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Laura Cersosimo, PhD



Job Title

Research Scientist

Academic Rank




Laura M. Cersosimo, Madeline Graham, Auriane Monestier, Aidan Pavao, N. Worley, Johann Peliter, Bruno Dupuy, Lynn Bry

Principal Investigator

Lynn Bry

Research Category: Allergy, Immunology, Inflammation, and Infectious Diseases


In vivo growth, toxin production, and metabolism are altered by a prdB mutation in Clostridioides difficile

Scientific Abstract

Clostridioides difficile (CD) is a spore-forming, nosocomial pathogen that opportunistically infects the gastrointestinal tract of antibiotic-exposed patients. CD utilizes energy from Stickland fermentations of amino acids, with proline being a preferred substrate. Proline advances CD growth as an electron acceptor for the proline reductase (PR) system that contains the prdB gene. We deleted the prdB gene to evaluate its in vivo role in infection and host outcomes. The growth, toxin production, and metabolism of CD were evaluated in germfree mice challenged with either wild-type CD ATCC43255 (WT) or the prdB mutant (ΔprdB). Host survival through early acute infection was extended in ΔprdB-infected mice, due to slowed growth in early stages of intestinal colonization, though animals infected with the WT or ΔprdB mutant ultimately succumbed from infection. Metabolically, removal of proline reductase altered the pathogen’s metabolism, with compensatory recruitment of pathways supporting Vitamin B12 and sulfur compound biosyntheses and switching of the pathogen’s metabolism for use of sugar alcohols, specifically for sorbitol. ΔprdB-infected mice also demonstrated reduced sporulation as compared to WT-infected mice. The present findings support the central role for proline reductase metabolism in early pathogen growth, metabolism, and toxin and as a potential therapeutic target against CD infection.

Lay Abstract

Clostridioides difficile (CD) is a hospital-acquired, spore-forming bacterium that typically infects the gut of patients on antibiotics. CD utilizes energy from amino acids, including proline, and produces toxins that contribute to the severity of the infection. Outside of the body, proline was shown to increase growth and toxin production of CD. In vivo studies have let us better understand the relationship between proline and CD within the body and on disease risk. In the present study, a gene associated with proline metabolism was deleted from CD. The growth, toxin production, and metabolism of CD were evaluated in mice orally dosed with normal or mutant CD. Gut contents were collected at 20 and 24 hr of infection. Toxin concentrations and total CD counts were decreased in mutant versus non-mutant-infected mice. Genes associated with proline and sugar alcohol metabolism (e.g., sorbitol and mannitol) were enriched in mice provided the mutant CD at each timepoint. Spore formation was enriched at 20 hr in mice administered with non-mutant CD. The present findings suggest that the mutated gene is key to growth, metabolism, and toxin production in the body and has the potential to be a target used to combat CD infection.

Clinical Implications

We define how the proline reductase enzyme system in Clostridioides difficile (CD) modulates disease risk and severity to inform better therapeutic interventions against CD infection.