The Effect of Commensal Microbial Communities on the Fecal Shedding of Shiga Toxin-Producing E. coli (STEC) in Beef Cattle

This ongoing study compares the gut microbial community composition between shedding steers high in shiga toxin-producing E. coli (STEC) counts and low-shedding steers. Shedders were identified among 170 beef animals over three time periods using selective microbiological culture media. The isolated bacterial cultures were confirmed to be STEC using PCR, 16s rRNA sequencing and a shiga toxin immunoassay. The most abundant strains found in the cattle feces were those belonging to the serogroups O111 (40.3%) and O157:H7 (37.3%), with O103 (8.3%), O26 (6.0%), O83 (4.5%), and O55 (3.0%) being detected in much lower numbers . Out of the 52 animals which were identified as super-shedders of STECs which were selected for microbial community analysis, 61.54% shed STEC in at least two of the three sampling time points. Currently, work is being carried out to evaluate the microbial community composition of the identified STEC high-shedding and low-shedding cattle populations using 454-pyrosequencing.