Pseudomonas aeruginosa is characteristically resistant to which antibiotic?

Clindamycin has NO activity against Pseudomonas aeruginosa. P. aeruginosa is an aerobic gram-negative rod that is inherently resistant to many antibiotics including clindamycin (which covers anaerobes and gram-positives), as well as first/second-gen penicillins, and many cephalosporins. It requires anti-pseudomonal agents: piperacillin-tazobactam, carbapenems, ceftazidime, ciprofloxacin, or aminoglycosides. Clindamycin is used for orofacial infections as a penicillin-allergic alternative.