 Dosing for infants receiving piperacillin-tazobactam per local standard of care Once an infant is enrolled in the study, steady state PK levels may be drawn after the 4th, 5th, or 6th dose of piperacillin-tazobactam. These doses may include both pre-study doses of piperacillin-tazobactam and post-consent, on-study, doses if the dosage and dosing interval of piperacillin-tazobactam remains the same. If a subject receives 4 doses of on-study piperacillin-tazobactam at the time of steady state PK sampling, 4 doses pre-study doses on study doses of piperacillin-tazobactam should be recorded on the Study Drug Administration CRF. 