home Journal club, Meeting Reports, Meetings New papers on Microbiology of the Built Environment, January 29, 2017

New papers on Microbiology of the Built Environment, January 29, 2017

Microbes indoors

Building-related symptoms are linked to the in vitro toxicity of indoor dust and airborne microbial propagules in schools: A cross-sectional study – JT Salin – Environmental Research ($41.95)

Graphical abstract

We examined whether the in vitro toxicity of indoor samples from school buildings was associated with work-related health symptoms (building-related symptoms, BRS). Administrators of the Helsinki City Real Estate Department selected 15 schools for the study, and a questionnaire on symptoms connected to work was sent to the teachers in the selected schools for voluntary completion. The cellular toxicity of classroom samples was determined by testing substances extracted from wiped indoor dust and by testing microbial biomass that was cultured on fallout plates. (…) Teachers working in classrooms where the samples showed high sperm toxicity had more BRS. The boar sperm cell motility inhibition assay appears promising as a tool for demonstrating the presence of indoor substances associated with BRS.

Microbial rRNA sequencing analysis of evaporative cooler indoor environments located in the Great Basin Desert region of the United States – Angela R. Lemons – Environmental Science: Processes & Impacts (£42.50)

Graphical abstract

(…) The objective of this study was to determine if the increased humidity previously reported in EC homes leads to varying microbial populations compared to homes with air conditioners (AC). Children with physician-diagnosed allergic rhinitis living in EC or AC environments were recruited into the study. Air samples were collected from the child’s bedroom for genomic DNA extraction and metagenomic analysis of bacteria and fungi using the Illumina MiSeq sequencing platform. The analysis of bacterial populations revealed no major differences between EC and AC sampling environments. The fungal populations observed in EC homes differed from AC homes. The most prevalent species discovered in AC environments belonged to the genera Cryptococcus (20%) and Aspergillus (20%). In contrast, the most common fungi identified in EC homes belonged to the order Pleosporales and included Alternaria alternata (32%) and Phoma spp. (22%). The variations in fungal populations provide preliminary evidence of the microbial burden children may be exposed to within EC environments in this region.

Molecular approaches for the detection and monitoring of microbial communities in bioaerosols: A review – Keunje Yoo – Journal of Environmental Sciences

Graphical abstract

Bioaerosols significantly affect atmospheric processes while they undergo long-range vertical and horizontal transport and influence atmospheric chemistry and physics and climate change. Accumulating evidence suggests that exposure to bioaerosols may cause adverse health effects, including severe disease. Studies of bioaerosols have primarily focused on their chemical composition and largely neglected their biological composition and the negative effects of biological composition on ecosystems and human health. Here, current molecular methods for the identification, quantification, and distribution of bioaerosol agents are reviewed. Modern developments in environmental microbiology technology would be favorable in elucidation of microbial temporal and spatial distribution in the atmosphere at high resolution. In addition, these provide additional supports for growing evidence that microbial diversity or composition in the bioaerosol is an indispensable environmental aspect linking with public health.

Reflections on the history of indoor air science, focusing on the last 50 years – Jan Sundell – Indoor Air ($6 to rent, $38 to own).

From the preview

The scientific articles and Indoor Air conference publications of the indoor air sciences (IAS) during the last 50 years are summarized.(…) The modern scientific history started in the 1970s with a question: “did indoor air pose a threat to health as did outdoor air?” Soon it was recognized that indoor air is more important, from a health point of view, than outdoor air. Topics of concern were first radon, environmental tobacco smoke and lung cancer, followed by volatile organic compounds, formaldehyde and sick building syndrome, house dust mites, asthma and allergies, Legionnaires disease and other airborne infections. Later emerged dampness/mold-associated allergies and today’s concern with “modern exposures-modern diseases.” Ventilation, thermal comfort, indoor air chemistry, semi volatile organic compounds, building simulation by computational fluid dynamics, and fine particulate matter are common topics today. From their beginning in Denmark and Sweden, then in the USA, the indoor air sciences now show increasing activity in East and Southeast Asia.

Forensic microbes

The background story was even more chillingFrozen: Thawing and Its Effect on the Postmortem Microbiome in Two Pediatric Cases – Jennifer L. Pechal – Forensic Sciences ($6 to rent, $38 to own).

Taxonomic hierarchies of the 16S rRNA gene amplicon analysis performed with QIIME throughout the thawing process.

