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Staphylococcus aureus may cause infections in humans from mild skin disorders to lethal pneumonia. Rapid and accurate monitoring of viable S. aureus is essential to characterize human exposure. This study evaluated quantitative PCR (qPCR) with propidium monoazide (PMA) to quantify S. aureus. The results showed comparable S. aureus counts between exclusively live cells and mixtures of live/dead cells by qPCR with 1.5 or 2.3 μg/mL PMA (P>.05), illustrating the ability of PMA-qPCR to detect DNA exclusively from viable cells. Moreover, qPCR with 1.5 or 2.3 μg/mL PMA performed optimally with linearity over 10 3 -10 8  CFU/mL (R 2 ≥0.9), whereas qPCR with 10, 23 or 46 μg/mL PMA significantly underestimated viable counts. Staphylococcus aureus and total viable bacteria were further determined with PMA-qPCR (1.5 μg/mL) from 48 samples from a public library and two university dormitories and four from outside. Viable bacteria averaged 1.9×10 4 cells/m 3 , and S. aureus were detected in 22 (42%) samples with a mean of 4.4×10 3 cells/m 3 . The number of S. aureus and viable bacteria were positively correlated (r=.61, P<.005), and percentages of S. aureus relative to viable bacteria averaged 12-44%. The results of field samples suggest that PMA-qPCR can be used to quantify viable S. aureus cells., (© 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Staphylococcus aureus has been detected indoors and is associated with human infection. Reliable quantification of S. aureus using a sampling technique followed by culture assay helps in assessing the risks of human exposure. The efficiency of five culture media and eight sampling methods in recovering S. aureus aerosols were evaluated. Methods to extract cells from filters were also studied. Tryptic soy agar (TSA) presented greater bacterial recovery than mannitol salt agar (MSA), CHROMagar staph aureus, Chapman stone medium, and Baird-Park agarose (P < 0.05). Moreover, 93 ± 2%-95 ± 2% and 42 ± 1%-49 ± 2% of S. aureus were, respectively, recovered by a 15-min heating of gelatin filters and 2-min vortex of polycarbonate (PC) filters. Evaluation of two filtration (IOM with gelatin filter and cassette with PC filter), two impaction (Andersen 1-STG loaded with TSA and MSA) and four impingement methods [AGI-30 and BioSampler filled with Tween mixture (TM) and phosphate-buffered saline (PBS)] revealed the BioSampler/TM performed best over 30 and 60 min of sampling (P < 0.05), while low recovery efficiencies were associated with the IOM/gelatin, cassette/PC, and AGI-30/PBS combinations (P < 0.05). In addition to BioSampler/TM, collecting S. aureus onto TSA from the Andersen 1-STG is also recommended, as it is the second best method at the 60-min sampling (P < 0.05)., (© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Staphylococcus aureus has been detected in indoor air and linked to human infection. Quantifying S. aureus by efficient sampling methods followed by appropriate sample storage treatments is essential to characterize the exposure risk of humans. This laboratory study evaluated the effects of sampler type (all-glass impinger (AGI-30), BioSampler, and Andersen one-stage sampler (Andersen 1-STG)), collection fluid (deionized water (DW), phosphate-buffered saline (PBS), and Tween mixture (TM)), and sampling time (3-60 min) on cell recovery. Effects of storage settings on bacterial concentration were also assessed over 48 h. Results showed BioSampler performed better than Andersen 1-STG and AGI-30 (P < 0.05) and TM was superior to PBS and DW (P < 0.05). An increase in sampling time negatively affected the recoveries of cells in PBS of BioSampler and AGI-30 (P < 0.05), whereas cell recoveries in TM were increased at sampling of 6-15 min compared with 3 min. Concentrations of cells collected in PBS were decreased with storage time at 4 and 23 °C (P < 0.05), while cells stored in TM showed stable concentrations at 4 °C (P > 0.05) and increased cell counts at 23 °C (P < 0.05). Overall, sampling by BioSampler with TM followed by sample transportation and storage at 4 °C is recommended., (© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Unlabelled: Staphylococcus aureus, Pseudomonas aeruginosa, and Legionella pneumophila have been detected in indoor air and linked to human infection. It is essential to adopt control methods to inactivate airborne pathogens. By passing bioaerosols horizontally into a UV device at two flow rates (Qs) and moving cells around a central UVC lamp at relative humidity (RH) of 12.7-16.7%, 58.7-59.6%, and 87.3-90%, the effects of swirling motion and 254-nm ultraviolet germicidal irradiation (UVGI) against bioaerosols were assessed under UV-off and UV-on settings, respectively. An inverse relationship between RH and UVGI effectiveness was observed for every test bioaerosol (r = -0.74 ∼ -0.81, P < 0.0001). Increased UV resistance with RH is likely associated with the hygroscopicity of bioaerosols, evident by increased aerodynamic diameters at high RH (P < 0.05). UVGI effectiveness was significantly increased with decreasing Q (P < 0.0001). Moreover, P. aeruginosa was the most susceptible to UVGI, while the greatest UV resistance occurred in L. pneumophila at low RH and S. aureus at medium and high RH (P < 0.05). Results of UV off show P. aeruginosa and L. pneumophila were more sensitive to air-swirling motion than S. aureus (P < 0.05). Overall, test bioaerosols were reduced by 1.7-4.9 and 0.2-1.7 log units because of the UVGI and swirling movement, respectively., Practical Implications: The studied UV device, with a combination of swirling motion and UVGI, is effective to inactivate airborne S. aureus, P. aeruginosa, and L. pneumophila. This study also explores the factors governing the UVGI and swirling motion against infectious bioaerosols. With understanding the environmental and operational parameters, the studied UV device has the potential to be installed indoors where people are simultaneously present, for example, hospital wards and nursing homes, to prevent the humans from acquiring infectious diseases., (© 2012 John Wiley & Sons A/S.)