The Effect of Norfloxacin and of Rosoxacin on the Colonization Resistance of the Digestive Tract in Mice

Conventional mice were treated orally with various doses of norfloxacin and rosoxacin, respectively, to determine to which extent the “colonization resistance” (CR) of the digestive tract is affected. In addition, the effect was studied of both drugs on the endogenous Enterobacteriaceae and enterococci in the digestive tract (faeces). According to parameters for the CR of the digestive tract, such as the appearance of β-aspartylglycine and the relative caecal weight, norfloxacin did not decrease the CR in a dose range of up to 0.30 mg/mouse/day. A dose of 0.05 mg/mouse/day sufficed to clear the digestive tract of endogenous Enterobacteriaceae within three days. The highest dose of rosoxacin of 6.0 mg/mouse/day did not decrease the CR. A dose of 0.9 mg/mouse/day cleared the digestive tract of endogenous Enterobacteriaceae. These two drugs could therefore be considered for use in selective decontamination of the digestive tract of neutropenic patients.