[Community-acquired pneumonia].

Community-acquired pneumonia accounts for about 1 p. 100 of all lower respiratory infections, i.e. 1 to 10 cases per 1,000 adults annually, depending on the country and the year. The causative organism is seldom identified since there is no simple, specific, non-invasive and cheap laboratory diagnostic method. Treatment therefore is empirical. It rests upon epidemiological and clinical data as well as upon a set of criteria concerning the acceptability of antibiotics and variations in bacterial resistance. The four principal antibiotic-sensitive microorganisms to be taken into account are pneumococci, Haemophilus influenzae, Mycoplasma pneumoniae and Legionella pneumophila. In practice, focal lung infections should initially be treated with penicillin A which is active against pneumococci and H. influenzae. In case of atypical pneumonia, preference should be given to macrolides since these drugs are active against M. pneumoniae and L. pneumophila. In initially severe or worsening pneumonia occurring in debilitated patients penicillins and macrolides should be given concomitantly from the start.