Current Scenario and Challenges in the Direct Identification of Microorganisms Using MALDI TOF MS

MALDI TOF MS-based microbial identification significantly lowers the operational costs because of minimal requirements of substrates and reagents for extraction. Therefore, it has been widely used in varied applications such as clinical, food, military, and ecological research. However, the MALDI TOF MS method is laced with many challenges including its limitation of the reference spectrum. This review briefly introduces the background of MALDI TOF MS technology, including sample preparation and workflow. We have primarily discussed the application of MALDI TOF MS in the identification of microorganisms. Furthermore, we have discussed the current trends for bioaerosol detection using MALDI TOF MS and the limitations and challenges involved, and finally the approaches to overcome these challenges.

Performance of Two Different Techniques to Concentrate Samples for Bioaerosol Quantification

We evaluated two concentrating techniques that could be used to improve bioaerosol detection and quantification: A BioChromato Smart Evaporator C1 (BioChromato, Inc.) and two Concentrating Pipette (CP) models (CP-150 and CP-Select) (InnovaPrep, LLC). We determined the concentration factor (CF) (the concentration of particles in the final solution compared to the concentration in the initial solution) and the particle losses when processing the samples with polystyrene latex (PSL) beads and different species of bacteria. When processing total particles, regardless of the culturability status, the losses for the Evaporator were 3.70–23.89%; for the CP-models, the losses ranged from 0.20% to 67.22%. For the culturable particles processed with the CP devices, the losses ranged from 42.85% to 90.19% and were higher for Gram-negative pseudomonads compared to Gram-positive B. subtilis. Despite the loss of particles, both devices yielded more concentrated final solutions. The CF for the Evaporator was 3.59–10.92; the CF values for the CP devices ranged from 55.77 to 184.64 for total particles and from 6.29 to 96.52 for culturable bacteria. This higher CF was mainly achieved due to lower final suspension volumes. The study demonstrated that the two concentrators can improve particle detection, but that one should take particle losses into account.

Klarite as a label-free SERS-based assay: a promising approach for atmospheric bioaerosol detection

We present a SERS-based Klarite interface for the rapid and culture-free detection and quantification of atmospheric bioaerosols in the real-world environment.

A Controlled Study on the Characterisation of Bioaerosols Emissions from Compost

Bioaerosol emissions arising from biowaste treatment are an issue of public concern. To better characterise the bioaerosols, and to assess a range of measurement methods, we aerosolised green waste compost under controlled conditions. Viable and non-viable Andersen samplers, cyclone samplers and a real time bioaerosol detection system (Spectral Intensity Bioaerosol Sensor (SIBS)) were deployed simultaneously. The number-weighted fraction of fluorescent particles was in the range 22–26% of all particles for low and high emission scenarios. Overall fluorescence spectral profiles seen by the SIBS exhibited several peaks across the 16 wavelength bands from 298 to 735 nm. The size-fractionated endotoxin profile showed most endotoxin resided in the 2.1–9 μm aerodynamic diameter fraction, though up to 27% was found in a finer size fraction. A range of microorganisms were detected through culture, Matrix Assisted Laser Desorption and Ionisation Time of Flight Mass Spectrometry (MALDI-TOF) and quantitative polymerase chain reaction (qPCR), including Legionella pneumophila serogroup 1. These findings contribute to our knowledge of the physico-chemical and biological characteristics of bioaerosols from composting sites, as well as informing future monitoring approaches and data interpretation for bioaerosol measurement.