Safety and Efficacy of Probiotics in Bangladeshi Infants

Inclusion Criteria: * Healthy infants. * Infants 1 -3 months of age at the beginning of the study. * Parents/guardians of each subject are able to understand study procedures and agree to participate in the study by giving consent. * Parents and child are planning to remain in Dhaka for the next four months. Exclusion Criteria: * Infants with known birth defects. * Infants who have been hospitalized. * Infants who have an acute infection or illness at the time of enrolment. * Infants who are currently taking antibiotics * Infants \<1 month of age or \>3 months of age. * Infants three standard deviations below mean on anthropometric measures (will be referred for medical care). * Infants who are already receiving a probiotic product or treatment. * A diagnosis or suspicion of immunodeficiency disorder. * A diagnosis or suspicion of bleeding disorder that would contraindicate venipuncture. * Family residence outside of Dhaka or families expecting to move outside of Dhaka in the next 4 months.