Medical Team


Dr. Derek DeWitt, Medical Director. Derek is a graduate of A.T. Still University School of Osteopathic Medicine in Arizona. He completed his residency in Family Medicine at Manatee Memorial Hospital in Bradenton, FL. He is board certified in Family Medicine by the American Osteopathic Board of Family Physicians. He is also credentialed as an HIV Specialist by the American Academy of HIV Medicine. He has been with The McGregor Clinic 4 years and has been the Medical Director for a year and a half. Derek is also a fountain of useless pop culture trivia and likes to travel in his spare time.






Carolyn Coleman, MSN, FNP, Nurse Practitioner. Carolyn began her nursing career as an LPN in 1992 in Queens, New York and has 25 years of nursing experience in a variety of clinical and academic settings including health promotion, disease prevention, diagnosis and care management. She has a Bachelor’s of Nursing Cum Laude from Lehman College in Bronx, New York and a Master’s of Nursing from the University of South Florida, where she is also a Golden Key Honor Society member. She is a certified HIV Specialist and has served in a variety of leadership roles including Charge Nursing, Preceptor and High-Risk Case Management.





Dr. Douglas Brust, Physician. Dr. Brust’s entire career has been committed to the care of people living with HIV.  He received his BA and PhD from Cornell University and his MD from Columbia University.  He completed residency training in internal medicine at Harvard University (Brigham and Women’s Hospital) and his fellowship in infectious diseases at the National Institutes of Health (National Institute of Allergy and Infectious Diseases) under the mentorship of Dr. Anthony Fauci.  After completing his fellowship training he was on the faculty of Columbia University where he served as the Infectious Diseases Fellowship Director. He moved to Fort Myers in 2006 and currently works as a staff physician at McGregor Clinic and as the HIV Program Director for Lee Health.  He is board certified in infectious diseases and has received multiple awards and recognitions for his work including a Fulbright Scholarship, a Howard Hughes Medical Scholarship, and being named Gulf Coast Magazine’s, “Top Doctor” for the past 9 years.





Johnna Dettis, MSN, MPH, ARNP, Nurse Practitioner. Johnna worked for 30 years as a Public Health Nurse Practitioner, Nurse Consultant and Educator in Florida before retiring in 2012. She currently serves as a part-time Nurse Practitioner for McGregor as well as an Advisory Board Member for the Immokalee Technical College’s Practical Nursing Program and teaches HIV nursing courses. She served for 26 years with the Navy Reserve Nurse Corps all over the world, retiring as a Captain. She has also been a Board Member and Medical Director for the Collier County Honor Flight since 2013, honoring local WWII and Korean War veterans by organizing trips for them to the war memorials in Washington, D.C.