Epidemiology of major respiratory pathogens.

A vast literature attests to the fact that Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis represent the prevailing bacterial pathogens of community-acquired lower respiratory tract infections. Their specific incidence as causative agents of the more common syndromes is known to vary even profoundly, depending on geographic area, and the same holds true for their rates of resistance to antimicrobial drugs. Europe does not escape the threat posed by the present pandemic spread of penicillin resistance in S. pneumoniae although, as expected, some countries like Spain and France are highly affected and others including Germany, Italy, The Netherlands and the Scandinavian region, are relatively spared. In several sites multiple resistance has been described in S. pneumoniae with the most affected drugs being penicillin, the macrolides, co-trimoxazole and tetracycline. In H. influenzae synthesis of beta-lactamases is the main resistance trait expressed. Lack of susceptibility to beta-lactams dictated by a different mechanism remains extremely rare. Large variations in the incidence of this character are apparent when considering European countries. France and Spain are again widely affected while Germany, The Netherlands and Italy display rates of beta-lactamase-positive H. influenzae of about 16%. M. catarrhalis must be considered generally resistant to non-protected aminopenicillins since over 90% of these organisms produce beta-lactamases.