Bacteriological Properties of Meropenem-resistant Escherichia coli Isolated from Seven Patients within a Month

: From April to May 2014, a total of seven cases of meropenem (MEPM)-resistant Escherichia coli were isolated from the sputum specimens in 7 different patients in a community hospital. The MICs of MEPM for isolates were 8 to 32 μg/mL, whereas the MICs of imipenem (IPM) were 0.5 μg/mL or 1 μg/mL. All of the isolates possessed the metallo β-lactamase (MBL) IMP-6 gene, and were CTX-M-2 type extended-spectrum β-lactamase (ESBL)-producers. Pulsed-field gel electrophoresis (PFGE) patterns for the isolates were identical. At the time of specimen collection, one patient had been hospitalized for a long time and the other six patients had been comparatively recently admitted to the hospital. Of the six patients, two had been staying in the same nursing facility before admission, whereas the remaining 4 patients had no relationship with each other because they had been in separate locations. Thus, these cases were not considered to be nosocomially-acquired infection. Our findings suggest that MBL-producing E. coli has been spreading widely in the community such as in local nursing facilities.