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 (Grade 1B).
We suggest that patients with pneumonia due to pneumococci that have intermediate susceptibility to penicillin be treated with higher doses of penicillin (Grade 2C).
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 (Grade 2C).
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.
Duration of therapy
There is limited evidence on which to base recommendations regarding the appropriate duration of antibiotic therapy. Therapy is generally continued for five to seven days for uncomplicated disease or until the patient is afebrile for three to five days in more severe cases. It should be noted, however, that some patients with pneumococcal pneumonia have a low-grade fever (≤38ºC) for several days, despite clinical improvement.
The duration of combination therapy in patients with severe bacteremic pneumococcal disease is also unclear but usually should not exceed three to five days followed by appropriate monotherapy for the remainder of the course. In patients who are improving on therapy, we suggest switching from combination therapy to monotherapy once susceptibilities are known, which is usually two to three days after cultures are obtained. For patients who remain critically ill in the intensive care unit, we suggest continuing combination therapy until a response to therapy is observed.
Patients with bacteremic pneumococcal disease should receive a total of 10 to 14 days of antimicrobial therapy.
A prospective, observational study of 638 patients with pneumococcal pneumonia identified the following features of the pneumonia associated with mortality by multivariate analysis :
●Bilateral disease – 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
Multivariate analysis identified the following independent predictors of death:
●Age >65 years – 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
Data from the mid to late 1990s show a decrease in mortality from the acute respiratory distress syndrome (ARDS). The decrease in mortality is probably due to several factors, including improved supportive care and a more thoughtful approach to mechanical ventilation.
●Key components of supportive care include intelligent use of sedatives and neuromuscular blockade, careful hemodynamic management, nutritional support, control of blood glucose, expeditious evaluation and treatment of nosocomial pneumonia, and prophylaxis against deep vein thrombosis (DVT) and gastrointestinal (GI) bleeding.
●Patients with hypoxic respiratory failure may benefit from strategies that decrease oxygen utilization, such as antipyretics to control fever and sedatives to control agitation. Occasionally, neuromuscular blockade is required, particularly when asynchrony with the ventilator persists despite adequate sedation. For patients with particularly severe gas exchange abnormalities (eg, PaO2/FiO2 ≤120 mmHg), up to 48 hours of neuromuscular blockade is probably safe and potentially beneficial, but requires additional investigation.
●Ventilator-associated pneumonia is a frequent complication of ARDS. Clinical guidelines designed to prevent, diagnose, and treat ventilator-associated pneumonia in the general ICU population also apply to those with ARDS.
●Data suggest that a conservative fluid management strategy that aims to minimize or eliminate positive fluid balance — for example, by aiming for a CVP <4 mmHg or a PAOP <8 mmHg — offers clinical advantages, including improved oxygenation, increased ventilator-free days, and ICU-free days.
●While blood transfusion and inotropes may augment oxygen delivery, most data caution against indiscriminate use of these strategies. For most patients, packed red blood cells can be withheld until the hemoglobin concentration drops below 7 g/dL, unless there are alternative reasons for transfusion. Similarly, there is no evidence that inotropes benefit ARDS patients with a normal cardiac function.