In vitro adherence of Streptococcus pneumoniae to oropharyngeal cells: enhanced activity and colonization of the upper respiratory tract in patients with recurrent respiratory infections

In vitro adherence of Streptococcus pneumoniae (S. pneumoniae) to oropharyngeal cells was assessed in 3 age matched groups of 29 subjects. The first group included patients with chronic pulmonary disease and recurrent respiratory infections due to S. pneumoniae or a recent respiratory infection caused by this organism. Patients of the second group has similar underlying pulmonary disease to the first group, but they had no S. pneumoniae respiratory infection for at least the past 3 years. Healthy subjects or patients without underlying pulmonary disease constituted the third group. The mean adherence of S. pneumoniae to oropharyngeal cells was 10.6 +/- 4.7 bacteria (bact.)/cell in the first group, 3.6 +/- 2.8 bact./cell in the second group and 1.9 +/- 2.1 bact./cell in the third group. A significant difference was found (p less than 0.01) when the mean of the first group was compared to those of the second and third groups, whereas there was no significant difference between the means of the second and third groups. In addition, a survey of bacterial colonization of the upper respiratory tract was conducted in all the subjects included in this study. Over 6 months, 5 of the 8 patients in the first group had throat cultures (5 cases) and nasal cultures (3 cases) positive for S. pneumoniae, while no one in the second or third group was a carrier of this bacterium in the upper respiratory tract during the same period. Patients with recurrent or recent respiratory infections caused by S. pneumoniae are characterised by an in vitro enhanced ability of this organism to adhere to their oropharyngeal cells. In vivo, this phenomenon is reflected by an increased susceptibility of the upper respiratory tract to colonization by S. pneumoniae.