Microorganisms are ubiquitous and are thus found everywhere including the soil. The soil no doubt is inundated with a wide variety of microorganisms including those that are pathogenic to humans, plants and animals and even microbes that are of immense industrial and economic importance to mankind and his environment. For example, the first commercial antibiotic penicillin was originally and naturally sourced from Penicillium species especially P. notatum and P. chrysogenum, which are prominent microbes found in the soil.
The soil is a dwelling place to a wide array of microorganisms including bacteria, protozoa, helminths, fungi and some viruses which cause a handful of disease in humans (Table 1). It is a multilayered surface of the earth crust made up of mineral and organic constituents that harbours a huge biodiversity of life that supports several biological processes of microorganisms, humans, plants and animals. The microorganisms found in the soil have several biological functions in the soil such as providing support to the ecosystem as well as proving growth support to plants and improvement of the fertility of the soil. The soil is also home to small animals such as rodents, snails and nematodes, and they give mechanical and protective support to plat roots. Microorganisms that are innately found in the soil help in the cycling of nutrients in the ecosystem.
Table 1. Microbial diseases transmissible through the soil
The soil is home to microbes that are of immense economic, health and industrial importance; and several antibiotics and/or antimicrobial agents have their source from microorganisms (especially bacteria and fungi) that dwells in the soil. Though they contain numerous microbes that are beneficial to mankind, animals, plants and the environment, the soil also contain microorganisms which are capable of causing diseases in humans and even in other animals and plants as well. Microbes that are found in the soil and which cause disease in humans and animals are generally known as soil-borne pathogens.
Most of these soil-borne pathogens are opportunistic pathogens, and they take advantage of the immune system status of susceptible individuals especially people who are immunocompromised (e.g. AIDS patients) to cause infection or disease. Soil-borne pathogens are able of surviving for long periods of time within the soil environment until they find a suitable human host to infect. Human infections with soil-borne pathogens is usually common amongst people who come into direct contact with contaminated soil especially soil contaminated with feacal matter of animal and human origin.
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