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Research Abstracts Online
January 2009 - March 2010

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University of Minnesota Twin Cities
College of Veterinary Medicine
Department of Veterinary and Biomedical Sciences

PI: Richard Isaacson

Potential Public Health and Food Safety Impacts Associated With Use of Antibiotic Growth Promoters

Antibiotics have been used extensively as growth promoters (AGPs) in agricultural animal production. However, the specific mechanism of action for AGPs has not yet been determined. Following early demonstrations that oral antibiotics do not have growth-promoting effects in germ-free animals, studies of the mechanism for growth promotion have focused on interactions between the antibiotics and the gut microbiota. Therefore, these researchers hypothesized that the effects of AGPs are mediated by influencing compositional changes of the pig distal gut microbiota. Fecal samples from tylosin (40mg/kg) treated (n=10) and tylosin-non-treated pigs (n=10) were collected 5 times at 3-week intervals starting when the pigs were 8 weeks of age. The sequences of the V3 hypervariable region of 16S rRNA were generated using the massively parallel pyrosequencing. Sequences were quality assessed, aligned, and manually curated. A phylogenetic assessment was conducted using RDP classifier, and richness and diversity indices were generated using Mothur with an Operational Taxonomic Unit definition at a similarity cutoff of 97%. Sequencing generated over a million sequence reads. The pig distal gut bacterial communities of both groups were dominated by Firmicutes and Bacterioidetes accounting for > 80% of total sequences, and showed highly diverse community structure (Shannon > 4.3, and Simpson 1-D > 0.9). Most of the sequences ( > 95% of the total sequences) were shared by pigs in the two treatment groups. Components of the classes Actinobacteria, Clostridia, Fibrobacter, and Erysipelotrichi were different between the groups. While there were no differences at the phylum between groups, at the genus differences were observed. However, the effects of the bacterial compositional differences on growth promotion should be evaluated to determine if these changes mediate growth promotion. These results also provide a reference of the pig distal gut microbiota profile and fundamental knowledge for later studies to design new strategic approaches to replace AGPs in the future, such as probiotics or prebiotics.

Group Members

Hyeun Bum Kim, Graduate Student
Srinand Sreevatsan, Faculty Collaborator