In-vitro activities of imipenem–colistin, imipenem–tigecycline, and tigecycline–colistin combinations against carbapenem-resistant Enterobacteriaceae*

Abstract

The aim of the study is to determine in-vitro effects of imipenem–tigecycline, imipenem–colistin and tigecycline–colistin against carbapenem-resistant Enterobacteriaceae (CRE) isolates. A total of 25 CRE isolates were included to the study. The minimum inhibition concentrations of imipenem, colistin-sulphate and tigecycline were determined with broth dilution method. Synergistic effects of imipenem–tigecycline, imipenem–colistin and tigecycline–colistin were investigated by microdilution checkerboard technique. All of the isolates were resistant to imipenem, whereas 25% of the isolates were resistant to colistin and tigecycline. Imipenem–colistin, imipenem–tigecycline and tigecycline–colistin combinations were synergistic against 40% (10/25), 24% (6/25), and 36% (9/25) of the isolates, respectively. Antagonism was observed in 8% (2/25) of the isolates in tigecycline–colistin combination. Tigecycline–colistin was the most effective (70% synergy) combination in Klebsiella spp. strains; whereas imipenem–colistin was the most effective (75% synergy) combination in Escherichia coli strains. Synergistic effect was variable and strain-depended against CRE isolates that have been tested.

Keywords:

• Imipenem
• colistin
• tigecycline
• synergy
• Carbapenem-resistant Enterobacteriaceae

Disclosure statement

The authors report no declarations of interest.

Additional information

Notes on contributors

Devrim Dundar

Devrim Dundar is a professor with research interest on antimicrobial susceptibility testing and resistance mechanisms.

Zehra Duymaz

Zehra Duymaz, Serpil Genc and Doganhan Kadir Er are research assistants in Microbiology Department.

Serpil Genc

Zehra Duymaz, Serpil Genc and Doganhan Kadir Er are research assistants in Microbiology Department.

Doganhan Kadir Er

Zehra Duymaz, Serpil Genc and Doganhan Kadir Er are research assistants in Microbiology Department.

Arzu İrvem

Arzu Irvem is MD in Microbiology Department.

Neslisah Kandemir

Neslisah Kandemir is a student in Molecular Biology and Genetics Department.

Devrim Dundardesigned the study, collected and analyzed the data, wrote and revised the article.Zehra Duymaz, Serpil GencandNeslisah Kandemir did lab work, collected and analyzed the data.Doganhan Kadir Er and Arzu Irvem wrote and revised the article. All of the authors approved the manuscript.