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Although the spread of plasmid-mediated antibiotic-resistant bacteria is a public health concern, food contamination with plasmid-mediated antibiotic-resistant Escherichia coli has not been well investigated in Vietnam. The aim of this study was to describe the prevalence of colistin-resistant, carbapenem-resistant and endemic blaCTX−M in extended-spectrum β-lactamase (ESBL)-producing E. coli isolates. Colistin- and carbapenem-resistant ESBL-producing E. coli were isolated from chickens in Vietnam and Japan. The results showed that 52% and 93% of Vietnamese chicken was isolated with colistin-resistant and AmpC/ESBL-producing E. coli, respectively, while 52.7% of Japanese chickens were isolated with AmpC/ESBL-producing E. coli. Carbapenem-resistant E. coli has not been isolated in Vietnam or Japan. Genotyping revealed that colistin-resistant E. coli harboured mcr-1, and most of the AmpC/ESBL-related genes were blaCTX−M−55 and blaCTX−M−65 together with blaTEM in Vietnamese chickens, and blaCMY−2 in Japanese chickens. Multidrug resistance analysis showed that ESBL-producing E. coli isolates were more resistant to quinolones, streptomycin, and chloramphenicol compared with colistin-resistant E. coli isolates from Vietnam, suggesting selection in ESBL-producing E. coli for multiple antibiotic resistance genes. In conclusion, colistin-resistant E. coli was detected in about half of the chicken meat samples, the majority of which were found to harbour mcr-1. The high prevalence of ESBL-producing E. coli has remained constant across the last five years, and the predominant blaCTX−M for ESBL-producing E. coli was found to be blaCTX−M−55 or blaCTX−M−65, with the coexistence of blaTEM in Vietnam. Our results can be implemented in monitoring systems to combat the development of antimicrobial resistance.

A novel method for regulating the activity of homodimeric proteins--"molecular gate" approach--was proposed and its usefulness illustrated for the type II restriction endonuclease SsoII (R.SsoII) as a model. The "molecular gate" approach is based on the modification of R.SsoII with azobenzene derivatives, which allows regulating DNA binding and cleavage via illumination with light. R.SsoII variants with single cysteine residues introduced at selected positions were obtained and modified with maleimidoazobenzene derivatives. A twofold change in the enzymatic activity after illumination with light of wavelengths of 365 and 470 nm, respectively, was demonstrated when one or two molecules of azobenzene derivatives were attached to the R.SsoII at the entrance of or within the DNA-binding site.