Meet the team

Karen C. Carroll, MD
Professor Emerita

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Karen C Carroll, M.D. is a Professor Emerita of Pathology in the Johns Hopkins University School of Medicine.  For 22 years she served as the Director of the Division of Medical Microbiology. Early in her tenure at Hopkins she also served as a consultant in the Division of Infectious Diseases. 

Dr. Carroll received her undergraduate degree in Biology at the College (now University) of Notre Dame of Maryland. She subsequently earned her medical degree at the University of Maryland School of Medicine, Baltimore in 1979 and she did her internship in internal medicine there as well.  Dr. Carroll transferred to the University of Rochester Associated Hospitals program to complete her residency where she was elected chief resident. She moved to Rochester to join her future husband who was a medicine resident at Strong Memorial Hospital.  After residency, Dr. Carroll did a Fellowship in Infectious Diseases at the University of Massachusetts in Worcester and a Fellowship in Medical Microbiology at the University of Utah, Associated Regional and University Pathologists (ARUP Laboratories, Inc.).  Upon completion of her fellowship she became the associate director of the Microbiology Laboratory, then later the director of the Infectious Diseases laboratories. Dr. Carroll advanced from assistant professor to associate professor of pathology and medicine.  During this time, she combined, infectious diseases consultation with of laboratory oversight.  In 2002, Dr. Carroll was recruited to the Johns Hopkins Faculty and was promoted to professor in 2006.

For more than 22 years, Dr. Carroll served many roles within the Department of Pathology.  She represented for Department on the Faculty Senate for 6 years and was an active participant on several departmental committees. For 2 years, she was Deputy Director of Clinical Affairs. Dr. Carroll was also instrumental in the laboratories’ support of the Johns Hopkins Hospital Biocontainment Unit and in the institutional response to COVID-19. The Microbiology Laboratory became a true system-wide laboratory and substantially grew its test menu during her time as director. 

Dr. Carroll’s research interests included the diagnosis and epidemiology of healthcare associated infections and novel diagnostics for the detection of bacteremia.  She enjoyed numerous collaborations with colleagues in the Departments of Emergency Medicine, Hospital Epidemiology and Infection Control and Biomedical Engineering.  These efforts resulted in more than 350 publications.  Dr. Carroll received the 2011 American Society for Microbiology Becton-Dickinson Award for Excellence in Clinical Research.  Dr. Carroll is also Co-Editor in Chief of the Manual of Clinical Microbiology.

Dr. Carroll was the Director of the ACGME Fellowship in Medical Microbiology.  She also trained and mentored countless residents and medical students.  She has been recognized 5 times with the Johns Hopkins Pathology Residents Teaching Award, regionally by the Illinois Society for Microbiology with the Pasteur Award and the University of Utah American Medical Women’s Association Inaugural Gender Equity award. 

As she has transitioned to retirement as of January, 2025, Dr. Carroll has enjoyed traveling with husband Bruce Marshall, M.D.  and spending quality time with their two sons and their families including three fun granddaughters.