Naso- and oropharyngeal bacterial carriage in nursing home residents: Impact of multimorbidity and functional impairment

OBJECTIVE: From April 2013 to February 2014 we performed a multicentre prospective cross-sectional study in 541 German nursing home residents. We determined pharyngeal carriage of Streptococcus pneumoniae (primary objective) and other bacteria (secondary objective) in naso- and oropharyngeal swabs by culture-based standard procedures and explored the influence of multimorbidity and functional status on bacterial carriage. METHODS: Socio-demographic data, vaccination status, multimorbidity, nutrition and functional status defined by Comprehensive Geriatric Assessment were evaluated. We estimated carriage rates with 95% confidence intervals (CI) and explored potential risk factors by logistic regression analysis. RESULTS: Pneumococcal post-serotyping carriage rate was 0.8% (95%CI 0.2–1.9%; 4/526). Serotyping revealed serotypes 4, 7F, 23B and 23F and S. pseudopneumoniae in two other cases. Odds of carriage were higher in men (Odds ratio OR 5.3 (95%CI 0.9–29.4)), in malnourished residents (OR 4.6 (0.8–25.7)), residents living in shared rooms (OR 3.0 (0.5–16.5)) or having contact with schoolchildren (OR 2.0 (0.2–17.6)). The most frequent pathogen was Staphylococcus aureus (prevalence 29.5% (25.6–33.6%)) with meticillin-resistant Staphylococcus aureus prevalence of 1.1%. Gram-negative bacteria (GNB) were found in 22.5% (19.0–26.3%) with a prevalence of extended-spectrum beta lactamase (ESBL) producing bacteria of 0.8%. Odds of S. aureus carriage were higher for immobility (OR 1.84 (1.15–2.93)) and cognitive impairment (OR 1.54 (0.98–2.40)). Odds of GNB carriage were higher in residents with more severe comorbidity (OR 1.13 (1.00–1.28)) and malnutrition (OR 1.54 (0.81–2.91)). CONCLUSIONS: Given the observed data, at least long-term carriage of S. pneumoniae in nursing home residents seems to be rare and rather unlikely to cause nursing home acquired pneumonia. The low rate of colonization with multi drug resistant (MDR) bacteria confirms that nursing home residency is not a risk factor for MDR pneumonia in Germany. For individual risk assessment in this susceptible population, immobility and malnutrition should be considered as signs of functional impairment as well as comorbidity.