Effect of Bovamine® on Prevalence and Concentration of Escherichia coli O157:H7 and Non-O157 Shiga Toxin-producing Escherichia coli (STEC) on Beef Feedlot Cattle

Introduction: Cattle are common reservoirs for STEC without presenting any clinical symptom. E. coli O157:H7 along with other non-O157 strains (O26, O45, O111, O121, O103, and O145) have been declared as adulterants in ground beef and its components. Bovamine^®, a combination of a lactic-acid-producing bacterium (Lactobacillus acidophilus NP51) and a lactic-acid-utilizing bacterium (Propionibacterium freudenreichii NP24) was tested as a direct-fed microbial to reduce the population of STEC in cattle.

Purpose: To evaluate the effect of Bovamine^®; rumen culture feeding programs, low dose (LD), high dose (HD), and a combination of LD and HD on prevalence and concentration of E. coliO 157:H7 and non-O157 STEC.

Methods: Steer were randomly allotted into 10 pens per treatment with 10 head per pen with the following treatments administered daily: High dose Bovamine (10⁹/head/day), Low Dose (10⁷/head/day), and Low/High (10⁷/head/day followed by 10⁹/head/day at the last 30 days of feeding period). Fecal samples were collected at harvest. E. coli O157:H7 were recovered through immunomagnetic separation (IMS) followed by confirmation and enumeration using most probable number technique. Non-O157 STEC were detected using the BAX^® System.

Results: The prevalence of O157 was low at 8-13%. The quantitative amount of O157 in the controls was 2.46 MPN/g, 0.14 MPN/g in the high dose, 1.04 MPN/g for the low dose, and 0.49 MPN/g in the Low/High dose. Prevalence of O26 was 61.7% in the control animals and 36.3% in the animals fed the high dose. The high dose also significantly reduced O103 from 55.6% in the control animals to 40%. Serogroup O45 was at 67.9% in the control animals and was reduced to 45% by the high-dose treatment. The prevalence of the other STECS was less than 10% with no differences detected among treatments.

Significance: Control of STEC in cattle using Bovamine may impact the prevalence of E. coli O157:H7 and non-O157 in meat products and have a positive result with regards to public health.