Background: Clostridium difficile (C.
difficile) is the leading identifiable cause of nosocomial diarrhea
worldwide due to its virulence, multi-drug resistance, spore-forming ability,
and environmental persistence. This bacterium has been implicated as the
causative organism for 10-25% of the reported cases of antibiotic-associated
diarrhea, 50-75% of antibiotic-associated colitis, and 90- 100% of
pseudomembranous colitis. The toxigenic strains of C. difficile produce two notable
proteins, toxin A and toxin B, which are important virulent factors in the
pathogenesis of C. difficile. Both
toxins have the same enzymatic cleavage activity and are cytotoxic to cultured
cells; however, toxin B is 100 to 1,000-fold more potent than toxin A in most
Competitors and Current
clinical methods for diagnosing C.
difficile infections are mostly qualitative tests that detect either the
bacteria or the toxins.
Current tests rely on a combination of at least two techniques, which may
include culture isolation, PCR detection of the toxin-encoding genes, the
Cyto-assay, and immunological detection of the toxins (ELISA). These tests
require a second confirmatory assay to determine if a strain is pathogenic. The
alarming emergence of hypervirulent strains of C. difficile with increased toxin
production, severity of disease, morbidity, and mortality emphasizes the need
for a culture method that permits simultaneous isolation and detection of
virulent strains. C. difficile
strains can either be toxin-producing (toxigenic) or non-toxin producing
(non-toxigenic). Only toxin A and/ or toxin B-producing strains cause disease.
Current culture methods do not differentiate toxigenic and non-toxigenic
strains, because they are unable to detect toxin activity.
The Technology: Dr. Herbert DuPont and colleagues
at UTHealth have developed a quantitative C. difficile activity assay that enables
cost-efficient, sensitive, quantitative measurement of the cleavage activities
of toxin A and toxin B of C.
difficile in both a culture supernatant and a selective and differential
agar-based assay. The plate assay enables identification of toxin-producing C. difficile without the need for
additional toxin-confirmatory tests by taking advantage of unique cleavage
characteristics of the toxins to differentiate activity simultaneously with
Ref. No.: 2010-0058
Herbert L. DuPont, Charles Darkoh, Dr. Heidi B. Kaplan
Patent Application filed
world-wide; exclusive or non-exclusive