Comparison of methods for assessing temporal variation of growth of fungi on building materials

Bioburden Assessment by Passive Methods on a Clinical Pathology Service in One Central Hospital from Lisbon: What Can it Tell Us Regarding Patients and Staff Exposure?

The assessment and control of microbial contamination in health care facilities is presently a mandatory and vital part of strategies to prevent and control hospital-acquired infections. This study aims to assess the bioburden with two passive sampling methods (30 ventilations grids swabs and 16 electrostatic dust collectors (EDCs)) at Clinical Pathology Services. The fungal burden was characterized through molecular tools, antifungal resistance, and the mycotoxins and cytotoxicity profile. Total bacteria presented the highest prevalence in both matrixes, whereas Gram-bacteria presented the lowest. Swabs presented a higher prevalence (27.6%) for fungal burden. Chrysonilia sitophila presented the highest prevalence in swabs, whereas for EDCs, C. sitophila and Mucor sp. were the most prevalent. Concerning Aspergillus genera on swabs, section Flavi was the one with the highest prevalence (58.02%), whereas, for EDCs, section Versicolores was the only section observed (100%). Aspergillus section Fumigati was detected in 10 swabs and 7 EDC samples and Aspergillus section Versicolores was detected in one EDC sample. Fungal growth on azole-supplemented media was observed in eight EDC samples. No mycotoxins were detected in any of the samples. A low cytotoxic effect was observed in two sites upon incubation of collected samples with A549 and SK cells and in two other sites upon incubation of collected samples with SK cells only. A medium cytotoxic effect was observed with one EDC sample upon incubation with A549 cells. This study reinforces the need of determination of the azole resistance profile for fungal species and allowed a preliminary risk characterization regarding the cytotoxicity. An intervention including the use of a ultraviolet with wavelength between 200 nm and 280 nm (UVC)—emitting device and an increased maintenance and cleaning of the central heating, ventilation, and air conditioning (HVAC) systems should be ensured to promote the reduction of microbial contamination.

Time-Dependent Changes in Morphostructural Properties and Relative Abundances of Contributors in Pleurotus ostreatus/Pseudomonas alcaliphila Mixed Biofilms

Pleurotus ostreatus dual biofilms with bacteria are known to be involved in rock phosphate solubilization, endophytic colonization, and even in nitrogen fixation. Despite these relevant implications, no information is currently available on the architecture of P. ostreatus-based dual biofilms. In addition to this, there is a limited amount of information regarding the estimation of the temporal changes in the relative abundances of the partners in such binary systems. To address these issues, a dual biofilm model system with this fungus was prepared by using Pseudomonas alcaliphila 34 as the bacterial partner due to its very fast biofilm-forming ability. The application of the bacterial inoculum to already settled fungal biofilm on a polystyrene surface coated with hydroxyapatite was the most efficient approach to the production of the mixed system the ultrastructure of which was investigated by a multi-microscopy approach. Transmission electron microscopy analysis showed that the adhesion of bacterial cells onto the mycelial cell wall appeared to be mediated by the presence of an abundant layer of extracellular matrix (ECM). Scanning electron microscopy analysis showed that ECM filaments of bacterial origin formed initially a reticular structure that assumed a tabular semblance after 72 h, thus overshadowing the underlying mycelial network. Across the thickness of the mixed biofilms, the presence of an extensive network of channels with large aggregates of viable bacteria located on the edges of their lumina was found by confocal laser scanning microscopy; on the outermost biofilm layer, a significant fraction of dead bacterial cells was evident. Albeit with tangible differences, similar results regarding the estimation of the temporal shifts in the relative abundances of the two partners were obtained by two independent methods, the former relying on qPCR targeting of 16S and 18S rRNA genes and the latter on ester-linked fatty acid methyl esters analysis.

Evaluation of different hurdles on Penicillium crustosum growth in sponge cakes by means of a specific real time PCR

