Clinical features of Clostridium difficile-associated infections and molecular characterization of strains:: Results of a retrospective study, 2000-2004

Background. Recent outbreaks of severe cases of Clostridium difficile-associated diarrhea (CDAD) reported in North America, the United Kingdom, and The Netherlands have emphasized the importance of an ongoing epidemiological surveillance of CDAD. Objective. To determine the epidemiology of CDAD over the years 2000-2004 and the rate of nosocomial transmission of C. difficile. Design. Retrospective survey of inpatients with CDAD and molecular characterization of the strains isolated. Setting. A 760-bed teaching hospital. Methods. All CDAD cases diagnosed from January 1, 2000, to December 31, 2004, were reviewed. A CDAD case was defined as diarrhea in a hospitalized patient who had a stool specimen that tested positive for C. difficile cytotoxin or had a positive toxigenic culture result. CDAD was considered to be severe if a patient fulfilled at least 1 of the following 3 criteria: (1) presence of a fever (defined as temperature higher than 38.5 degrees C), abdominal pain, and leukocyte count greater than 10,000 cells/mm(3); (2) endoscopically or histologically proven pseudomembranous colitis; or (3) complications (defined as death with C. difficile infection as the primary or a contributing cause, toxic megacolon, perforation, toxic shock, and/or colectomy). CDAD was considered community-acquired if the diarrhea occurred in the patient within 72 hours after admission and if the patient had no history of hospitalization in the previous month; otherwise, CDAD was considered healthcare-associated. All the strains isolated were serogrouped and were characterized by toxinotyping and PCR ribotyping. Detection of toxin A, toxin B, and binary toxin was performed by PCR. Results. One hundred fifty-one cases of CDAD were diagnosed; 147 clinical records could be reviewed, and 131 strains were studied. The overall incidence of CDAD was 1.1 cases per 1,000 patients admitted, but incidence rates were higher in 2003-2004, compared with 2000-2002 (P = .017). Diarrhea was community acquired in 28 patients (19%). For patients with healthcare-associated CDAD, transmission of the strain from patient to patient (ie, infection with a strain of the same serogroup and PCR ribotype as the strain isolated from another patient hospitalized in the same ward or in a linked ward in the previous 2 months) was demonstrated in 12 cases (10.1%). Eleven percent of strains were positive for binary toxin. Binary toxin-positive strains were associated with more-severe diarrhea (P = .01) and with a higher case-fatality rate (P = .03). A specific clone of C. difficile (serogroup H, PCR ribotype sa026) accounted for 35 (26.7%) of all the strains isolated, but this clone was found both in healthcare-associated and community-acquired cases. Three strains belonged to toxinotype III, but only 1 was related to the hypervirulent clone involved in recent outbreaks. Conclusion. The incidence of CDAD is low in our hospital, and cross-infection is limited. These results also suggest that strains with binary toxin might be more virulent.