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Longitudinal Study of Escherichia coli O157:H7 in a Beef Cattle Feedlot and Role of High-Level Shedders in Hide Contamination

Arthur, Terrance M., Keen, James E., Bosilevac, Joseph M., Brichta-Harhay, Dayna M., Kalchayanand, Norasak, Shackelford, Steven D., Wheeler, Tommy L., Nou, Xiangwu, Koohmaraie, Mohammad
Applied and environmental microbiology 2009 v.75 no.20 pp. 6515
beef cattle, Escherichia coli O157:H7, Escherichia infections, microbial detection, feces, hairs, bacterial contamination, feedlots, longitudinal studies
The objectives of the study described here were (i) to investigate the dynamics of Escherichia coli O157:H7 fecal and hide prevalence over a 9-month period in a feedlot setting and (ii) to determine how animals shedding E. coli O157:H7 at high levels affect the prevalence and levels of E. coli O157:H7 on the hides of other animals in the same pen. Cattle (n = 319) were distributed in 10 adjacent pens, and fecal and hide levels of E. coli O157:H7 were monitored. When the fecal pen prevalence exceeded 20%, the hide pen prevalence was usually (25 of 27 pens) greater than 80%. Sixteen of 19 (84.2%) supershedder (>10⁴ CFU/g) pens had a fecal prevalence greater than 20%. Significant associations with hide and high-level hide (greater-than-or-equal40 CFU/100 cm²) contamination were identified for (i) a fecal prevalence greater than 20%, (ii) the presence of one or more high-density shedders (greater-than-or-equal200 CFU/g) in a pen, and (iii) the presence of one or more supershedders in a pen. The results presented here suggest that the E. coli O157:H7 fecal prevalence should be reduced below 20% and the levels of shedding should be kept below 200 CFU/g to minimize the contamination of cattle hides. Also, large and unpredictable fluctuations within and between pens in both fecal and hide prevalence of E. coli O157:H7 were detected and should be used as a guide when preharvest studies, particularly preharvest intervention studies, are designed.