Pneumococcal Pneumonia

Infection of the lung by Streptococcus pneumoniae, a Gram positive encapsulated diplococcus, and the commonest cause of community acquired pneumonia (about 30 to 50% of identified causes). The organism colonises the nasopharynx of about 5 to 10% of adults and 20 to 60% of children.

• Invasive disease (bacteraemia in about 10 to 30% of hospitalised patients) carries mortality of about 10 to 20%, higher in the elderly, in asplenia and with shock.
• Risk factors: age over 65 or under 2, asplenia (including sickle cell disease), HIV, alcohol misuse, COPD, chronic kidney disease, nephrotic syndrome, diabetes, cirrhosis, immunoglobulin deficiency, myeloma, smoking, recent influenza, cochlear implants, cerebrospinal fluid leak.
• Resistance: penicillin non-susceptibility varies from about 5 to 30% by region (for pneumonia, treatable with high dose beta lactams unless the minimum inhibitory concentration is 2 mg/L or more); macrolide resistance about 20 to 40%; fluoroquinolone resistance is low.

• Abrupt onset with rigors, high fever, pleuritic chest pain, productive cough with rust coloured sputum, dyspnoea, and often herpes labialis. Elderly patients may present with confusion or falls.
• Signs: lobar consolidation (dullness, bronchial breathing, crackles), pleural rub, tachypnoea, hypoxaemia, tachycardia, hypotension in sepsis.
• Differential diagnosis: Klebsiella and staphylococcal pneumonia, atypical pneumonia, tuberculosis, pulmonary embolism with infarction, lung cancer with obstruction, heart failure.
• Complications: parapneumonic effusion and empyema (about 2 to 10%), pericarditis, endocarditis with aortic valve destruction (Austrian syndrome with meningitis), meningitis, septic arthritis, peritonitis, ARDS, septic shock, and overwhelming sepsis with purpura fulminans in asplenia.

• Chest X-ray: lobar or segmental consolidation with air bronchograms; effusion.
• Blood cultures before antibiotics (positive in about 20 to 30%); sputum Gram stain (lancet shaped Gram positive diplococci) and culture; pneumococcal urinary antigen (sensitivity about 70%, remains positive after antibiotics); PCR where available. Test susceptibility including penicillin and ceftriaxone minimum inhibitory concentrations.
• Full blood count (leucocytosis, or leucopenia in severe disease), CRP, procalcitonin, urea and electrolytes, liver function, lactate, arterial blood gas, HIV test.
• Lumbar puncture if headache, neck stiffness or reduced consciousness. Pleural fluid analysis for effusion. Echocardiography if bacteraemic with a murmur.
• Assess for asplenia, immunoglobulin deficiency and HIV in invasive or recurrent disease.

• Penicillin susceptible or oral treatment for non-severe disease:
  • Amoxicillin 1 g orally three times daily (or 500 mg to 1 g three times daily).
  • Benzylpenicillin 1.2 g (2 million units) IV every 4 to 6 hours, or ampicillin 1 to 2 g IV every 6 hours, for admitted patients; step down to oral amoxicillin 1 g three times daily when stable.
• Intermediate or resistant (minimum inhibitory concentration 2 mg/L or more), severe disease, or meningitis not excluded:
  • Ceftriaxone 2 g IV daily (or cefotaxime 2 g IV every 8 hours); for meningitis give ceftriaxone 2 g IV every 12 hours with vancomycin 15 to 20 mg/kg IV every 8 to 12 hours until susceptibility is known, plus dexamethasone 10 mg IV every 6 hours for 4 days started before or with the first antibiotic dose.
  • Vancomycin or linezolid 600 mg twice daily for highly resistant strains.
• Beta lactam allergy: levofloxacin 750 mg daily or moxifloxacin 400 mg daily; doxycycline 100 mg twice daily for mild disease.
• Duration: 5 to 7 days for non-severe disease once afebrile and stable for 48 hours; 7 to 10 days for bacteraemic pneumonia; 14 days or longer for empyema, endocarditis or other extrapulmonary disease; meningitis 10 to 14 days.
• Severe pneumonia: add a macrolide (clarithromycin 500 mg twice daily) to a beta lactam for the first 3 days when atypical co-infection is possible. Hydrocortisone 200 mg/day IV for up to 7 days in severe pneumonia with respiratory failure or shock (evidence is moderate; avoid in influenza).
• Supportive care: oxygen to SpO2 94 to 98%, IV fluids 30 mL/kg for hypotension, noradrenaline 0.05 to 0.5 micrograms/kg/min for septic shock, non-invasive or invasive ventilation, enoxaparin 40 mg SC daily, analgesia with paracetamol 1 g four times daily.
• Empyema: chest drain, with intrapleural alteplase 10 mg plus dornase alfa 5 mg twice daily for 3 days, or video assisted thoracoscopic surgery.
• Asplenia and hyposplenism:
  • Give antibiotics at the first sign of fever (do not wait for the blood result).
  • Lifelong penicillin V 250 mg twice daily (or erythromycin 250 mg twice daily if allergic), plus a rescue supply of amoxicillin to use when febrile while seeking care.
  • Vaccinate at least 2 weeks before elective splenectomy (or 2 weeks after emergency splenectomy).
• Prevention:
  • Adults 65 or older and those with chronic disease or HIV: 20-valent pneumococcal conjugate vaccine as a single dose, or 15-valent conjugate vaccine followed by 23-valent polysaccharide vaccine 8 weeks or more later.
  • Children: conjugate vaccine in a 3-dose schedule in the first year (for example at 6, 10 and 14 weeks) with or without a booster at about 9 to 12 months by the local programme.
  • Smoking cessation; yearly influenza vaccine.
• Special groups:
  • Children: amoxicillin 80 to 90 mg/kg/day in 2 to 3 divided doses; IV ampicillin 200 mg/kg/day in 4 divided doses or ceftriaxone 50 to 100 mg/kg/day (maximum 4 g) if severe.
  • Pregnancy: amoxicillin or ceftriaxone; avoid fluoroquinolones and doxycycline.
  • HIV: antiretroviral therapy, co-trimoxazole prophylaxis 960 mg daily if CD4 count is less than 200, and vaccination.
  • Renal impairment: adjust vancomycin and ampicillin doses.
• Red flags: shock, multilobar disease, bacteraemia, confusion or meningism, large effusion, asplenia with fever.
• Follow up: clinical review at 48 to 72 hours and 6 weeks; repeat chest X-ray at 6 weeks in smokers over 50; investigate for asplenia, HIV, immunoglobulin deficiency and cerebrospinal fluid leak in recurrent or invasive disease; update vaccination.