Limited shelf life of bakery products, caused by microbial deterioration, is a concern for industries due to economic losses. Fungal spoilage of sponge cakes industrially produced in Montevideo was caused mainly by Penicillium species, in particular by Penicillium crustosum. The combination of different hurdles was studied to inhibit P. crustosum growth in sponge cakes. A full factorial design was performed to study the effect of the concentration of potassium sorbate, pH, packaging atmosphere and storage time. The results showed that packaging atmosphere and storage time were the significant factors in the ranges tested. No growth was detected in cakes stored in modified atmosphere packaging (MAP) (N₂:CO₂ 50:50) at room temperature (25 °C) for 15 days. The effect of MAP on P. crustosum growth in cakes at room temperature was compared with the effect of air-packaging and storage at low temperature (4 °C) for 30 days. P. crustosum growth was not detected in cakes packaged in MAP, whereas it was detected after 20 days in cakes packaged in air and stored at 4 °C. This growth was quantified by a specific real time PCR developed in this work. Specific primers were designed using the sequence of β-tubulin gene of P. crustosum as a target and PCR conditions were adjusted to ensure specificity. PCR efficiency was 107%, with a detection limit of 0.0014 ng of DNA. The qPCR method presented here, resulted specific and sensitive enough to detect the growth of P. crustosum even before biodeterioration signs were visible.

Martin-Sanchez, Meyer W, Seung-Yoon Oh, Jose Paulo Sampaio, Seifert KA, Sklenář F, Dirk Stubbe, Suh SO, Summerbell R, Svantesson S, Martin Unterseher, Cobus M. Visagie, Weiss M, Woudenberg JHC, Christian Wurzbacher, den Wyngaert SV, Yilmaz N, Andrey Yurkov, Kõljalg U, Abarenkov K. Taxonomic annotation of public fungal ITS sequences from the built environment - a report from an April 10-11, 2017 workshop (Aberdeen, UK)

Recent DNA-based studies have shown that the built environment is surprisingly rich in fungi. These indoor fungi - whether transient visitors or more persistent residents - may hold clues to the rising levels of human allergies and other medical and building-related health problems observed globally. The taxonomic identity of these fungi is crucial in such pursuits. Molecular identification of the built mycobiome is no trivial undertaking, however, given the large number of unidentified, misidentified, and technically compromised fungal sequences in public sequence databases. In addition, the sequence metadata required to make informed taxonomic decisions - such as country and host/substrate of collection - are often lacking even from reference and ex-type sequences. Here we report on a taxonomic annotation workshop (April 10-11, 2017) organized at the James Hutton Institute/University of Aberdeen (UK) to facilitate reproducible studies of the built mycobiome. The 32 participants went through public fungal ITS barcode sequences related to the built mycobiome for taxonomic and nomenclatural correctness, technical quality, and metadata availability. A total of 19,508 changes - including 4,783 name changes, 14,121 metadata annotations, and the removal of 99 technically compromised sequences - were implemented in the UNITE database for molecular identification of fungi (https://unite.ut.ee/) and shared with a range of other databases and downstream resources. Among the genera that saw the largest number of changes were Penicillium, Talaromyces, Cladosporium, Acremonium, and Alternaria, all of them of significant importance in both culture-based and culture-independent surveys of the built environment.

Fungal Exposure and Asthma: IgE and Non-IgE-Mediated Mechanisms

Fungi are ubiquitous in indoor and outdoor environments and have been associated with respiratory disease including childhood and adult asthma. A growing body of evidence from human and animal studies has revealed a link between fungal exposure, especially indoor fungal exposure, with asthma initiation, persistence, and exacerbation. Despite the overwhelming evidence linking mold exposure and asthma, the mechanistic basis for the association has remained elusive. It is now clear that fungi need not be intact to impart negative health effects. Fungal components and fungal fragments are biologically active and contribute to asthma development and severity. Recent mechanistic studies have demonstrated that fungi are potent immunomodulators and have powerful effects on asthma independent of their potential to act as antigens. This paper will review the connection between fungal exposure and asthma with a focus on the immunological mechanisms underlying this relationship.

Retention of fungal enzyme activity in environmental liquid and filter samples

Fungal biomass can be determined by measuring the beta-N-acetylhexos-aminidase (NAHA) enzyme activity. NAHA, an enzyme present in fungal mycelium and spores, has been detected in inactive, dormant and non-viable cells. Very little information is available on the enzyme activity of different species or retention of the activity under various storage conditions. This study used fluorometry to evaluate the enzyme activity of liquid and filter samples containing spores of four fungal species from genera Penicillium, Cladosporium, Aspergillus, and Acremonium. When fungal spores were stored on a filter, enzyme activity was more stable than when the spores were maintained in suspension for one year. The enzyme activity in suspension samples increased with most of the differences detected between the values at the baseline and 12 months being statistically significant. The results indicate that enzyme activity varies between species. Cladosporium spores had highest NAHA content per spore, whereas Acremonium did not exhibit any detectable enzyme activity even when viability was detected. The results indicated that samples should be stored as dry filter samples.