Soil-Related Bacterial and Fungal Infections

Abstract

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.

Fungal Infections From Human and Animal Contact

“…31 Malassezia pachydermatis fungemia has occurred as outbreaks in neonatal intensive care units, including one case in which the employee acquired the strain from a household dog. 49 Sporotrichosis (discussed in detail in previous articles 1,2 in this series) may be a zoonotic infection in some cases. 10 There have been epidemiologic associations of this disease with armadillo hunting, fire-ant bites and contact with domestic cats infected with Sporothrix schenckii.…”

Freshwater Fungal Infections

“…1,2 In this third article of the series, we will review the much less common occurrence of human fungal infections resulting from freshwater exposure. These infections often involve immunocompromised hosts, but may occur following water-associated trauma (either in freshwater or in the presence of freshwater such that associated organisms may enter the body).…”

Primary Care Research Conducted in Networks: Getting Down to Business

“…Articles by Baumgardner 16 and Messina et al 17 review soil-related infections and cognitive-behavioral clues to Kleinfelter syndrome in adolescents, respectively. Force et al 13 documented that, because of the increasing incidence of diabetes, hypertension, and hyperlipidemia in women of childbearing age, a substantial number of these women are taking medications with potential fetal toxicity, and documentation of informed consent in these cases was infrequent.…”