Colistin Resistance in a Clinical Acinetobacter baumannii Strain Appearing after Colistin Treatment: Effect on Virulence and Bacterial Fitness

Abstract

ABSTRACTThe fitness and virulence costs associated with the clinical acquisition of colistin resistance byAcinetobacter baumanniiwere evaluated. The growth of strain CR17 (colistin resistant) was less than that of strain CS01 (colistin susceptible) when the strains were grown in competition (72-h competition index, 0.008). In a murine sepsis model, CS01 and CR17 reached spleen concentrations when coinfecting of 9.31 and 6.97 log10CFU/g, respectively, with anin vivocompetition index of 0.016. Moreover, CS01 was more virulent than CR17 with respect to mortality and time to death.