Whole-Cell Fatty Acid Composition of Total Coliforms to Predict Sources of Fecal Contamination

The objective of this study was to test the hypothesis that total coliforms isolated from human and nonhuman sources have distinctly different whole-cell fatty acid methyl ester (FAME) profiles. The FAME profiles studied included total coliforms isolated from sewage; feces of livestock, including bovine (dairy cattle), poultry, and swine; and feces of wildlife, including waterfowl and deer. Multiple samples within each category were collected and 303 total coliform isolates were cultured. It was found that the FAMEs 12:0 2OH and 14:0 2OH were exclusively associated with sewage samples, whereas the FAMEs 18:0 and 19:0 ISO were identified only in isolates from the livestock samples. In addition to the presence of signature FAMEs, the average relative masses of 16:1 ω7c, 18:1 ω7c, and 19:0 CYCLO ω8c were significantly different between human and nonhuman sources of total coliforms. A linear discriminant function based on these differences discriminated total coliform isolates of human origin against the other five host categories at a 77% rate of correct classification (RCC). These results strongly support the validity of our hypothesis and suggest that the FAME profiles of total coliforms have the potential to be used as a phenotypic microbial source tracking (MST) tool for predicting the sources of microbial contamination in water environments.