Investigating novel treatment approaches to combat Clostridioides difficile Rusha Pal ABSTRACT Clostridioides difficile is the leading cause of antibiotic-induced diarrhea and colitis in hospitals and communities worldwide. The enteric pathogen, classified to be an "urgent threat" by the United States Center for Disease Control and Prevention (CDC), capitalizes on disrupted intestinal microbiome to establish infection with disease symptoms ranging from mild diarrhea to potentially fatal conditions.
Disruption of the intestinal microbiome, caused mostly by antibiotic use, enables C. difficile to colonize and proliferate within the host. Paradoxically, antibiotics are used to treat C. difficile infection. These antibiotics decimate the gut microbial community further, thus priming the gastrointestinal tract to become more prone to recurrence of infection. To tackle this clinical setback, we utilized a combination of traditional and non-traditional drug discovery approaches and identified chemical entities and targeted treatment options effective against this toxin-producing intestinal pathogen.
Herein, we exploited the strategy of high-throughput screening to identify leads that harbor anticlostridial activity. Our primary phenotypic screen of FDA-approved drugs and natural product libraries led to the identification of novel molecules that were further characterized for their anticlostridial efficacy both in vitro and in vivo. The most potent scaffolds identified were those of mitomycin C, mithramycin A, aureomycin, NP-003875, NAT13-338148, NAT18-355531, and NAT18-355768. Of these, mithramycin A, aureomycin, and NP-003875 were also found to harbor anti-virulence properties as they inhibited toxin production by the pathogen. Furthermore, natural product NP-003875 could confer protection to 100% of the infected mice from clinical manifestations of the disease in a primary infection model of C. difficile.
Our final approach has been to develop targeted therapeutics called peptide nucleic acids (PNAs). PNAs are antisense agents capable of inhibiting gene expression in bacteria. In this study, antisense inhibition of the RNA polymerase subunit gene (rpoA) of C. difficile was found to be bactericidal for the pathogen and could also inhibit the expression of its virulence factors. Additionally, antisense inhibition of the C. difficile rpoA gene was found to be non-deleterious for the tested commensal microflora strains.
Given their intriguing anticlostridial properties, it can be concluded that our research opened exciting possibilities that can be further evaluated to uncover new treatments for CDI. / Doctor of Philosophy / Investigating novel treatment approaches to combat Clostridioides difficile Rusha Pal LAYMAN LANGUAGE ABSTRACT Clostridioides difficile is a prominent human pathogen that can colonize the gut and cause fatal infections. C. difficile is the most common cause of microbial healthcare-associated infection and results in substantial morbidity and mortality. The "most urgent worldwide public health threat" label has been assigned to C. difficile by the United States Centers for Disease Control and Prevention (CDC). There is a pressing need to develop new classes of antibiotics with improved efficacy to treat C. difficile infections (CDI).
To address the need for novel strategies to combat the growing problem of CDI, we screened FDA-approved drugs and natural products library in search of novel drugs that possess potent and specific anticlostridial activity. Several promising hits were identified and evaluated successfully both in vitro and in vivo. The most potent and novel hits that displayed exceptional activity were mitomycin C, mithramycin A, aureomycin, NP-003875, NAT13-338148, NAT18-355531, and NAT18-355768. Furthermore, a murine model of C. difficile infection revealed that compound NP-003875 conferred 100% protection to the infected mice from clinical manifestations of the disease. Interestingly, these compounds were non-toxic to the gut microflora and human cells.
Our final approach has been to develop non-traditional therapeutics to target specific genes in C. difficile. These novel therapeutics are called peptide nucleic acids (PNA). Herein, we designed a PNA targeting RNA polymerase subunit gene (rpoA) of C. difficile. The designed PNA could successfully inhibit the growth of the pathogen and expression of its virulence factors.
In conclusion, our research opened exciting possibilities that can be further evaluated to uncover new treatments for CDI.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/113162 |
| Date | 12 January 2023 |
| Creators | Pal, Rusha |
| Contributors | Biomedical and Veterinary Sciences, Seleem, Mohamed N., Lowell, Andrew Nesemann, Sriranganathan, Nammalwar, Caswell, Clayton Christopher |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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