Respiratory tract infection: epidemiology and surveillance.

Streptococcus pneumoniae and Haemophilus influenzae are the key pathogens implicated in bacterial infections of the upper and lower respiratory tract. Choice of empiric oral antimicrobial chemotherapy is guided by the clinical presentation, severity of the infection and epidemiological knowledge. beta-Lactams and the macrolides are the two major groups of antibiotics used to treat respiratory tract infections. The prevalence of penicillin-resistant strains of S. pneumoniae is increasing world-wide (up to 30% in the USA), as is the prevalence of beta-lactamase-producing strains of H. influenzae. Macrolide resistance in S. pneumoniae is increasing and is absolute, and some of the macrolides have only limited activity against H. influenzae. Knowledge of local and global antibiotic resistance patterns should be used as the key to directing empiric choice of antibiotic treatment.