Case fatality associated with a hypervirulent strain in patients with culture-positive Clostridium difficile infection: a retrospective population-based study.

Background: Clostridium difficile is a major infectious cause of healthcare-associated diarrhea. The epidemiology of C. difficile infection (CDI) is changing, with evidence of increased incidence and severity. The first patient with a hypervirulent strain type in Pirkanmaa Hospital District, Finland was reported in September 2008.

Methods: We reviewed all culture-positive C. difficile episodes that occurred in Pirkanmaa Hospital District during the period September 2008 to May 2010.

Results: A total of 780 episodes of C. difficile occurred in 622 patients. A hypervirulent strain caused 14.2% of all episodes. The day 30 case fatality associated with CDI was 8.5% in episodes with a non-hypervirulent strain and 20.7% in episodes with a hypervirulent strain type (p<0.001, odds ratio 2.8, 95% confidence interval 1.6-4.8). The median age among those infected by a hypervirulent strain was higher than among those infected by a non-hypervirulent strain (83 vs. 75 years, p<0.001). Hypervirulent strain type remained a significant factor associated with case fatality in a logistic regression model. Blood leukocytes were significantly higher in episodes due to a hypervirulent strain (11.0 vs. 9.4 × 10(9)/l, p=0.007). Blood leukocytes and C-reactive protein (CRP) on the day of diagnosis were significantly higher in non-survivors compared to survivors in CDI (13.2 vs. 9.6 × 10(9)/l, p=0.009, and 106.0 vs. 79.4 mg/l, p<0.001, respectively).

Conclusions: Infection due to a hypervirulent strain is a factor associated with increased case fatality in CDI. Blood leukocytes are significantly higher in CDI caused by a hypervirulent strain. Leukocyte count and CRP are useful prognostic biomarkers in patients with CDI.