REFILE-Hospital-acquired C. difficile infections plummet in Canada

Last Updated: 2018-07-26

(Modifies 2nd sentence of para 8 to "spell out" 10 to the 9th power (to address coding issue experienced by some clients) and adds the "a" to the odds ratio 2.96.)

By Marilynn Larkin

NEW YORK (Reuters Health) - Rates of Clostridium difficile infections have decreased by more than a third in hospitals across Canada, although the most virulent strain is still the most common, researchers say.

"We think this is good news," Dr. Kevin Katz of North York General Hospital in Toronto told Reuters Health by email. "Across a large network of hospitals, we found that the healthcare-acquired rate of C. difficile fell by 35.8% from a peak in 2011 to 2015."

"Mostly notably, the North American pulsed-field gel electrophoresis type 1 (NAP1) strain responsible for large institutional outbreaks 15 years ago appears to be receding and being replaced by other strains," he said. "This is important because NAP1 was found to be associated with infections in more elderly patients, as well as mortality."

In Canada, between 2009 and 2015, there were 20,623 cases of hospital-acquired C. difficile. Diagnosis was based on laboratory confirmation of infection and a compatible clinical syndrome developing at least 72 hours after admission, or within less than 72 hours if patients had been discharged from the admitting hospital within the previous month.

Most cases occurred in hospitals with more than 200 beds, Dr. Katz and colleagues noted online June 25 in CMAJ.

The researchers studied 17,202 adults for whom full data were available. The mean age was 69; two-thirds were 65 or older. Microbiological data were available for 2,690 patients who underwent molecular typing and susceptibility testing.

The national rate of health care-associated C. difficile infection fell from 5.9 to 4.3 per 10,000 patient-days during the study period. NAP1 was the dominant strain type, but as Dr. Katz noted, infection with the strain decreased significantly over time, followed by an increasing trend of infection with NAP4 and NAP11 strains.

The NAP1 strain was significantly associated with a higher rate of death attributable to C. difficile infection compared with non-NAP1 strains (adjusted odds ratio, 1.91). Age (aOR, 2.45) and leukocyte count greater than 15 x 1,000,000,000/L (aOR 2.96) were significantly associated with mortality. There was no significant association between NAP strain type (NAP1 vs. non-NAP1) and all-cause death.

Significantly more younger patients acquired C. difficile infection over time, and they represented an increasing proportion of reported cases.

Microbiological analyses showed that isolates were universally susceptible to metronidazole, whereas one NAP1 strain was not susceptible to vancomycin. For every 10% increase in the proportion of NAP1 strains, the rate of infection increased by 3.3%.

"Infection prevention and control practices, antimicrobial stewardship and environmental cleaning should continue to be strengthened at the local level, as these areas positively affect institutional rates of health care-associated C. difficile infection, regardless of circulating strain types," the authors state.

"Multifaceted strategies are required to reduce C. difficile rates," Dr. Katz noted, "and because 5%-7% of people are colonized naturally, it is not feasible to reduce the rate to zero."

Some countries have successfully reduced rates, he added, "whereas others continue to struggle with high rates."

"Even our study data shows that rates fell during the study period from higher levels to lower levels in the Western and Central provinces, while the Eastern provinces maintained low rates throughout," he concluded.

Dr. Ashley Drews, an infectious disease physician at Houston Methodist Hospital in Texas, said in an email to Reuters Health, "This is a large surveillance study so (the authors) can only confidently say there was a decrease in C. difficile rates over the time period. Any statements regarding why the rates went down are only their postulates and were not studied specifically in this study".

"It is reasonable to postulate that improved infection control measures, including hand hygiene and environmental cleaning combined with improved antimicrobial stewardship would have a positive impact on rates of C. difficile, but this was not specifically studied," she said.

"As the authors note, they saw a reduction in circulation of the virulent NAP1 strain during this time period, which could also have impacted their outcomes," Dr. Drews concluded.

SOURCE: http://bit.ly/2lvYxCC

CMAJ 2018.