Optimization of a Portable Adenosine Triphosphate Bioluminescence Assay Coupled with a Receiver Operating Characteristic Model to Assess Bioaerosol Concentrations on Site.

Kai-Chih Chang,Yi-Chian Lu,Chun-Chieh Tseng,Chien-Che Hung

doi:10.3390/microorganisms8070975

Abstract

Rapid monitoring of the microbial content in indoor air is an important issue. In this study, we develop a method for applying a Coriolis sampler coupled with a portable ATP luminometer for characterization of the collection efficiency of bioaerosol samplers and then test this approach in field applications. The biological collection efficiencies of the Coriolis sampler and a BioSampler for collecting four different types of bioaerosols, including Escherichia coli, Staphylococcus aureus, Candida famata and endospores of Bacillus subtilis, were compared in a chamber study. The results showed that the ATP assay may indicate the four microbes’ viability, and that their defined viabilities were positively correlated with their culturability. In addition, the optimal sampling conditions of the Coriolis sampler were a 200 L/min flow rate and a sampling time of 30 min. Under these conditions, there was no significant difference in sampling performance between the BioSampler and Coriolis sampler. In field applications, the best ATP benchmark that corresponded to culturable levels of < 500 CFU/m3 was 287 RLUs (sensitivity: 100%; specificity: 80%) for bacteria and 370 RLUs (sensitivity: 79%; specificity: 82%) for fungi according to receiver operating characteristic curve analysis. Consequently, an ATP criterion is recommended for indicating whether the corresponding airborne culturable concentrations of microbes meet those of published guidelines.

Highlights

The many different microbes in indoor air are referred to as bioaerosols and may pose health threats to humans by inhalation [1]
In all six sampling locations, aerosol samples were collected in triplicate using the Coriolis sampler because our preliminary study demonstrated that the Coriolis sampler had no significant difference in collecting performance from the BioSampler under specific sampling conditions
A high sampling flow rate may decrease the viability of bioaerosols [37], our results demonstrated that the mechanical stress caused by impaction and washing steps has a limited effect on the recovered adenosine triphosphate (ATP) of bioaerosols

Summary

Introduction

The many different microbes in indoor air are referred to as bioaerosols and may pose health threats to humans by inhalation [1]. To prevent the transmission of bioaerosols, efficient methods for their rapidly detection are urgently required. Culture assays are the most widely used method for bioaerosol detection. Most microbes in the viable but nonculturable (VBNC) stage cannot be detected by culture methods [3]. To overcome the disadvantages of culture-based methods, several nonculture approaches, such as epifluorescence microscopy, flow cytometry, PCR, and NanoGene assays, have already been applied to bioaerosol detection [4,5,6,7,8]. Some nucleic acid assays with high sensitivity and specificity can provide quick results but may not provide the viability of bioaerosols unless the method has been modified [8,9]

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Conclusion