Oral Antibiotics for Pneumonia

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.

Community-acquired pneumonia. Diagnostic and therapeutic approach

Optimal empiric therapy of CAP is with appropriate monotherapy (e.g., doxycycline, levofloxacin). Combination therapy is problematic because of potential side effects and high cost. Empiric coverage should have a high degree of activity against both typical and atypical pathogens. The antibiotic selected should have an excellent side-effect profile and be relatively inexpensive. Clinicians should be selective in their choice of antibiotic for CAP and choose an antimicrobial that has little or no resistance potential, is relatively inexpensive, and permits i.v.-to-PO switch monotherapy.

The antibiotic treatment of community-acquired, atypical, and nosocomial pneumonias

Optimal antibiotic regimens and duration of treatment are not universally agreed on for community-acquired or nosocomial pneumonias. Experience suggests that community-acquired pneumonias may be treated for less than 2 weeks with a combination of intravenous and oral antibiotics of appropriate spectrum that penetrate the lung, have a good safety profile, do not foster the development of resistance, and are cost-effective. After initial intravenous therapy, oral switch therapy may be begun as soon as the patient defervesces clinically, which is usually 3 days after admission. Switching to oral therapy does not invariably lead to earlier hospital discharge. There is no "standard of care" for pneumonias, but guidelines for empiric use have existed for decades. The least expensive beta-lactamase stable antibiotic should be used as monotherapy for the empiric treatment of community-acquired pneumonia. Because community-acquired atypical pneumonias are clinically distinct from bacterial pneumonias owing to their extrapulmonary features, clinicians should be able to differentiate atypical pneumonias from bacterial pneumonias, which permits prompt and appropriate treatment. Nosocomial pneumonias remain a difficult diagnostic challenge. Therapeutically the most important principle in treating nosocomial pneumonia is to provide for double-drug coverage against P. aeruginosa. Differentiation of respiratory tract colonization from respiratory tract invasion remains the central key issue in patients with pulmonary infiltrates acquired during hospitalization. Most patients complete their course of intravenous therapy for nosocomial pneumonia leaving little or no time for completion of their therapy by oral antibiotics. Hospital-acquired atypical pneumonias are largely limited to legionnaires' disease, which is a more difficult diagnosis than in the community-acquired setting. Clinicians taking care of patients with pneumonia should employ a simplified therapeutic approach using a single drug for community-acquired infections. The use of additional antibiotics to increase gram-negative coverage is medically unjustified and not cost-effective and is to be discouraged. The most cost-effective strategy for the treatment of community-acquired pneumonias is to switch the patient from an intravenous to an oral antibiotic as soon as the patient clinically defervesces and is able to take oral medications. Antimediator therapies have no role in the treatment of community-acquired or nosocomial pneumonias.