Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 2, 2010
Publication Date: N/A
Technical Abstract: The complex effects of antibiotics on indigenous microbial ecosystems are poorly understood despite the widespread use of antibiotics in agricultural animals. An increase in resistant bacteria is one obvious effect of antibiotics; additional activities of some antibiotics at subinhibitory concentrations include the modulation of gene expression and the stimulation of gene transfer. Previous work from our lab showed that the veterinary antibiotic carbadox induced a phage-like gene transfer agent in the swine intestinal pathogen Brachyspira hyodysenteriae. We therefore hypothesize that one collateral effect of antibiotic treatment in animals is an increase in phage lysis in the gastrointestinal microbiota. The current study aims to characterize shifts in the swine intestinal phage population following different antibiotic dosages. Feces were collected at one day, three days, and 14 days post-dosage from 18 piglets that were reared on antibiotic-free feed, or feed containing subtherapeutic or therapeutic levels of carbadox. We developed a method to isolate phage from 10 grams of feces that included blending, centrifugation, cesium chloride gradient separation, and syringe filtration. Phage particles were then visualized by electron microscopy prior to DNA isolation for pyrosequencing. Electron microscopy showed many different viral morphologies in both control and treated animals, including enveloped virions and morphotypes of the myoviridae, siphoviridae, and podoviridae phage families. The results show a great diversity of viruses in the swine intestinal microbiome. Sequencing the viral assemblage followed by comparative metagenomic analyses will demonstrate the effect of antibiotics on the phage population in the gastrointestinal tract. Learning the effect of antibiotics on intestinal phage is critical to understanding all of the ecosystem-level effects of agricultural antibiotics, which in turn is essential to animal health and food safety.