The macrolides (especially azithromycin) and the respiratory quinolones are now the antibiotics of choice and are effective as monotherapy. Compared with erythromycin, the newer macrolides have superior in vitro activity, display greater intracellular activity, reach higher concentrations in respiratory secretions and lung tissue, and have fewer adverse effects. Ref: Sabria M., Yu V.L. (2012). Chapter 147. Legionella Infections. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds), Harrison's Principles of Internal Medicine, 18e.