Bacterial pneumonia

Bacterial (pyogenic) pneumonia is common and is a major cause of morbidity and mortality globally.

Clinical presentation

Bacterial pneumonia has symptoms similar to other pneumonia. When a productive cough is present, purulent or blood-stained sputum may indicate bacterial pneumonia ^ref.

Pathology

Bacterial pneumonia may be primary, secondary to a viral infection, or a co-infection with a virus ². They are a common cause of community-acquired pneumonia (CAP) and nosocomial pneumonia. 

Etiology

Typical bacteria that cause pneumonia include ¹:

• Streptococcus pneumoniae: most common cause of CAP
• Streptococcus anginosus group (formerly Streptococcus milleri)
• Staphylococcus aureus
• group A Streptococcus
• Klebsiella pneumonia (Klebsiella pneumonia)
• Haemophilus influenzae (pulmonary Haemophilus influenzae infection)
• Moraxella catarrhalis
• anaerobes
• Gram-negative organisms

Radiographic features

Plain radiograph / CT

Chest x-ray and CT are unable to differentiate bacterial pneumonia from non-bacterial pneumonia ⁶. There is also a large overlap of imaging features with non-pneumonic processes ³. 

Bacterial pneumonia characteristically produces focal segmental (i.e. bronchopneumonia) or lobar pulmonary opacities (i.e. lobar pneumonia) ^4-6. Expansion characterized by bulging fissures has typically been attributed to lobar pneumonia, in particular Klebsiella pneumonia, but there are many non-bacterial causes ⁶. 

Treatment and prognosis

Treatment is with antibiotic therapy, with both oral and intravenous options available depending on the severity and local guidelines.

Complications

Complications common for bacterial pneumonia include ^3,6:

• cavitation
• lung abscess
• pneumatocele
• parapneumonic effusion
• empyema