Nurse Practitioner/PA-C


Brian Cronk, PA-C

After earning his Masters of Public Health from Loma Linda University in California in 1996, Brian attended the Primary Care Physician Assistant Program at Western University of Health Sciences in Pomona, CA. His prior medical setting experience includes family practice, urgent care, and internal medicine. He has a special interest in treating patients diagnosed with hepatitis. Brian joined Centers for Gastroenterology in 2007.


Tara Jewell, DNP, NP-C

Tara is a Doctor of Nursing Practice as well as a board certified Adult – Gerontology Nurse Practitioner with experience working with acute and chronically ill patients. Her prior medical experience includes caring for patients in the intensive care, cardiology, and oncology units in the hospital; as well as caring for patients in a gastroenterology practice. Tara earned her bachelor’s degree in nursing from the University of Iowa in 2004. While working as a registered nurse she obtained her Doctor of Nursing Practice at the University of Iowa in 2013. She is a member of the American Association of Nurse Practitioners. She joined the Centers for Gastroenterology in 2015.


Sharon Margraf, BSN, MSN, NP

Sharon earned both her BSN and MSN from Loyola University in Chicago. She received her Adult-Gerontology Primary Care Nurse Practitioner Certification in 2013. Sharon has worked in gastroenterology at Loyola University Medical Center, Rush-Presbyterian St. Luke’s Medical Center, and at the University of Chicago Medical Center. Her prior medical experience also includes work in cancer care, hematology and general surgery. Sharon has made presentations on “Advanced Provider Perspectives: Treatment for Inflammatory Bowel Diseases, Best Practices in IBD Management, and Living with a J-Pouch for the Crohn’s and Colitis Foundation of America. Sharon joined Centers for Gastroenterology in 2016.