C. difficile cases are still on the rise

Key Points

C. difficile disease, often associated with use of antimicrobial medications, may now be causing 500,000 U.S. nursing-home and hospital-onset cases a year and contributing to more than 20,000 deaths, Clifford McDonald, MD, said in Bethesda, Md., at the annual conference on antimicrobial resistance, sponsored by the National Foundation for Infectious Diseases.

That is an extrapolation from reports from Ohio, McDonald said, where C. difficile in hospital or nursing-home patients was a reportable disease during 2006, due to public pressure arising after prominent outbreaks in the Cleveland area. Fred Tenover, PhD, head of CDC's Office of Antimicrobial Resistance, also cited the Ohio data in telling a June 24 Senate committee hearing that C. difficile is perhaps contributing to 15,000 to 30,000 deaths per year. Ohio recorded 14,100 cases in 2006, with 6,200 in hospitals and 7,900 in nursing homes. McDonald said the state also looked at its death certificates and found a marked increase in mortality related to the disease, with about 500 deaths in which the disease was reported as the primary underlying cause and a total of nearly 900 deaths for which the disease was included in any reported cause of death.

Displaying a U.S. map with most states in pink, McDonald told attendees that if their states were not pink, "it's probably just because no one has cultured for C. difficile."

Indeed, McDonald said, the fact that the disease is not usually cultured for is "a tremendous, tremendous barrier for us to understand C. difficile from a public health standpoint."

More than 90 percent of hospital laboratories and others are using tests that look for a free toxin to diagnose this, he said, adding that he is not suggesting that the practice is wrong, but "this is why we don't have large data sets of isolates or good historic data to really figure out what happened to us."

Tenover told the Senate committee that challenges to surveillance include limited public health infrastructure for detecting resistance and heavy reliance on hospital microbiology labs for antibiotic resistance data. He said many labs report that they face increasing pressures to cease these services due to limited resources.

He told the committee that CDC will begin to collect data to track C. difficile from healthcare institutions using the National Healthcare Safety Network (NHSN). According to CDC, the NHSN is an Internet-based system that integrates safety surveillance systems for patients and healthcare personnel. It was opened nationally last year for enrollment by hospitals and outpatient hemodialysis centers.

McDonald noted that a Washington University study found histamine-2 blockers and proton pump inhibitors to be independent risk factors. Several large observational studies suggest that these medications, which suppress stomach acid, may increase C. difficile risk, but other studies contradict that. Another risk factor is intravenous (IV) vancomycin, which McDonald said is thought of as a treatment.

But IV vancomycin may just leave people with a low level of exposure in their intestinal tracts, which is probably enough to alter the GI flora but not to suppress the C. difficile growth.

However, the same study also indicates that hospital patients are at higher risk of contracting C. difficile if they are in wards with a higher number of people symptomatic for the disease.