Zhanbo Wen

Impact of relative humidity and collection media on mycobacteriophage D29 aerosol.

ABSTRACT This study was conducted to evaluate the effect of aerosol generation, methods of sampling, storage conditions, and relative humidity on the culturability of the mycobacteriophage D29. The lytic phage D29 can kill Mycobacterium tuberculosis, and the phage aerosol can be treated as a potential tool for tuberculosis treatment. The culturability of D29 was tested using a test chamber designed for the bioaerosols research against three spray liquids (deionized water, phosphate-buffered saline [PBS], and normal saline), four collection media (suspension medium [SM], nutrient broth, PBS, and deionized water), two sampling systems (the all-glass impinger AGI-30 and the Biosampler) and across a range of humidities (20 to 90%). The effect of storage conditions on the culturability of collected sample was also evaluated for the AGI-30 impinger. The results proved that viable phage D29 particles generated by deionized water were approximately 30- and 300-fold higher than PBS and normal saline, respectively. As collection media, SM buffer and nutrient broth were observed to yield a higher number of plaques compared to PBS and deionized water. No difference was observed in collection efficiency between AGI-30 and Biosampler with two detection methods (culture-based technique and real-time PCR). The culturability of collected D29 in SM buffer or nutrient broth can be maintained up to 12 h irrespective of storage temperature. Relative humidity was found to strongly influence airborne D29 culturability which is 2- to 20-fold higher in low humidity (25%) than medium (55%) or high (85%) humidity. This research will help identify the optimal means for the application of D29 aerosol in animal inhalation experiments.

Purification and concentration of mycobacteriophage D29 using monolithic chromatographic columns

Bacteriophages are used widely in many fields, and phages with high purity and infectivity are required. Convective interaction media (CIM) methacrylate monoliths were used for the purification of mycobacteriophage D29. The lytic phages D29 from bacterial lysate were purified primarily by polyethylene glycol 8000 or ammonium sulphate, and then the resulting phages were passed through the CIM monolithic columns for further purification. After the whole purification process, more than 99% of the total proteins were removed irrespective which primary purification method was used. The total recovery rates of viable phages were around 10-30%. Comparable results were obtained when the purification method was scaled-up from a 0.34 mL CIM DEAE (diethylamine) monolithic disk to an 8 mL CIM DEAE monolithic column.

Effects of different sampling solutions on the survival of bacteriophages in bubbling aeration

The present study focuses on the effects of three different sampling solutions, namely distilled water, phosphatic buffer solution, and suspension medium (SM), adding antifoam or not, on the survival probability of several different bacteriophages (EcP1,PhiX174,SM702, and F2) as surrogates for the mammalian viruses in the bubbling process. AGI-10 impinger was used as the representative for all the impingers which would bubble during operation. It was found that the survival probability of the same bacteriophage bubbling with different sampling solutions was different except that there was no significant difference observed for the bacteriophage F2. The use of SM as the collection fluid was relative to a high survival probability for the four bacteriophages. And the endurance or resistance of different kinds of bacteriophages in the same sampling solution was different. We conclude that SM is a promising sampling solution for liquid impingers in the process of sampling phages.

Study on the Testing Method to Determine the Performance of Personal Respiratory Protection Equipment against a Viral Aerosol

Respiratory illnesses are increasingly recognized as a growing concern for healthcare workers (HCWs) and patients. The 2003 hospital-based outbreak of Severe Acute Respiratory Syndrome (SARS) has once again highlighted the vulnerability of HCWs to aerosol-transmitted viral infections. Personal respiratory protective equipment was one of the key means for the HCWs to avoid nosocomial transmission of the virus. This article studied a testing method for determining the performance of personal respiratory protection equipment against a viral aerosol. Full-mask respirators with HEPA filters were selected for this study. Phage f2 was used as a surrogate for a viral pathogen. A viral aerosol was generated and then sampled in front of and behind the test respirators, allowing a percentage efficiency value to be calculated against viral aerosols. HEPA-filtered respirators demonstrated a high filtration efficiency of >99.99% and can protect the wearers against the viral aerosol transmission. This test methodology can be used to assess the filtration efficacy of personal respiratory protection equipment against a viral aerosol.

Assessment of the risk of infectious aerosols leaking to the environment from BSL-3 laboratory HEPA air filtration systems using model bacterial aerosols

Abstract To assess the risk of infectious bacterial aerosols leaking to the environment, the filtration efficiency of a biosafety level 3 (BSL-3) laboratory high-efficiency particulate (HEPA) filter was investigated using the aerosolized bacteria Serratia marcescens. The aerosol size was measured using an Andersen sampler. Eight first stage HEPA filters (numbered 1–8) were distributed in contaminated labs and exhausts from each of the first stage HEPA filters were aggregated and filtered through one second stage HEPA filter before being released to the environment. In total, 8 first-stage and 1 second-stage HEPA filters from the BSL-3 air purification system were analyzed. No S. marcescens was detected in first stage filters 1, 2, 4, 5, 7 and 8 and the second stage HEPA filter. The filtration efficiencies against aerosolized S. marcescens were >99.9999%. First stage filter numbers 3 and 6 had filtration efficiencies of 99.9825% and 99.9906%, respectively. When filter number 3 was replaced by a new filter and the bracket for filter number 6 was sealed, no aerosolized S. marcescens was detected in the filtered air. Our work suggests that the BSL-3 laboratory HEPA filter air purification system is effective against bacterial aerosols, with little to no bacterial leakage into the environment.