A variety of classic and emerging soil-related bacterial and fungal pathogens cause serious human disease that frequently presents in primary care settings. Typically, the growth of these microorganisms is favored by particular soil characteristics and may involve complex life cycles including amoebae or animal hosts. Specific evolved virulence factors or the ability to grow in diverse, sometimes harsh, microenvironments may promote pathogenesis. Infection may occur by direct inoculation or ingestion, ingestion of contaminated food, or inhalation. This narrative review describes the usual presentations and environmental sources of soil-related infections. In addition to tetanus, anthrax, and botulism, soil bacteria may cause gastrointestinal, wound, skin, and respiratory tract diseases that also should be considered, particularly in the case of wound, respiratory tract, or gastrointestinal infections. The purpose of this article is to review bacterial and fungal infections for which the source of contact is primarily the soil (eg, Clostridium tetani) or for which soil is an important or emerging secondary site of contact (eg, Legionella). The emphasis of this article will be on the epidemiology of significant soil-related human pathogens and their common disease presentations such that these entities will be considered promptly during relevant patient evaluations. (The reader is referred to recent texts and manuscripts for details regarding unusual presentations and the diagnosis and treatment of these infections and for discussion of superficial soil-related infections, such as dermatophyte infections, which will not be covered here.) Soil MicrobiologySoil 1,3 is a multilayered surface complex of mineral and organic (humus) constituents present in solid, liquid, and gaseous states. The mineral portion of soil results from the actions of weathering and erosion on rock. Broad soil type-sand, silt, or clay-is defined, largest to smallest, by particle size. These particles pack loosely, and pore spaces of varying sizes are formed. Particle surfaces, pore spaces, and plant roots are particular habitats for microorganisms, often in biofilms. Soil also contains plants, animals, carcasses, and man-made materials.The quantity and type of microorganisms in a particular portion of soil are determined by a complex interaction of varying amounts of sunlight, temperature, moisture, soil pH, nutrients, and reThis article was externally peer reviewed.

The clinical and epidemiologic features of 73 patients with laboratory-confirmed blastomycosis who were identified over an 11-year period in North Central Wisconsin are presented. Pulmonary disease was the sole manifestation in 77% of patients. More than one-half of all patients had symptoms that included fever, cough, weight loss, night sweats, and pleuritic chest pain. Virtually all were previously healthy, and most did not have an outdoor occupation. However, 82% of these patients lived or had visited within 500 m of rivers or associated waterways. The majority experienced the onset of symptoms between December and April. The estimated mean annual incidence rate of infection for Vilas County was 40.4 cases per 100,000 persons, and that for the largest city in the county was 101.3 cases per 100,000 persons. Several areas with an exceptionally high incidence of the infection were observed. We suggest that, in regions where blastomycosis is hyperendemic, clinical disease is most often pulmonary and occurs in immunocompetent individuals and that residence near an ecological focus may be a greater risk factor for acquisition of blastomycosis than is occupation.