Evaluation of solar light inactivation on multidrug-resistant Escherichia coli CGMCC 1.1595

This study investigated the simulated solar light disinfection of Escherichia coli CGMCC 1.1595, a multidrug-resistant (MDR) strain resistant to tetracycline and ampicillin. With the increase of light intensity, the maximum inactivation efficiency reached 0.74 log in 60 min following visible light irradiation with an intensity of 115.8 mW/cm2 and following UVA–visible light irradiation, using a 98% UVA-ray contribution at 6.5 mW/cm2 and 95% contribution at 20.0 mW/cm2, the inactivation efficiency was up to 6.09 log. The inactivated MDR E. coli did not regrow after light irradiation or in the dark after 24 or 48 h after visible light disinfection, demonstrating that visible light disinfection can prevent MDR E. coli self-repair. The MDR E. coli plasmid electrophoresis band gradually went dark with increase of the light irradiation time and could be completely eliminated by high UVA light intensity treatment, however, simulated sunlight irradiation had minimal influence on both tetracycline and ampicillin resistance of the MDR E. coli strain.