The prevalence of potential pathogenic bacteria in nasopharyngeal samples from individuals with a respiratory tract infection and a sore throat - implications for the diagnosis of pharyngotonsillitis

Background. Treatment failure in patients with pharyngotonsillitis after a traditional course of penicillin V is a common finding. Several factors hav e been proposed to explain the failure rate, but the presence of aetiologic al agents other than group A beta -haemolytic streptococci has attracted li ttle attention. Objectives. The aim of the present study was to investigate if a nasopharyn geal sample could suggest the aetiology of a sore throat in patients with a respiratory tract infection. Methods. The prevalence of potentially pathogenic bacteria (Streptococcus p neumoniae, Haemophilus influenzae and Moraxella catarrhalis) in nasopharyng eal samples from 618 healthy individuals was compared with that from 108 pa tients with a respiratory tract infection and a sore throat. Results. The prevalence of H. influenzae was higher in patients with a sore throat than in healthy individuals of the same age. For the adult patients with a sore throat, the prevalence was 27.5% compared with 2.7% for the he althy carriers (P < 10(-7)). The corresponding figures for schoolchildren w ere 31.3% versus 6.1% (P = 0.004) and for pre-school children 37.8% versus 13.2% (P = 0.0003). Conclusions. If H. influenzae is found in a nasopharyngeal sample from a pa tient with a respiratory tract infection and a sore throat, it might be the aetiological agent.