Meet the Faculty

Mark Darrow, MD, FACP
Graduate Medical Education Director
Mark D. Darrow, MD, FACP is director of Gwinnett Medical Center’s Graduate Medical Education program. He joined GMC in October 2012 bringing his vast experience as a geriatrician, internist, family doctor and medical educator. In his role at GMC, he will work with the Medical Center and the community to create residency training programs in Family Medicine and Internal Medicine. He will also deliver patient care in the inpatient, outpatient and nursing home settings.

Dr. Darrow joined GMC from South East Area Health Education Center (SEAHEC), a non-profit organization based in Wilmington, N.C. where he was the president/CEO. SEAHEC is a private, not-for-profit organization that provides medical education at all levels of training. Servicing in this role, he was also the vice president for Graduate Medical Education and designated institutional officer of New Hanover Regional Medical Center’s four residency training programs.

He received his medical doctorate from State University of New York – Stony Brook and completed an internal medicine residency at The Mary Imogene Bassett Hospital. He is a fellow of the American College of Physicians and completed a Faculty Development Fellowship in Family Medicine at the University of North Carolina. Dr. Darrow was also a visiting clinical fellow with The Columbia College of Physicians. He holds a certification in internal medicine from the American Board of Internal Medicine and is a diplomate in Geriatric Medicine.

Kevin E. Johnson, MD, FAAFP
Family Medicine Program Director
Dr. Johnson in the Program Director and holds a Certificate of Added Qualification in Hospice and Palliative Medicine. A graduate of the University of Oklahoma Health Sciences Center, he completed his residency in Family Medicine at New Hanover Regional Medical Center in Wilmington, North Carolina and a fellowship in Faculty Development in Family Medicine at the University of North Carolina at Chapel Hill. Through his diverse experiences as a faculty physician, a hospitalist for a military hospital and as a solo practice family physician in rural Oklahoma, he maintains a broad clinical teaching skillset. He also has expertise in health informatics and practice management issues, and has published and presented on a wide variety of clinical and medical education topics.

Martin Austin, MD
Dr. Martin Austin serves Gwinnett Medical Center as the medical director of hospitalists and as clinical faculty for internal medicine. Working in the medical director role since 1999, he is responsible for direct patient care, medical consults and coordination of care with medical and surgical specialists and overseeing the clinical quality of care provided by the hospitalists. He serves as the primary representative of the inpatient medicine group to hospital administration and the medical staff and as the physician service line coordinator for internal medicine.

Dr. Austin obtained a medical degree from New York University School of Medicine and completed his residency at Bellevue Hospital, where he was chief resident. He is board certified by the American Board of Internal Medicine and by the National Hospice and Palliative Care Organization. 

He is a fellow of the Society of Hospital Medicine, a board member of the Atlanta chapter of the Society of Hospital Medicine and a member of the American College of Physicians.

William Bostock, DO, FAAFP 
Dr. William Bostock is a native of Georgia and has practiced Family Medicine in Lawrenceville, Georgia since 1986. Dr. Bostock graduated physician’s assistant school from the Medical College of Georgia and graduated medical school from the Kansas City University of Medicine and Biosciences. He completed his Family Medicine Residency at the Medical College of Georgia.

A member of Phi Sigma Alpha, National Honor Fraternity of Scholastic Excellence. Dr. Bostock was a Promina Health System Board Member and served as Chairman of the Board of the Gwinnett Hospital System PHO. 

Dr. Bostock is Board Certified in Family Medicine by the American Academy of Family Practice and in 1993, he became a Fellow of the American Academy of Family Practice. 

Dr. Bostock is a member of many state and national medical societies, including the American College of Osteopathic Physicians, American Osteopathic Association, American Academy of Family Physicians, and American Medical Association.  

Linda Casteel, MD
Dr. Casteel received a Bachelors degree in Chemistry and Math from Westminster College in New Wilmington, Pennsylvania in 1984 and the MD from Jefferson Medical College in Philadelphia, Pa. in 1988. She completed her Residency in Family Medicine in the Department of Family Medicine, Bryn Mawr Hospital, Bryn Mawr, Pa. from 1988 – 1991 sharing Chief Resident duties. Dr. Casteel has maintained continuous Board Certification by the American Academy of Family Physicians since 1991.

