Intrinsically resistant to beta-lactams. TMP-SMX is probably the most reliable agent, followed by Ticarcillin-clavulanate. Other drugs such as Ceftazidime, Aztreonam, Levofloxacin, Moxifloxacin, and Tigecycline are sometimes used if susceptible. Minocycline has excellent in vitro activity but limited experience.