Karen C. Carroll, M.D.

Headshot of Karen C. Carroll
  • Director, Division Medical Microbiology
  • Professor of Pathology


Medical Microbiology

Research Interests

Evaluation of novel diagnostic platforms and epidemiology of healthcare associated infections and bloodstream infections. ...read more


Dr. Karen Carroll is a professor of pathology at the Johns Hopkins University School of Medicine. Her areas of clinical expertise include Medical Microbiology and Infectious Diseases. Dr. Carroll serves as the Director of the Division of Medical Microbiology and the Director of the ACGM-accredited fellowship program in medical microbiology in the Department of Pathology.

Dr. Carroll earned her M.D. from the University of Maryland School of Medicine. She completed her residency at the University of Rochester Medical Center, and performed a fellowship in medical microbiology at the University of Utah and a fellowship in infectious disease at the University of Massachusetts Medical School.

Her research interests include the evaluation of novel diagnostic platforms, diagnosis of bloodstream infections/sepsis, and the diagnosis and epidemiology of healthcare-associated infections, such as MRSA and Clostridium difficile.

Dr. Carroll has received numerous awards for excellence in teaching and was the recipient of the BD Award for Research in Clinical Microbiology from the American Society of Microbiology in 2011, the Infectious Diseases Society Kass Award and named lecture in 2015, and the Illinois Society for Microbiology Pasteur Award in 2017.  She is an active member of several professional organizations, including the American Society for Microbiology. For the latter, she has served on numerous committees and on the Board of Directors as well as an Associate Editor of the Journal of Clinical Microbiology. She also achieved fellowship status in the American Academy of Microbiology, the College of American Pathologists, and the Infectious Diseases Society of America.  Dr. Carroll is currently the co-editor in chief of the Manual of Clinical Microbiology 13th edition. She has published more than 300 peer-reviewed publications and numerous reviews and book chapters.

...read more


  • Director, Division Medical Microbiology
  • Director, ACGME Accredited Medical Microbiology Fellowship Program
  • Section Director Molecular Epidemiology, Rapid Response Laboratory
  • Associate Director, Bacteriology Laboratory
  • Professor of Pathology
  • Joint Appointment in Medicine

Departments / Divisions

Research & Publications

Research Summary

Dr. Carroll's research interests include diagnostic test evaluation and development for the detection of microbial pathogens in clinical specimens. Projects have included implementation of MALDI-TOF MS for microbial identification, evaluation of molecular strain typing techniques for epidemiological analysis; development of molecular and non-molecular assays for rapid identification and susceptibility testing of MRSA; and evaluation of methods for Clostridium difficile detection. In addition, her research has focused on evaluation and implementation of syndromic panel tests for bacteremia and fungemia detection. More recently Dr. Carroll has collaborated with researchers on novel rapid microfluidics platforms and next generation sequencing technologies for detection of a variety of pathogens.  She has participated in programs to foster appropriate test utilization and diagnostic stewardship.

Selected Publications

Mostafa HH*, Carroll KC*, Hicken R, Berry GJ, Manji R, Smith E, Rakeman JL, Fowler RC, Leelawong M, Butler-Wu SM, Quintero D, Umali-Wilcox M, Kwiatkowski RW, Persing DH, Weir F, Loeffelholz MJ. 2021. Multi-center evaluation of the Cepheid Xpert Xpress SARS-CoV-2/Flu/RSV test. J Clin Microbiol. 2021 Feb18;59:e02955-20:doi10.1128

Carroll KC, Reid JL, Thornberg A, Whitfield NN, Trainor D, Lewis S, Wakefield T, Davis TE, Church KG, Samuel L, Mills R, Jim P, Young S, Nolte FS. 2020. Clinical performance of the novel GenMark Dx ePlex Blood Culture ID Gram-Positive Panel. J Clin Microbiol 2020 Mar 25;58(4):e01730-19. doi: 10.1128/JCM.01730-19. Print 2020 Mar 25

Hansen G, Young S, Wu AHB, Herding E, Nordberg V, Mills R, Griego-Fullbright C, Wagner A, Ong CM, Lewis S, Yoon J, Estis J, Sandlund J, Friedland E, Carroll KC. 2019. Ultrasensitive detection of Clostridioides difficile toxins in stool using single molecule counting technology: Comparison with CCCNA free toxin detection. J Clin Microbiol 2019 Oct 23;57(11):e00719-19. doi: 10.1128/JCM.00719-19. Print 2019 Nov

Simner PJ, Miller HB, Breitweiser FP, Pinilla Monsalve G, Pardo CA, Salzberg SL, Sears C, Thomas DL, Eberhart CG, Carroll KC. 2018. Development and Optimization of Metagenomic Next-Generation Sequencing Methods for Cerebral Spinal Fluid Diagnostics. J Clin Microbiol 2018 Aug 27;56(9).

Mizusawa M, Small BA, Hsu YJ, Sharara SL, Advic E, Kauffman C, Milstone AM, Feldman L, Pahwa AK, Trivedi JB, Landrum MB, Maragakis LL, Carroll KC, Cosgrove SE, Rock C, for the CDC Prevention Epicenter Program. 2019. Prescriber behavior in Clostridioides difficile testing: A three hospital diagnostic stewardship intervention. Clin Infect Dis. 69: 2019-21

Contact for Research Inquiries

Johns Hopkins Hospital
600 N Wolfe St
Meyer B121
Baltimore, MD 21287 map
Phone: 410-955-5077

Academic Affiliations & Courses

Courses and Syllabi

  • Genes to Society Microbiology and Infectious Diseases
    Johns Hopkins University School of Medicine
    2019 - 2022

Activities & Honors


  • BD Award for Research in Clinical Microbiology, American Society of Microbiology, 2011
  • 25th Edward H Kass Award and Named Lecture, Infectious Diseases Society of America, 2015
  • Illinois Society for Microbiology Pasteur Award, Illinois Society for Microbiology, 2017


  • American Academy of Microbiology
  • American Society for Clinical Pathology
  • American Society for Microbiology


  • College of American Pathologists
  • Infectious Diseases Society of America
  • European Society for Microbiology and Infectious Diseases


Professional Activities

  • Cohort, Leadership Program for Women Faculty, 2012 - 2013
  • Committee on Laboratory Practices Liaison, American College of Microbiology
  • Faculty Senate, Johns Hopkins University School of Medicine, 2009 - 2014
  • Director Microbiology Laboratory, Johns Hopkins Hospital
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