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 Yamamoto<sup>1,7,8

1</sup>Department 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, 2013

Abstract: 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 bla_CTX-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