Abstract

Viable bacteria and Staphylococcus aureus in air have been linked to human diseases and considered as the threats in occupational health. Rapidly and accurately monitoring these bioaerosols by a reliable method is essential in characterising human exposure and health risk. This study first evaluated quantitative PCR (qPCR) with propidium monoazide (PMA) of 1.5–46 µg/mL to exclusively quantify viable S. aureus of 3–8 log CFU/mL. Results showed qPCR with 1.5 and 2.3 µg/mL PMA performed optimal with a great linearity over six orders of magnitude (R² ≥0.9). Viable bacteria and S. aureus were further determined with PMA-qPCR for air samples collected from places including cafeteria, kitchen, food waste recycling site and public library. Viable bacteria averaged 1.9×10⁴ cells/m³ ranging from 4.7×10² to 1.2×10⁵ cells/m³. S. aureus were detected in 42.3% of samples for which cell levels varied between 4.2×10¹ and 2.8×10⁴ cells/m³. Concentrations of S. aureus and viable bacteria were positively correlated (r=0.61, p<0.005) and the percentages of S. aureus among viable bacteria averaged 22.7% with 11.6%–43.6% in various locations. With the PMA-qPCR technique, this study demonstrates that the abundance of viable S. aureus and total viable bacterial aerosols in various types of occupational fields can be simultaneously quantified. This molecular assay should be taken into account as it will assist occupational hygienists and epidemiologists obtain reliable exposure data in assessing exposure and health risk, managing occupational health and protecting people from biohazards.