Department of Infectious Diseases and Hospital Hygiene, Kantonsspital Aarau, Switzerland
Thank you for your interest in our local Swiss data on Clostridioides difficile infections recently published in this journal [1, 2]. As you say, understanding of the local epidemiology is key to guide possible interventions. Similarly, local treatment strategies need to be addressed, especially if they differ from the latest international guidelines. Of interest, the Clostridioides difficile Asia-Pacific Study, which included eight Chinese centres, recently published data describing overall mostly mild presentations and low recurrence rates , emphasising the need to base local guideline decisions on appropriate regional data. We believe that our epidemiological, treatment and outcome data, which to our knowledge are the only Swiss data published so far, are not only representative for our institution, but also for many, if not most, hospitals throughout Switzerland.
We deliberately chose >70 years of age on the basis that our data suggested that this margin best discriminates for recurrence risk. The age difference between ≥65 and >70 years is clinically probably less meaningful than the cumulative burden of comorbidity. Because of the higher life expectancy of our population, age >70 years may be more useful for Switzerland. Similar reasoning might explain the different cut off values found in literature.
You stated that there is only literature suggesting risk for C. difficile carriage in patients with haematological malignancy. Our local data suggested a high burden of morbidity from C. difficile infection (CDI) in these patients, though discrimination between colonisation and infection might indeed be difficult, as diarrhoea is frequent in severe neutropenia. The adequate clinical response to CDI-targeted therapy suggested causality, however.
As our sample size was limited we abstained form multivariable analyses and decided to report probable associations by comparing Kaplan-Meier curves instead. We then compared our findings with international guidelines, confirming the higher recurrence rate reported in the literature, while still suggesting metronidazole use in a defined subset of patients. Remarkably, these conclusions are very much in line with the recently released Swiss Society of Infectious Diseases (SSI) guidelines by Tschudin et al. 
No commercial sponsor had any involvement in the design and conduct of the original study, namely collection, management, analysis and interpretation of the data; and preparation, decision to submit, review, or approval of the manuscript. CAF has received honoraria paid to the hospital research funds for advisory boards from Astellas, Gilead, MSD, Pfizer and Viiv. SH has received honoraria for advisory boards from Gilead Sciences; all remunerations went to his home institution.
Dr S. Haubitz, MD, Department of Infectious Diseases, Kantonsspital Aarau, Tellstrasse, CH-5000 Aarau, sebastian.haubitz[at]gmail.com
1 Haubitz S, Bartlomé N, Bucheli Laffer E, Spelters C, Fankhauser H, Fux CA. Outcome of Clostridioides difficile infections treated in a Swiss tertiary care hospital: an observational study. Swiss Med Wkly. 2020;150:w20173. doi:. http://dx.doi.org/10.4414/smw.2020.20173 PubMed
2 Zha M, Rena X, Lub J, Luoc J. Comment on: Haubitz et al. Outcome of Clostridioides difficile infections treated in a Swiss tertiary care hospital: an observational study. Swiss Med Wkly. 2020;150:w20310.
3 Collins DA, Sohn KM, Wu Y, Ouchi K, Ishii Y, Elliott B, et al.; Clostridioides difficile Asia-Pacific Study Group. Clostridioides difficile infection in the Asia-Pacific region. Emerg Microbes Infect. 2020;9(1):42–52. doi:. http://dx.doi.org/10.1080/22221751.2019.1702480 PubMed
4 Tschudin Sutter S, Boggian K, Bernasconi E, Guery B, Achermann Y. Clostridioides difficile-Infektion. 22 January 2020. Available at: https://ssi.guidelines.ch/guideline/3120 [cited 2020 May 14].
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