In vitro activity of various antibiotics against clinical strains of Legionella species isolated in Japan.

The activities of various antibiotics against 58 clinical isolates of Legionella species were evaluated using two methods, extracellular activity (minimum inhibitory concentration [MIC]) and intracellular activity. Susceptibility testing was performed using BSYEα agar. The minimum extracellular concentration inhibiting intracellular multiplication (MIEC) was determined using a human monocyte-derived cell line, THP-1. The most potent drugs in terms of MICs against clinical isolates were levofloxacin, garenoxacin, and rifampicin with MIC90 values of 0.015 µg/ml. The activities of ciprofloxacin, pazufloxacin, moxifloxacin, clarithromycin, and azithromycin were slightly higher than those of levofloxacin, garenoxacin, and rifampicin with an MIC90 of 0.03-0.06 µg/ml. Minocycline showed the highest activity, with an MIC90 of 1 µg/ml. No resistance against the antibiotics tested was detected. No difference was detected in the MIC distributions of the antibiotics tested between L. pneumophila serogroup 1 and L. pneumophila non-serogroup 1. The MIECs of ciprofloxacin, pazufloxacin, levofloxacin, moxifloxacin, garenoxacin, clarithromycin, and azithromycin were almost the same as their MICs, with MIEC90 values of 0.015-0.06 µg/ml, although the MIEC of minocycline was relatively lower and that of rifampicin was higher than their respective MICs. No difference was detected in the MIEC distributions of the antibiotics tested between L. pneumophila serogroup 1 and L. pneumophila non-serogroup 1. The ratios of MIEC:MIC for rifampicin (8) and pazufloxacin (2) were higher than those for levofloxacin (1), ciprofloxacin (1), moxifloxacin (1), garenoxacin (1), clarithromycin (1), and azithromycin (1). Our study showed that quinolones and macrolides had potent antimicrobial activity against both extracellular and intracellular Legionella species. The present data suggested the possible efficacy of these drugs in treatment of Legionella infections.

[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 ß-lactamase (MBL) IMP-6 gene, and were CTX-M-2 type extended-spectrum ß-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.