Rapid Monitoring by Quantitative Polymerase Chain Reaction for Pathogenic Aspergillus During Carpet Removal From a Hospital

Indoor fungal contamination: health risks and measurement methods in hospitals, homes and workplaces

Indoor fungal contamination has been associated with a wide range of adverse health effects, including infectious diseases, toxic effects and allergies. The diversity of fungi contributes to the complex role that they play in indoor environments and human diseases. Molds have a major impact on public health, and can cause different consequences in hospitals, homes and workplaces. This review presents the methods used to assess fungal contamination in these various environments, and discusses advantages and disadvantages for each method in consideration with different health risks. Air, dust and surface sampling strategies are compared, as well as the limits of various methods are used to detect and quantify fungal particles and fungal compounds. In addition to conventional microscopic and culture approaches, more recent chemical, immunoassay and polymerase chain reaction (PCR)-based methods are described. This article also identifies common needs for future multidisciplinary research and development projects in this field, with specific interests on viable fungi and fungal fragment detections. The determination of fungal load and the detection of species in environmental samples greatly depend on the strategy of sampling and analysis. Quantitative PCR was found useful to identify associations between specific fungi and common diseases. The next-generation sequencing methods may afford new perspectives in this area.

Discrimination of viable from non-viable gram-negative bacterial pathogens in airborne particles using propidium monoazide-assisted qPCR

The presence of bacterial pathogens in airborne particulate matter (PM) has been of considerable concern from the public health standpoint. Conventional culture-based methods are tedious, time consuming and are unable to quantify stressed viable but non-culturable (VBNC) populations of these pathogens. This study reports the optimization, validation and application of a new and rapid quantitative method for enumeration of four live potential Gram-negative bacterial pathogens (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Aeromonas hydrophila) in PM of biomass burning origin. This method makes use of an intercalating dye (propidium monoazide, PMA) in conjunction with real-time PCR (qPCR) analysis following DNA extraction from PM samples for distinguishing viable from non-viable potential bacterial pathogens. This method was not affected by the complex matrix of the environmental samples, nor by any PCR inhibition effects. The number of viable pathogens ranged from 0 to 8×10(4) gene copies/m(3) in PM. With the exception of A. hydrophilia, all the three pathogens were found to be present in PM. The correlation between the counts obtained using the PMA-qPCR (modified qPCR) and those from the culture-based method was very high with R(2)~1.0 and p value<0.0001.

Traditional mould analysis compared to a DNA-based method of mould analysis

Traditional environmental mould analysis is based on microscopic observations and counting of mould structures collected from the air on a sticky surface or culturing of moulds on growth media for identification and quantification. These approaches have significant limitations. A DNA-based method of mould analysis called mould specific quantitative PCR (MSQPCR) was created for more than 100 moulds. Based on a national sampling and analysis by MSQPCR of dust in US homes, a scale for comparing the mould burden in homes was created called the Environmental Relative Mouldiness Index (ERMI).

Detection of Aspergillus fumigatus by quantitative polymerase chain reaction in air samples impacted on low-melt agar

BACKGROUND

The standard procedure for routine environmental sampling for the prevention of invasive aspergillosis outbreaks is culturing of Aspergillus fumigatus after impaction of air. Time to results is usually 7 days. A preliminary study was carried out to compare the time to results and sensitivity of culturing and quantitative polymerase chain reaction (QPCR) in the detection of airborne A fumigatus.

METHODS

Fungal DNA was extracted from 43 samples of impacted low-melt agar by a 3-step extraction method and amplified by QPCR. Identification was made using a specific A fumigatus probe.

RESULTS

With QPCR, 19 of the 43 samples were positive for A fumigatus; with culturing, 7 of these 19 samples were positive, and 12 were negative. The cycle threshold (Ct) values for the 12 culture-negative samples were between 39 and 43 cycles, and the Ct values for 6 of the 7 culture-positive samples were <38 cycles, suggesting that the amount of DNA detected by QPCR was higher in the presence of viable conidia.

CONCLUSION

QPCR detection of airborne A fumigatus in impacted low-melt agar significantly reduces the period of time between sample collection and results (48 hours), suggesting that this new approach can be beneficial for routine environmental sampling.

Quantitative PCR analysis of fungal DNA in Swedish day care centers and comparison with building characteristics and allergen levels

Abstract Sweden has had allergen-avoidance day care centers (AADCs) since 1979. The aim of this study was to measure fungal DNA by quantitative polymerase chain reaction (qPCR), a new method, in AADCs and ordinary day care centers (ODCs) and examine associations between allergen levels and building characteristics. Dust samples were collected by swabbing doorframes, vacuum-cleaning, and using Petri dishes. In total, 11 AADCs and 11 ODCs were studied (70 rooms). Total fungal DNA, measured by qPCR in the swab dust, was detected in 89%, Aspergillus or Penicillium (Asp/Pen) DNA in 34%, and Stachybotrys chartarum DNA in 6% of the rooms. Total fungal DNA was significantly higher in rooms with linoleum floor (P = 0.02), textile carpets (P = 0.03), reported dampness/molds (P = 0.02) and reported odor (P < 0.001) in the buildings, and significantly lower in wooden facade buildings (P = 0.003). Reported odor was related to the amount of sieved fine dust, reported dampness/molds and type of building construction. Total fungal DNA was related to cat, dog, horse and total allergen levels (P = 0.003) in the day care centers. In conclusion, total fungal DNA is related to reported dampness/molds, reported odor, and type of wall construction. The association between fungal and allergen contamination indicated a general 'hygiene factor' related to biological contaminants. Practical Implications The associations between fungal DNA, reported dampness/molds, and odor support the view that buildings with odor problems should be investigated for possible hidden fungal growth. There is a need to measure fungal biomass in different types of building constructions by monitoring fungal DNA. Analysis of fungal DNA with quantitative PCR can be a fast and practical way to study indoor fungal contamination. Swabbing dust from the doorframe of the main entrance to the room can be a convenient method of sampling dust for fungal DNA analysis. The high prevalence of reported dampness/molds and the common occurrence of fungal DNA indicate the need to improve the indoor environment of Swedish day care centers.

Aspergilluspolymerase chain reaction (PCR) diagnosis

In recent years novel molecular methods, notably polymerase chain reaction (PCR) assays, have been developed to improve the diagnosis of life-threatening invasive aspergillosis in patients at high risk, especially patients with malignant hematological disease. Early diagnosis and treatment are essential for adequate therapeutic management. Management, however, often remains difficult since most of the diagnostic tools used clinically at present either lack specificity or acceptable sensitivity. The clinical value, advantages and remaining problems of PCR approaches to detect the emerging fungal pathogen are reviewed.