March 21, 2012 — The absolute risk for secondary Clostridium difficile infection (CDI) among household contacts of index patients is low, and interventions therefore are unnecessary, according to the findings of a new study published online December 26 and in the April print issue of the Journal of Infection.
The researchers found that 5 of 1061 spouses and 3 of 501 children (younger than 25 years) living in the same household as the index patient developed CDI. All but 1 of these secondary cases occurred within 2 months of the index case. Among spouses and children, the attack rate was 4.71/1000 and 5.99/1000, respectively, and the relative risk was 7.61 (95% confidence interval [CI], 5.77 - 9.78) and 90.6 (95% CI, 33.89 - 487.64) for the 3 months after the diagnosis in the index case.
"Little is known about the risk of secondary cases among household contacts of index cases, whether the index case had acquired CDI at the hospital or in the community," Jacques Pépin, MD, from the Department of Microbiology-Infectious Diseases, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Quebec, Canada, and colleagues write.
"This study is the first exploring this component of the epidemiology of CDI. CDI person-to-person transmission in the community has been described in a small number of case-reports but this has never been quantified systematically."
Medical and census data for 2222 patients diagnosed with CDI between January 1998 and December 2009 at the Centre Hospitalier Universitaire de Sherbrooke and from the surrounding area were collected. Patients were diagnosed with C difficile either by positive cytotoxicity assay or by endoscopy and pathology. Patients with the same telephone number were contacted to verify whether they were related. Patients were considered related if there were 2 or more cases of CDI among people living in the same household who were diagnosed within 1 year of each other.
Because the medical database did not include information on each patient's marital status or number of children living with the index patient, this information was estimated from census data and divided into 10-year age strata.
Patients with leukocyte counts of 15,000/μL or higher and/or a serum creatinine level 1.5 times or more higher than the premorbid level were classified as having severe CDI. A positive C difficile toxin assay within 2 months of the end of treatment of the previous episode was considered a recurrence.
The study authors hypothesize that although there may be several reasons for the low transmission rate of C difficile, the most important is that the majority of household contacts do not receive antimicrobial therapy during the time when they might be colonized with a C difficile strain from the index patient.
The authors acknowledge study limitations such as the retrospective design, estimated numbers of children and spouses, and possible underestimation of secondary cases in children living under shared custody. The researchers note, however, that the strength of their study lies in their ability to diagnose CDI within a large population using a gold standard diagnostic assay (direct cytotoxicity with neutralization).
Dr. Pepin and colleagues conclude that "although the relative risk of CDI among household contacts is somewhat increased for a few months, the absolute risk is too low to justify interventions, apart from avoiding unnecessary courses of antimicrobial agents."
According to independent commentator Loren Miller, MD, director of the Infection Prevention and Control Program at Harbor–University of California, Los Angeles, Medical Center: "This is the first systematic examination of apparent transmission within a household."
"Those household members that got CDI were almost all persons who took antibiotics," Dr. Miller told Medscape Medical News. "Given the large amount of inappropriate antibiotic therapy prescribed and taken worldwide, one may add CDI infection as [a] complication that could be avoided by efforts to improve appropriate prescribing of antibiotics in the community."
The study was funded by the Department of Microbiology-Infectious Diseases, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Quebec, Canada. Dr. Pepin has served on advisory boards for Pfizer, Wyeth, Ortho, Merck, Acambis, Iroko, and The Medicines Company. One coauthor has served on advisory boards for Oryx, Iroko, Abbott, and Wyeth, and has received compensation to conduct clinical trials involving antibacterials from Genzyme, Wyeth, Pfizer, BioCryst, Trius, Cempra, Optimer, and Arpida. The other author and Dr. Miller have disclosed no relevant financial relationships.
J Infect. 2012;64:387-390. Abstract
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Cite this: Clostridium difficile: Low Risk for Household Contacts - Medscape - Mar 21, 2012.
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