- Although Helicobacter spp. have been viewed as bacteria with low pathogenicity, many investigators have shown that these low-grade pathogens have the potential to become a severe threat in immunocompromised, inbred, and transgenic animals. Therefore the presence of Helicobacter spp. in experimental animals is considered to be an unacceptable variable. In this study a formulation of medicated feed was designed and tested in an attempt to eradicate Helicobacter spp. from an infected rat breeding colony. Two feeding protocols were used: 1) treating Helicobacter-infected pregnant dams to produce clean offspring and 2) treating infected adult animals long enough to eliminate the organisms. Bacterial DNA was extracted from feces and amplified using primers that recognized the Helicobacter spp.-specific region of the 16S rRNA gene. Fecal samples from the weanlings from protocol 1 tested negative for Helicobacter spp. at 1 week before and 2 and 12 weeks after weaning. Infected adult rats from protocol 2 tested negative after three cycles of 2 weeks on and 2 weeks off the medicated feed. Animals from both protocols have remained Helicobacter-free for 8 months.