Screening for carriers may reduce hospital-acquired cases of C difficile diarrhoea
About 5% of healthy adults carry Clostridium difficile bacteria in their bowel, where normal gut bacteria keep them in check. Once they leave the body C difficile bacteria become resistant spores. If spores are ingested by people with low resistance, particularly those whose normal gut bacteria have been altered by antibiotic treatment, C difficile bacteria multiply and produce toxins that cause conditions ranging from mild diarrhoea to a rare but serious and potentially life-threatening condition, toxic megacolon. C difficile is a major cause of hospital-acquired infection worldwide.
Research workers from Québec, Canada noted that current hospital control measures for C difficile do not target carriers, although there is evidence that carriers can contaminate health workers’ hands and the environment. They carried out a 15 month study to find out whether the detection and isolation of carriers among those patients admitted to the acute care Québec Heart and Lung Institute through the emergency department would reduce the incidence of hospital-acquired C difficile infections. Patients admitted directly to the wards were not screened.
Rectal swabs taken on admission and during admission, were tested using a one-step polymerase chain reaction (BD GeneOhm Cdiff Assay, BD Diagnostics) to detect the tcdB gene that codes for the B toxin of C difficile. Of the 7,599 patients tested, 368 (4.8%) were identified as asymptomatic carriers and were placed in contact isolation (with the modifications that gowns were not used when caring for them, and they could share a room with non-carriers with privacy curtains drawn).
The investigators compared the incidence of C difficile infections during the 15 month study period with the incidence during the preceding six years. The introduction of screening was followed by a significant progressive decrease in infections. The diagnosis was made in 38 patients, giving an overall incidence of 3.0 per 10,000 patient-days, less than half the incidence of 6.9 per 10,000 patient-days experienced during the preceding six years. During the study period no significant decreases in C difficile infection trends were seen in six other institutions in Québec City or in 94 institutions in Québec province.
The authors pointed to several limitations of their work. For example, compliance with isolation was not assessed and patients and staff could not be masked to the study. Knowledge of carrier status could have influenced the diagnosis of C difficile infection and could also have reduced the use of antibiotics for other infections for fear of decreasing patients’ resistance to C difficile.
The authors concluded that further investigations including randomised controlled trials will be required to confirm their findings. However, they believe their study had been essential to justify such more expensive studies.