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Microbial Exposure Assessments in Different Occupational and Indoor Settings

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A special issue of Microorganisms (ISSN 2076-2607). This special issue belongs to the section "Environmental Microbiology".

Deadline for manuscript submissions: closed (15 October 2023) | Viewed by 12032

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Prof. Dr. Carla Viegas

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1. H & TRC—Health & Technology Research Center, ESTeSL—Escola Superior de Tecnologia e Saúde, Instituto Politécnico de Lisboa, 1990-096 Lisbon, Portugal
2. Public Health Research Centre, NOVA National School of Public Health, Universidade NOVA de Lisboa, 1099-085 Lisbon, Portugal
3. Comprehensive Health Research Center (CHRC), NOVA Medical School, Universidade NOVA de Lisboa, 1169-056 Lisbon, Portugal
Interests: fungal occupational exposure; indoor air quality; aspergillus epidemiology
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Dear Colleagues,

Microorganisms are present in different occupational and indoor settings. Thus, workers/occupants are constantly exposed to a wide range of species, including those that are a part of our natural flora, as well as opportunistic and pathogenic, which may potentiate the development of adverse health outcomes. Different sampling methods as well as assays can be employed to obtain useful information in the scope of exposure assessment to microbial contamination and, consequently, to risk characterization and management. Culture-dependent and, more recently, culture-independent methodologies have been applied for the analysis of microbial communities in different indoor environments. The use of different analysis methods can provide different and divergent perspectives on the stages of microbial growth and quantity. This Special Issue will focus on various occupational/indoor sources of microbial exposures, sampling and analysis methods, as well as potential health consequences of those exposures.

Prof. Dr. Carla Viegas
Guest Editor

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Keywords

indoor air quality
occupational exposure
microbial contamination
fungi
bacteria
viruses
sampling and analysis methods
workers/occupants health

Published Papers (8 papers)

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Research

14 pages, 2116 KiB

Open AccessArticle

Analysis of Mould Exposure of Immunosuppressed Patients at a German University Hospital

by Danuta Puhlmann, Dominic Bergmann, Silke Besier, Michael Hogardt, Thomas A. Wichelhaus, Sabine Langhans, Daniel Hack, Claudia Reinheimer, Maria J. G. T. Vehreschild, Jens Jung and Volkhard A. J. Kempf

Microorganisms 2023, 11(11), 2652; https://doi.org/10.3390/microorganisms11112652 - 28 Oct 2023

Viewed by 785

Abstract

Moulds are ubiquitous components of outdoor and indoor air and local conditions, temperature, humidity and season can influence their concentration in the air. The impact of these factors on mould exposure in hospitals and the resulting risk of infection for low to moderately immunocompromised patients is unclear. In the present retrospective analysis for the years 2018 to 2022, the monthly determined mould contamination of the outdoor and indoor air at the University Hospital Frankfurt am Main is compared with the average air temperature and the relative humidity. Mould infections (Aspergillus spp., Mucorales) of low to moderately immunosuppressed patients of a haematological-oncological normal ward were determined clinically according to the criteria of the European Organisation for Research and Treatment of Cancer (EORTC, Brussels, Belgium) and of the National Reference Centre for Surveillance of Nosocomial Infections (NRC-NI, Berlin, Germany). The data revealed that in the summer months (May–October), increased mould contamination was detectable in the outdoor and indoor air compared to the winter months (November–April). The mould levels in the patient rooms followed the detection rates of the outdoor air. Two nosocomial Aspergillus infections, one nosocomial Mucorales (Rhizopus spp.) infection (according to both NRC-NI and EORTC criteria) and five Aspergillus spp. infections (according to EORTC criteria) occurred in 4299 treated patients (resulting in 41,500 patient days). In our study, the incidence density rate of contracting a nosocomial mould infection (n = 3) was approximately 0.07 per 1000 patient days and appears to be negligible. Full article

(This article belongs to the Special Issue Microbial Exposure Assessments in Different Occupational and Indoor Settings)

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13 pages, 3524 KiB

Open AccessArticle

Microbial Detection and Quantification of Low-Biomass Water Samples Using an International Space Station Smart Sample Concentrator

by Adriana Blachowicz, Camilla Urbaniak, Alec Adolphson, Gwyn Isenhouer, Andy Page and Kasthuri Venkateswaran

Microorganisms 2023, 11(9), 2310; https://doi.org/10.3390/microorganisms11092310 - 13 Sep 2023

