To the Editor—I would like to comment on the paper by Ponnado et alReference Ponnado, Guerrero and Jury ¹ published in the September 2017 issue of Infection Control and Hospital Epidemiology. The authors describe a study evaluating Clostridium difficile (CD) acquisition and infection after admission to a single long-term-care facility (LTCF). The authors hypothesized that patients admitted to the study facility who develop CD infection (CDI) are colonized with CD after admission to the facility rather than at the time of admission. This hypothesis contrasts with a hypothesis I published in 2008 stating that CD colonization usually occurs during hospitalization and is present on admission to an LTCF in those who develop CDI within 4 weeks of admission to the facility.Reference Mylotte ² This hypothesisReference Mylotte ² was based on observations during care of patients in post-acute care and long-term care in community skilled-nursing facilities.

The study by Ponnado et alReference Ponnado, Guerrero and Jury ¹ was conducted in a Veterans Affairs LTCF during a 5-month period in 2009. Perianal swabs were cultured for CD on new admissions (N=110) and weekly thereafter for 6 weeks. Study enrollees were monitored for CDI during the 6-week follow-up. Ribotyping was done on the initial CD-positive isolate and on isolates from those with CDI. Of 110 enrollees, 12 (11%) had CD colonization on admission to the facility. Of 98 enrollees with negative perianal swabs on admission, 82 (83%) had follow-up cultures and 22 (27%) developed CD colonization during the follow-up period. Only 4 cases of incident CDI were detected in the 6-week follow-up: 1 in the admission colonized group and 3 in the group with follow-up colonization. These findings were not consistent with my hypothesis.Reference Mylotte ²

I would like to call attention to several considerations regarding the report by Ponnada et al.Reference Ponnado, Guerrero and Jury ¹ First, this study was done 9 years ago—why did it take so long to be submitted for publication? Can we assume that it is still relevant? Second, a report from the same LTCF in the study by Ponnada et alReference Ponnado, Guerrero and Jury ¹ that covered the period from 2006 to 2008 found that, of 40 newly admitted people who developed CDI after admission, 85% did so within 30 days.Reference Guerrero, Nerandzic, Jury, Chang, Jump and Donskey ³ In the discussion section of that paper, the authors state that CD may have been acquired in the hospital (as I hypothesized) but that definitively pinpointing the site of acquisition of CD required serial stool cultures and typing. This finding may have been the motivation for the study by Ponnado et al,Reference Ponnado, Guerrero and Jury ¹ but the authors did not provide more detail about this study in their paper. Third, in the 34 asymptomatic CD carriers (12 on admission and 22 after admission) detected in the study, 15 different ribotypes were identified. Unfortunately, the authors did not comment on this in their discussion. The source or sources of a relatively large number of colonizing ribotypes of CD in a small group of residents raises concerns about infection control procedures at the facility. For example, disinfection procedures may have been ineffective in the facility environment that was contaminated with spores of multiple ribotypes, and these spores were transmitted to residents after admission. Fourth, it would have been useful for the authors to provide information about the incidence of CDI in long-term residents who were not hospitalized; another aspect of my hypothesisReference Mylotte ² was that the incidence is low in this group compared to newly admitted people. I documented this finding in a study conducted in 4 community LTCFs.Reference Mylotte, Russell, Sackett, Vallone and Antalek ⁴ Lastly, care should be taken when extrapolating the results of a study from a single facility to all LTCFs, and the authors briefly mention this in their discussion. This principle is exemplified by Brown et alReference Brown, Jones and Daneman ⁵ in a study that evaluated the variability of CDI rates in all LTCFs across all healthcare regions of the VA from 2006 to 2012. They found that CDI incidence varied widely by region (from 0.6 to 31 cases per 10,000 resident days). They also identified resident-level and region-level risk factors for CDI. Ponnado et alReference Ponnado, Guerrero and Jury ¹ refer to the study by Brown et al,Reference Brown, Jones and Daneman ⁵ but they do not mention the wide range of CDI incidence in Veterans Affairs healthcare regions. The findings of Brown et alReference Brown, Jones and Daneman ⁵ demonstrate the variability of CDI incidence within a single large healthcare system, and the findings from a single facility in the system may not be relevant in general.

I agree with Ponnado et alReference Ponnado, Guerrero and Jury ¹ that antibiotic use in the hospital may alter colonic flora, making CD colonization more likely in the hospital or LTCF. I also agree that efforts to improve prescribing in both settings are required to reduce CDI occurrence regardless of the site of acquisition. Large-scale studies in community LTCFs to determine the site of acquisition of CD need to be conducted, but they will be costly and time-consuming. However, documenting the site of acquisition of CD has important implications for CDI surveillance and for public reporting of CDI incidence in hospitals and nursing homes.