The increased incidence of nosocomial infections by multi-drug resistant Acinetobacter baumannii creates demand on the application of some combinations of older antimicrobials on that species. We conducted the present observational study to evaluate the efficacy of intravenous and aerosolized colistin combined with rifampicin in the treatment of critically patients with nosocomial infections caused by multiresistant A. baumannii.

Critically ill patients with nosocomial infections caused by A. baumannii resistant to all antibiotics except colistin in a medical intensive care unit. Diagnosis of infection was based on clinical data and isolation of bacteria. The bacterial susceptibilities to colistin were tested. Clinical response to colistin+rifampicin was evaluated.

Twenty-six patients (43.58±18.29 years, Acute Physiology and Chronic Health Evaluation II Score (APACHE II): 6.35±2.99), of whom 16 cases of nosocomial pneumonia treated by aerosolized colistin (1×10⁶IU three times/day) associated with intravenous rifampicin (10mg/kg every 12h), nine cases of bacteraemia treated by intravenous colistin (2×10⁶IU three times/day) associated with intravenous rifampicin (10mg/kg every 12h) in which three cases associated with ventilator associated pneumonia and one case of nosocomial meningitis treated by intrathecal use of colistin associated with intravenous rifampicin. The clinical evolution was favourable for all ill patients. Concerning side effects, we have noticed a moderate hepatic cytolysis in three patients.

This is the first clinical report of colistin combined with rifampicin for treatment of A. baumannii infection. Despite the lack of a control group and the limited number of patients, the results seem to be encouraging.