Viewed by 860

Abstract

The pressing need to safeguard the health of astronauts aboard the International Space Station (ISS) necessitates constant and rigorous microbial monitoring. Recognizing the shortcomings of traditional culture-based methods, NASA is deliberating the incorporation of molecular-based techniques. The challenge, however, lies in developing and validating effective methods for concentrating samples to facilitate this transition. This study is dedicated to investigating the potential of an ISS Smart Sample Concentrator (iSSC) as an innovative concentration method. First, the iSSC system and its components were tested and optimized for microgravity, including various testing environments: a drop tower, parabolic flight, and the ISS itself. Upon confirming the system’s compatibility with microgravity, we further evaluated its proficiency and reliability in concentrating large volumes (i.e., 1 L) of water samples inoculated with different microbes. The samples carried 10² to 10⁵ colony-forming units (CFUs) of Sphingomonas paucimobilis, Ralstonia pickettii, or Cupriavidus basilensis per liter, aligning with NASA’s acceptable limit of 5 × 10⁴ CFU/L. The average retrieved volume post-concentration was ≈450 µL, yielding samples that were ≈2200 times more concentrated for subsequent quantitative PCR (qPCR) and CFU analysis. The average microbial percent recovery, as assessed with CFU counts, demonstrated consistency for C. basilensis and R. pickettii at around 50% and 45%, respectively. For S. paucimobilis, the efficiency oscillated between 40% and 80%. Interestingly, when we examined microbial recovery using qPCR, the results showed more variability across all tested species. The significance of these findings lies not merely in the successful validation of the iSSC but also in the system’s proven consistency, as evidenced by its alignment with previous validation-phase results. In conclusion, conducted research underscored the potential of the iSSC in monitoring microbial contamination in potable water aboard the ISS, heralding a paradigm shift from culture-based to molecular-based monitoring methods. Full article

(This article belongs to the Special Issue Microbial Exposure Assessments in Different Occupational and Indoor Settings)

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14 pages, 3483 KiB

Open AccessArticle

Exposure Levels of Airborne Fungi, Bacteria, and Antibiotic Resistance Genes in Cotton Farms during Cotton Harvesting and Evaluations of N95 Respirators against These Bioaerosols

by Atin Adhikari, Pratik Banerjee, Taylor Thornton, Daleniece Higgins Jones, Caleb Adeoye and Sonam Sherpa

Microorganisms 2023, 11(6), 1561; https://doi.org/10.3390/microorganisms11061561 - 12 Jun 2023

Cited by 1 | Viewed by 1307

Abstract

The USA is the third-leading cotton-producing country worldwide and cotton farming is common in the state of Georgia. Cotton harvest can be a significant contributor to airborne microbial exposures to farmers and nearby rural communities. The use of respirators or masks is one of the viable options for reducing organic dust and bioaerosol exposures among farmers. Unfortunately, the OSHA Respiratory Protection Standard (29 CFR Part 1910.134) does not apply to agricultural workplaces and the filtration efficiency of N95 respirators was never field-tested against airborne microorganisms and antibiotic resistance genes (ARGs) during cotton harvesting. This study addressed these two information gaps. Airborne culturable microorganisms were sampled using an SAS Super 100 Air Sampler in three cotton farms during cotton harvesting, and colonies were counted and converted to airborne concentrations. Genomic DNA was extracted from air samples using a PowerSoil^® DNA Isolation Kit. A series of comparative critical threshold (2^−ΔΔCT) real-time PCR was used to quantify targeted bacterial (16S rRNA) genes and major ARGs. Two N95 facepiece respirator models (cup-shaped and pleated) were evaluated for their protection against culturable bacteria and fungi, total microbial load in terms of surface ATP levels, and ARGs using a field experimental setup. Overall, culturable microbial exposure levels ranged between 10³ and 10⁴ CFU/m³ during cotton harvesting, which was lower when compared with bioaerosol loads reported earlier during other types of grain harvesting. The findings suggested that cotton harvesting works can release antibiotic resistance genes in farm air and the highest abundance was observed for phenicol. Field experimental data suggested that tested N95 respirators did not provide desirable >95% protections against culturable microorganisms, the total microbial load, and ARGs during cotton harvesting. Full article

(This article belongs to the Special Issue Microbial Exposure Assessments in Different Occupational and Indoor Settings)

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14 pages, 1077 KiB

Open AccessArticle

Quantitative and Qualitative Airborne Mycobiota Surveillance in High-Risk Hospital Environment

by Aleksandra Górzyńska, Aneta Grzech, Paulina Mierzwiak, Marek Ussowicz, Monika Biernat and Urszula Nawrot

Microorganisms 2023, 11(4), 1031; https://doi.org/10.3390/microorganisms11041031 - 14 Apr 2023

