Oropharyngeal Staphylococcus aureus is linked to higher mortality in long-term aged care residents

Abstract

Background: Biological ageing, healthcare interactions, and pharmaceutical and environmental exposures in later life alter the characteristics of the oropharyngeal (OP) microbiome. These changes, including an increased susceptibility to colonisation by pathobiont species, have been linked with diverse health outcomes.

Objectives: To investigate the relationship between OP microbiome characteristics and all-cause mortality in long-term aged care residents.

Methods: OP swabs were collected from 190 residents of five aged care facilities in South Australia. Microbiota composition was assessed by shotgun metagenomics and related to health outcomes during a 12-month follow-up period. OP carriage of Staphylococcus aureus and methicillin resistance was confirmed by qPCR.

Results: OP carriage of S. aureus was identified in 13 (6.8%) residents. Detection of S. aureus was significantly associated with an increased risk of mortality (adjusted HR [95% CI]: 9.7 [3.8-24.9], P < .0001), compared with non-carriers, independent of methicillin resistance. Staphylococcus aureus carriage demonstrated a stronger association with mortality risk than the total number of comorbidities at the univariate level (S. aureus HR [95% CI]: 7.2 [3.4-15.5], P < .0001 vs. comorbidity count HR [95% CI]: 1.1 [1.0-1.3], P = .03), and remained significant after multivariable adjustment. Staphylococcus aureus detection was significantly associated with total number of comorbidities (adjusted OR [95% CI]: 1.4 [1.0-2.0], P = .04).

Conclusion: OP S. aureus carriage predicts all-cause mortality in long-term aged care. We speculate that S. aureus carriage represents a marker of general health, including prior healthcare exposures. OP S. aureus carriage could contribute to estimations of general health in older individuals and thereby inform care strategies.

Keywords: methicillin-resistant Staphylococcus aureus (MRSA); methicillin-susceptible S. aureus (MSSA); microbiome; nursing homes; older people.

Figure 1

(A) Kaplan–Meier 12-month all-cause mortality estimates among OP S. aureus carriers and non-carriers. Staphylococcus aureus carriage was determined by detection of the nuc gene using qPCR. (B) Kaplan–Meier 12-month all-cause mortality estimates among S. aureus carriers that were also mecA-positive (dashes) and mecA-negative (dots) compared to non-carriers. Adjusted HR, 95% CI and P-values are reported for all.