[The etiology of bacterial respiratory infections in adulthood]

Upper and lower respiratory tract infections are the most frequently reported pathologies both in children and in adults. In particular, the most common clinical pictures are otitis media, principally chronic, and acute and chronic sinusitis. The microbiology of otitis media, which has been investigated thoroughly in the last year, confirmed a bacterial origin in 90% of the cases (while the incidence of the viral form is low). The etiologic agents responsible for chronic infections are Gram-negative bacteria, staphylococci and anaerobic bacteria, while in the acute forms, which are rare in adults but frequent in children, the responsible pathogens are principally Haemophilus influenzae, Streptococcus pyogenes and Branhamella catarrhalis. Among the etiologic agents of chronic sinusitis, which, from a clinical point of view, is the most frequently observed, there are staphylococci, Streptococcus pyogenes and many anaerobic bacteria. As regards lower respiratory tract infections, chronic bronchitis is the most frequent pathology in adults. But, in this case, the etiologic agents are more difficult to identify. Analysing the above-mentioned clinical pictures and their relevant etiologic agents, among the different therapeutic proposals, one of the most innovative and recent is represented by azithromycin. Azithromycin is the first of a new class of macrolides termed "Azalides" which shows particular microbiological and pharmacokinetic characteristics. As compared to other macrolides, it has an higher distribution volume, a longer half-life, a deeper intracellular penetration and a wider spectrum of action. It is rapidly concentrated in leukocytes PMN, monocytes, macrophages and fibroblasts and slowly released by these cells to the infected tissues. Azithromycin concentrations in tissues and sites of infection can be increased by the phagocyte uptake.(ABSTRACT TRUNCATED AT 250 WORDS)