Provided herein are pharmaceutical compositions comprising an antibiotic encapsulated in liposomes. The lipid membrane component of the liposomes, or portion thereof comprises an unsaturated phospholipid. The antibiotic-to-lipid component weight ratio of the liposomes ranges from about 0.5-to-1 to about 3-to-1. The pharmaceutical compositions in some embodiments also include free antibiotic, in addition to encapsulated antibiotic. Methods for treating bacterial infections, e.g., pulmonary bacterial infections such as nontuberculous mycobacterial infections with the pharmaceutical compositions are also provided.