% # # SCIENCE
A German cross-sectional study involved enrollment of a convenience sample of geo- graphically diverse households ( n = 415) that had a dog and/or a cat. The study aim was to estimate frequency of possible exposures to pets as a source of C. dicile (Rabold et al., 2018). Fecal samples were collected from companion animal owners ( n = 578) and animals ( n = 1,447) to determine CDI status (i.e., positive or negative) as well as gather information on intensity of contact between owners and pets (e.g., sleeping in same bed, washed in tub or shower, licking face of owner) and health status of the humans (e.g., diarrhea, chronic disease). Incidence Study A Canadian study was conducted with patients who had been diagnosed with CDI in tertiary care centers to measure incidence in household contacts (Loo et al., 2016). Case participants ( n = 51) and household contacts ( n = 67) provided stool or rectal swabs and responded to a survey on risk fac- tors on enrollment. The swabs and survey were repeated during home visits that were conducted monthly for 4 months. The study defined probable transmission in household contacts (i.e., humans or animals) as con- version of a negative to positive C. dicile result on one of the monthly fecal samples with an identical or closely related pulsed- field gel electrophoresis (PFGE) pattern as the index case.
24), remote controls ( n = 24), and telephones ( n = 24) during all household visits. The study also involved collection of stool samples from household contacts ( n = 12) of index cases of patients with recurrent CDI who were undergoing FMT and were ana- lyzed for C. dicile colonization. Informa- tion on household cleaning practices (e.g., frequency and use of bleach), hand hygiene, and CDI knowledge was also collected. Fecal samples were also collected from pets ( n = 8) in households of individuals about to undergo or who had recently undergone FMT and compared with pets in households of those controls without CDI. Compari- sons were made between cases and controls (case-control) and before and after FMT (quasi-experimental). Simulation Study A simulation study conducted in Canada involved the review of CDI cases in the data- base of a Quebec hospital (Pépin et al., 2012). Cases in the same household were identified by searching the hospital database to find individuals with the same phone number at the time of diagnosis. Census data were used to estimate the number of spouses, parents, and children of the cases and to estimate the expected number of cases in household members to calculate an estimated risk of transmission to household contacts living with a case of CDI.
ervoirs of C. dicile —but by nature of their design, they lack control groups and are there- fore not appropriate to evaluate risk factors associated with CDI infection. Most of the outcomes of the studies could be considered process or proxy outcomes in the sense that they are not measuring the most desirable outcome of incidence of CDI in response to transmission of C. di- cile . The complexity of the transmission of C. dicile makes it a dicult disease to study with respect to definitively identifying when transmission of an infection has occurred. A sucient (and currently undefined) num- ber of C. dicile spores must be ingested and subsequent disruption of the intestinal microbiome must also happen for an infec- tion to occur, but there can be significant time in between these two occurrences. This review identified only one study that defined and measured probable transmission within household members and that study followed subjects only for a 4-month period (Loo et al., 2016). This lack of longitudinal studies designed to estimate transmission risk is a significant gap in knowledge. C. dicile is known to colonize in humans and animals and to survive in the environ- ment, including in food and water (Warriner et al., 2017). While the specific transmission dynamics in the household are unknown, there is likely to be interaction among these three reservoirs. Only three studies identified by this review used a holistic or One Health approach to examine all potential C. dicile reservoirs in the household (i.e., humans, animals, and the environment). Future stud- ies should be designed to consider all risks in household transmission. Limitations While the goal of this review was to identify all research related to C. dicile transmission in the household environment, it is possible that some relevant research was not identified in our search. One limitation of this study is that it did not intentionally search for stud- ies related to C. dicile using “domestic pets” or “food” in the search terms because these studies might not be limited to the house- hold environment. Thus, studies related to these two elements could have been missed. There was also a potential for language bias, because we excluded seven articles because they were in a language other than English.
Discussion
Case-Control and Quasi- Experimental Study
Summary of Evidence This scoping review describes the literature examining household transmission of C. dif- ficile. The results highlight several gaps in knowledge about the role of the household environment in transmission of C. dicile . There were no experimental studies among the literature identified in this review, which is significant, as experimental studies provide an opportunity to minimize confounding factors and provide greater evidence to infer causal- ity than observational studies (Dohoo et al., 2012). The studies that were most common in the current body of literature were prevalence studies of C. dicile in humans, animals, or the environment, the results of which cannot be used to infer causality related to the cause of infection. Prevalence studies can be infor- mative in identifying the environmental res-
A U.S. study involved adults experiencing recurrent CDI who were scheduled for fecal microbiota transplantation (FMT) as treat- ment (Shaughnessy et al., 2016). Cases were identified from patients at a University of Minnesota gastroenterology clinic. Controls were matched on age and geographic location and were recruited from outside the health- care setting. The investigators visited each of the 16 participating households (8 of the individuals undergoing FMT and 8 controls). The households of those undergoing FMT were visited twice (7 days prior and 10 days post-FMT). Environmental samples were col- lected from vacuum cleaners ( n = 27), toilets ( n = 30), bathrooms ( n = 29), computers ( n = 24), bathroom doors and light switches ( n = 27), microwaves ( n = 24), refrigerators ( n =
12
%74<5. • <5+.9
Powered by FlippingBook