The purpose of this study is to evaluate the efficacy in preterm infants following treatment with BSSL when administered in pasteurized breast milk.

In this double-blind crossover study, patients will be randomized to receive pasteurized breast milk including BSSL or pasteurized breast milk without BSSL for the first 7 days. After a wash-out period of 2 days the patients will "crossover" to the other treatment regimen and receive an additional 7 days treatment. The primary efficacy measurements will be made by collecting stool during the last three days of each treatment period.

Inclusion Criteria:

• Preterm infants
• less than or equal to 32 weeks of gestational age
• appropriate for gestational age
• enterally fed with pasteurized breast milk