Effect of Citrus Byproducts on Survival of O157:H7 and Non-O157Escherichia coliSerogroups withinIn VitroBovine Ruminal Microbial Fermentations

Abstract

Citrus byproducts (CBPs) are utilized as a low cost nutritional supplement to the diets of cattle and have been suggested to inhibit the growth of bothEscherichia coliO157:H7 andSalmonella. The objective of this study was to examine the effectsin vitrothat varying concentrations of CBP in the powdered or pelleted variety have on the survival of Shiga-toxinEscherichia coli(STEC) serotypes O26:H11, O103:H8, O111:H8, O145:H28, and O157:H7 in bovine ruminal microorganism media. The O26:H11, O111:H8, O145:H28, and O157:H7 serotypes did not exhibit a change in populations in media supplemented with CBP with either variety. The O103:H8 serotype displayed a general trend for an approximate1log10reduction in 5% powdered CBP and 20% pelleted CBP over 6 h. There was a trend for reductions in populations of a variant form of O157:H7 mutated in thestx1 andstx2 genes in higher concentrations of CBP. These results suggest that variations exist in the survival of these serotypes of STEC within mixed ruminal microorganism fluid media when supplemented with CBP. Further research is needed to determine why CBPs affect STEC serotypes differently.