Legionella as a lower respiratory pathogen in north India.

One hundred patients of lower respiratory tract infection (LRTI) were prospectively studied over 2 years to find out if Legionella is a causative agent in these patients. In addition, 50 environmental samples and 50 age and sex matched controls were studied. Culture and direct fluorescent antibody testing (DFA) of respiratory tract secretions, and serodiagnosis by indirect immunofluorescence (IIF) and ELISA, were employed to detect Legionella. Respiratory tract secretions from all patients were negative for Legionella on culture and DFA. Low antibody titters to Legionella were observed in 21 patients and these could be attributed to cross reaction with other gram-negative bacteria. All environmental samples and controls tested negative for Legionella. Legionella does not seem to be an important lower respiratory tract pathogen in this part of the country and empirical addition of erythromycin to treatment regimens for pneumonia is not warranted in our setting.