Pharmaceutical compositions and methods for treating or preventing bacterial infections are disclosed. The pharmaceutical compositions typically comprise pharmaceutically effective amount of: (a) at least one beta-lactam antibiotic or a pharmaceutically acceptable salt thereof, (b) sulbactam or a pharmaceutically acceptable salt thereof, and (c) at least one beta-lactamase inhibitor or a pharmaceutically acceptable salt thereof, with the provision that the beta-lactamase inhibitor is not sulbactam.