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A New, More Virulent Strain of C. difficile

The new strain appears to be responsible for unusually severe hospital-acquired disease and possibly some unexpected cases of community-acquired disease.

Clostridium difficile has been a familiar nosocomial pathogen for decades, but its well-known disease patterns are changing: Studies are finding unusual frequency and severity of hospital-acquired disease and unexpected cases of community-acquired disease. Is a new strain responsible?

Researchers studied 187 isolates of C. difficile collected from patients at eight healthcare facilities in six states where outbreaks of C. difficile-associated disease (CDAD) had occurred. About half of the isolates proved to be the strain associated with recent hospital outbreaks. This strain has a unique toxin profile thought to represent increased virulence and also has more extensive quinolone resistance than most other strains.

Canadian researchers studied a CDAD epidemic involving 1719 episodes of infection in 12 Montreal-area hospitals. A case-control analysis confirmed that prior use of cephalosporins and quinolones were independent risk factors for CDAD, but clindamycin use was not. Of 157 isolates, 132 were similar or identical to the epidemic strain described above, and severe illness was more common in patients with this strain than in others.

In 2005, Pennsylvania health authorities identified two cases of severe community-based CDAD. A 31-year-old woman pregnant with twins developed severe colitis that evolved into toxic megacolon; both the patient and the fetuses died. The patient's only antibiotic exposure was to trimethoprim-sulfamethoxazole, prescribed for a urinary tract infection about 3 months before the illness. A 10-year-old girl with no antibiotic exposure developed severe CDAD requiring hospitalization. She might have been infected by a younger brother, who had a febrile diarrheal illness that resolved without treatment; he also had no recent antibiotic exposure. Ten additional reports of peripartum CDAD and 23 of community-acquired CDAD were obtained from nearby states. Eight of the 33 patients reported no antibiotic use within 3 months of illness. Two isolates available for analysis had some of the virulence features identified in the epidemic hospital strain described above.

Comment: These reports read like the rumble of distant thunder, announcing trouble ahead. More surveillance is needed to characterize the prevalence and virulence of this new strain of C. difficile and to determine if person-to-person transmission is now occurring in the community as well as in hospitals. The only remedy at this point is what editorialists concisely describe as "antibiotic stewardship," especially in limiting unnecessary use of quinolones, which are a specific risk factor for this new strain.

— Abigail Zuger, MD

Published in Journal Watch General Medicine December 20, 2005

Citation(s):

McDonald LC et al. An epidemic, toxin gene-variant strain of Clostridium difficile. N Engl J Med 2005 Dec 8; 353:2433-41.

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Loo VG et al. A predominantly clonal multi-institutional outbreak of Clostridium difficile-associated diarrhea with high morbidity and mortality. N Engl J Med 2005 Dec 8; 353:2442-9.

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Centers for Disease Control and Prevention. Severe Clostridium difficile-associated disease in populations previously at low risk — Four states, 2005. MMWR Morb Mortal Wkly Rep 2005 Dec 2; 54:1201-5.

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Bartlett JG and Perl TM. The new Clostridium difficile — What does it mean? N Engl J Med 2005 Dec 8; 353:2503-5.

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• Medline abstract (Free)