Previous postmortem microbiome studies have focused on characterizing taxa turnover during an undisturbed decomposition process. How coexisting conditions (e.g., frozen, buried, burned) affect the human microbiome at the time of discovery is less well understood. Microbiome data were collected from two pediatric cases at the Wayne County Medical Examiner in Michigan. The bodies were found frozen, hidden in a freezer for an extended time. Microbial communities were sampled from six external anatomic locations at three time points during the thawing process, prior to autopsy. The 16S rRNA V4 gene amplicon region was sequenced using high-throughput sequencing (Illumina MiSeq). Microbial diversity increased, and there was a distinct shift in microbial community structure and abundance throughout the thawing process. Overall, these data demonstrate that the postmortem human microbiome changes during the thawing process, and have important forensic implications when bodies have been substantially altered, modified, and concealed after death.

Microbes on a plane

Assessment of the Bacterial Diversity of Aircraft Water: Identification of the Frequent Fliers – Harald Handschuh  – PLOS ONE (OA)

Number of isolates within each bacterial class identified across the aft and fwd galley of a fleet of short haul aircraft.

The aim of this study was to determine and identify bacteria inhabiting the supply chain of an airline’s drinking water using phenotypic and 16S rDNA sequence-based analysis. Water samples (n = 184) were sourced from long-haul and short-haul aircraft, the airline water source and a water service vehicle. In total, 308 isolates were characterised and their identity determined, which produced 82 identified bacterial species belonging to eight classes: γ-Proteobacteria; β-Proteobacteria; α-Proteobacteria; Bacilli; Actinobacteria; Flavobacteria; Sphingobacteria and Cytophaga. Statistical differences in bacterial diversity were found to exist across sampling locations (X2 = 39.220, p = 0.009) and furthermore, differences were observed (X2 = 15.475, p = 0.030) across aircraft type (long- or short-haul). This study demonstrates the diverse nature of microorganisms within the aircraft drinking water supply chain. To the best of our knowledge, this is the most extensive study undertaken to date of microbial diversity in aircraft drinking water.

Microbes and food production

Differential Attachment of Salmonella enterica and Enterohemorrhagic Escherichia coli to Alfalfa, Fenugreek, Lettuce, and Tomato Seeds – Applied and Environmental Microbiology – Yue Cui ($25 for one day)

Fenugreek seeds. Source: Wikipedia.

Vegetable seeds have the potential to disseminate and transmit foodborne bacterial pathogens. This study was undertaken to assess the abilities of selected Salmonella and enterohemorrhagic Escherichia coli (EHEC) strains to attach to fungicide-treated vs. untreated, and intact vs. mechanically-damaged seeds of alfalfa, fenugreek, lettuce, and tomato. Surface-sanitized seeds (2 g) were exposed to 4 individual strains of Salmonella or EHEC at 20°C for 5 h. (…) Unit weight of lettuce seeds had the highest numbers of attached Salmonella or EHEC cells, followed by tomato, alfalfa, and fenugreek seeds. In contrast, individual fenugreek seeds had more attached pathogen cells followed by lettuce, alfalfa, and tomato seeds. Significantly more Salmonella and EHEC cells attached to mechanically-damaged seeds than to intact seeds (P < 0.05). Although on average, significantly more Salmonella and EHEC cells were recovered from untreated, than fungicide-treated seeds (P < 0.05), fungicide treatment did not significantly affect the attachment of individual bacterial strains to vegetable seeds (P > 0.05), with a few exceptions. This study fills gaps in the current body of literature and helps explain bacterial interactions with vegetable seeds with varying surface characteristics.

Microbiological Load of Edible Insects Found in Belgium – Rudy Caparros Megido – Insects (OA)

Toffee coconut mealworms, from: EdibleInsects.com

(…) this study aims to characterize the microbial load of edible insects found in Belgium (i.e., fresh mealworms and house crickets from European farms and smoked termites and caterpillars from a traditional Congolese market) and to evaluate the efficiency of different processing methods (blanching for all species and freeze-drying and sterilization for European species) in reducing microorganism counts. All untreated insect samples had a total aerobic count higher than the limit for fresh minced meat (6.7 log cfu/g). Nevertheless, a species-dependent blanching step has led to a reduction of the total aerobic count under this limit, except for one caterpillar species. Freeze-drying and sterilization treatments on European species were also effective in reducing the total aerobic count. Yeast and mold counts for untreated insects were above the Good Manufacturing Practice limits for raw meat, but all treatments attained a reduction of these microorganisms under this limit. These results confirmed that fresh insects, but also smoked insects from non-European trades, need a cooking step (at least composed of a first blanching step) before consumption. Therefore, blanching timing for each studied insect species is proposed and discussed.

Human Microbiome Congress San Diego

This is not directly related to the topic of this blog, but possibly of interest for some readers here. A couple of days ago, I attended the Human Microbiome Congress in San Diego, and I live-tweeted all the talks that I attended. The result is a collection of over 400 tweets, which I brought together in this Storify of the Human Microbiome Congress San Diego.

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