simple and effective aerosol pathogen disinfection test for a flowing air disinfector

Aerosol transmission is an important disease transmission route and has been especially pertinent to hospital and biosafety laboratories during the SARS-CoV-2 pandemic.The thermal resistance of airborne SARS-CoV-2 is lower than that of Bacillus subtilis spores,which are often used to test the effectiveness of SARS-CoV-2 and other pathogen disinfection methods.Herein,we propose a new method to test the disinfection ability of a flowing air disinfector(a digital electromagnetic induction air heater)using B.subtilis spores.The study provides an alternative air disinfection test method.The new test system combined an aerosol generator and a respiratory filter designed in-house and could effectively recover spores on the filter membrane at the air outlet after passing through the flowing air disinfector.The total number of bacterial spores used in the test was within the range of 5×10^(5)–5×10^(6)colony-forming units(CFUs)specified in the technical standard for disinfection.The calculation was based on the calculation method in Air Disinfection Effect Appraisal Test in Technical Standard for Disinfection(2002 Edition).At an air speed of 3.5 m/s,we used a digital electromagnetic induction air heater to disinfect flowing air containing 4.100×10^(6)CFUs of B.subtilis spores and determined that the minimum disinfection temperature was 350℃for a killing rate of 99.99%.At 400℃,additional experiments using higher spore concentrations(4.700×10^(6)±1.871×10^(5)CFU)and a higher airspeed(4 m/s)showed that the killing rate remained>99.99%.B.subtilis spores,as a biological indicator for testing the efficiency of dry-heat sterilization,were killed by the high temperatures used in this system.The proposed method used to test the flowing air disinfector is simple,stable,and effective.This study provides a reference for the development of test systems that can assess the disinfection ability of flowing air disinfectors.

Micro-droplet Digital Polymerase Chain Reaction and Real-Time Quantitative Polymerase Chain Reaction Technologies Provide Highly Sensitive and Accurate Detection of Zika Virus

The establishment of highly sensitive diagnostic methods is critical in the early diagnosis and control of Zika virus(ZIKV)and in preventing serious neurological complications of ZIKV infection. In this study, we established micro-droplet digital polymerase chain reaction(ddPCR) and real-time quantitative PCR(RT-qPCR) protocols for the detection of ZIKV based on the amplification of the NS5 gene. For the ZIKV standard plasmid, the RT-qPCR results showed that the cycle threshold(Ct) value was linear from 10~1 to 10~8 copy/l L, with a standard curve R^2 of 0.999 and amplification efficiency of 92.203%;however, a concentration as low as 1 copy/l L could not be detected. In comparison with RT-qPCR, the dd PCR method resulted in a linear range of 10~1–10~4 copy/l L and was able to detect concentrations as low as 1 copy/l L. Thus, for detecting ZIKV from clinical samples, RT-qPCR is a better choice for high-concentration samples(above 10~1 copy/l L),while ddPCR has excellent accuracy and sensitivity for low-concentration samples. These results indicate that the ddPCR method should be of considerable use in the early diagnosis, laboratory study, and monitoring of ZIKV.