Respiratory infections in Down syndrome:a study of bacterial adhesion

Respiratory infections have a higher incidence among Down syndrome people, increasing with age. Bacterial adhesion to mucosal surfaces is the first essential event before colonization. Bacteria adhere to host tissues through a mechanism of specific "adhesin-receptor" interaction which leads to the formation of a stable relationship between bacterium and cell. The aim of this study was to evaluate the bacterial adhesion in individuals with Down syndrome (DS) compared to a group of healthy control subjects. We studied: 30 DS subjects affected by recurrent respiratory infections, 30 DS subjects without recurrent respiratory infections and 30 healthy subjects. We collected buccal epithelial cells from all patients in stable conditions. They were incubated with standardized suspensions of Staphylococcus aureus ATCC 12598. The mean number of adhering bacteria per 100 epithelial cells for each experiment was recorded. The group of DS affected by recurrent respiratory infections showed adhesion values higher (35.08 ± 4.8) than DS subjects without recurrent respiratory infections (22.82 ± 7.85, p=0.01) and controls (25.26 ± 6.97, p=0.01), while the two latter groups showed no significant differences in bacterial adhesion (p=0.07). The highest number of adherent bacteria in DS subjects with recurrent respiratory infections is probably due to increased expression of cell surface receptors specifically capable of binding to bacteria, although this is an indirect evidence; a direct proof of the number of receptors would require more complex molecular biochemical studies. These data suggest that bacterial adhesion studies could help to identify and monitor over time subjects at risk for developing recurrent respiratory infections.