Sampling port for real-time analysis of bioaerosol in whole body exposure system for animal aerosol model development

Abstract

Introduction Multiple factors influence the viability of aerosolized bacteria. The delivery of aerosols is affected by chamber conditions (humidity, temperature, and pressure) and bioaerosol characteristics (particle number, particle size distribution, and viable aerosol concentration). Measurement of viable aerosol concentration and particle size is essential to optimize viability and lung delivery. The Madison chamber is widely used to expose small animals to infectious aerosols. Methods A multiplex sampling port was added to the Madison chamber to measure the chamber conditions and bioaerosol characteristics. Aerosols of three pathogens (Bacillus anthracis, Yersinia pestis, and Mycobacterium tuberculosis) were generated under constant conditions and their bioaerosol characteristics were analyzed. Airborne microbes were captured using an impinger or BioSampler. The particle size distribution of airborne microbes was determined using an aerodynamic particle sizer (APS). Viable aerosol concentration, spray factor (viable aerosol concentration/inoculum concentration), and dose presented to the mouse were calculated. Dose retention efficiency and viable aerosol retention rate were calculated from the sampler titers to determine the efficiency of microbe retention in lungs of mice. Results B. anthracis, Y. pestis, and M. tuberculosis aerosols were sampled through the port. The count mean aerodynamic sizes were 0.98, 0.77, and 0.78 μm with geometric standard deviations of 1.60, 1.90, and 2.37, and viable aerosol concentrations in the chamber were 211, 57, and 1 colony-forming unit (CFU)/mL, respectively. Based on the aerosol concentrations, the doses presented to mice for the three pathogens were 2.5e5, 2.2e4 and 464 CFU. Discussion Using the multiplex sampling port we determined whether the animals were challenged with an optimum bioaerosol based on dose presented and respirable particle size.

Ultra-low dose of Mycobacterium tuberculosis aerosol creates partial infection in mice

“…Using the stochastic assumption, the ID50 of 1.9 CFU correlates with an infectious quantum of 2.8 CFU presented dose. Since only a portion of the presented dose is delivered to the lungs (18), these data are consistent with an infectious quantum of a single CFU. Mycobacteria aggregate in growth media, so one MTB CFU in our aerosol may correspond to multiple bacteria.…”

“…A whole-body Madison exposure chamber connected to a Class III biological safety cabinet was used for aerosol challenges (18). Aerosol was generated using a 6-jet Collision nebulizer (CN25, BGI Inc.).…”

“…The chamber has been validated to disperse particles of consistent size and concentration. We have previously demonstrated reproducible pulmonary delivery among mice using this chamber (18). …”

“…At these low doses, sentinel necropsy does not provide a reliable estimate of the retained dose. Instead, we measured the presented dose using Guyton’s formula to estimate the minute ventilatory volume of the mice and a BioSampler to measure the viable aerosol concentration (18). …”

Impact of Surfactant Protein D, Interleukin-5, and Eosinophilia on Cryptococcosis

“…They were then kept in hermetically sealed cages. The aerosol concentration of C. neoformans was measured via a BioSampler (SKC Incorporated) attached to the Madison chamber as previously described (18).…”