The Antimicrobial Resistance Characteristics of Imipenem-Non-Susceptible, Imipenemase-6-Producing Escherichia coli

Reo Onishi, Katsumi Shigemura, Kayo Osawa, Young Min Yang, Koki Maeda, Shiuh Bin Fang, Shian Ying Sung, Kenichiro Onuma, Atsushi Uda, Takayuki Miyara, Masato Fujisawa

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


Imipenemase-6 (IMP-6) type carbapenemase-producing Enterobacteriaceae is regarded as dangerous due to its unique lack of antimicrobial susceptibility. It is resistant to meropenem (MEPM) but susceptible to imipenem (IPM). In addition to carbapenemase, outer membrane porins and efflux pumps also play roles in carbapenem resistance by reducing the antimicrobial concentration inside cells. Extended-spectrum β-lactamase (ESBL) is transmitted with IMP-6 by the plasmid and broadens the spectrum of antimicrobial resistance. We collected 42 strains of IMP-6-producing Escherichia coli and conducted a molecular analysis of carbapenemase, ESBL, porin, efflux, and epidemiological characteristics using plasmid replicon typing. Among the 42 isolates, 21 strains were susceptible to IPM (50.0%) and 1 (2.4%) to MEPM. Seventeen strains (40.5%) co-produced CTX-M-2 type ESBL. We found that the relative expression of ompC and ompF significantly correlated with the MIC of IPM (p = 0.01 and p = 0.03, respectively). Sixty-eight% of CTX-M-2-non-producing strains had IncI1, which was significantly different from CTX-M-2-producing strains (p < 0.001). In conclusion, 50.0% of our IMP-6-producing strains were non-susceptible to IPM, which is different from the typical pattern and can be attributed to decreased porin expression. Further studies investigating other types of carbapenemase are warranted.

Original languageEnglish
Article number32
Issue number1
Publication statusPublished - Jan 2022


  • Carbapenemase
  • Efflux pump
  • IMP-6
  • Plasmid
  • Porin

ASJC Scopus subject areas

  • Microbiology
  • Biochemistry
  • Pharmacology, Toxicology and Pharmaceutics(all)
  • Microbiology (medical)
  • Infectious Diseases
  • Pharmacology (medical)


Dive into the research topics of 'The Antimicrobial Resistance Characteristics of Imipenem-Non-Susceptible, Imipenemase-6-Producing Escherichia coli'. Together they form a unique fingerprint.

Cite this