A Review on Airborne Microbes: The Characteristics of Sources, Pathogenicity and Geography

Microbes are widespread and have been much more studied in recent years. In this review, we describe detailed information on airborne microbes that commonly originate from soil and water through liquid–air and soil–air interface. The common bacteria and fungi in the atmosphere are the phyla of Firmicutes, Proteobacteria, Bacteroides, Actinobacteria, Cyanobacteria and Ascomycota, Basidiomycota, Chytridiomycota, Rozellomycota that include most pathogens leading to several health problems. In addition, the stability of microbial community structure in bioaerosols could be affected by many factors and some special weather conditions like dust events even can transport foreign pathogens to other regions, affecting human health. Such environments are common for a particular place and affect the nature and interaction of airborne microbes with them. For instance, meteorological factors, haze and foggy days greatly influence the concentration and abundance of airborne microbes. However, as microorganisms in the atmosphere are attached on particulate matters (PM), the high concentration of chemical pollutants in PM tends to restrain the growth of microbes, especially gathering atmospheric pollutants in heavy haze days. Moreover, moderate haze concentration and/or common chemical components could provide suitable microenvironments and nutrition for airborne microorganism survival. In summary, the study reviews much information and characteristics of airborne microbes for further study.

Hand Sanitizers: A Review on Formulation Aspects, Adverse Effects, and Regulations

Hand hygiene is of utmost importance as it may be contaminated easily from direct contact with airborne microorganism droplets from coughs and sneezes. Particularly in situations like pandemic outbreak, it is crucial to interrupt the transmission chain of the virus by the practice of proper hand sanitization. It can be achieved with contact isolation and strict infection control tool like maintaining good hand hygiene in hospital settings and in public. The success of the hand sanitization solely depends on the use of effective hand disinfecting agents formulated in various types and forms such as antimicrobial soaps, water-based or alcohol-based hand sanitizer, with the latter being widely used in hospital settings. To date, most of the effective hand sanitizer products are alcohol-based formulations containing 62%–95% of alcohol as it can denature the proteins of microbes and the ability to inactivate viruses. This systematic review correlated with the data available in Pubmed, and it will investigate the range of available hand sanitizers and their effectiveness as well as the formulation aspects, adverse effects, and recommendations to enhance the formulation efficiency and safety. Further, this article highlights the efficacy of alcohol-based hand sanitizer against the coronavirus.

Exposure to Bacterial and Fungal Aerosols: Microorganism Indices in A Waste-Sorting Plant in Poland

An increased understanding of airborne microorganism populations should enable a better interpretation of bioaerosol exposure found in a working environment. An assessment of the contamination levels of mesophilic bacterial aerosol (MBA) and fungal aerosol (FA) was carried out using two evaluation indices for microbiological pollution—the total index of microbiological contamination per cubic meter (TIMC/m3) and the indoor–outdoor index (IOI). An advantage of selected indices is the inclusion of several co-existing factors that have an impact on the formation of bioaerosol. When properly used, they also highlight the low efficiency of the ventilation system caused by an insufficient air exchange. In this study, the microbial air quality (MAQ) of the working environment was assessed during the spring season at a sorting plant located in Southern Poland. Sampling was undertaken in the plant using an Andersen six-stage impactor which allows the obtainment of information about the size distribution of the air microflora. The value of average concentrations of MBA and the average concentration of FA collected in the preliminary cabin of the sorting plant (PCSP) and the cleaning cabin of the sorting plant (CCSP) were analyzed. The obtained values of MBA were 1.6 times higher indoors, compared to outdoors, while FA was 1.7 times higher outdoors than indoors. The maximum TIMC/m3 value was obtained in PCSP (2626). The calculated IOI in this study suggests that MBA concentrations are influenced by internal sources, as opposed to FA. The purpose of this work was to present the usefulness of using indices in assessing air quality.

Application of Airborne Microorganism Indexes in Offices, Gyms, and Libraries

The determination of microbiological air quality in sporting and working environments requires the quantification of airborne microbial contamination. The number and types of microorganisms, detected in a specific site, offer a useful index for air quality valuation. An assessment of contamination levels was carried out using three evaluation indices for microbiological pollution: the global index of microbiological contamination per cubic meter (GIMC/m3), the index of mesophilic bacterial contamination (IMC), and the amplification index (AI). These indices have the advantage of considering several concomitant factors in the formation of a microbial aerosol. They may also detect the malfunction of an air treatment system due to the increase of microbes in aeraulic ducts, or inside a building compared to the outdoor environment. In addition, they highlight the low efficiency of a ventilation system due to the excessive number of people inside a building or to insufficient air renewal. This study quantified the levels of microorganisms present in the air in different places such as offices, gyms, and libraries. The air contamination was always higher in gyms that in the other places. All examined environments are in Northern Italy.

