Contemporary near-real-time bioaerosol identifiers that read labeled DNA require a minimum DNA length of about 500,000 base pairs; and for critical applications, instrumental identification results must be verified through the use of classical microbiological culturing techniques. A 300 L/min Wetted Wall Cyclone (WWC) and an 800 L/min inertial impactor were used in a comparative study to collect aerosolized single cells of Escherichia coli (E. coli) at temperatures of 24°C and 46°C. Classical microbiological plating techniques showed that the culturability of E. coli collected with a WWC is a factor of about 100 higher than that of the impactor when the sampled aerosol is at room temperature (RT) and a factor of about 4000 higher when the sampled aerosol is at 46°C. DNA integrity was qualitatively evaluated with pulsed field gel electrophoresis (PFGE) and photographic evidence shows a significant difference in the amount of high molecular weight DNA (molecules larger than 500,000 base pairs) collected with the WWC compared with the impactor. Extracted DNA was also digested by the NotI enzyme, and the qualitative results of the restriction analysis showed there to be high integrity of the WWC-collected DNA, whereas the impactor-collected DNA showed considerable fragmentation. Real-Time polymerase chain reaction (RT-PCR) showed samples required for E. coli identification need to be about 100 times more concentrated if they are collected with the impactor rather than that of the WWC. Also, it appears that only the intact genomic DNA of the culturable cells provides adequate templates for traditional and RT-PCR amplification. Copyright 2012 American Association for Aerosol Research

In recent years, much attention has been drawn to the exposure to bioaerosols in both occupational and indoor environments due to adverse effects on human health. Exposure to these agents may cause infectious diseases, allergic diseases, acute toxic effects, respiratory diseases, neurological effects, and cancer. Bioaerosols play a significant role in air quality studies, as well as in industrial and agricultural regulations. There is a diversity of sources for bioaerosol exposures, which include occupational activities such as waste disposal, sorting and composting, agricultural and food processing, livestock production and handling, healthcare, and fungal growth following flooding. Bioaerosol monitoring includes the measurement of viable (culturable and nonculturable) and nonviable microorganisms in both indoor and outdoor environments. The development of standardized methods for the detection and quantitation of bioaerosols has become an important issue. Technologies, including microbial plating, physical-chemical assays, and molecular techniques, have been adapted for the assessment of collected bioaerosol particles. In this review, we will discuss traditional and modern assays that have been applied in bioaerosol enumeration based on culturability, optical properties, immunoreactions, and nucleic acid amplification and sequencing of biological particles. The analysis of additional characteristics of bioaerosols including microbiome and antimicrobial resistance is also discussed. Finally, concluding thoughts are offered regarding the challenges and perspectives in the field. Copyright © 2020 American Association for Aerosol Research

While antibiotic resistance poses a threat from both Gram-positive bacteria (GPB) and Gram-negative bacteria (GNB), GNB pose a more imminent public health hazard globally. GNB are a threat to growing antibiotic resistance because of the complex makeup of the membrane. The AcrAB-TolC efflux pump is a known resistance mechanism of Escherichia coli (E. coli) cells. This study utilized molecular dynamics modeling to visualize some of the changes occurring at a molecular level when airborne bacteria are exposed to stress and antibiotics. This study was conducted to build upon previous experimental research showing that there is an increase in antibiotic resistance and efflux pump activity when exposed to aerosolization. AcrB and AcrAB-TolC proteins were simulated under standard and increased pressure to compare the effect of aerosolization on the binding to the three different antibiotics (puromycin (PUY), ampicillin (AMP) and sulfamethoxazole-trimethoprim (SXT)) to the AcrB binding site. Analysis such as root-mean-square deviation of atomic positions and root-mean-square fluctuation, the opening of TolC, and the significant molecular mechanics with generalized Born and surface area solvation (MM-GBSA) scores associated with specific ligands were recorded. Resistance in experimental data indicated a relationship between the docking scores and some ligand–protein interactions. Results showed that there was more flexibility in the proteins within simulations conducted under standard pressure for the AcrB protein and the full tripartite complex AcrAB-TolC, showing that increased pressure causes more rigidity. MM-GBSA scores, used to calculate the free energy of ligand–protein binding, did not show a significant change, but interestingly, the strongest MM-GBSA scores were for ligands that moved to another binding pocket and did not result in resistance or opening of the efflux pump. However, the ligand moved from the binding site and did not cause the opening of TolC to increase significantly, whereas PUY and AMP were bound to the binding site for the duration of all simulations. AMP ligands under increased pressure showed the largest change in opening of the TolC efflux pump and aligns with experimental data showing E. coli cells had the most resistance to AMP after aerosolization. These results, in addition to other real-time changes such as OM proteins and mutations of targets within the cell, could be used to delineate and mitigate antibiotic resistance mechanisms.