Assumptions and Limitations Associated with Microbial Source Tracking Methods

Abstract

This chapter provides a critical evaluation of microbial source tracking (MST) methods, including an analysis of the current expectations of MST tools. The ultimate goal of all microbial source tracking studies is to link fecal contamination with its host source, whether contamination is a concern in water or food. Characteristics considered desirable for an “ideal” MST tool are presented in the chapter, followed by a discussion of the assumptions made about tools currently used, research studies that have addressed these assumptions, and known limitations of the tools. Host specificity of commensal and mutualistic microflora of the gastrointestinal (GI) tract may, however, be the exception rather than the rule, particularly among the culturable fraction of the inhabitants of the GI tract. MST methods as related to food are also concerned with direct detection and tracking of the source of food-borne pathogens, some of which are zoonotic and are easily transmitted from animal hosts to humans. An MST tool that is adopted for beach water quality monitoring, total maximum daily load (TMDL) assessment, and food quality programs throughout the United States should meet the assumptions listed in the chapter. Several studies on the distribution of Escherichia coli species/pattern/markers (SPMs) in primary versus secondary habitats noted distinct differences in the populations.