Influence of crossdrafts on the performance of a biological safety cabinet.
A biological safety cabinet was tested to determine the effect of crossdrafts (such as those created by normal laboratory activity or ventilation) upon the ability of the cabinet to protect both experiments and investigators. A simple crossdraft, controllable from 50 to 200 feet per min (fpm; 15.24 to 60.96 m/min), was created across the face of the unit. Modifications of standardized procedures involving controlled bacterial aerosol challenges provided stringent test conditions. Results indicated that, as the crossflow velocities exceeded 100 fpm, the ability of the cabinet to protect either experiments or investigators decreased logarithmically with increasing crossdraft speed. Because 100 fpm is an airspeed easily achieved by some air conditioning and heating vents (open windows and doorways may create velocities far in excess of 200 fpm), the proper placement of a biological safety cabinet within the laboratory--away from such disruptive air currents--is essential to satisfactory cabinet performance. (+info)
How a fungus escapes the water to grow into the air.
Fungi are well known to the casual observer for producing water-repelling aerial moulds and elaborate fruiting bodies such as mushrooms and polypores. Filamentous fungi colonize moist substrates (such as wood) and have to breach the water-air interface to grow into the air. Animals and plants breach this interface by mechanical force. Here, we show that a filamentous fungus such as Schizophyllum commune first has to reduce the water surface tension before its hyphae can escape the aqueous phase to form aerial structures such as aerial hyphae or fruiting bodies. The large drop in surface tension (from 72 to 24 mJ m-2) results from self-assembly of a secreted hydrophobin (SC3) into a stable amphipathic protein film at the water-air interface. Other, but not all, surface-active molecules (that is, other class I hydrophobins and streptofactin from Streptomyces tendae) can substitute for SC3 in the medium. This demonstrates that hydrophobins not only have a function at the hyphal surface but also at the medium-air interface, which explains why fungi secrete large amounts of hydrophobin into their aqueous surroundings. (+info)
Contaminations occurring in fungal PCR assays.
Successful in vitro amplification of fungal DNA in clinical specimens has been reported recently. In a collaboration among five European centers, the frequency and risk of contamination due to airborne spore inoculation or carryover contamination in fungal PCR were analyzed. The identities of all contaminants were specified by cycle sequencing and GenBank analysis. Twelve of 150 PCR assays that together included over 2,800 samples were found to be contaminated (3.3% of the negative controls were contaminated during the DNA extraction, and 4.7% of the PCR mixtures were contaminated during the amplification process). Contaminants were specified as Aspergillus fumigatus, Saccharomyces cerevisiae, and Acremonium spp. Further analysis showed that commercially available products like zymolyase powder or 10x PCR buffer may contain fungal DNA. In conclusion, the risk of contamination is not higher in fungal PCR assays than in other diagnostic PCR-based assays if general precautions are taken. (+info)
Density and molecular epidemiology of Aspergillus in air and relationship to outbreaks of Aspergillus infection.
After five patients were diagnosed with nosocomial invasive aspergillosis caused by Aspergillus fumigatus and A. flavus, a 14-month surveillance program for pathogenic and nonpathogenic fungal conidia in the air within and outside the University Hospital in Rotterdam (The Netherlands) was begun. A. fumigatus isolates obtained from the Department of Hematology were studied for genetic relatedness by randomly amplified polymorphic DNA (RAPD) analysis. This was repeated with A. fumigatus isolates contaminating culture media in the microbiology laboratory. The density of the conidia of nonpathogenic fungi in the outside air showed a seasonal variation: higher densities were measured during the summer, while lower densities were determined during the fall and winter. Hardly any variation was found in the numbers of Aspergillus conidia. We found decreasing numbers of conidia when comparing air from outside the hospital to that inside the hospital and when comparing open areas within the hospital to the closed department of hematology. The increase in the number of patients with invasive aspergillosis could not be explained by an increase in the number of Aspergillus conidia in the outside air. The short-term presence of A. flavus can only be explained by the presence of a point source, which was probably patient related. Genotyping A. fumigatus isolates from the department of hematology showed that clonally related isolates were persistently present for more than 1 year. Clinical isolates of A. fumigatus obtained during the outbreak period were different from these persistent clones. A. fumigatus isolates contaminating culture media were all genotypically identical, indicating a causative point source. Knowledge of the epidemiology of Aspergillus species is necessary for the development of strategies to prevent invasive aspergillosis. RAPD fingerprinting of Aspergillus isolates can help to determine the cause of an outbreak of invasive aspergillosis. (+info)
Microscopic fungi in dwellings and their health implications in humans.
