Investigating the associations between oral colonisation with respiratory commensal pathogens, oral hygiene and hospital acquired pneumonia in older patients with lower limb fracture

Abstract

Hospital acquired pneumonia (HAP) occurs in 1% of all hospital in-patients, and in around 10% of patients with lower limb fracture, with a mortality of 18- 43%. HAP arises from interactions between three main risk factor groups: resident oral microbiota, aspiration potential (dysphagia, reduced conscious level) and host factors (age, frailty, comorbidity). In this work novel multiplex real time PCR assays were used to study prospectively the oral colonisation dynamics of seven major commensal pathogens over the first fortnight after hospital admission in relation to oral health variables, medical variables and subsequent development of HAP. Of the 93 patients recruited, 10% developed HAP and 60% of in-hospital deaths after lower limb fracture were due to HAP. Persistent oral colonisation with E. coli or S. aureus was significantly associated with HAP or HAP/lower respiratory tract infection in older patients with lower limb fracture. In turn, S. aureus was associated with increased dental plaque at admission and with increased xerostomia indices at 14 days. Other factors such as witnessed aspiration and post-operative cough were also strongly associated with subsequent development of HAP. HAP was associated with increased risk of death and increased length of hospital admission. These findings suggest several potentially modifiable clinical risk factors, and a high risk population for HAP, to whom interventions could be targeted. Given the rise in the older population and the increased costs associated with HAP, early detection and prevention will become increasingly important. Further work is needed to understand the relationships between dental plaque, S. aureus and xerostomia, and also to identify microbial biomarkers which could be used at the start of hospital admission to stratify patients’ risk of HAP.