Staphylococcal pneumonia

Etiology

• a form of nosocomial pneumonia
• uncommon cause of community-acquired pneumonia (< 1%)
• risk factors for Staphylococcal pneumonia
  • diabetes mellitus
  • recent history of influenza or measles
  • institutionalized or hospitalized patients
  • immunocompromised patients
  • intravenous drug abuse
  • dialysis patients
• risk factors for Staphylococcal pneumonia due to MRSA
  • prior treatment for MRSA (strongest risk factor)
  • hospitalization or parenteral antibiotics within 90 days
  • preceding influenza-like illness
  • failure of conventional therapy
  • injection drug use

Clinical manifestations

• exacerbation of respiratory symptoms & fever after a period of initial improvement of acute influenza symptoms
• higher fevers than were present with influenza & a cough producing purulent sputum

Radiology

• chest X-ray
  • consolidation
  • bronchopneumonia
  • abscess with air-fluid level
  • pneumatocele
  • pleural-based lung nodules suggestion septic pulmonary emboli)*
  • cavitary lung lesions*

* risk factors for MRSA

Complications

• septicemia
• abscess formation
• empyema
• high mortality (> CAP due to Streptococcus pneumoniae)
• prolonged hospitalization

Differential diagnosis

• Klebsiella pneumoniae
  • patients with alcohol use disorder, diabetes mellitus, or severe COPD
• Mycoplasma pneumoniae
  • unilateral or bilateral reticulonodular &/or patchy opacities
  • no cavitary lesions
• Streptococcus pneumoniae
  • although more common cause than S. aureus of post influenza pneumonia, cavitary lesions unlikely

Management

• empiric antimicrobial therapy:
• beta-lactamase-resistant penicillin 6-12 g/day IV
  • nafcillin 1.0-1.5 g every 4 hours
  • oxacillin 2.0 g every 4 hours
  • methicillin (high incidence of interstitial nephritis)
  • gentamicin may be added for 1st 48-71 hours for synergy
• vancomycin 1 g IV every 12 hours if methicillin-resistant (MRSA)
  • do not use daptomycin, inactivated by pulmonary surfactant
• duration of treatment:
  • 3-4 weeks
  • 6 weeks if septicemia

More general terms

• bacterial pneumonia
• Staphylococcal infection