ESSENTIALS OF DIAGNOSIS
Productive cough, fever, rigors, dyspnea, early pleuritic chest pain.
Consolidating lobar pneumonia on chest radiograph.
Gram-positive diplococci on Gram stain of sputum.
Pneumococcus is the most common cause of community-acquired pyogenic bacterial pneumonia. Alcoholism, asthma, HIV infection, sickle cell disease, splenectomy, and hematologic disorders are predisposing factors. Mortality rates remain high in cases of advanced age, multilobar disease, hypoxemia, extrapulmonary complications, and bacteremia.
Presenting symptoms and signs include high fever, productive cough, occasional hemoptysis, and pleuritic chest pain. Rigors may occur initially but are uncommon later in the course. Bronchial breath sounds are an early sign.
Pneumococcal pneumonia classically is a lobar pneumonia with radiographic findings of consolidation and occasionally effusion. However, differentiating it from other pneumonias is not possible radiographically or clinically because of significant overlap in presentations. Diagnosis requires isolation of the organism in culture, although the Gram stain appearance of sputum can be suggestive. Sputum and blood cultures, positive in 60% and 25% of cases of pneumococcal pneumonia, respectively, should be obtained prior to initiation of antimicrobial therapy in patients who are admitted to the hospital. A good-quality sputum sample (less than 10 epithelial cells and greater than 25 polymorphonuclear leukocytes per high-power field) shows gram-positive diplococci in 80–90% of cases. A rapid urinary antigen test for Streptococcus pneumoniae, with sensitivity of 70–80% and specificity greater than 95%, can assist with early diagnosis.
Parapneumonic (sympathetic) effusion is common and may cause recurrence or persistence of fever. These sterile fluid accumulations need no specific therapy. Empyema occurs in 5% or less of cases and is differentiated from sympathetic effusion by the presence of organisms on Gram-stained fluid or positive pleural fluid cultures.
Pneumococcal pericarditis is a rare complication that can cause tamponade. Pneumococcal arthritis also is uncommon. Pneumococcal endocarditis usually involves the aortic valve and often occurs in association with meningitis and pneumonia (sometimes referred to as Austrian or Osler triad). Early heart failure and multiple embolic events are typical.
Initial antimicrobial therapy for pneumonia is empiric (see Table 9–9) pending isolation and identification of the causative agent. Once S pneumoniae is identified as the infecting pathogen, any of several antimicrobial agents may be used depending on the clinical setting, community patterns of penicillin resistance, and susceptibility of the particular isolate. Uncomplicated pneumococcal pneumonia (ie, arterial PO2 greater than 60 mm Hg, no coexisting medical problems, and single-lobe disease without signs of extrapulmonary infection) caused by penicillin-susceptible strains of pneumococcus may be treated on an outpatient basis with amoxicillin, 750 mg orally twice daily for 7–10 days. Cephalosporins including cefpodoxime, 200 mg orally twice daily, and cefdinir, 300 mg twice daily, may also be used. For penicillin-allergic patients, alternatives are azithromycin, one 500-mg dose orally on the first day and 250 mg for the next 4 days; clarithromycin, 500 mg orally twice daily for 10 days; doxycycline, 100 mg orally twice daily for 10 days; levofloxacin, 750 mg orally for 5 days; or moxifloxacin, 400 mg orally for 7–14 days. Patients should be monitored for clinical response (eg, less cough, defervescence within 2–3 days) because pneumococci have become increasingly resistant to penicillin and the second-line agents.
Parenteral therapy is generally recommended for the hospitalized patient at least until there has been clinical improvement. Aqueous penicillin G, 2 million units intravenously every 4 hours, or ceftriaxone, 1 g intravenously every 24 hours, is effective for strains that are penicillin-susceptible (ie, strains for which the minimum inhibitory concentration [MIC] of penicillin is 2 mcg/mL or less for non-CNS specimens). For serious penicillin allergy or infection caused by a highly penicillin-resistant strain, vancomycin, 1 g intravenously every 12 hours, is effective. Alternatively, a respiratory fluoroquinolone (eg, levofloxacin, 750 mg) can be used. The total duration of therapy is not well defined but 5 days is appropriate for patients who have an uncomplicated infection and demonstrate a good clinical response. Corticosteroid use remains controversial in community-acquired pneumonia and should not be administered routinely.
