Community Acquired Pneumonia (CAP)

The British Thoracic Society defines community acquired pneumonia (CAP) as the presence of symptoms and signs consistent with acute lower respiratory tract infection, in association with new radiographic shadowing for which there is no alternative explanation, which is managed as pneumonia and is the main reason for seeking healthcare advice.¹

• Features such as fever (< 38 °C), pleural pain, dyspnoea, tachypnoea and signs on physical examination of the chest (particularly when new and localising) seem most useful when compared with the gold standard of radiological diagnosis of CAP.²
• The British Thoracic Society recommends abandoning the term 'atypical' pneumonias because there is no typical characteristic presentation of pneumonia.
• Common causes of CAP include Streptococcus pneumoniae, Mycoplasma pneumoniae, Haemophilus influenzae, Chlamydophila (Chlamydia) pneumoniae and respiratory viruses.¹

• The annual incidence of community acquired pneumonia in the United Kingdom is 5-11 cases per 1000 adult population.¹
• CAP is the fifth leading cause of death in the UK.
• A recent study found that the organism was an atypical one (e.g. Mycoplasma pneumoniae, Chlamydia pneumoniae and Legionella spp.) in 22% of cases of community acquired pneumonia where an organism was identified.¹
• The frequency of pathogens can vary in specific patient groups, e.g. Mycoplasma and Legionella infections are less frequent in the elderly.
• Community acquired MRSA is rare in Europe.
• Risk factors include:
  • Winter months
  • The very young and the very old
  • Chronic lung, heart, renal and liver disease
  • Diabetes mellitus
  • Immunosuppression

• Symptoms: cough, purulent sputum which may be blood stained or rust coloured, breathlessness, fever, malaise.
• Diagnosis is unlikely if no focal chest signs and normal heart rate, respiratory rate and temperature.
• Elderly may present with mainly systemic complaints of malaise, fatigue, anorexia and myalgia. Young children may present with non-specific symptoms or abdominal pain.
• Signs: bronchial breathing, crepitations, pleural rub, dullness with percussion.

• General investigations, including a chest x-ray, are not necessary for the majority of patients with suspected community acquired pneumonia who are managed in the community.
• Out of hours and emergency general practitioner assessment centres should consider using pulse oximeters to allow for simple assessment of oxygenation.
• Sputum samples should be sent for culture and sensitivity tests from patients with non-severe CAP who are able to expectorate purulent samples and have not received prior antibiotic therapy.
• Specimens should be transported rapidly to the laboratory. Sputum cultures should also be performed for patients with severe CAP, or those who fail to improve.
• Examination of sputum for Mycobacterium tuberculosis should be considered for patients with a persistent productive cough, especially if malaise, weight loss or night sweats, or risk factors for tuberculosis (e.g. ethnic origin, social deprivation, the elderly) are present.
• Serological investigations may be considered during outbreaks (e.g. Legionnaires' disease) or epidemic mycoplasma years, or when there is a particular clinical or epidemiological reason.

Severity scores are helpful but are not a substitute for clinical judgement; all cases that cause concern should be referred for further investigation.¹

• CURB-65 severity score; score 1 point for each of following features that are present:¹
  • Confusion (mental test score 8 or below, new disorientation in person, place or time)
  • Urea >7 mmol/L
  • Respiratory rate 30 breaths/min or higher
  • Blood pressure (systolic below 90 mm Hg, or diastolic 60 mm Hg or lower)
  • Age 65 years or older
• Interpretation of CURB-65 score:
  • 0-1: probably suitable for home treatment; low risk of death
  • 2: are at increased risk of death and hospital referral and assessment should be considered, particularly with Score 2
  • 3 or higher: manage in hospital as severe pneumonia; high risk of death
• Additional clinical adverse prognostic features:
  • Co-existing disease, e.g. diabetes, heart failure
  • Hypoxaemia (SaO₂ <92% or PaO₂ <8 kPa) regardless of FiO₂
  • Bilateral or multilobe involvement on the chest x-ray

For all other patients the decision to treat at home or refer to hospital is a matter of clinical judgement. When deciding on home treatment, the patient's social circumstances and wishes must be taken into account in all instances.

