BIOM3005 Outbreaks 1: Clostridioides (Clostridium) Difficile (Dr Locker Week 11)

Clostridioides difficile (C. difficile)

  • Anaerobic, spore-forming, Gram-positive bacterium found in the natural environment.

  • Transmission: fecal-oral route.

  • Can be a starter flora in babies.

  • Associated with antibiotic-associated diseases, especially Clindamycin.

Diseases Caused by C. difficile

  • C. difficile Infection (CDI): Acute onset diarrhea, leading cause of hospital-acquired diarrhea.

  • Ranges from asymptomatic carriage to severe conditions like toxic megacolon and sepsis.

  • Symptoms include abdominal pain, fever (>38.5°C), loss of appetite, and foul-smelling diarrhea.

Risk Factors

  • Elderly (>65), female.

  • Broad-spectrum antibiotic exposure (e.g., cephalosporins).

  • Recent GI surgery or prolonged healthcare stay.

  • Use of proton pump inhibitors or corticosteroids.

  • Compromised immune system, chronic kidney disease, HIV infection.

Pathogenesis

  • C. difficile spores germinate into toxin-producing vegetative cells.

  • Toxins disrupt the intestinal epithelial barrier, causing inflammation.

  • Neutrophil influx leads to pseudomembrane formation.

Other Potential Pathogenic Factors

  • Capsule: anti-phagocytic factor.

  • Proteolytic enzymes: mucus penetration.

  • Adhesins & Fimbriae: cell association/attachment

  • Flagella: motility/adherence.

Diagnosis

  • Test patients with unexplained new-onset diarrhea (>3 episodes in 2424 hrs).

  • Stool tests include:

    • ELISA GDH detection (primary screen).

    • ELISA toxin detection (A&B).

    • PCR (expensive but becoming more common).

    • Culture & Identification (phenotypic method).

    • Tissue culture toxin detection.

    • Full differential blood count.

Culture Methods

  • Selective medium: Cycloserine-Cefoxitin-Fructose agar (CCFA).

  • Pre-culture step: Alcohol shock for 11 hr.

  • Incubation: AnO2, 37°C37°C, 4848 hr.

Identification from Culture

  • Latex agglutination (somatic Ag).

  • Enzymatic ID (e.g., RAPID-ANA II).

  • Mass Spectrometry (MALDI TOF).

Toxin Detection

  • Tissue Culture: Observe cytopathic effect (CPE) on HeLa cells.

  • ELISA: Detects toxins A & B in a few hours.

Glutamate Dehydrogenase (GDH) ELISA Screening

  • GDH is produced by all C. difficile strains; used as a primary screening assay.

  • High negative predictive value (NPV).

  • Positive results require secondary testing (toxin test, inflammatory marker, or PCR ID).

Molecular Diagnostics (PCR)

  • Sensitive method for detecting toxin genes, resistance markers, and ribotypes.

  • Rapid turnaround times.

Treatments

  • Change or stop antibiotics.

  • Oral Metronidazole or Vancomycin.

  • Replace fluids/electrolytes; avoid anti-peristaltic drugs.

  • Stop Proton Pump Inhibitors (PPIs).

  • Fecal microbial transplant (re-colonization with normal stool).