Fecal carriage of CTX-M β-lactamase-producing Enterobacteriaceae in nursing homes in the Kinki region of Japan Ulzii-Orshikh Luvsansharav,1 Itaru Hirai,1 Marie Niki,1 Arisa Nakata,1 Aya Yoshinaga,1 Akira Yamamoto,2 Mayumi Yamamoto,3 Hiroyuki Toyoshima,4,† Fusao Kawakami,5 Nariaki Matsuura,6 Yoshimasa Yamamoto1,7,8 1Department of Bioinformatics, Osaka University Graduate School of Medicine, Osaka, 2Blueberry, Amagasaki Health Care Facilities for the Elderly, Hyogo, 3Health Administration Center, Gifu University, Gifu, 4Nursing home Minoh, Osaka, 5Nursing home Itami, Hyogo, 6Department of Molecular Pathology, Osaka University Graduate School of Medicine, Osaka, 7Osaka Prefectural Institute of Public Health, Osaka, 8Osaka University Global Collaboration Center, Osaka, Japan†Hiroyuki Toyoshima passed away on February 21, 2013Abstract: The detection rate of CTX-M-type β-lactamase-producing Enterobacteriaceae in Japan has significantly increased. Nursing homes may be a reservoir of antibiotic-resistant bacteria. Therefore, we determined the prevalence of, and risk factors associated with, fecal carriage of CTX-M-type β-lactamase-producing Enterobacteriaceae among nursing home residents. A total of 225 stool samples were collected for phenotypic and genotypic identification of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae. Multivariate analysis was performed to identify the risk factors associated with fecal carriage of CTX-M producers. The prevalence of CTX-M-type ESBL-producing Enterobacteriaceae, as confirmed by phenotypic and genotypic methods, was 19.6% (44 of 225 samples). Escherichia coli was the predominant CTX-M-type ESBL-producing bacterium among these isolates (41 of 44 isolates). Genotyping of blaCTX-M gene-positive isolates showed that 30 (68.2%), 13 (29.5%), and 1 (2.3%) of 44 samples belonged to groups CTX-M-9, CTX-M-1 and CTX-M-2, respectively. Among the CTX-M-type ESBL-producing Enterobacteriaceae found in nursing homes, 95.5% (42 of 44 isolates) were co-resistant to quinolone antibiotics. In multivariate logistic regression analysis, inability to turn over in bed, diabetes, and invasive procedures within the last 2 years were the only variables independently associated with fecal carriage of CTX-M-type ESBL producers. Nursing home residents in Japan exhibit a high prevalence of CTX-M-type ESBL-producing Enterobacteriaceae carriage, with a high level of co-resistance to quinolones.Keywords: Enterobacteriaceae, extended-spectrum beta-lactamase (ESBL), risk factors, fecal carriage, nursing homes, Japan