Long-term viable bioaerosol sampling using a temperature- and humidity-controlled filtration apparatus, a laboratory investigation using culturable E. coli.

Abstract

2017) Longterm viable bioaerosol sampling using a temperature-and humidity-controlled filtration apparatus, a laboratory investigation using culturable E.coli., Aerosol Science and Technology, 51:5, 576-586, ABSTRACT Sampling for culturable (e.g., viable) aerosolized microbes (bioaerosols) is a useful means to provide information for public health monitoring and studies. However, it is challenging to maintain microbe culturability when sampling at high flow rates (>12 L/min) and extended periods of time (4 h). We developed a first-generation, viable bioaerosol collection system (VBCS) utilizing temperature (T) and relative humidity (RH)-conditioned filtration at a flow rate of 25 L/min. A twostage system of tube-in-shell Nafion TM exchange units provides cooling to 10 C and RH conditioning to 80-95%. Aerosol particles are collected on a polyurethane nanofiber filter providing a physical collection efficiency of >95% for sizes 0.06-10 mm. The T and RH conditions at the collection filter are maintained, despite changes to ambient conditions. The initial testing of the VBCS was done under indoor, laboratory conditions with aerosolized, vegetative E. coli. A scenario of a 30-min challenge of bioaerosol followed by continued sampling of clean air for various times was used to judge culturability maintenance under extended-term sampling. An initial loss of culturability upon collection onto the filter was observed; 23 § 13% relative to 4-mm all-glass impinger. However once collected, 98% of culturability was maintained for an additional 4.5 h of sampling. An exponential decay in culturability was observed from 8 h to 15 h of sampling. Also, 24h cold storage of the filters collected was studied. The VBCS is based on the use of dry filter cassettes, needs minimal maintenance, and preserves culturability of vegetative bacteria for >4 h. EDITOR Tiina Reponen

Airborne contamination in the food industry: An update on monitoring and disinfection techniques of air

“…In addition, during air sampling, different environmental parameters can cumulatively stress microorganisms affecting (through desiccation) their viability. In long-term (> 30 min) sampling of bioaerosols, especially for vegetative bacteria, the combination of controlled humidity and refrigerated temperature of air sampler should provide viability maintenance (Walls et al, 2017). The literature provides little information on the causative variables that lead to differing colony recoveries (Wirtanen et al, 2002).…”

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“…; Walls et al . ). Relatively better collection efficiencies were achieved by these modified samplers compared with traditional ones, especially under extreme conditions (dry or cold conditions), as extreme sampling environments can lead to the inactivation of the micro‐organisms.…”

“…Walls et al . () designed a temperature and RH‐conditioned filtration process, although it has only been tested for bacteria, wherein their polyurethane nanofibre filter could be used for as long as 5 h of sampling without affecting the viability of Escherichia coli . Similarly, Springorum et al .…”

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“…All experimental conditions should be recorded accurately. 41 This is important as cellular stress and dissipation rates rise with decreases in RH and increases in temperature. 39 When measuring contamination of a ventilation system, louvers are preferable for sample collection.…”

“…For exposure-related studies, samples should be collected from inhabited areas. All experimental conditions should be recorded accurately . This is important as cellular stress and dissipation rates rise with decreases in RH and increases in temperature …”