14 research outputs found

    Identifying Factors that Protect the Host from Clostridium difficile Infection

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    Clostridium difficile is the most prevalent single cause of nosocomial infection in the United States. A major risk factor for Clostridium difficile infection (CDI) is exposure to antibiotics. Antibiotics increase susceptibility to CDI by altering the gut microbial community, enabling increased germination of spores and growth of vegetative cells. Despite being a major risk factor, antibiotics are currently the principal treatment for the disease. The cycle of antibiotic usage associated with CDI is likely why twenty-five percent of patients with CDI fail antibiotic therapy and experience recurrent disease. An alternative treatment, such as limiting colonization with toxigenic C. difficile by prior colonization of susceptible patients with non-toxigenic strains of C. difficile has been utilized with some success in clinical trials. However the mechanisms underlying how prior colonization with C. difficile limits disease are unknown. The work described in this dissertation sought to determine the relative contribution of host and bacterial factors in mediating protection from CDI. Using a murine model of C. difficile, I present evidence in support of a novel paradigm of colonization resistance. In this model depletion of the amino acid glycine by prior colonization with one strain of C. difficile protects from lethal CDI by limiting germination of the incoming strain. Additionally, I show that unlike other gastrointestinal infections, adaptive immunity is not required for clearance of C. difficile, rather clearance is associated the presence of two members of the Lachnospiraceae family in the indigenous untreated microbial community. Finally, I describe the use of human intestinal organoids to study CDI in the context of a complex human epithelium. Together these results underscore the importance of bacterial interactions in providing protection from colonization while attributes of the host and pathogen may alter the pathogenesis of the infection. These results are important because they provide new insights into this important nosocomial infection. Furthermore the role of glycine in providing colonization resistance provides a novel target for the development of next-generation probiotic therapies for CDI.PHDMicrobiology & ImmunologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/138523/1/jlleslie_1.pd

    Clostridioides difficile binary toxin binding component (cdtb) increases virulence in a hamster model

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    Background Clostridioides difficile is the leading cause of hospital-acquired gastrointestinal infection, in part due to the existence of binary toxin (CDT)-expressing hypervirulent strains. Although the effects of the CDT holotoxin on disease pathogenesis have been previously studied, we sought to investigate the role of the individual components of CDT during in vivo infection. Methods To determine the contribution of the separate components of CDT during infection, we developed strains of C difficile expressing either CDTa or CDTb individually. We then infected both mice and hamsters with these novel mutant strains and monitored them for development of severe illness. Results Although expression of CDTb without CDTa did not induce significant disease in a mouse model of C difficile infection, we found that complementation of a CDT-deficient C difficile strain with CDTb alone restored virulence in a hamster model of C difficile infection. Conclusions Overall, this study demonstrates that the binding component of C difficile binary toxin, CDTb, contributes to virulence in a hamster model of infection

    Overdiagnosis of Clostridium difficile Infection in the Molecular Test Era.

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    ImportanceClostridium difficile is a major cause of health care-associated infection, but disagreement between diagnostic tests is an ongoing barrier to clinical decision making and public health reporting. Molecular tests are increasingly used to diagnose C difficile infection (CDI), but many molecular test-positive patients lack toxins that historically defined disease, making it unclear if they need treatment.ObjectiveTo determine the natural history and need for treatment of patients who are toxin immunoassay negative and polymerase chain reaction (PCR) positive (Tox-/PCR+) for CDI.Design, setting, and participantsProspective observational cohort study at a single academic medical center among 1416 hospitalized adults tested for C difficile toxins 72 hours or longer after admission between December 1, 2010, and October 20, 2012. The analysis was conducted in stages with revisions from April 27, 2013, to January 13, 2015.Main outcomes and measuresPatients undergoing C difficile testing were grouped by US Food and Drug Administration-approved toxin and PCR tests as Tox+/PCR+, Tox-/PCR+, or Tox-/PCR-. Toxin results were reported clinically. Polymerase chain reaction results were not reported. The main study outcomes were duration of diarrhea during up to 14 days of treatment, rate of CDI-related complications (ie, colectomy, megacolon, or intensive care unit care) and CDI-related death within 30 days.ResultsTwenty-one percent (293 of 1416) of hospitalized adults tested for C difficile were positive by PCR, but 44.7% (131 of 293) had toxins detected by the clinical toxin test. At baseline, Tox-/PCR+ patients had lower C difficile bacterial load and less antibiotic exposure, fecal inflammation, and diarrhea than Tox+/PCR+ patients (P < .001 for all). The median duration of diarrhea was shorter in Tox-/PCR+ patients (2 days; interquartile range, 1-4 days) than in Tox+/PCR+ patients (3 days; interquartile range, 1-6 days) (P = .003) and was similar to that in Tox-/PCR- patients (2 days; interquartile range, 1-3 days), despite minimal empirical treatment of Tox-/PCR+ patients. No CDI-related complications occurred in Tox-/PCR+ patients vs 10 complications in Tox+/PCR+ patients (0% vs 7.6%, P < .001). One Tox-/PCR+ patient had recurrent CDI as a contributing factor to death within 30 days vs 11 CDI-related deaths in Tox+/PCR+ patients (0.6% vs 8.4%, P = .001).Conclusions and relevanceAmong hospitalized adults with suspected CDI, virtually all CDI-related complications and deaths occurred in patients with positive toxin immunoassay test results. Patients with a positive molecular test result and a negative toxin immunoassay test result had outcomes that were comparable to patients without C difficile by either method. Exclusive reliance on molecular tests for CDI diagnosis without tests for toxins or host response is likely to result in overdiagnosis, overtreatment, and increased health care costs
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