Patients with CABP are started on antibacterial drugs as soon as possible. Because the causative organism is difficult to identify, physicians choose antibacterial drugs for the most common pathogen(s) associated with the condition and the severity of illness. Most CABP patients improve with antibacterial drug treatment. For those patients whose conditions do not improve, physicians look for unusual organisms, resistance to the antibacterial drug used for treatment, infection with a second organism, or some other disorder (such as a problem with the immune system or a lung abnormality) that might be delaying recovery.
In the absence of comorbidities and a low-risk determination, a patient is typically treated on an outpatient basis. The preferred antibacterial drugs for outpatient treatment are macrolides (azithromycin, clarithromycin, or erythromycin), and doxycycline (Vibramycin), a tetracycline. The preferred antibacterial drug treatment for high-risk patients with comorbidities is an intravenous beta-lactam (cefotaxime, ceftriaxone, or ampicillin) plus a macrolide or a fluoroquinolone alone delivered in an inpatient setting