Antibiotic macrolides are used to treat infections caused by Gram-positive bacteria (e.g., "Streptococcus pneumoniae") and limited Gram-negative bacteria (e.g., "Bordetella pertussis", "Haemophilus influenzae"), and some respiratory tract and soft-tissue infections. The antimicrobial spectrum of macrolides is slightly wider than that of penicillin, and, therefore, macrolides are a common substitute for patients with a penicillin allergy. Beta-hemolytic streptococci, pneumococci, staphylococci, and enterococci are usually susceptible to macrolides. Unlike penicillin, macrolides have been shown to be effective against Legionella pneumophila, mycoplasma, mycobacteria, some rickettsia, and chlamydia.