EXTON, Pa., April 14, 2005 (PRIMEZONE) — ViroPharma Incorporated today announced the presentation of data by industry experts describing the sharp increase in severity and incidence of disease caused by the bacterium Clostridium difficile. An emerging strain is causing an increase in severe diarrhea and colitis, which can require surgical removal of the colon, and in some cases, is fatal. These data were featured prominently this week at the 15th Annual Scientific Session of the Society for Healthcare Epidemiology of America (SHEA.)

Dale Gerding, M.D., Associate Chief of Staff for Research and Development at Hines VA Hospital and professor of medicine at the Loyola University Stritch School of Medicine gave a presentation entitled “New Issues in Clostridium difficile” as part of the “Gastrointestinal Pathogens in Healthcare – Containing the Explosion” symposium. According to Dr. Gerding, the new emerging strain has been found in U.S. hospitals in a dozen or more states and in multiple hospitals in Quebec, Canada. The isolates have been typed by DNA fingerprinting methods and belong to a single group designated as BI. The BI group contains a new third toxin called binary toxin and has a deletion in a gene that regulates production of toxins A and B, the usual toxins produced by C. difficile. In addition, the BI strains have acquired high-level resistance to newer fluoroquinolone antibiotics widely used in hospitals, namely gatifloxacin, moxifloxacin, and levofloxacin. This BI strain is not a new organism, but one that Dr. Gerding’s laboratory had obtained from patients in the 1980s and 1990s. However, at that time the organisms were not resistant to the fluoroquinolone antibiotics. This resistance acquisition has likely occurred which is enabling the organism to spread in the hospital environment.

In addition, a session entitled “Clostridium difficile: Apocalypse Next” was moderated by Dr. Gerding and L. Clifford McDonald, M.D. from the U.S. Centers for Disease Control and Prevention, providing further evidence of the increased incidence and severity of disease.

“We know that the overall incidence of C. difficile-associated disease has been increasing, particularly over the past few years,” commented Dr. Colin Broom, Chief Scientific Officer, ViroPharma. “However, what has been most alarming are the reports of severe disease and increased mortality. The data presented at the SHEA meeting confirmed what we had suspected for some time: There is an emerging strain of C. difficile that produces a substantially increased quantity of toxin and is associated with rapidly progressive, severe disease. This puts even more emphasis on prompt diagnosis and early treatment with an effective therapy.”

Key messages from the 10 abstracts, 9 oral presentations and symposium session on C. difficile disease at the SHEA meeting included:

— The incidence and severity of disease caused by C. difficile
is increasing.
— An emerging strain of C. difficile produces increased amounts
of toxin leading to severe diarrhea, the need for surgical
removal of the colon and, in some cases, death.
— Infectious disease experts who were surveyed about C. difficile
associated diseases reported significant increases in the number
and the severity of cases over two, six-month periods in 2004.
— Disease caused by C. difficile is almost always related to
antibiotic use.