Airborne Aspergillus fumigatus levels outside and within a large clinical center.

Most considerations of Aspergillus fumigatus prevalence have implied that patterns of occurrence observed within London hospitals are generally applicable. Since prevalence data are almost nonexistent elsewhere, this assumption remains untested. To provide a comparison relevant to North America, we have monitored thermotolerant fungi outside as well as at two sites within the University Hospital, Ann Arbor, Michigan, during one year. Collections were made with paired Andersen samplers and malt agar for 30- to 40-min periods in a hallway adjacent to 6W, a general medical ward (47 days), and 2W, a lower level service and supply area (40 days); in addition, 10-min outdoor samples (44 days) were taken on an unobstructed hospital rooftop (out). Recoveries were analyzed after 3 and 7 days of 37 degrees C aerobic incubation. Virtually complete suppression of Cladosporium form species at 37 degrees left a mycoflora with A. fumigatus, A. niger, Paecilomyces spp., Mucor spp., and yeast/bacteria predominating. Although the proportions of samples yielding A. fumigatus were 76% for 6W, 57% for 2W, and 56% (out), levels exceeded 40 isolates/m3 only twice and were over 10 isolates/m3 on only 10 of 131 total samples. For 6W, 2W and out, respectively, means were 4.78, 1.97, and 6.25 isolates/m3; medians were 1.20, 1.05 and 1.75/m3 without annual trends indoors and with only a limited outdoor summer increase. Our data fail entirely to show the fall-winter abundance observed in the London report and suggest substantially lower indoor exposure levels of A. fumigatus than those noted in London.

Comparative merits of eight popular media in aerometric studies of fungi.

Although cultural surveys of airborne fungi are pursued widely, the comparative virtues of popular media have not been systematically tested. To facilitate an informed choice, eight different agar media were compared using paired single-plate exposures of identical, wind-oriented, Andersen samplers. Modified Mehrlich's (MM), Sabouraud's dextrose (SAB), malt extract (MALT), V8 juice (V8), and potato dextrose-rose bengal (PDAR) agar were compared initially; potato dextrose (PDA), MALT, rose bengal streptomycin (RBS), and casein hydrolysate (CH) agar were compared during a subsequent series, as were PDA and PDAR. Overall, SAB, MALT, V8, and PDA total recoveries were similar, while MM, CH, PDAR, and RBS were significantly low in paired comparisons with one or more media. MALT and SAB produced the highest frequencies of recovery of most colony types. Bacteria were infrequently recovered on any of the media. CH and MM excluded Epicoccum but are of potential use in surveys that focus sharply on high concentrations of Cladosporium. Rose bengal-containing media performed poorly in this study and must be approached with caution and under properly controlled conditions.

Performance of adhesives for rotating-arm impactors.

Particle collections by paired rotoslide surfaces coated differentially with either of two silicone greases, white petrolatum or Lubriseal, were compared in two series of studies. Three samplers were employed, and adhesives were assigned randomly to the six available positions. Recovery differences were small but occasionally significant, with counts generally highest for silicone grease and lower with Lubriseal. During natural and simulated rainfall relative performances were similar, although differences were accentuated.

Exclusion of particulate allergens by window air conditioners.

Effects of window air-conditioner operation on intramural particle levels were assessed in the bedrooms of 20 homes and in 10 outpatient clinic examining rooms during late summer periods. At each site, pollen and spore collections in the mechanically cooled room and a normally ventilated counterpart were compared using volumetric impactors. Substantially lower particle recoveries (median = 16/m3) were found in air-conditioned rooms than in those with open windows alone (median = 253 particles/m3). Furthermore, substantial exclusion of small (e.g., Ganoderma spores) as well as large (ragweed pollens) aerosol components were found by window units. Control studies within normally ventilated rooms and outside their open windows showed a marked but variable inward flux of particles. Window units appear to substantially reduce indoor allergan levels by maintaining the isolation of enclosed spaces from particle-bearing outdoor air.

