Associate Professor

Division of Infectious Diseases

University Medical Center Freiburg (Freiburg, Germany)

Pathogenesis, treatment, and prevention of enterococcal infections

Dr. Huebner's primary research project involves the study and characterization of capsular polysaccharides of Enterococcus faecalis and Enterococcus faecium. Enterococci are now the second most common cause of hospital-acquired infection and are especially common in patients receiving immunosuppresive therapy, patients in intensive care, and neonates. In recent years, many strains of enterococci have developed resistance to all known antibiotics, and lethality due to these infections can be up to 100% in certain patient populations. Until recently, it was not appreciated that enterococci, like many other gram-positive bacteria, possess a capsule. Our results clearly showed that enterococci possess an extracellular carbohydrate and that this capsule may be used as a vaccine, offering new options for the treatment of these often untreatable infections. One of these cell-wall carbohydate antigens has been shown to be lipoteichoic acid consisting of a glycerophosphate backbone substituted with kojibiose, alanine, or both. We could demonstrate that both E. faecalis and E. faecium strains express an identical lipoteichoic acid. This antigen is also a target for opsonic antibodies. Mice challenged intravenously with live enterococci showed high levels of bacteria in kidneys, spleens, and livers. However, animals immunized with purified lipoteichoic acid were protected against challenge with a number of E. faecalis strains and vancomycin-resistant E. faecium strains. Rabbit serum raised against the purified lipoteichoic acid reduced bacterial counts in organs of mice as compared with normal rabbit serum or sterile saline and was also effective as a therapeutic reagent in mice when passive therapy was initiated 48 hours after challenge with live bacteria. This antigen can therefore be used to develop active or passive immunotherapy regimens for the treatment and prevention of enterococcal infections in immunocompromised patients. Further understanding of the interaction of these bacteria with the human host defense system will give new insights into how to prevent enterococcal infections.

2004-present Director of Infectious Disease Research and Attending Physician, Division of Infectious Diseases, University Hospital Freiburg,

2000-2004 Principal Investigator and Assistant Professor of Medicine, Channing Laboratory, Brigham and Womens Hospital, Harvard Medical School, Boston, MA

1992-2000 Resident, Children´s University Hospital, University Freiburg

1996-1998 Research Fellow, Channing Laboratory, Brigham and Women´s Hospital, Harvard Medical School, Boston Ma

1991-1992 Research Fellow, Division of Infectious Diseases, Children´s Hospital, Harvard Medical School, Boston MA

1991 Research Fellow, Institute for Medical Microbiology, University Zurich, Switzerland

1986-1991 Resident, Department of Hospital Epidemiology, University Hospital Freiburg