Reduction of escherchia coli O157 and non-O157 O serogroups in the feces of commercial and research feedlot cattle using a high-dose of NP51, a lactobacillus-based pre-harvest intervention

Date
2013-12
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Abstract

Lactobacillus acidophilus strain NP51 is a commercially available direct-fed microbial. This specific direct-fed microbial is recommended by the United States Department of Agriculture, Food Safety and Inspection Service (USDA FSIS) to be a pre-harvest management control and intervention option for the reduction of Escherichia coli (E. coli) O157:H7 in cattle. The addition of NP51 to cattle diets at a dose of 109 /head/day (high dose) has been proven to reduce E. coli O157:H7 and Salmonella in cattle feces. Currently, there has been no research conducted on the impact of feeding NP51 and the reduction of the “Big Six” non-O157 O serogroups which include E. coli O26, O45, O103, O111, O121 and O145 in cattle feces. The purpose of these studies was to evaluate the impact of NP51 fed at a dose of 109/head/day on the reduction of E. coli O157:H7 and six non-O157 O serogroups in cattle feces in two separate cattle feeding studies. Both studies were randomized complete block design. In one study, conducted in a commercial feedlot, approximately 1,800 cattle were blocked by weight and randomized into treatment and control pens. The pens contained 75 head/pen and included 12 control pens and 12 treatment pens. The control pens included cattle not fed NP51 and treatment pens included cattle supplemented with 109 CFU/head/day NP51 (Bovamine Defend®). Twenty-five fecal pats were taken from each pen (n = 600 samples) prior to transport for slaughter. In the research feedlot study, 112 head of cattle were blocked by weight and randomized into treatment or control pens at the Texas Tech University Research Feedlot. The pens included 14 control pens and 14 treatment pens and four head per pen. Fecal grabs were collected from each animal (n = 112 samples) prior to transport for slaughter. All samples were analyzed for the presence E. coli O157 using Immunomagnetic separation (IMS) and the genes that encode for the “Big 6” non-O157 serogroup (E. coli O26, O45, O103, O111, O121 and O145) antigens using a commercially available real time PCR system (BAX Q7, DuPont Qualicon, Wilmington, DE). Quantitative estimates were derived from fecal samples that were positive for E. coli O157 using direct-plating and MPN analysis. Generalized linear mixed models were used to analyze the qualitative data and general linear mixed models were used to analyze the quantitative data. In the commercial feedlot study, a significant (44%) reduction of E. coli O157 in fecal samples was observed when comparing control groups to treatment groups (P = 0.001) in that E. coli O157 was recovered from 15.7% of the treatment cohort and 28.0% of the control cohort. Overall E. coli O157 enumeration resulted in a significant reduction of 0.33 log10 CFU/g when comparing control and treatment groups (P = 0.1). Of the “Big Six” Non-O157 serogroups, results indicated a reduction in O serogroups O26, O45, O103 and O121 with a reduction of 52.7% (P = 0.02), 36.0% (P = 0.001), 33.0% (P = 0.03) and 42.0% (P = 0.02), respectively.
In the research feedlot study, a significant (60%) reduction of E. coli OI57 was observed among the treatment cohort compared to the controls (P = 0.08). The prevalence of E. coli O157 for treatment and control cohorts was 3.7% and 14.8%, respectively. Of the “Big Six” Non-O157 serogroups, results indicated a numerical reduction in O serogroups O26, O45, O103, O111 and O145. In conclusion, NP51 serves as a successful pre-harvest food safety intervention.

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Keywords
Escherichia coli, Beef cattle, Lactobacillus
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