Cited by 1 | Viewed by 1368

Abstract

(1) Background: The primary aim of the presented study was to assess the prevalence of fungi in the indoor air of selected hospital wards, and the additional goal was to evaluate the susceptibility of cultured isolates of Aspergillus fumigatus to triazoles. (2) Methods: Three hematology departments and a hospital for lung diseases were surveyed in 2015 and/or 2019. Air samples were taken with a MicroBio MB1 air sampler on Sabouraud agar. The susceptibility of Aspergillus fumigatus isolates to voriconazole, posaconazole and itraconazole was tested with a microdilution method, according to EUCAST. (3) Results: The amount of fungi cultured from rooms equipped with sterile air circulation, as well as flow devices for air disinfection, was significantly lower compared to that from unprotected rooms. The areas most contaminated with fungi were corridors and bathrooms. The dominant species were Cladosporium and Penicillium. A. fumigatus was rare in hematological departments (6/61, 9.8% examinations performed in 2014 and 2/40, 5% in 2019), whereas in the hospital for lung diseases an outbreak of A. fumigatus spores with up to 300 CFU/m³ was noted in March 2015. No triazole-resistant A. fumigatus isolate was detected. (4) Conclusions: Regular microbiological testing of the hospital environment can contribute to the detection of spore outbreaks, and thus enable the implementation of corrective procedures (e.g., additional disinfection, changing of HEPA filters). Full article

(This article belongs to the Special Issue Microbial Exposure Assessments in Different Occupational and Indoor Settings)

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18 pages, 5136 KiB

Open AccessArticle

Risk of Exposure to Coccidioides spp. in the Temblor Special Recreation Management Area (SRMA), Kern County, CA

by Antje Lauer, Jocelyne Jassiri Lopez, Michael Chabolla and Carl Kloock

Microorganisms 2023, 11(2), 518; https://doi.org/10.3390/microorganisms11020518 - 17 Feb 2023

Cited by 2 | Viewed by 1311

Abstract

The Temblor Mountain Special Recreation Area (SRMA) on the western flank of the San Joaquin Valley, CA, is located in the endemic area of Coccidioides, a fungal pathogen responsible for the increasing incidence of coccidioidomycosis (Valley fever). Recreationists in the SRMA, such as off-highway vehicle (OHV) drivers and mountain bikers who disturb the soils, are at risk of being exposed to airborne arthroconidia (asexual spores) of the pathogen. To reduce the risk of pathogen exposure for visitors, the Bureau of Land Management (BLM) plans to limit recreational activities to areas with a reduced pathogen presence. They envision an official OHV park in the future, by also restricting access to areas with ongoing restoration efforts and by limiting soil erosion in sensitive areas. To investigate which soils in the Temblor SRMA are most likely to support the growth of Coccidioides spp., soil samples were collected over a 3-year period from dominant soil types in a northern and a southern sampling area and analyzed for the pathogen using a culture-independent PCR-based method. In addition, soil pH and electrical conductivity were determined. The results of this study revealed slight genetic variance in the Coccidioides sequences obtained from the soils of the Temblor SRMA. An analysis of variance (ANOVA) could not confirm differences in soil pH and electrical conductivity (EC) between the different soil types investigated and between sites where the pathogen was detected compared to sites where it could not be found. However, the year of sampling appeared to have an influence on observed soil pH and EC, and the presence of the pathogen. Of all dominant soil types investigated, those belonging to the Littlesignal–Cochora association were the least likely to contain the pathogen, whereas soils of the Beam–Panoza–Hillbrick association appeared more supportive. In addition to pointing out OHV areas with lower pathogen exposure risk in the Temblor SRMA, recommendations were made to educate visitors and BLM workers about the risk of contracting Valley fever. Full article

(This article belongs to the Special Issue Microbial Exposure Assessments in Different Occupational and Indoor Settings)

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10 pages, 1039 KiB

Open AccessArticle

Temporal Variation of SARS-CoV-2 Levels in Wastewater from a Meat Processing Plant

by Meiyi Zhang and Maria D. King

Microorganisms 2023, 11(1), 174; https://doi.org/10.3390/microorganisms11010174 - 10 Jan 2023

Cited by 1 | Viewed by 1518

Abstract

Wastewater-based surveillance (WBS) on SARS-CoV-2 has been proved to be an effective approach to estimate the prevalence of COVID-19 in communities and cities. However, its application was overlooked at smaller scale, such as a single facility. Meat processing plants are hotspots for COVID-19 outbreaks due to their unique environment that are favorable for the survival and persistence of SARS-CoV-2. This is the first known WBS study in meat processing plants. The goal was to understand the temporal variation of the SARS-CoV-2 levels in wastewater from a meat processing plant in Canada during a three-month campaign and to find any correlation with clinically confirmed cases in the surrounding city area. Higher SARS-CoV-2 concentrations and detection frequencies were observed in the solid fraction compared to the liquid fraction of the wastewater. The viruses can be preserved in the solid fraction of wastewater for up to 12 days. The wastewater virus level did not correlate to the city-wide COVID-19 cases due to the unmatching scales. WBS on SARS-CoV-2 in meat processing plants can be useful for identifying COVID-19 outbreaks in the facility and serve as an effective alternative when resources for routine individual testing are not available. Full article