Ice nucleators, bacterial cells and <i>Pseudomonas syringae</i> in precipitation at Jungfraujoch

Ice nucleation is a means by which the deposition of an airborne microorganism can be accelerated under favourable meteorological conditions. Analysis of 56 snow samples collected at the high-altitude observatory Jungfraujoch (3580 m a.s.l.) revealed an order-of-magnitude-larger dynamic range of ice-nucleating particles active at −8 °C (INPs−8) compared to the total number of bacterial cells (of which on average 60 % was alive). This indicates a shorter atmospheric residence time for INPs−8. Furthermore, concentrations of INPs−8 decreased much faster, with an increasing fraction of water precipitated from the air mass prior to sampling, than the number of total bacterial cells. Nevertheless, at high wind speeds (> 50 km h−1) the ratio of INPs−8 to total bacterial cells largely remained in a range between 10−2 and 10−3, independent of prior precipitation, likely because of recent injections of particles in regions upwind. Based on our field observations, we conclude that ice nucleators travel shorter legs of distance with the atmospheric water cycle than the majority of bacterial cells. A prominent ice-nucleating bacterium, Pseudomonas syringae, has been previously supposed to benefit from this behaviour as a means to spread via the atmosphere and to colonise new host plants. Therefore, we targeted this bacterium with a selective cultivation approach. P. syringae was successfully isolated for the first time at such an altitude in 3 of 13 samples analysed. Colony-forming units of this species constituted a minor fraction (10−4) of the numbers of INPs−8 in these samples. Overall, our findings expand the geographic range of habitats where this bacterium has been found and corroborate theories on its robustness in the atmosphere and its propensity to spread to colonise new habitats.

Ice nucleators have shorter persistence in the atmosphere than other airborne bacteria

Ice nucleation is a means by which the deposition of an airborne microorganism can be accelerated under favourable meteorological conditions. Analysis of 56 snow samples collected at the high altitude observatory Jungfraujoch (3580 m a.s.l.) revealed an order of magnitude larger dynamic range of ice nucleating particles active at −8 °C (INPs−8) compared to the total number of bacterial cells (60 % was on average living). This indicates a shorter atmospheric residence time for INPs−8. Furthermore, concentrations of INPs-8 decreased much faster, with an increasing fraction of water precipitated from the air mass prior to sampling, than the number of total bacterial cells. Nevertheless, at high wind speeds (> 50 km h−1) the ratio of INPs−8 to total bacterial cells largely remained in a range between 10−2 to 10−3, independent of prior precipitation, perhaps because of recent injections of particles in regions upwind. Based on our field observations, we conclude that ice nucleators travel shorter legs of distance with the atmospheric water cycle than the majority of bacterial cells. Pseudomonas syringae, a prominent ice nucleating bacterium, was successfully isolated from 3 of 13 samples analysed. Colony forming units of this species constituted a minor fraction (10−4) of the numbers of INPs−8 in these samples. Overall, our findings expand the geographic range of habitats where this bacterium has been found and corroborates theories on its robustness in the atmosphere and its propensity to spread and to colonise new plants.

The Evaluation of Indoor Microbial Air Quality in Two New Commissioning Higher Educational Buildings in Johor, Malaysia

The proliferation of indoor airborne microorganism in public institutional buildings such as schools and universities is often regarded as a potential health hazards to the buildings’ users. This issue is not new in Malaysia, a country with humid climate which favours the growth of microorganism. However, there is lack of research’s data, especially in higher institutional buildings in this country. The assessment of the indoor air quality is conducted in a university’s two new commissioning buildings located at Southern Peninsular of Malaysia. Both buildings utilized centralized air conditioning system. Concentrations of airborne microorganism were determined using a single-stage impacter (biosampler) as per requirement of National Institute of Occupational Safety and Health (NIOSH) Manual Analytical Method 0800. The acquired readings were compared to the standard level determined in Industry Code of Practice on Indoor Air Quality (ICOP IAQ) 2010. Other parameters such as relative humidity, temperature, and air velocity were recorded along the assessment. The mean concentrations of the total bacteria at the affected area of the two buildings are 1102.5 CFU/m3 and 813 CFU/m3 respectively and it is significantly higher compared to the maximum exposure limit of 500 CFU/m3. While, the mean concentration of total fungi at the affected area for two buildings are 805.7 CFU/m3 and 509 CFU/m3 respectively which are both higher than the reading of outdoors and unaffected indoor area although slightly lower than the maximum exposure limit of 1000 CFU/m3. This study provides a glance of the poor indoor microbiological air quality in new higher institutional buildings in this humid region.