Asymptomatic carriers are a potential source for transmission of epidemic and nonepidemic Clostridium difficile strains among long-term care facility residents

Clin Infect Dis. 2007 Oct 15;45(8):992-8. doi: 10.1086/521854. Epub 2007 Sep 4.


Background: Asymptomatic fecal carriage of Clostridium difficile is common in patients staying in health care facilities, but the importance of asymptomatic carriers with regard to disease transmission is unclear.

Methods: We prospectively examined the prevalence of asymptomatic carriage of epidemic North American pulsed-field gel electrophoresis type 1 and nonepidemic toxigenic C. difficile strains among long-term care patients in the context of an outbreak of C. difficile-associated disease and evaluated the frequency of skin and environmental contamination. Molecular typing was performed by pulsed-field gel electrophoresis. Logistic regression was used to assess factors associated with asymptomatic carriage, and a sensitive and specific prediction rule was developed to identify high-risk patients.

Results: Thirty-five (51%) of 68 asymptomatic patients were carriers of toxigenic C. difficile, and 13 (37%) of these patients carried epidemic strains. Compared with noncarriers, asymptomatic carriers had higher percentages of skin (61% vs. 19%; P=.001) and environmental contamination (59% vs. 24%; P=.004). Eighty-seven percent of isolates found in skin samples and 58% of isolates found in environmental samples were identical to concurrent isolates found in stool samples. Spores on the skin of asymptomatic patients were easily transferred to investigators' hands. Previous C. difficile-associated disease (P<.001) and previous antibiotic use (P=.017) were associated with asymptomatic carriage, and the combination of these 2 variables was predictive of asymptomatic carriage (sensitivity, 77%; specificity, 58%; positive predictive value, 66%; negative predictive value, 70%).

Conclusions: Our findings suggest that asymptomatic carriers of epidemic and nonepidemic C. difficile strains have the potential to contribute significantly to disease transmission in long-term care facilities. Clinical factors, such as previous C. difficile-associated disease and recent antibiotic use, may be predictive of asymptomatic carriage.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Aged
  • Aged, 80 and over
  • Anti-Bacterial Agents / therapeutic use
  • Bacterial Toxins / biosynthesis
  • Bacterial Typing Techniques
  • Carrier State / epidemiology*
  • Carrier State / microbiology*
  • Clostridioides difficile / classification
  • Clostridioides difficile / genetics
  • Clostridioides difficile / isolation & purification*
  • Cross Infection / epidemiology
  • Cross Infection / transmission*
  • DNA, Bacterial / genetics
  • Disease Outbreaks*
  • Electrophoresis, Gel, Pulsed-Field
  • Enterocolitis, Pseudomembranous / epidemiology
  • Enterocolitis, Pseudomembranous / transmission*
  • Environmental Microbiology
  • Feces / microbiology
  • Humans
  • Infectious Disease Transmission, Patient-to-Professional
  • Logistic Models
  • Long-Term Care
  • Male
  • Middle Aged
  • Prevalence
  • Prospective Studies
  • Risk Factors
  • Skin / microbiology
  • Spores, Bacterial / isolation & purification


  • Anti-Bacterial Agents
  • Bacterial Toxins
  • DNA, Bacterial