Effects of daily oral administration of rifaximin and neomycin on faecal aerobic flora in rats

The aim of this study was to compare the influence of rifaximin and neomyci n on faecal flora in rats. The study was performed on 18 Wistar rats (three groups of six male animals). Group I received rifaximin (50 mg kg(-1)/day) , group 2, neomycin (50 mg kg(-1)/day) and group 3 was used as control. Dru gs were administered orally, once daily for 3 days. Faecal specimens, colle cted from each rat on day 3, were cultured for the quantitative and qualita tive determination of aerobic microorganisms. Rifaximin treatment produced a marked reduction in the number of total aerobic bacteria and Salmonellae; neomycin caused reduction in Salmonellae, but did not cause statistically significant changes in total aerobic bacterial count. The binding of neomyc in with faeces could explain this limited activity, which does not correlat e with the in vitro susceptibility of the organism affected. These results confirm that rifaximin is suitable for topical treatment to reduce selected bacterial load in the gut intestines. (C) 2001 Academic Press.