The article reviews the quantitative and qualitative incidence of microscopic filamentous fungi in dwellings, methods for their detection, mycotoxins, glucans and volatile organic compounds produced by microscopic fungi in the indoor air of homes. Characteristics and properties of the most important species of fungi in dwellings (Alternaria spp., Aspergillus spp., Cladosporium spp., Fusarium spp., Penicillium spp., Stachybotrys spp., and Wallemia spp.) and the health problems of occupants of the "moldy homes are also discussed. (+info)
Exposure to airborne microorganisms and volatile organic compounds in different types of waste handling.
Occupational exposure of workers to airborne microorganisms and volatile organic compounds (VOC) in different types of waste treatment situations was examined during summer time. Microorganisms were collected as stationary samples using a six-stage Andersen impactor, while for VOCs both personal and stationary sampling was conducted. The exposure at the waste handling facility was considerably greater than at landfill sites or in waste collection. The concentrations of viable fungi were maximally 10(5) cfu/m3, and the concentrations of both total culturable bacteria and Gram-negative bacteria exceeded the proposed occupational exposure limit values (OELV), being 10(4) and 10(3) cfu/m3, respectively. Exposure to VOCs in the waste handling facility was three times higher than at the landfill sites, being at highest 3000 microg/m3, considered to be the limit for discomfort. The use of personal protective equipment at work, thorough hand washing and changing clothes after the work shift are strongly recommended in the waste handling facility and the landfill sites. (+info)
Application of the classic Limulus test and the quantitative kinetic chromogenic LAL method for evaluation of endotoxin concentration in indoor air.
The classic (gel-clot procedure) Limulus test (CLT) and the quantitative kinetic chromogenic LAL method (KQCL) used for the evaluation of bacterial endotoxin concentration in the indoor air of dwellings were compared. The scientific procedure included analyses of 40 air samples supplemented by the analysis of 20 sample duplicates (selected at random) which were taken during the fall season from 10 flats located in 3 towns of the Upper Silesian region (southern Poland). The particulate aerosol probes were sampled by Harvard impactor and Casella sampler. The same samples were analyzed in the Netherlands using the quantitative kinetic chromogenic LAL method, and in Poland using the classic Limulus test. Comparison of both methods revealed that the quantitative kinetic chromogenic LAL method was more precise, with better reproducibility (the coefficient of variation between analyses of the main probe and its duplicate was over two times smaller in the KQCL method than in the CLT method), fully automated in the phase of analysis and data reading, and faster and more effective than the classic Limulus test. Nevertheless, on the basis of the obtained results, the usefulness of the classic Limulus method for assessment of the degree of pollution of indoor air with bacterial endotoxin seems to be confirmed as in the majority of examined samples (21 out 40) the results obtained by both methods were of the same order of magnitude, and in the remaining 19 samples did exceed one order of magnitude. Thus, the data received by means of the classic Limulus test may be regarded as acceptable. (+info)
Risk of infection from heavily contaminated air.
In a factory processing shea nuts the dust concentrations were found to be up to 145 mg/m3 [80% respirable (1--5 micrometer)]. Bacterial examination of the dust revealed that under the worst conditions observed a worker might inhale 350,000 bacteria per 8 h. Of these, 3,000 were Ps. aeruginosa and 1,500 Salmonella spp. of nine different types. The possible health effects of these findings are discussed. (+info)