She is currently a member of the American Medical Association, American Academy of Family Physicians and the Georgia Academy of Family Physicians. She proudly serves on the Board of Covenant Christian counseling and volunteers her time at the Gwinnett Clinic. She has received several awards including the Janet M. Glasgow American Medical Women’s Association Scholarship Achievement Citation, election to Alpha Omega Alpha (National Medical Honor Society), and the Hobart Amory Hare Medical Society.

Dr. Casteel’s professional experience has included work in physician shortage areas in South Carolina and Texas, serving as a member of the Board, Consultant and Associate Medical Director of several hospices and non-profit medical organizations, and Assistant Professor in the Department of Family Medicine at Texas Tech University Health Sciences Center in Amarillo, Tx,. She is a well-respected member of the medical community and is founder, president and physician of Gwinnett Family Medical Care.

David Goo, MD
Dr. David Goo is a Gwinnett Medical Center-affiliated physician supporting the Pediatric Emergency Department.  In regards to Graduate Medical Education, he is clinical faculty for emergency care.  Dr. Goo has practiced pediatrics since 1989 when he graduated from Emory University. He spent an additional year as chief resident in pediatrics before he completed a fellowship in pediatric emergency medicine at Scottish Rite Children’s Hospital in Atlanta.

Dr. Goo has been board certified in pediatrics since 1990 and board certified in pediatric emergency medicine since 1994. He has worked in pediatric emergency departments all of his professional career and spent more than 17 years at Emory teaching pediatric emergency medicine.

In terms of education, he was the residency program coordinator for pediatric emergency medicine at Children’s Healthcare of Atlanta (CHOA) at Egleston and Hughes Spalding. He holds the designation as an American Heart Association training center faculty in PALS and was in charge of the PALS/PEARS education at Children’s Healthcare of Atlanta for many years.

Holly RichardsDr Holly Richards
Holly Richards serves as the director of Gwinnett Medical Center’s Office of Research, supporting internal departments at the hospitals in Duluth and Lawrenceville, Gwinnett Medical Group physicians and external community physician groups who use GMC’s facilities when conducting research. 

As the office’s director, she manages all aspects of research administration including regulatory compliance and financial affairs and enforces FDA, Good Clinical Practice and The International Conference on Harmonisation mandated research standards at GMC. The Office of Research oversees research logistic reviews, contracts and budget negotiations and management, Medicare coverage analysis and billing compliance, among others. Richards also manages the office’s staff which includes regulatory compliance, financial and clinical associates.

She came to GMC in March 2013 with more than 20 years of experience in clinical research operations and administration and specializes in oncology and cardiovascular services. Most recently, Richards was with Genocea Biosciences, based in Cambridge, Mass., as director of clinical operations and quality assurance where she oversaw all clinical operations in regards to research and development of the company's vaccine pipeline. 

Bedri Yusuf, MD
Dr. Bedri Yusuf serves Gwinnett Medical Center as the associate medical director of the inpatient medical group and as a clinical faculty for internal medicine.  He provides direct patient care and facilitates communications between the inpatient medicine group to hospital administration and the medical staff. He is also a member of the Graduate medical education committee.

As vice president of GMC’s medical staff, he has accountability to the Board for providing oversight of the quality of care, treatment and services and for ensuring a high level of performance by all 800+ members of the medical staff.

Dr. Yusuf obtained a medical degree from Gondar Medical College at Addis Ababa University in Gondar, Ethiopia.  He completed a residency in dermatology from the University of Leipzig’s Dermatology Hospital in Leipzig, Germany and a residency in internal medicine at Atlanta Medical Center.  He is also a senior fellow of the Society of Hospital medicine as well as a fellow of the American College of Physicians. He is board certified by the American Board of Internal Medicine and received a certification as a Physician Executive.