Isolation and Enumeration of Escherichia coli from Soil and Water

Abstract

Water is one of the basic componentsfor man’s continued existence1. Water plays a central role in the regulation of nutrient transport, toxic waste removal, thermal regulation and digestion and digestion, organ functioning and metabolic activities. But fecally contaminated water is able to spread diseases in consumers to a great number of people2.The World Health Organization estimated in 2000 that there are four billion cases of diarrhea each year in addition to millions to other casesof illness associated with the lack access of clean water3. It is recommended that water supplies contaminated with human and animal excreta particularly feces can transmit infectious diseases4.Out breaks of water borne diseases continue to occur throughout the world but are especially serious in developing countries5-6. Another important component of environment is soil which is the region on earth’s crust where geology and biology meet the land surface that provides a home to plant, animal and microbial life7. Soil teems with microscopic life (bacteria, fungi, algae, protozoa and viruses as well as macroscopic life such as earthworms, nematodes, mites and insects and also the root systems of plants. The number and kinds of microorganisms present in soil depend on many environmental factors: amount and type of nutrients available, available moisture, degree of aeration, pH, temperature etc. Soil is generally a favourable habitat for the proliferation of microorganisms with micro colonies developing around soil particles. Number of microorganisms in soil habitats normally are much higher than those in fresh water or marine habitats8.Escherichia coliis a common bacteria found in the human intestine. Under certain conditions, E. coli can become pathogenic,i.e., it gains the ability to cause disease. It almost goes without saying that E. coliis an important model organism and has been for more than 120 years. For a long time E. coli has become a common resident of the environment. Moreover, as the environmental conditions are significantly different from what exists in the human intestine, E. coli fails to survive long outside of the human host. For these reasons, E. coli has been used as an indicator of recent fecal contamination and represents a threat to human and environmental health9.However, for rapid detection of indicator organisms in drinking water as well as in soil, the most probable number (MPN) method, which is not that common in usage, might be considered10-11. It is actually a qualitative test rather than quantitative indicating only the presence of coliforms, not their numerical presentation.