Imipenem, doxycycline and amikacin in monotherapy and in combination in Acinetobacter baumannii experimental pneumonia

Acinetobacter baumannii is a common cause of nosocomial pneumonia and other nosocomial infections. Multiresistant A. baumannii has also a high prevale nce, which can make effective treatment difficult. We designed a new model of A. baumannii experimental pneumonia using C57BL/6 immunocompetent mice. This model was used to compare the efficacy of imipenem, doxycycline and am ikacin in monotherapy, and the combination of imipenem plus amikacin and do xycycline plus amikacin. Doxycycline plus amikacin were synergic in vitro a fter 24 h incubation, whereas imipenem plus amikacin showed no in vitro syn ergy. The number of sterile lungs and the lung clearance of A. baumannii we re greater in the group treated with imipenem than in those treated with am ikacin or doxycycline in monotherapy (P < 0.05). The combination of imipene m plus amikacin and doxycycline plus amikacin was no more effective than im ipenem alone in the clearance of organisms from lungs (2.42 +/- 1.46 cfu/g versus 2.7 +/- 1.5 cfu/g versus 1.23 +/- 1.02 cfu/g). These results suggest that the addition of amikacin does not improve the results obtained by imi penem monotherapy. Doxycycline plus amikacin is an alternative to imipenem in the therapy of A. baumannii pneumonia.