Targeted C. diff screenings uncovered asymptomatic infections
■ Illnesses caused by the bacterium remain at historically high levels, while most other health care-associated infections are declining.
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Dr. Surbhi Leekha, MPH, worked at a Minnesota hospital where cases of health care-associated Clostridium difficile infection steadily increased from 2004 to 2008 despite efforts to prevent spread of the illness.
“We instituted several measures recommended by national guidelines for infection prevention. … Despite doing that, our rates increased,” said Dr. Leekha, now an assistant professor of epidemiology and public health at the University of Maryland School of Medicine. Similar problems have been reported nationwide at hospitals, and more recently at outpatient centers, as the prevalence of C. diff infections and mortality remain at historic highs, infectious diseases experts said.
To better understand what's contributing to the spread of the illness in hospitals, Dr. Leekha and her colleagues examined the prevalence of and risk factors for patients with asymptomatic C. diff upon hospital admission. The authors wanted to see whether such patients could be a potential source for the pathogen being transmitted in the health care setting. The findings were in the May issue of the American Journal of Infection Control.
While people admitted to a hospital are screened for methicillin-resistant Staphylococcus aureus in an effort to prevent transmission, patients are not tested for asymptomatic C. diff, the study authors said. They found that nearly one in 10 study participants had an asymptomatic form of the illness. Forty-eight percent of those patients had at least one of these three risk factors upon hospital admission: chronic dialysis, corticosteroid use and recent hospitalization.
Although the findings aren't necessarily groundbreaking, they support previously reported data and strengthen the call for studies on the efficacy of screening patients for asymptomatic C. diff, infectious diseases experts said. “It's important that researchers take it to the next level and do similar studies in larger populations,” Dr. Leekha said.
Key issues that need to be examined are whether “asymptomatic carriers are a source of transmission to other patients in the hospital [and whether] asymptomatic carriers are developing symptomatic infections,” said Erik R. Dubberke, MD, MSPH. He is an assistant professor of medicine in the infectious diseases division at Washington University School of Medicine in St. Louis.
C. diff bucking the trend
Although most health care-associated infections are declining, an opposite trend has been seen with C. diff, according to the Centers for Disease Control and Prevention. Prevalence of the infection remains at elevated levels nationwide, and in some health centers it's continuing to rise.
C. diff is linked to about 14,000 deaths a year in the U.S., according to the CDC. More than 90% of those deaths occur in people 65 and older. In 1999-2000, the infection was attributed to about 3,000 deaths a year, data show.
Ninety-four percent of C. diff infections reported in 2010 were associated with receiving health care, according to a report published in the March 9, 2012, issue of Morbidity and Mortality Weekly Report. People taking antibiotics are more susceptible, because the drugs also destroy beneficial bacteria that protect people from infections, medical experts said.
For the American Journal of Infection Control study, researchers analyzed stool samples from 320 adults who were admitted to a 1,249-bed tertiary care hospital in Rochester, Minn., between March 1 and April 30, 2009, who had no C. diff symptoms. Excluded from the study were patients discharged within 24 hours of admission and those with diarrhea or other colitis symptoms. For each participant, researchers tested the first stool sample after admission for the presence of toxigenic C. diff using a real-time polymerase chain reaction assay. Molecular techniques, such as PCR-based methods, make it easier to detect organisms in stool compared with a traditional culture, Dr. Leekha said.
Eighty percent of the samples were received within 48 hours of admission, and the remainder were received within five days of the start of the hospital stay, the study said. Researchers also collected data on the patients' recent antibiotic use, hospitalizations, residence in long-term-care facilities and previous C. diff cases.
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C. diff is linked to about 14,000 deaths a year in the U.S., mostly in people 65 and older.
The study found that 9.7% of the stool samples tested positive for the bacteria. Screening asymptomatic patients at hospital admission who had one of the three risk factors would have detected 74% of those infected, researchers concluded.
One limitation of the study is that it might not be representative of all patients because of its relatively small size and its limitation to one hospital, Dr. Leekha said. But infectious disease experts said the findings still are important for health care.
“While more research needs to be conducted … this study may help institutions with persistently high rates of transmission develop an expanded strategy for targeted C. difficile surveillance,” said Patricia S. Grant, president of the Assn. for Professionals in Infection Control and Epidemiology. The association publishes the journal in which the study appeared.