The purpose of this protocol is to provide a mechanism for the ongoing collection of blood and urine samples in newborns that will be used to measure levels of antimicrobial products used in the newborn population where there are limited pharmacokinetic data in either premature or term infants.

Greater than 90% of infants born <32 weeks admitted to critical care nurseries are treated with antimicrobial agents during their NICU hospitalization. Most antimicrobial products used in the neonatal population lack some aspect of pharmacokinetic information specific to neonates. Dosing is based largely on pharmacokinetic data from older children or in some cases, adults. This study will also establish a bank of urine samples from newborns treated with antimicrobial and/or antifungal therapy and to characterize the urinary proteome in selected samples. The sites of the NIH-sponsored Pediatric Pharmacology Research Network (PPRU) have access to appropriate assays using microliter amounts of serum and a large pool of potential subjects to generate meaningful data that will

1. Guide dosing of commonly used antimicrobial agents, and
2. Provide preliminary data for future industry and government trials in the nursery.

Inclusion Criteria:

• Infants ≤32 weeks and 6 days EGA with high probability of receiving one of the antimicrobial agents listed are eligible for study.
• Age younger than 120 days
• Written informed consent from parent or legal guardian
• Infants likely to survive beyond 48 hours after enrollment

Exclusion Criteria:

• Failure to consent

Premature infants <32 weeks gestational age at birth at risk of infections.