(This article belongs to the Special Issue Microbial Exposure Assessments in Different Occupational and Indoor Settings)

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17 pages, 1351 KiB

Open AccessArticle

Dealing with Hidden Threats: The Antimicrobial Effect of the Embalming Process

by Benedict Uy, Simon Swift, Francesca Casu, David Mahuika, Maurice A. Curtis and Deborah Prendergast

Microorganisms 2022, 10(11), 2180; https://doi.org/10.3390/microorganisms10112180 - 03 Nov 2022

Viewed by 2375

Abstract

Individuals naturally carry bacteria and other microbes as part of their natural flora, with some being opportunistic pathogens. Approximately 30% of the population is known to carry Staphylococcus aureus in their nasal cavity, an organism that causes infections ranging from soft tissue abscesses to toxic shock syndrome. This problem is compounded by the presence of antibiotic-resistant strains such as Methicillin-Resistant Staphylococcus aureus (MRSA). Commensal bacteria present on cadavers pose a risk to those who handle the body. As a Medical School Anatomy laboratory that performs hands-on cadaveric dissection, we wanted to know whether the embalming process is sufficient to kill all commensal bacteria that pose a risk to staff and students. Even if these strains do not cause disease in these individuals, secondary transmission could occur to friends and family, who may be at higher risk of acquiring an infection. Embalming is assumed to eliminate all microbial contamination on the body. However, there are limited studies to confirm this. This study characterises the incidence of antibiotic sensitive and resistant bacteria in cadavers donated for medical teaching and research. We have screened for Methicillin-Resistant Organisms (MRO) and Extended-Spectrum Beta-Lactamase (ESBL) producing bacteria. In this study group of cadavers, approximately 46% (16/35) carry an MRO, while 51% (18/35) carry an ESBL positive organism prior to embalming. By determining the organisms’ presence pre- and post-embalming, we can evaluate the embalming procedure’s effectiveness. Our results show embalming eliminates detectable microbes in about 51% (18/35) of the cadavers. MRO dropped by 75% (16 to 4 positive cadavers), while ESBL organisms went down by almost 95% (from 18 to 1 positive cadaver). There was a further decrease in the number of positive cadavers after storage at 4 °C to 6% (2/32). Thus, although the embalming process does not immediately sterilise all the cadavers, prolonged storage at 4 °C can further reduce the number of viable bacteria. Full article

(This article belongs to the Special Issue Microbial Exposure Assessments in Different Occupational and Indoor Settings)

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16 pages, 3382 KiB

Open AccessArticle

Unveiling the Occupational Exposure to Microbial Contamination in Conservation–Restoration Settings

by Carla Viegas, Renata Cervantes, Marta Dias, Bianca Gomes, Pedro Pena, Elisabete Carolino, Magdalena Twarużek, Robert Kosicki, Ewelina Soszczyńska, Susana Viegas, Liliana Aranha Caetano and Ana Catarina Pinheiro

Microorganisms 2022, 10(8), 1595; https://doi.org/10.3390/microorganisms10081595 - 08 Aug 2022

Cited by 5 | Viewed by 1639

Abstract

Assuring a proper environment for the fulfillment of professional activities is one of the Sustainable Development Goals and is contemplated in the One Health approach assumed by the World Health Organization. This particular study is applied to an often neglected sector of our society—the conservators/restorers—despite the many health issues reported by these professionals. Three different specialties (textiles, paintings and wood sculpture) and locations were selected for evaluation by placement of electrostatic dust cloths. After treatment of the samples, bacterial and fungal contamination were assessed, as well as mycotoxin determination, the presence of azole-resistant strains and cytotoxicity of the microorganisms encountered. Bacteria were only present in one of medias used and showed relatively low numbers. The highest level of contamination by fungi was identified in one of the textiles settings. The textile area also showed the highest variability for fungi. Aspergillus sp. are one indicator of possible environmental issues, and A. sections Fumigati and Circumdati were particularly relevant in two of the settings and identified in all of them. No mycotoxins were detected and the large majority of the fungi identified were non-cytotoxic. Overall, these can be considered low-contaminated environments but attention should be given to the Aspergillus sp. contamination. Additional studies are needed not only to make these results more robust, but also to test if the environmental sampling alone is the best approach in a setting where there is very little movement and dust displacement and where professionals are in very close proximity to the artefacts being treated, which may suggest the existence of a micro-atmosphere worth evaluating and comparing to the obtained results. Full article

(This article belongs to the Special Issue Microbial Exposure Assessments in Different Occupational and Indoor Settings)

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