Microbial prevalence in domestic humidifiers.

The prevalence of viable thermophilic bacteria and actinomycetes and mesophilic fungi was examined in 145 samples from 110 domestic humidifiers. A total of 72 and 43% of furnace and console humidifier samples, respectively, contained viable thermophilic bacteria, whereas 60 and 72% of these samples produced mesophilic fungal growth. Thermophilic actinomycetes were recovered from seven humidifier samples. Efforts to detect thermophilic actinomycete antigens in 15 humidifier fluid samples were not successful. Antifoulants added to humidifier fluid reservoirs had no apparent effect on microbial frequency. Airborne microbial recoveries did not reflect patterns of humidifier contamination with respect to either kinds or numbers of microorganisms in 20 homes in which volumetric air samples were obtained during humidifier operation.

An appraisal of Impregon as a deterrent of domestic fungus growth.

Impregon brand of tetrachlorsalicylanilide (TCSA) has been profferred widely as a household fungistatic agent, although its value remains unproved. To assess its effects, this agent was used as a laundry and paint additive and as a treatment for burlap rug backing; after recommended applications of Impregon, coded replicate materials were inoculated with mixed suspensions of fungus particles. No difference was evident in fungus growth points on fabric swatches washed in tap water with and without Impregon. However, growth on both of these was significantly greater than on samples laundered in tap water using only a commercial soap or liquid detergent. Fungus soiling of burlap was not clearly diminished by prescribed applications of Impregon solution 3 mo previously. Similarly, the addition of this agent to paint did not suppress fungus growth on Masonite plaques to which it had been applied. However, comparable levels of Impregon incorporated into agar media substantially inhibited spore germination. These findings suggest that the bioavailability of TCSA is insufficient to provide desired household antifungal effects when Impregon is used in accord with current recommendations.

Fungi in libraries: an aerometric survey.

The possible role of fungi as allergic contaminants in book collections has been investigated in eleven University of Michigan Libraries. Air in the stacks of each of the eleven libraries was sampled on three occasions (2 or 4--10 minute samples on each occasion) with Andersen Volumetric viable particle samplers. Books were handled during sampling in half the samples each day. In addition on each sampling day a location in the same building away from book storage and an outdoor location were sampled. Library spore levels were generally low. Outdoor levels consistently exceeded indoor levels. Air conditioned (AC) libraries had lower spore levels and indoor/outdoor ratios than conventionally ventilated (CV) libraries. Handling books during sampling increased spore counts in all libraries, but strikingly in CV libraries. Fungus taxa recovered were similar to those encountered in domestic interiors and outside locations in our area. The overall low spore levels and lack of a distinctive library mycoflora suggest that other sources should be sought for library-based respiratory symptoms.

Comparative recoveries of airborne fungus spores by viable and non-viable modes of volumetric collection.

The suitability of viable and non-viable volumetric collectors as prevalence indicators for potentially allergenic airborne fungi was studied during 124 paired exposures of the Burkard (Hirst) spore trap and a modified, wind-oriented Andersen sampler. Overall, viable recoveries of several Cladosporium form species varied directly with microscopic spore counts (p less than or equal to 0.0001). However, as spore levels rose, culture plate data progressively underestimated prevailing concentrations (recoveries falling below 5% at levels above 500 spores/M3). Viable collections yielded low estimates of prevalence (20-40%) even at modest Cladosporium levels (less than 100 spores/M3) and substantially understated the abundance and regularity in air of several additional taxa. Spores typical of Penicillium and Aspergillus form species were not sought in spore trap deposits. Careful examination of these failed to reveal typical arthrospores or Fusarium macrospores despite substantial recoveries of corresponding growth in culture. Correlations in the occurrence patterns of arthrospore-forming and non-sporulating colonies with those of Coprinus and 'other basidiospores' (excluding Ganoderma) were noted.