MIC distribution among wild-type strains of Legionella pneumophila identify a subpopulation with reduced susceptibility to macrolides owing to genes coding for an efflux pump. L. pneumophila WT MICs and macrolides efflux

The purpose of this study was to describe the susceptibility of clinical strains of Legionella pneumophila to seven antibiotics used for legionellosis treatment. The minimum inhibitory concentrations (MICs) of 109 well-characterized clinical strains of L. pneumophila serogroup 1 were determined using a broth microdilution method without charcoal and compared to antibiotic-resistant strains selected in vitro. All strains were inhibited by low concentrations of fluoroquinolones, macrolides, and rifampicin