Imipenem

A total of 20 carbapenem-resistant A. baumannii clinical isolates with various morphology and resistance profiles were obtained without preference from a strain repository at the Department of Microbiology, King Chulalongkorn Memorial Hospital. Clinical isolates used in this study had been isolated during 2016–2018 from infected patients as part of standard care of the patients and were unrelated to the present study. Susceptibility to imipenem (Apollo Scientific, UK), colistin, rifampicin, chlorhexidine, and resveratrol (Sigma-Aldrich, Germany) was determined by broth microdilution method according to the Clinical and Laboratory Standards Institute (CLSI) guidelines [17 ]. resveratrol solution in all experiments was prepared in 0.5% v/v DMSO. Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853 were used as control strains for susceptibility testing. This study was approved by the Institutional Review Board of the Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand (IRB 571/61).

All antibiotic susceptibilities were performed according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines [39 ]. The minimum inhibitory concentrations (MICs) of imipenem (Apollo Scientific, Manchester, UK), meropenem (Sigma-Aldrich, Steinheim, Germany), ertapenem (MSD, Kenilworth, NJ, USA), ceftriaxone (Sigma-Aldrich, Steinheim, Germany), and amikacin (Sigma-Aldrich, Germany) were determined by using broth microdilution method with cation-adjust Mueller–Hinton broth (CAMHB) (Becton Dickenson BBL, Sparks, MD, USA). Fosfomycin (Wako Pure Chemical Industries, Osaka, Japan) susceptibility was performed by agar dilution method using Mueller–Hinton agar supplemented with 25 mg/L of glucose-6-phosphate (G6P) (Sigma-Aldrich, Steinheim, Germany). Azithromycin (Sigma-Aldrich, Steinheim, Germany) susceptibility test was determined by broth microdilution method. E. coli ATCC 25922 and P. aeruginosa ATCC 27853 were used as reference control strains for susceptibility testing. The antibiotic susceptibility was interpreted according to EUCAST guidelines (Supplementary Materials Table S2).

Susceptibility testing to imipenem (Apollo Scientific, Manchester, UK) meropenem (Sigma-Aldrich, Steinheim, Germany) and amikacin (Sigma-Aldrich, Steinheim, Germany) was determined by agar dilution method. Fosfomycin (Wako Pure Chemical Industries, Osaka, Japan) susceptibility testing was performed on Mueller-Hinton agar (MHA) (Becton Dickinson BBL, MD, USA) supplemented with 25 mg/L glucose-6-phosphate (G6P) (Sigma-Aldrich, Steinheim, Germany). E. coli ATCC 25922 and P. aeruginosa ATCC 27853 were used as reference control strains. Susceptibility of imipenem, meropenem, and Fosfomycin was interpreted according to the breakpoints and guidance of the European Committee on Antimicrobial Susceptibility Testing (EUCAST 2020).