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Newly identified C. difficile strain highly virulent
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Researchers from Monash University in Australia have found that the RT244 Clostridium difficile strain, which was associated with severe disease and a high mortality rate, has significant pathogenic potential.
They conducted a retrospective cohort study that included 12 patients with the RT244 strain and 24 matched patients with a non-RT244/non-RT027 strain. They performed whole-genome sequencing on the strains to understand how the RT244 strain was related to other strains. There was no difference in age or comorbidities between the two groups and most patients had antibiotic exposure.
They found that the patients with the RT244 strain had more severe disease, renal impairment and hypoalbuminemia compared with non-RT244 patients. These patients also were more likely to die: They had a 30-day mortality of 42% and four of the five deaths were attributed to CDI. There were no deaths among patients with non-RT244 strains. Patients with the RT244 strain were 13 times more likely to die compared with those with non-RT244 strains.
In a phylogenomic analysis, the researchers found that the RT244 strain is in the same genetic clade as the strain RT027 (clade 2). In further analyses, the researchers found that the RT244 strain produced a variant toxin B, which may be the contributing factor to the strain’s virulence.
“The overall clinical significance of RT244 cannot be clearly determined at present,” the researchers wrote in Clinical Infectious Diseases. “At our laboratory, C. difficile RT244 has spontaneously declined and the epidemiological data available to us provided no clear evidence for the source of the strain, how it disseminated in our community or why its incidence has declined. Further studies are required to answer these questions, and to better understand the virulence of the strain, and its potential to become endemic and to cause further outbreaks.”
Disclosure: The researchers report no relevant financial disclosures.
Perspective
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Dale Gerding, MD
The report by Lim and colleagues is reflective of the constantly evolving epidemiology of C. difficile infection, demonstrating the emergence of new strains that arise to cause infection in susceptible populations. Ribotype 244 strains have emerged as the cause of severe CDI in New Zealand and Australia and are closely related to the well-known epidemic BI/NAP1/027 group of C. difficile strains that have been causing severe CDI around the world for over 15 years. They differ, however, in that 244 lacks fluoroquinolone resistance, but has a variant toxin B that is not produced in high levels as it is in 027 strains. Although Australia is a long way off, Americans should not relax as isolates with the same REA type as ribotype 244 have been found in the United States since the 1980s. However, there have been no known outbreaks or mortality reported with these strains.
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