B. Treatment of Complications
Pleural effusions developing after initiation of antimicrobial therapy usually are sterile, and thoracentesis need not be performed if the patient is otherwise improving. Thoracentesis is indicated for an effusion present prior to initiation of therapy and in the patient who has not responded to antibiotics after 3–4 days. Chest tube drainage may be required if pneumococci are identified by culture or Gram stain, especially if aspiration of the fluid is difficult.
Echocardiography should be done if pericardial effusion is suspected. Patients with pericardial effusion who are responding to antibiotic therapy and have no signs of tamponade may be monitored and treated with indomethacin, 50 mg orally three times daily, for pain. In patients with increasing effusion, unsatisfactory clinical response, or evidence of tamponade, pericardiocentesis will determine whether the pericardial space is infected. Infected fluid must be drained either percutaneously (by tube placement or needle aspiration), by placement of a pericardial window, or by pericardiectomy. Pericardiectomy eventually may be required to prevent or treat constrictive pericarditis.
Endocarditis should be treated for 4 weeks with 3–4 million units of penicillin G every 4 hours intravenously; ceftriaxone, 2 g once daily intravenously; or vancomycin, 15 mg/kg every 12 hours intravenously. Mild heart failure due to valvular regurgitation may respond to medical therapy, but moderate to severe heart failure is an indication for prosthetic valve implantation, as are systemic emboli or large friable vegetations as determined by echocardiography.
C. Penicillin-Resistant Pneumococci
Resistance breakpoints for parenterally administered penicillin and high-dose oral amoxicillin (2 g twice daily) are as follows: susceptible, penicillin MIC of 2 mcg/mL or less; intermediate, MIC of 4 mcg/mL; resistant, MIC of 8 mcg/mL or more. Note, however, that these breakpoints do not apply to orally administered penicillin, which are the same as for use of penicillin in treatment of meningitis. In cases of pneumococcal pneumonia where the isolate has a penicillin MIC greater than 2 mcg/mL, cephalosporin cross-resistance is common, and a non–beta-lactam antimicrobial, such as vancomycin, 1 g intravenously every 12 hours, or a fluoroquinolone with enhanced gram-positive activity (eg, levofloxacin, 750 mg intravenously or orally once daily, or moxifloxacin, 400 mg intravenously or orally once daily), is recommended. Penicillin-resistant strains of pneumococci may be resistant to macrolides, trimethoprim-sulfamethoxazole, and chloramphenicol, and susceptibility must be documented prior to their use. All blood and cerebrospinal fluid isolates should still be tested for resistance to penicillin. There has been no change to the penicillin susceptibility breakpoint for pneumococcal isolates causing meningitis, nor any change in treatment recommendations.
See Chapter 30 for discussion of pneumococcal vaccines. All patients should have screening for smoking cessation.
All patients with suspected pneumococcal endocarditis or meningitis to an infectious disease specialist.
Seriously ill patient with pneumonia, particularly in the setting of comorbid conditions (eg, liver disease).
Progression of pneumonia or failure to improve on antibiotics.
All patients in whom pneumococcal endocarditis or meningitis is suspected or documented should be admitted for observation and empiric therapy.
All patients with pneumococcal pneumonia that is multilobar or associated with significant hypoxemia.
Failure of outpatient pneumonia therapy, including inability to maintain oral intake and medications.
Exacerbations of underlying disease (eg, heart failure) by pneumonia that would benefit from hospitalization.
et al. Bacteremic pneumococcal pneumonia in adults. Arch Bronconeumol. 2018 Jan;54(1):54–5.
et al. Duration of antibiotic treatment in community-acquired pneumonia: a multicenter randomized clinical trial. JAMA Intern Med. 2016 Sep 1;176(9):1257–65.
et al. Advances in the causes and management of community acquired pneumonia in adults. BMJ. 2017 Jul 10;358:j2471.