Overview of lower respiratory tract infections: diagnosis and treatment

Because the diagnosis and treatment of community-acquired pneumonia (CAP) continue to present decision-making challenges, a number of professional organizations have developed treatment guidelines to provide parameters for diagnosis and treatment. The Infectious Diseases Society of America (IDSA) and the American Thoracic Society (ATS) both recently updated their guidelines for the treatment of CAP to take into account the changes that have occurred in antimicrobial susceptibility and the availability of newer antimicrobial agents. Both the IDSA and ATS guidelines stratify treatment according to where the patient is treated, but the ATS guidelines further characterize patients according to the presence or absence of cardiopulmonary disease or other modifying factors. For outpatients with CAP, doxycycline, a macrolide, or a newer fluoroquinolone with enhanced activity against Streptococcus pneumoniae are the IDSA-preferred agents for empiric treatment. The ATS recommends monotherapy with a macrolide or doxycycline in patients without modifying factors, or combination therapy with a β-lactam plus a macrolide, or monotherapy with an antipneumococcal fluoroquinolone in patients with modifying factors. For empiric therapy of CAP in hospitalized patients, the IDSA recommendations are as follows: an extended-spectrum cephalosporin plus a macrolide, a β-lactam/β-lactamase inhibitor plus a macrolide, or a fluoroquinolone with extended activity against S. pneumoniae. For hospitalized patients without modifying factors, the ATS recommends monotherapy with azithromycin or an antipneumococcal fluoroquinolone. For hospitalized patients with modifying factors, combination therapy with a β-lactam plus a macrolide, doxycycline, or monotherapy with a respiratory fluoroquinolone are recommended. Given the increasing resistance of S. pneumoniae to macrolides and doxycycline, a respiratory fluoroquinolone may represent the best choice of therapy.