Chronic bronchitis in immunocompromised patients: association with a novel Mycoplasma species.

Patients with primary antibody deficiency are prone to recurrent bronchitis, often caused by nonencapsulated Haemophilus influenzae and streptococcal infection. Productive cough often persists even after elimination of these organisms with antibiotics. During an investigation into the cause of unexplained chronic bronchitis in these patients, a novel Mycoplasma species (designated A39) was first isolated from the sputum of a man with X-linked agammaglobulinaemia. Screening of sputa from a further 45 patients with primary antibody deficiency showed that 10 were positive for a similar organism using culture and/or a polymerase chain reaction based on sequences within the 16S ribosomal RNA gene. A comparison of the sequence data showed that the organism was distinct from but similar to Mycoplasma pneumoniae and other closely related mycoplasmas found in humans and animals. Electron microscopy showed some unique morphological characteristics. Although respiratory symptoms improved after elimination of A39 from the sputum of the patient with X-linked agammaglobulinaemia, further work is needed to establish the organism as a pathogen.