a1 Departments of Microbiology, The University of Nottingham, The City Hospital, Hucknall Rd, Nottingham NG5 1PB
a2 Respiratory Medicine, The City Hospital
a3 PHLS Laboratory, Queen’s Medical Centre, Nottingham, UK
The presence of pneumococcal capsular antigen (PCA) in the oropharynx was sought in subjects without respiratory tract infection. Saliva specimens from 239 subjects were analysed by counter-current immunoelectrophoresis using ‘Omni-serum’. 15.5% gave positive reactions but only 24% of positive samples were typable and therefore due to pneumococcal or pneumococcal-like antigens. Given that oropharyngeal production of antigens occurs we investigated whether PCA in expectorated sputum arose from oropharyngeal contamination. Sixteen patients with pneumococcal pneumonia, and with sputum positive for PCA, were investigated in detail. On the basis of serotyping and concentration the PCA in sputum was thought to arise from the lower respiratory tract in all cases. This was confirmed by a simple, novel approach involving the comparison of concentrations in concomitant samples of saliva and sputum. Thus while oropharyngeal production of antigens poses a potential diagnostic problem the latter approach can be used to exclude contamination.
(Accepted December 08 1992)
p1 Present address: Department of Infectious Diseases, Hammersmith Hospital, London, UK