This study plans to learn more about the impact of enteral nutrition on bacteria in critically ill trauma patients with brain injury. Specifically, it seeks to understand the effect that a prebiotic containing enteral feeding formula (Nutraflora scFOS in Vital AF) has on the gut, oral, and skin bacteria. A prebiotic is a special form of dietary fiber that acts as a fertilizer for good bacteria. The prebiotic Nutraflora scFOS has been cleared by the U.S. Food and Drug Administration and is not considered investigational as used in this study. Enteral feeding is a way to give nutrition to critically ill people who are unable to eat.

Inclusion Criteria:

1. Adult major neurological injury trauma patients between 18-70 years of age who have been admitted directly to trauma ICU following major trauma
2. Expected length of mechanical ventilation > 48 hours (as judged by admitting clinician)
3. Expected length of ICU stay > 3 days (as judged by admitting clinician)
4. Expected to survive > 48 hours (as judged by admitting clinician)
5. Requiring enteral nutrition at any time in Intensive Care Unit (ICU) stay
6. Chronic illnesses must be under control (as determined by the Principal Investigator).

Exclusion Criteria:

1. Previous hospitalization within one month prior to ICU admission (no hospital floor transfers to eliminate confounding effect of previous hospital therapy)
2. Use of prebiotic fiber containing enteral or oral formula or probiotic preparations within one week
3. Received antibiotics within the previous month
4. On steroids or immunosuppressants at time of admission
5. All transplant patients
6. Chronic inflammatory disease that requires steroids or other biologic therapy intervention (e.g.: RA, IBD that requires steroids or Humira)
7. Undergoing active chemotherapy/radiation treatment
8. Renal failure requiring dialysis
9. Liver cirrhosis class C