Annual incidence of the multiple recurring form of Clostridium difficile infection (mrCDI) soared nearly 200% in slightly more than a decade.

That’s according to a report in the Annals of Internal Medicine, which also found that during the same period of time — from 2001 to 2012 — the incidence of standard CDI increased by only about 40%.

Background information in the article points out that CDI is the most frequent healthcare-linked infection in the United States, affecting about a half million Americans each year. Overall, the infection costs the nation’s healthcare system about $5 billion.

Researchers from the Perelman School of Medicine at the University of Pennsylvania analyzed a large nationwide health insurance database to track trends in CDI increases.

While the exact reasons for the sharp rise in mrCDI's incidence remains unclear, the authors note, their results underscore how much the burden on the healthcare system is increasing.

"The increasing incidence of C. difficile being treated with multiple courses of antibiotics signals rising demand for fecal microbiota transplantation in the United States," said study senior author James D. Lewis, MD, MSCE, professor of gastroenterology and senior scholar in the medical school’s Center for Clinical Epidemiology and Biostatistics. "While we know that fecal microbiota transplantation is generally safe and effective in the short term, we need to establish the long-term safety of this procedure."

The database used by researchers in their analysis of CDI trends included records on more than 40 million U.S. patients enrolled in private health insurance plans. Cases of CDI were considered to have multiple recurrences when three closely spaced courses of appropriate antibiotics were administered.

The report found that the incidence of CDI rose by about 43% from 2001 to 2012, but the incidence of mrCDI rose by 189% over the same period.

MrCDI patients were found to be older (median age of 56 vs. 49) and more likely to be female (64% vs. 59%) compared to CDI patients whose infections resolved after just one or two courses of therapy.

In addition, those patients whose infection took longer to respond to antibiotics were more likely to have been previously exposed to medications such as corticosteroids, proton-pump inhibitors, and antibiotics, according to the report.

While use of those drugs might be linked with the rapid rise in the incidence of mrCDI, that doesn’t completely explain the increases, said Lewis, who added, "An additional driver of this rise in incidence could be the recent emergence of new strains of C. difficile, such as NAP1, which has been shown to be a risk factor for recurrent CDI.”