How do you decide between ceftolozane/tazobactam and ceftazidime/avibactam for empiric treatment of an infection due to difficult-to-treat Pseudomonas aeruginosa while awaiting additional susceptibilities?  

Either is generally acceptable. The choice of empiric therapy in this circumstance may be dependent on additional information, if available. As an example, a patient with cystic fibrosis may have recent microbiological data that could guide the decision. Such information, however, is not often avail...