd., Tochigi, Japan
3) Department of Microbiology Laboratory, Tokyo Medical University Hospital, Tokyo, Japan |
| Publication |
J.J.C.M.: 22 (1), 20-27, 2012 |
| Received |
October 19, 2011 |
| Accepted |
December 13, 2011 |
| Abstract |
The purpose of this study was to examine the influence of calcium (Ca2+) concentration on in vitro activity of oxacillin (MPIPC) using various concentrations of Ca2+ (3.5-50 mg/L) against Staphylococcus aureus clinical isolates. The activity of MPIPC was compared with the activities of 17 other agents against 50 strains of methicillin-sensitive S. aureus (MSSA) and 40 strains of methicillin-resistant S. aureus (MRSA) which were isolated at microbiology laboratory of Tokyo Medical University Hospital. Susceptibility testing was performed by the CLSI broth microdilution method, with one exception: Mueller-Hinton Broth (MHB) was supplemented to various levels of Ca2+. All MRSA isolates showed increase in MICs of MPIPC when Cation-adjusted MHB (CAMHB, Ca2+: 25 mg/L) were used compared to the MICs of MHB. Similar results were observed with MSSA strains. Five of forty strains (12.5%) of mecA- positive isolates have been diagnosed as MPIPC susceptible strains by using CAMHB, whereas all of the strains were adequately diagnosed as MPIPC resistant strains by using the modified-CAMRSA (Ca2+: 50 mg/L). Increases of MICs against MPIPC by adding Ca2+ to the media were observed in a dose-dependent manner. These results suggest that accurate detection of MPIPC resistance would have failed if we use MHB with lower concentration of Ca2+. |
| Keywords |
methicillin-resistant Staphylococcus aureus, cation, MPIPC, Mueller-Hinton Broth |
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