Testing patients with just three risk factors upon hospital admission has potential to identify nearly 3 out of 4 asymptomatic carriers of C. difficile, according to a new study published in the May issue of the American Journal of Infection Control.
Researchers from the Mayo Clinic in Rochester, MN analyzed stool samples from 320 patients showing no symptoms of C. difficile at hospital admission using a real-time polymerase chain reaction (PCR) assay. Samples from 31 of 320 patients tested positive for C. difficile, resulting in a colonization rate of 9.7 percent. The authors wanted to estimate the reservoir of colonized patients as a source of potential transmission because despite rigorous infection control measures, C. difficile infection was increasing at their institution.
In this study, independent predictors of C. difficile colonization were found to be recent hospitalization, chronic dialysis and corticosteroid use. According to the authors, one or more of the three independent risk factors were present in 155 (48 percent) of study participants, and screening only those with one or more of these factors would have identified 23 C. difficile carriers (74 percent).
In our population, by targeting those with identified risk factors, we would need to screen approximately half of those patients with anticipated stays longer than 24 hours, to identify three-fourths of those colonized with C. difficile, say the authors. This is in the range of previously published screening efficiency rates for MRSA.
However, the authors also state that these results should be interpreted keeping in mind that only 22 percent of all eligible patients provided stool for C. difficile PCR, and the study population was not representative of all patients admitted to the hospital.
Our objective was to estimate the burden of asymptomatic C. difficile carriers at admission because that constitutes an important checkpoint where risk factors can be assessed and infection prevention measures instituted, say the authors. This is the first study to demonstrate the feasibility of performing C. difficile surveillance on hospitalized patients at admission. The role of asymptomatic carriers in transmitting C. difficile should be studied further, and the utility of PCR-based targeted surveillance to detect asymptomatic carriers should be explored in areas of high endemicity or outbreak settings when other control measures have been exhausted.
While more research needs to be conducted on the transmission of C. difficile infection from colonized patients, this study may help institutions with persistently high rates of transmission develop an expanded strategy for targeted C. difficile surveillance, says 2013 APIC president Patti Grant, RN, BSN, MS, CIC. The study does not indicate necessity for all healthcare facility implementation, yet provides a step-wise progressive approach to help impede C. difficile activity when considering the overall epidemiologic impact of transmission.