Streptococcus pneumoniae is the most common cause of community-acquired pneumonia (CAP), although the organism is frequently not isolated but believed to be the cause of many culture-negative cases of CAP.
Pneumococcal pneumonia is the paradigm of classic lobar bacterial pneumonia. Although commonly carried asymptomatically in the nasopharynx, pneumococci cause invasive disease when the host is exposed to large aerosolized inocula of new serotypes.
The classic presentation of pneumococcal pneumonia, with abrupt onset of fever, chills, cough, and side pain, occurs more commonly in the younger patient. Physical examination typically reveals signs of consolidation.
Infectious complications involving other organ systems, once prevalent with pneumococcal infection, are now rare with antibiotic use. However, overwhelming infection can still lead to early mortality (often in the first 24 hours), despite use of antibiotics. Pulmonary complications associated with bacteremic illness and comorbidities include empyema, necrotizing pneumonia, and lung abscess.
While sputum Gram stain can suggest pneumococcal infection, the diagnosis of pneumococcal pneumonia should be confirmed by blood culture or urinary antigen. Although lobar consolidation is suggestive of bacterial pneumonia, radiographs cannot reliably differentiate bacterial from nonbacterial pneumonia.
The majority of patients with community-acquired pneumonia are treated empirically with a regimen that includes coverage against the pneumococcus.
We recommend that patients with documented penicillin-sensitive pneumococci be treated with a beta-lactam antibiotic．grade1B
We suggest that patients with pneumonia due to pneumococci that have intermediate susceptibility to penicillin be treated with higher doses of penicillin ．grade2C
We suggest treatment with a combination antibiotic therapy (beta-lactam plus either a macrolide or fluoroquinolone) for patients with bacteremic pneumococcal pneumonia who require intensive care unit care．grade2C
We typically give antibiotic therapy for five to seven days or until the patient is afebrile for three to five days in more severe cases. Patients with bacteremic pneumococcal disease should receive a total of 10 to 14 days of antimicrobial therapy.
Intravenous antimicrobials for pneumococcal pneumonia in adults
Penicillin G 2 to 3 million units Every 4 hours
Ampicillin 2 grams Every 6 hours
Ampicillin/sulbactam 2 grams ampicillin plus 1 gram sulbactam Every 6 hours
Amoxicillin/clavulanate 1 gram amoxicillin plus 0.125 grams clavulanate Every 6 hours
Cefotaxime 2 grams Every 6 hours
Ceftriaxone 1 gram Every 12 hours
The mortality rate for pneumococcal pneumonia varies by severity at presentation and host factors, ranging from 16 to 55 percent
●Bilateral disease – Hazard ratio (HR) 2.0, 95% CI 1.2-3.2
●Suspected aspiration – HR 2.8, 95% CI 1.6-5.0
●Shock – HR 5.8, 95% CI 3.4-9.8
●HIV infection – HR 2.1, 95% CI 1.1-3.8
●Renal failure – HR 1.9, 95% CI 1.1-3.1
●Pneumonia severity index (PSI) – HR for class IV versus classes I to III: 2.6, 95% CI 1.3-5.4 and for class V versus I to III: 3.2, 95% CI 1.5-6.9
●Age >65 years – odds ratio (OR) 2.2
●Residence in a nursing home – OR 2.8
●Presence of chronic lung disease – OR 2.5
●Need for mechanical ventilation – OR 4.4
●High acute physiology and chronic health (APACHE) – For scores of 9 to 14, OR 7.6; for scores 15 to 17, OR 22; for scores >17, OR 41