Neisseria meningitidis: Isolation from the lower respiratory tract secretions in adult patients

Objective. A bibliographic research was made using the Medline system of the clinico-microbiological features of reported, cases of Neisseria meningitidis (NM) bronchopulmonary infection, as well as a retrospective study of NM isolation from lower respiratory tract secretions from adult inpatients. Materials and methods. All specimens from respiratory secretions were Gram stained and cultured onto blood, MacConkey and chocolate (quantitative) agar plates; a BCYE-α agar plate was also used when pneumonia was diagnosed. Fifty-five clinical records were retrospectively reviewed of patients with positive cultures for NM, for a 12-year period (1983-1994). Results. A total of 67 samples were positive among the 55 patients studied; sputum and tracheobronchial samples predominated. NM was recovered in pure culture from 48 specimens (71.6%) and with counts higher than 10 6 colony forming units/ml (CFU). Twenty-seven isolates (40.3%) corresponded to serogroup B and 21 isolates (31.3%) did not group with serogroups A, B and C. Twenty-two patients were diagnosed of pneumonia; eleven of these 22 patients had an underlying chronic lung disease. Ten patients had a respiratory overinfection, in eight cases an episode of acute bronchitis was recorded and, finally, in 15 patients there was NM colonization only. Conclusion. The pathogenic role of NM in lower respiratory tract infections is probably underestimated because its isolation is difficult, particularly when there is oropharyngeal flora present, since in our study, in which only conventional culture media were used, samples which had NM recovered had a high number of colonies, in pure culture in most cases.