Naoki Kakuta1, Ryuichi Nakano2, Akiyo Nakano3, Yuki Suzuki4, Takashi Masui5, Saori Horiuchi6, Risako Kakuta7, Kohsuke Tsubaki8, Miho Ogawa9, Hisakazu Yano10. 1. Department of Microbiology and Infectious Diseases, Nara Medical University, Nara, Japan. Electronic address: kaku-n@naramed-u.ac.jp. 2. Department of Microbiology and Infectious Diseases, Nara Medical University, Nara, Japan. Electronic address: rnakano@naramed-u.ac.jp. 3. Department of Microbiology and Infectious Diseases, Nara Medical University, Nara, Japan. Electronic address: akiyo@naramed-u.ac.jp. 4. Department of Microbiology and Infectious Diseases, Nara Medical University, Nara, Japan. Electronic address: suzuki-y@naramed-u.ac.jp. 5. Department of Otolaryngology-Head and Neck Surgery, Nara Medical University, Nara, Japan. Electronic address: masui@naramed-u.ac.jp. 6. Department of Microbiology and Infectious Diseases, Nara Medical University, Nara, Japan. Electronic address: saorih@naramed-u.ac.jp. 7. Department of Microbiology and Infectious Diseases, Nara Medical University, Nara, Japan; Department of Otolaryngology-Head and Neck Surgery, Tohoku University Graduate School of Medicine, Miyagi, Japan. Electronic address: kakuta-r@med.tohoku.ac.jp. 8. Department of Microbiology and Infectious Diseases, Nara Medical University, Nara, Japan. Electronic address: inaneas1@gmail.com. 9. Department of Bacteriology, BML, Inc., Saitama, Japan. Electronic address: miho-o@bml.co.jp. 10. Department of Microbiology and Infectious Diseases, Nara Medical University, Nara, Japan. Electronic address: yanohisa@naramed-u.ac.jp.
Abstract
OBJECTIVE: To provide data on the molecular characteristics of extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae clinical isolates in Japan. METHODS: A total of 100 clinical isolates of ESBL-producing K. pneumoniae collected throughout Japan between June and July 2018 were studied. ESBL genes were analyzed using PCR and DNA sequencing. Transferability of ESBL genes was investigated by conjugation experiments. Plasmid replicon types, virulence genes (rmpA, rmpA2, iucA, iroB, and peg-344) associated with hypervirulent K. pneumoniae (hvKp), and capsule types were detected using PCR. Genotyping was performed using multilocus sequence typing. RESULTS: All ESBL-producing isolates carried blaCTX-M genes. The most predominant CTX-M-type identified was CTX-M-15 (n = 55). We identified 24 sequence types (STs) among the CTX-M-15 producers, with ST25 (n = 8) being the most common. Most of the transconjugants carrying blaCTX-M-15 contained the FIIk replicon. Of the 100 ESBL-producing isolates, 31 were hvKp defined by the presence of the virulence genes. These ESBL-producing hvKp isolates belonged to eight STs (STs 23, 25, 36, 65, 86, 268, 412, and 4492), with five capsule types (K1, K2, K20, K57, and undefined). CONCLUSIONS: CTX-M-15 was the predominant ESBL among K. pneumoniae isolates from Japan. This study shows that ESBL-producing hvKp strains comprising various clones are emerging in Japan.
OBJECTIVE: To provide data on the molecular characteristics of extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae clinical isolates in Japan. METHODS: A total of 100 clinical isolates of ESBL-producing K. pneumoniae collected throughout Japan between June and July 2018 were studied. ESBL genes were analyzed using PCR and DNA sequencing. Transferability of ESBL genes was investigated by conjugation experiments. Plasmid replicon types, virulence genes (rmpA, rmpA2, iucA, iroB, and peg-344) associated with hypervirulent K. pneumoniae (hvKp), and capsule types were detected using PCR. Genotyping was performed using multilocus sequence typing. RESULTS: All ESBL-producing isolates carried blaCTX-M genes. The most predominant CTX-M-type identified was CTX-M-15 (n = 55). We identified 24 sequence types (STs) among the CTX-M-15 producers, with ST25 (n = 8) being the most common. Most of the transconjugants carrying blaCTX-M-15 contained the FIIk replicon. Of the 100 ESBL-producing isolates, 31 were hvKp defined by the presence of the virulence genes. These ESBL-producing hvKp isolates belonged to eight STs (STs 23, 25, 36, 65, 86, 268, 412, and 4492), with five capsule types (K1, K2, K20, K57, and undefined). CONCLUSIONS:CTX-M-15 was the predominant ESBL among K. pneumoniae isolates from Japan. This study shows that ESBL-producing hvKp strains comprising various clones are emerging in Japan.