Thermal Fogging with Disinfectant Didecyl Dimethyl Ammonium Bromide Effectively Kills A Coronavirus, An Influenza Virus and Two Indicator Bacteria in Subzero Cold-Chain Environment

Background The origin of several local COVID-19 outbreaks in China in 2020 were confirmed to be frozen food or packages contaminated with SARS-CoV-2, revealing the lack of effective disinfection measures in the frozen food chain. Objective To evaluate the disinfection efficacy at −20°C of a recently marketed thermal fogging disinfection product, with disinfectant-antifreeze combination being didecyl dimethyl ammonium bromide (DDAB) - propylene glycol (PPG). Method Carriers with porcine epidemic diarrhea virus (PEDV) YN1, a coronavirus, and a swine influenza virus H1N1 (SIV-H1N1), and three indicator bacteria, E. coli, S. aureus, and B. subtilis endospores, were respectively placed in a −20°C freezer warehouse with or without DDAB-PPG fogging and activities of the microorganisms were tested. Results At −20°C, DDAB-PPG fogging, which fully settles in 3.5−4.5 hours, fully inactivated PEDV of 10−3.5 TCID50/0.1ml and SIV-H1N1 of 26 hemagglutination titer within 15-30 min, and inactivated S. aureus and E. coli vegetative cells (106/ml) within 15 or 60 min, respectively, but had little effect on B. subtilis spores. The bactericidal effect lasted at least 3 hours for bacteria on carrier plates and for 6 hours for airborne bacteria. Conclusions A practical subzero temperature disinfection technology was confirmed its efficacy in killing enveloped viruses and vegetative bacteria. It would help to meet the urgent public health need of environmental disinfection in frozen food logistics against pandemic and other potential pathogens and to enhance national and international biosecurity. Highlights First report of efficacy of disinfectant didecyl dimethyl ammonium bromide (DDAB) at subzero temperatures The customized thermal fogging machine makes fine droplets of DDAB-propylene glycol (PPG) fog which can suspend for ~4 hours at −20°C DDAB-PPG thermal fogging at −20°C effectively inactivated a coronavirus and an influenza virus DDAB-PPG thermal fogging at −20°C for effectively killed S. aureus and E. coli DDAB-PPG thermal fogging at −20°C inactivated airborne microorganism for up to 6 h