This drug has activity against many strains of P. aeruginosa. However, when it is used alone, resistance has emerged during the course of treatment. The drug should not be used in penicillin-allergic patients. Its activity against gram-negative rods is enhanced if it is given in combination with tazobactam. Which of the following drugs is being described?

Antipseudomonal penicillins: Piperacillin and Ticarcillin are called antipseudomonal penicillins because of their activity against Pseudomonas aeruginosa. Piperacillin and Ticarcillin are effective against many gram-negative bacilli But not against Klebsiella because of its constitutive penicillinase. Formulation of ticarcillin or piperacillin with clavulanic acid or tazobactam, respectively, extends the antimicrobial spectrum of these antibiotics to include penicillinase-producing organisms.