The invention provides a newly discovered oxadiazole class of antibiotics. The oxadiazoles impair cell-wall biosynthesis and exhibit activities against the Gram-positive bacteria such as the bacterium Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA) and vancomycin-resistant and linezolid-resistant S. aureus. For example, 5-(1H-indol-5-yl)-3-(4-(4-(trifluoromethyl)phenoxy)phenyl)-1,2,4-oxadiazole (antibiotic 75b) was efficacious in a mouse model of MRSA infection, exhibiting a long half-life, a high volume of distribution, and low clearance. Antibiotic 75b antibiotic is bactericidal and is orally bioavailable. This class of antibiotics can be used as a therapeutic agent against infections by Gram-positive bacteria such as MRSA.