Clinical Aspects of Upper and Lower Respiratory Tract Infections

Respiratory tract infections are among the most common illnesses leading to medical consultation, and are associated with significant mortality. Community-acquired pneumonia is a common illness and, while Streptococcus pneumoniae continues to be the most frequent causative agent, atypical pathogens such as Mycoplasma pneumoniae, Chlamydia pneumoniae and Legionella species are now identified as additional common aetiological agents. Since clinical and roentgenographic features poorly predict the aetiological agent in most cases of community-acquired pneumonia, empirical therapy is generally recommended. Nosocomial pneumonia is the second most common hospital-acquired infection and is associated with significant mortality. Aerobic Gram-negative bacilli and Staphylococcus aureus are the predominant causative pathogens. New techniques to improve the diagnosis of nosocomial pneumonia have been introduced, but their role has not been entirely clarified. Therapy directed toward the most likely pathogens (aerobic Gram-negative species and S. aureus) on an empirical basis is recommended until more specific information is obtained. Acute exacerbations of chronic bronchitis should be treated with antimicrobial therapy directed toward S. pneumoniae, Haemophilus influenzae or Moraxella catarrhalis. Because of the emergence of β-lactamase-producing strains of H. influenzae and M. catarrhalis, the choice of an antimicrobial agent has to be carefully considered. Group A β-haemolytic streptococci are the most common cause of bacterial pharyngitis and penicillin remains the drug of choice. Patients suffering from otitis media and sinusitis are infected with the same organisms as those patients with acute exacerbations of chronic bronchitis and antibacterial choices are therefore similar.