Exploring the link between oral bacterial flora and hospital acquired pneumonia using a novel screening assay.

Lead Research Organisation: Newcastle University
Department Name: Institute of Cellular Medicine


When people become ill and are admitted to hospital, different bacteria, which can cause chest infections, are found in their mouths. Some, but not all, then develop chest infections. Up to 40% of people may die from chest infections in hospital. These bacteria probably cause chest infections by travelling down from the mouth into the lungs silently. It might be that larger numbers of bacteria lead a chest infection.

Newer scientific techniques may identify bacteria better and more rapidly than traditional ways. I will design a test for bacteria which cause chest infections in hospital using a scientific technique called real-time multiplex PCR. I will use the test on throat swabs taken from hospital patients who have broken their hips to see how many harbour these bacteria. Then I will follow these patients to find out whether having certain bacteria in the throat puts people at higher risk of getting chest infections in hospital.

This information could help unravel why people develop chest infections in hospital and to help decide what could be done to stop this happening.

Technical Summary

Translational research in an ageing population is now recognised as being of the utmost importance. This project which is hosted by the Biomedical Research Centre, addresses one important cause of mortality in ageing people, that of hospital acquired pneumonia (HAP). HAP is common and carries an unacceptable mortality of up to 40% 1-3 in older people. Currently it is difficult to predict which patients will develop HAP. After hospitalisation or illness, the oral cavity becomes colonised with bacteria known to cause HAP. While these bacteria are rarely present (0-6%) in healthy adults5, they are seen in 14-40% of hospitalised or institutionalised older people6 7. It is proposed that HAP develops secondary to silent aspiration of these bacteria into the lungs. Evidence suggests that HAP may be preventable by reducing the number of oral bacteria via rigorous oral hygiene9, even in frail patients. As yet, few cohort studies have been undertaken to link oral HAP pathogens with subsequent development of pneumonia.

1. Develop an assay to detect prevalent bacterial pathogens in HAP.
2. Define the prevalence of HAP pathogens in the throats of patients with new hip fracture admitted to the acute orthopaedic unit in Newcastle using the assay.
3. Describe the incidence of acquisition within the first 14 days of admission of HAP pathogens in the throats of patients whom were not carriers on admission.
4. Explore whether either presence or high numbers of respiratory bacteria in the throats of these patients within the first 14 days of admission is associated with subsequent development of HAP.

Development of screening assay, followed by cohort study.

Phase 1. Development and validation of real-time multiplex PCR assay.

Phase 2. A cohort of hip fracture patients will be screened for oropharyngeal carriage of HAP bacteria within 14 days of admission using the assay. Cases of HAP will be detected up to three months post discharge. Plaque scores and other oral hygiene indices will also be assessed.

Scientific and medical opportunities of the study
This study will give detailed information regarding the biological gradient of exposure and define antecedent exposure among cases. The anticipated outcome is that patients at high risk of developing HAP may be identified and targeted early in admission for preventative strategies including improving oral hygiene. Preventing pneumonia is likely to reduce morbidity and mortality, and may lead to savings in health care costs 10.


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