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PubMed · 12751259

Blastomycosis.

Abstract

Blastomycosis is an endemic mycoses in the central United States caused by a dimorphic fungus, Blastomyces dermatitidis, that exists in nature in mycelial phase and converts to yeast phase at body temperature. The organism may produce epidemics of infection following a point source of infection or sporadic endemic infection. Blastomycosis can be a subclinical illness with subsequent protection against progressive infection afforded by cellular immune mechanisms, but it may present with progressive disease with either pulmonary or extrapulmonary disease or both. Itraconazole has been shown to be the drug of choice for both infections, except in cases of life-threatening infection when amphotericin B should be used.

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BibTeXRIS

Robert W Bradsher, Stanley W Chapman, Peter G Pappas. 2003. Blastomycosis.. https://doi.org/10.1016/s0891-5520(02)00038-7

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Geographic distribution of human blastomycosis cases in Milwaukee, Wisconsin, USA: association with urban watersheds.

Most studies of endemic blastomycosis and outbreaks have involved rural areas. Case homesites in rural Northern Wisconsin have been associated with waterways and sand soils. ARC-GIS was used to geocode addresses and to observe geographic features of homesites from 45 State-mandated reports of human blastomycosis in urban Milwaukee County, Southeastern Wisconsin 2000-2004. Each case property was directly observed, and houses and duplexes (N = 38) were compared with 151 same-street control homesites. Categorical data was analyzed using a chi-square or Fisher's exact test; continuous variables by Kruskal-Wallis test. One case cluster was seen on Milwaukee's North side where the estimated annual incidence was 2.8/100,000 compared to 0.96/100,000 for the entire county. Cases were less common in the most urbanized watersheds (0.49/100,000/yr) versus Lake Michigan shores (0.85) versus remaining three open watersheds (1.4) [P<0.01]. Case homesites averaged 1067 m to waterways and none were on sand soils. (Comparison is made to a Northern Wisconsin community where case homesites averaged 354 m to waterways, 24/25 were on sand soils and annual incidence was 74/100,000.) No unique features of case homesites were identified in Milwaukee County. In this urban area of Wisconsin, relatively low incidence rates may be explained, in part, by lower density of inland waterways and lack of sand soils, however, blastomycosis cases appear to be associated with open watersheds.

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PCR-based detection of DNA from the human pathogen Blastomyces dermatitidis from natural soil samples.

Blastomyces dermatitidis is the dimorphic fungal agent of blastomycosis, a disease that primarily affects humans and dogs. The clinical appearance of this mycosis is well characterized, but there is still little known about its environmental niche, having been isolated from nature only 21 times. We have developed a PCR-based assay to detect B. dermatitidis from soil samples using primers specific to a portion of the promoter region of the BAD1 virulence gene. An internal standard control, pTJV2, was constructed to validate the results from soil samples. Amplification of this control indicated adequate removal of ambient soil inhibitors. The PCR detection limits for the control plasmid and B. dermatitidis genomic DNA were 0.1 and 500 femtograms, respectively. No PCR cross-reactivity was observed against bacteria, actinomycetes, and 13 other fungi that were genetically related or found in the same geographic areas. In spiked soil samples, this method was sensitive to 304 copies of pTJV2 DNA and 8,450 live B. dermatitidis yeast cells. Three of eight natural soil samples from a dog kennel near Lexington, KY in which dogs suffered from blastomycosis were positive using the described method, demonstrating its utility in detecting B. dermatitidis in its natural surroundings.

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