Characterisation of chromosomally-located blaCTX-M and its surrounding sequence in CTX-M-type extended-spectrum β-lactamase-producing Escherichia coli isolates

Kouta Hamamoto; Itaru Hirai

doi:10.1016/j.jgar.2018.11.006

Characterisation of chromosomally-located bla_CTX-M and its surrounding sequence in CTX-M-type extended-spectrum β-lactamase-producing Escherichia coli isolates

J Glob Antimicrob Resist. 2019 Jun:17:53-57. doi: 10.1016/j.jgar.2018.11.006. Epub 2018 Nov 13.

Authors

Kouta Hamamoto¹, Itaru Hirai²

Affiliations

¹ Laboratory of Microbiology, School of Health Sciences, Faculty of Medicine, University of the Ryukyus, 207 Uehara, Nishihara, Okinawa 903-0215, Japan; Japan Society for the Promotion of Science (JSPS), Japan.
² Laboratory of Microbiology, School of Health Sciences, Faculty of Medicine, University of the Ryukyus, 207 Uehara, Nishihara, Okinawa 903-0215, Japan; Japan Agency for Medical Research and Development (AMED)/Japan International Cooperation Agency (JICA), Science and Technology Research Partnership for Sustainable Development (SATREPS), Japan. Electronic address: hiraii@med.u-ryukyu.ac.jp.

PMID: 30445208
DOI: 10.1016/j.jgar.2018.11.006

Abstract

Objectives: Although it has been regarded that the CTX-M-type extended-spectrum β-lactamase (ESBL) gene bla_CTX-M is mainly carried by antimicrobial resistance plasmids, Escherichia coli possessing chromosomally-located bla_CTX-M has been reported in previous studies. This study aimed to characterise the genetic structure of the chromosomally-located bla_CTX-M transposition unit and its surrounding sequence in ESBL-producing E. coli isolated in a Japanese hospital.

Methods: A total of 81 ESBL-producing E. coli isolates were studied. The existence of chromosomally-located bla_CTX-M was confirmed by S1 nuclease-digested pulsed-field gel electrophoresis (PFGE) and Southern blot hybridisation and by sequencing analysis of the PCR-amplified DNA fragments.

Results: Chromosomally-located bla_CTX-M was confirmed in 22 (27.2%) of the 81 E. coli isolates examined; five and four location types of chromosomally-located bla_CTX-M-14 and bla_CTX-M-15 were determined, respectively. Among the 22 E. coli isolates, 15 (68.2%) possessed single chromosomally-located bla_CTX-M gene, probably due to single transposition of a plasmidic bla_CTX-M to the chromosome. In isolate N0057, the bla_CTX-M-15 transposition unit was transferred from a plasmid into two different chromosomal regions. In addition, 'recurrent' transposition of already existing chromosomally-located bla_CTX-M-14 to another chromosomal region was observed in isolates N0211, N0214, N01127, N1682 and N1753; consequently, these isolates possessed two copies of chromosomally-located bla_CTX-M-14.

Conclusion: Considering that isolates N0211, N0214, N01127, N1682 and N1753 in which the 'recurrent' transposition event occurred were genetically related according to PFGE, these data suggest the possibility of accumulation of bla_CTX-M on the chromosome in CTX-M-type ESBL-producing E. coli.

Keywords: Chromosomally-encoded; ESBL; Escherichia coli; Extended-spectrum &-; bla(CTX-M); lactamase.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Anti-Bacterial Agents / pharmacology
Chromosomes, Bacterial / genetics*
Drug Resistance, Bacterial
Escherichia coli / classification
Escherichia coli / drug effects
Escherichia coli / genetics*
Escherichia coli / isolation & purification
Escherichia coli Infections / microbiology*
Escherichia coli Proteins / genetics
Escherichia coli Proteins / metabolism
Humans
Plasmids / genetics
Plasmids / metabolism
beta-Lactamases / genetics
beta-Lactamases / metabolism

Substances

Anti-Bacterial Agents
Escherichia coli Proteins
beta-Lactamases
beta-lactamase CTX-M, E coli