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12th C. L. Oakley lecture. Pathogenesis of Clostridium difficile infection of the gut
1Microbial Pathogenicity Research Group, MRC Clinical Research Centre, Harrow, Middlesex.
Insights
Clostridioides difficile (C. difficile) colonization varies by age and antibiotic use. In susceptible hosts, C. difficile can adhere to the intestinal lining, forming microcolonies and producing toxins that increase gut permeability.
Area of Science:
- Microbiology
- Gastroenterology
- Infectious Diseases
Background:
- Clostridioides difficile (C. difficile) is a significant cause of infectious diarrhea, particularly in healthcare settings.
- Neonates often experience asymptomatic C. difficile colonization, while antibiotic-treated adults show variable colonization outcomes.
- The elderly are considered more susceptible to C. difficile colonization due to a compromised intestinal flora.
Purpose of the Study:
- To propose a sequence of events following C. difficile exposure.
- To elucidate factors influencing C. difficile colonization and disease development in different host populations.
- To understand the mechanisms of C. difficile pathogenesis, including toxin effects on the intestinal mucosa.
Main Methods:
- The study proposes a hypothetical sequence of events based on existing findings.
- It analyzes factors such as host age, antibiotic treatment, and C. difficile virulence.
- Mechanisms of bacterial adherence and toxin-mediated mucosal damage are discussed.
Main Results:
- Neonatal C. difficile colonization is typically transient and asymptomatic.
- Antibiotic-treated adults exhibit variable C. difficile colonization, which can be transient and asymptomatic or symptomatic.
- In susceptible hosts, C. difficile may adhere to the mucosa, form microcolonies, and produce toxins (e.g., Toxin A) that increase vascular and mucosal permeability.
Conclusions:
- Host susceptibility, influenced by age and antibiotic exposure, significantly impacts C. difficile colonization and disease.
- C. difficile adherence via fimbriae and formation of protected microcolonies are early pathogenic steps.
- Toxins produced by C. difficile play a crucial role in disrupting intestinal barrier function and promoting disease development.
Abstract:
On the basis of the above findings it is possible to propose a sequence of events following exposure to C. difficile. Exposure of neonates to C. difficile leads to transient colonisation which is almost invariably asymptomatic; the reasons why colonisation is asymptomatic are not known. Exposure of antibiotic-treated adults to C. difficile does not invariably lead to colonisation; however, in those instances where colonisation occurs, it may be transient and asymptomatic or transient and symptomatic. The transient nature of the colonisation could be because the infecting strain is poorly virulent, or because the degree of compromise of the intestinal flora is insufficient to permit establishment and full expression of virulence. It is likely that it is easier to fully compromise the intestinal flora of the elderly so that they more readily become fully susceptible to colonisation by C. difficile. In a fully susceptible host and with a highly virulent strain, the following sequence of events could occur. The organism may associate with the intestinal mucosa possible via fimbriae, and form a microcolony of capsulate cells protected by a glycocalyx. The toxins, or other factors, produced may facilitate the interaction with mucosa and toxin A will result in increased vascular and mucosal permeability resulting in intra-luminal accumulation of serum-albumin-rich fluid. Although C. difficile does not appear to be capable of using serum albumin nutritionally, it may utilise other serum proteins, and the serum proteins in general may compete with host proteases and help prevent degradation of the toxins produced.(ABSTRACT TRUNCATED AT 250 WORDS)