The impact of respiratory infections and probiotic use on the nasal microbiota of frail residents in long-term care homes

Background: Residents in long-term care (LTC) homes, who tend to be of advanced age and frail, are at increased risk of respiratory infections. The respiratory microbiota is known to change with age, but whether these changes contribute to the risk of infection is not known. Our goal was to determine how the nasal microbiota of frail older adults changes during symptoms of influenza-like illness (ILI) and how this may be impacted by enrollment in a placebo-controlled trial testing the feasibility of administering a Lactobacillus rhamnosus GG probiotic to prevent respiratory infection (2014 - 2017). The microbiome of the nasal (mid-turbinate) of 150 residents of LTC homes was interrogated using 16S rRNA gene sequencing. Results: We identified a diverse and individualized microbiota which could be separated into 9 distinct clusters based on Bray Curtis distances. Samples collected during symptoms of influenza-like illness (ILI) differed statistically from those collected pre- and post-cold and influenza season, and we observed decreased temporal stability - as measured by movement between clusters - in individuals who experienced ILI compared to those who did not. Conclusions: The use of probiotics decreased ILI-induced changes to the microbiota; however, it is not clear whether this decrease is sufficient to prevent respiratory illness. ### Competing Interest Statement The authors have declared no competing interest. ### Clinical Trial NCT01720329 ### Funding Statement This work was funded by research grants from the Labarge Optimal Aging Initiative, and the W. Garfield Weston Family Foundation. FJW is an Anne McLaren Fellow funded by the University of Nottingham and was supported by a Marie Skłodowska-Curie Individual Fellowship (GA no. 793818) during some of this work. DMEB is the Canada Research Chair in Aging and Immunity. MGS is the Canada Research Chair in Interdisciplinary Microbiome Research. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Informed consent was received by the participants or their substitute decision makers. All protocols were approved by the Hamilton Integrated Research Ethics Board. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present work are contained in the manuscript or online at locations detailed in the manuscript and/or its supplemental material.