The Use of Ampicillin-Medicated Diet to Treat Segmented Filamentous Bacteria in a Mouse (Mus musculus) Colony

Segmented filamentous bacteria (SFB), or Candidatus savagella, are gram-positive, spore-forming, filamentous commensal bacteria that colonize the ilea of mice and rats. SFB can impact certain research studies due to their effect on the innate and adaptive immune system. Therefore, there is a need to eliminate SFB from some rodent colonies. Antibiotics are an effective treatment method that have been shown to be successful at eradicating this bacterium. Commonly, antibiotics are supplied to rodents via water. However, antibiotics in water have several limitations, depending on the type of water and the length of time in water, and administration is labor intensive. Therefore, this study sought to create a rodent diet containing the antibiotic ampicillin. The feed was constructed to counter an expected ampicillin concentration decrease from the pelleting process and irradiation. Mice were placed on the ampicillin feed for 4 weeks, and SFB was measured via PCR fecal analysis. After one week of feeding the ampicillin diet, all mice in the treatment group were negative for SFB. These mice remained negative for 2 additional weeks after treatment cessation. This study shows ampicillin diet is an effective method to eliminate SFB from mouse colonies.