*6.8. Colistin*

Colistin, previously studied in combination with pexiganam against Gram-negative bacterial infection [67], was also combined with teicoplanin or daptomycin in an experimental mouse model of multiresistant *Acinetobacter baumannii* infection. The permeabilising effect of colistin on the *A. baumannii* outer membrane allows glycopeptide and lipopeptide molecules to enter, which are normally excluded due to their size, resulting in a better patient outcome in severe infections caused by multiresistant microorganisms like *A. baumannii* (6.7. × <sup>10</sup><sup>4</sup> ± 1.1 × <sup>10</sup><sup>4</sup> colistin alone, 5.0 × 109 ± 1.6 × 109 daptomycin alone, 7.3 × <sup>10</sup><sup>9</sup> ± 1.8 × 109 teicoplanin alone, 2.9 × 102 ± 0.4 × 102 colistin + daptomycin, and 3.1 × <sup>10</sup><sup>2</sup> ± 0.2 × 102 colistin + teicoplanin) [83].
