Oral ciprofloxacin treatment for Salmonella typhimurium infection of normal and immunocompromised mice.

Oral treatment of Salmonella typhimurium infection with ciprofloxacin was compared with conventional chemotherapy with ampicillin or chloramphenicol in normal (CFW1) and immunocompromised (C57BL/6) mice. Administration of the antibiotics for 12 days reduced the number of bacteria in livers and the mortality of C57BL/6 mice significantly. Ciprofloxacin was considerably more effective than ampicillin in prolongation of the mean survival time of these mice. Similar to conventional chemotherapeutic agents, ciprofloxacin did not prevent fatal disease in most C57BL/6 mice when the treatment lasted 12 days only. On the other hand, ciprofloxacin cured lethal S. typhimurium illness in immunocompromised mice after long-term oral chemotherapy for 26 days at a dosage of 100 mg/kg twice a day. This was not achieved by either ampicillin or chloramphenicol. In normal mice, 12 days of therapy with ciprofloxacin was sufficient for a significant decrease in both the number of viable bacteria in livers and the mortality of lethally infected mice. The results provide a basis for an alternative antibiotic treatment by the oral route in immunocompromised hosts with systemic infections.