Antimicrobial agents used included ampicillin, gentamicin, and imipenem Ku0059436 (MSD, Tokyo, Japan), clindamycin and linezolid (Pfizer Japan,

Tokyo, Japan), dripenem and vancomycin (Shionogi Pharmaceutical, Osaka, Japan), levofloxacin (Daiichi-Sankyo, Tokyo, Japan), and meropenem (Dainippon Sumitomo Pharma, Osaka, Japan). MICs were determined using an agar dilution method as described by the CLSI (CLSI 2009). Susceptibility testing was performed on Mueller-Hinton agar (Nippon Becton Dickinson) in accordance with the manufacturer’s instructions. MIC breakpoints for B. cereus were not defined by CLSI. The MicroScan broth microdilution system (Siemens Healthcare Diagnostics, Tokyo, Japan) was employed for susceptibility testing. For the MicroScan system, a single fresh colony was used to prepare an inoculum this website equivalent to a turbidity of 0.5 McFarland standard in distilled water containing a detergent (Pluronic). The MicroScan Pos Breakpoint Combo Panel Type 3.2A panel containing Mueller-Hinton

broth filled with inoculum diluted 250-fold was incubated at 35 °C under aerobic conditions and was read visually after 18 h of incubation. Then the results were compared with the agar dilution susceptibility test (reference) results. ‘Essential agreement’ was defined as agreement within ± 2 log2 dilutions between the MicroScan broth microdilution test and the reference agar dilution susceptibility test. Etest susceptibility testing was performed on Mueller-Hinton agar in accordance with the Etest

technical guide (AB Biodisk, Solna, Sweden). ‘Essential agreement’ was defined as agreement within ± 2 log2 dilutions between the Etest and the reference agar dilution susceptibility test. Paired data were compared using Fisher’s exact test using jstat for Windows version 10.0 (http://www8.ocn.ne.jp/˜jstat/) and probability (P) 6-phosphogluconolactonase values of less than 0.05 were considered significant. All 26 isolates were identified phenotypically as B. cereus group, i.e. facultatively anaerobic, endospore-forming, gram-positive rods that were positive for the egg yolk reaction and utilized d-trehalose (Logan et al., 2007). None of the 26 isolates carried the emetic toxin (ces) gene, the NRPS gene or the nheBC gene. The genes encoding enterotoxins (EntFM and EntS) and the piplc gene were commonly found in the isolates. The profile of the other virulence genes in the 26 B. cereus isolates and ATCC14579 is shown in Table 2. The epidemiologic relations of the 26 isolates were analyzed by PFGE. The PFGE patterns of 24 isolates were different from each other, suggesting that these isolates were epidemiologically unrelated, while the other two isolates (strains 17 and 25) were related (Fig. 1). The susceptibilities (MIC range, MIC50 and MIC90) of the 26 isolates determined using the agar dilution (reference) method are shown in Table 3.