• Patients with suspected CAP should be advised not to smoke, to rest, and to drink plenty of fluids.
• Pleuritic pain should be relieved using simple analgesia such as paracetamol.
• Nutritional support with supplements should be considered in prolonged illness.
• Review of patients in the community with CAP is recommended after 48 hours or earlier if clinically indicated. 'Core' and 'additional' adverse prognostic features should be assessed as part of the clinical review.
• Those who fail to improve after 48 hours of treatment should be considered for hospital admission or a chest x-ray.

Antibiotics

• Antibacterials are recommended in all suspected cases of pneumonia, starting as soon as possible.³ Choice should be based on culture results, local resistance patterns and prescribing policies.
• Uncomplicated community-acquired pneumonia:⁴
  • Amoxicillin if previously healthy chest (or erythromycin/clarithromycin if penicillin-allergic).
  • Add flucloxacillin if staphylococci suspected, e.g. in influenza or measles (or vancomycin if MRSA suspected).
  • Add erythromycin if 'atypical' pathogens are suspected.
• Initial empirical treatment of adults with community acquired pneumonia treated in hospital:¹
  • Non-severe disease: oral amoxicillin plus erythromycin or clarithromycin; alternatively oral moxifloxacin or levofloxacin.
  • Severe disease: intravenous co-amoxiclav or cefuroxime or cefotaxime plus erythromycin/clarithromycin; alternatively intravenous levofloxacin plus benzylpenicillin.
• Severe community-acquired pneumonia of unknown aetiology:⁴
  • Cefuroxime (or cefotaxime) plus erythromycin.
  • Add flucloxacillin if staphylococci suspected (or vancomycin if MRSA suspected).
• Pneumonia possibly caused by atypical pathogens:⁴
  • Erythromycin.
  • Severe Legionella infections may require addition of rifampicin.
  • Tetracycline is an alternative for chlamydophilal and mycoplasma infections.

BTS guidelines suggest at least 7 days for patients managed in the community and 10 days for patients with severe disease. Recent studies have suggested that short course therapy is as effective as the longer courses recommended by guidelines. The decision to stop antibiotics should depend upon clinical judgment and the patient’s response to treatment.¹

Follow up

• Clinical review should be arranged for all patients at around 6 weeks.
• A chest x-ray should be arranged at that time for those patients who have persistent symptoms or physical signs or who are at higher risk of underlying malignancy (especially smokers and those over 50 years).
• In a patient who is improving clinically and for whom there are no concerning clinical features, it will usually not be necessary to perform further investigations just because radiological improvement lags behind clinical recovery.
• Further investigations, which may include bronchoscopy, should be considered in patients with persisting signs, symptoms, and radiological abnormalities about 6 weeks after completing treatment.

• Pleural effusion - usually sterile
• Empyema: a reactive effusion can occur but is trivial. Empyema is potentially more serious and presents as the persistence of fever and leucocytosis after 4-5 days of appropriate antibiotic therapy.
• Lung abscess: can occur in disease due to S. pneumoniae and is classically seen in patients with staphylococcal or klebsiellar pneumonia.
• Pneumatocoele
• Pneumothorax
• Pyopneumothorax - eg. following rupture of a staphylococcal lung abscess in the pleural cavity.
• Deep vein thrombosis
• Septicaemia, pericarditis, endocarditis, osteomyelitis, septic arthritis, cerebral abscess, meningitis (particularly in pneumococcal pneumonia)
• Post-infective bronchiectasis
• Acute renal failure

• Mortality from community-acquired pneumonia is about 1%. Mortality from community acquired pneumonia has changed little since penicillin became routinely available.¹
• For patients in hospital, mortality is approximately 13-15% and it ranges from 22-54% in patients requiring intensive care.
• Early appropriate antibiotic therapy reduces mortality and morbidity.

• Influenza immunisation and pneumococcal immunisation.
• Smoking cessation.