TECHNICAL NOTE: Long-chain fatty acid profile of cattle fecal samples as an indicator for the shedding of Escherichia coli O157

We analyzed methyl esters of long-chain fatty acids (LCFA) in fecal samples obtained from crossbred heifers to determine whether these compounds could be useful indicators of the presence or absence of Escherichia coli O157. Fecal samples were characterized for presence or absence of E. coli O157 using immunomagnetic separation, LCFA were determined by gas chromatography, and a stepwise regression technique was used to evaluate the relationship between presence of E. coli O157 and LCFA. Of the 39 LCFA evaluated, only eicosapentaenoic acid concentration was associated with presence of the pathogen in feces (P < 0.0153). Eicosapentaenoic acid is not produced by E. coli O157; however, its increased concentration in O157-positive samples cannot be directly attributed to the pathogen. The overall lack of differences between fatty acid profiles of E. coli O157 positive and negative samples may be explained by limited sensitivity of the immunomagnetic separation technique used to classify the samples. Our results suggest that LCFA measurements had no utility for determining E. coli O157 presence in cattle feces.