The new C diff strain may turn out to be particularly severe and requires sufficient monitoring.
A strain of Clostridioides difficile (C diff) has been identified, despite being previously misclassified, according to a paper from in the US Centers for Disease Control and Prevention’s Emerging Infectious Diseases journal.
Investigators from Loyola University Chicago Stritch School of Medicine identified a C diff strain related to the epidemic ribotype 027 strain which is associated with hospital outbreaks of severe disease. Using a polymerase chain reaction (PCR) test, which reports if a C diff strain is related to strains known for increased disease severity and complications, they found 15 patients infected with this strain, called DQ/591. This was detected throughout February to August 2012 during a surveillance study of 2 Veterans Affaris long-term care facility and their affiliated acute care facilities, the study authors wrote.
After conducting whole-genome sequencing, they learned that it is a member of the same multilocus sequence clade 2 as the 027 ribotype but in a separate cluster. The 2 C diffs produced similar cytopathic effects, yet DQ/591 showed delayed toxin production, comparatively.
Their study showed that the PCR test misidentified a new C diff strain, originally labeling it BI/027. However, it should now be classified as DQ/591 despite being genomically similar to BI/027.
“The potential for worse clinical outcomes with this new strain is unknown but warrants continued surveillance,” study author Andrew Skinner, MD, Division of Infectious Diseases, Loyola University Medical Center, told Contagion®. “Our results, along with other reports show that clinical laboratories must exercise caution when using these tests to identify the epidemic BI/027 strain as there have been multiple strains misidentified by PCR testing. We also stress that choice of treatment for individual patients with C diff infection should be based primarily on clinical findings and history of prior C diff infection episodes.”
The investigators said DQ/RT591 was susceptible to moxifloxacin but highly resistant to clindamycin. DQ/RT591 demonstrated how closely related it is to the 027 ribotype because the investigators determined they are both resistant to fluoroquinolone as well.
“In our study, despite the close relationship with BI/027, we found that the DQ/591 strain does not show any significant resistance towards moxifloxacin but was highly resistant to clindamycin,” Skinner continued. “Furthermore, the exposure to clindamycin was limited in the patients found to be infected or colonized with DQ/591.”
He cautioned that the lack of exposure could be explained by the study’s relatively small sample size. But ,he added, that alone reinforces the need to continued monitoring of DQ/591 if the strain turns out to be linked to increased morbidity and mortality. Further research could determine if there are any other risk factors or antibiotics associated with DQ/591, he said.
The investigators used the Society for Healthcare Epidemiology of America and Infectious Diseases Society of America guidelines for standard treatment during their study period, Skinner said. (They recommend the use of oral vancomycin and oral fidaxomicin for C diff treatment.)
“The individuals in our study who were treated with these standard of care antibiotics responded well to therapy, and our study shows no indication that we should change the current recommendations for primary episodes of CDI or recurrent CDI,” Skinner added.
Since the conclusion of their work, the study authors wrote that DQ/591 was reported as the most prevalent C diff strain in 3 tertiary hospitals in Colombia. They stressed that further monitoring is required to determine whether the strain carries risk for increased illness and death or if it has the capability of widespread dissemination.