Antimicrobial blue light inactivation of international clones of multidrug-resistant Escherichia coli ST10, ST131 and ST648.

Abstract Background International clones of multidrug-resistant Escherichia coli have been a leading cause of human and animal infections worldwide. Microbial inactivation by blue light has been proposed as an effective treatment for superficial infections and surface contamination. Aim To evaluate the inactivation efficacy of blue light irradiation against high-risk multidrug-resistant strains of E. coli. Methods Blue LED light (λ = 410 nm) was used to inactivate in vitro suspensions of colistin- broad-spectrum cephalosporin-, or carbapenem-resistant E. coli strains belonging to sequence types (STs) ST10, ST131 and ST648, carrying mcr-1, blaCTX-M or blaKPC-2 genes. Results Our results showed that all E. coli strains were susceptible to blue light irradiation, independently of antibiotic resistance and virulence profiles. In addition, blue light irradiation induced a strain-specific and dose-dependent bacterial effect. Conclusion Our results support use of blue light as a promising antimicrobial option against MDR pathogens, including high-risk clones of E. coli displaying resistance to polymyxins or broad-spectrum β-lactam antibiotics.