Colistin resistance in a clinical Acinetobacter baumannii strain appearing after colistin treatment: effect on virulence and bacterial fitness.

The fitness and virulence costs associated with the clinical acquisition of colistin resistance by Acinetobacter baumannii were 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 log10 CFU/g, respectively, with an in vivo competition index of 0.016. Moreover, CS01 was more virulent than CR17 with respect to mortality and time to death.

Journal Article; Research Support, Non-U.S. Gov't;

This work was supported in part by the Consejería de Salud of the Junta de Andalucía (PI-0044-2011) and by the Ministerio de Economía y Competitividad, Instituto de Salud Carlos III, cofinanced by European Development Regional Fund “A way to achieve Europe” (ERDF), Spanish Network for the Research in Infectious Diseases (REIPI RD12/0015). M.J.M. is supported by the Subprograma Miguel Servet from the Ministerio de Economía y Competitividad of Spain (CP11/00314).