Pneumonia is a commonly used term in both medical practice and the community at large. It is often used synonymously (and erroneously) with terms such as ‘chest infection’, ‘bronchitis’, or ‘infective exacerbation of COPD’. It is subdivided into several different entities reflecting the different epidemiology, presentation, bacteriology, and therapy required.
The definition of community-acquired pneumonia (CAP) in the hospital setting is as follows.
• Symptoms and signs consistent with an acute lower respiratory tract infection associated with new radiographic shadowing for which there is no other explanation (e.g. not pulmonary oedema or infarction).
• Symptoms and signs occur at presentation or within 48 hours of hospital admission.
• Annual incidence in the community is 5–11 in 1000 adults.
• Between 22% and 42% of adults with CAP are admitted to hospital.
• Between 5% and 10% of adults admitted with CAP are managed on ICU.
• Mortality in those admitted to hospital is reported to be 5–12%.
• Mortality in those admitted to UK ICUs is as high as 50%.
• Chronic cardiorespiratory disease.
• Oral corticosteroids or other immunosuppression, in whom typical features may be absent.
The causative agent cannot be accurately predicted from the clinical, laboratory, or radiographic data available. No pathogen is isolated in approximately 40–70% of cases in routine clinical practice. Potential organisms include the following.
• Streptococcus pneumoniae: most common pathogen in CAP.
• Haemophilus influenzae: common in acute exacerbations of COPD.
• Staphylococcus aureus: often following viral infection.
• Moraxella catarrhalis.
• Gram-negative bacteria, e.g. Klebsiella, Pseudomonas.
• Anaerobic bacteria.
• Mycoplasma pneumoniae: occurs in 4-yearly cycles.
• Legionella pneumophilia: common in severe CAP.
• Chlamydia pneumoniae and Chlamydia psittaci (psittacosis).
• Influenza A and B.
Once pneumonia is diagnosed the assessment of severity forms a key part of effective patient care. Poor prognosis is indicated by:
• Increasing age.
• Coexisting disease.
• Absence of fever.
• Elevated respiratory rate.
• Elevated blood urea.
• Hypotension and tissue hypoperfusion (↑lactate).
• WCC <4 or >20 × 109/L.
• Bilateral radiographic infiltrates.
• Positive blood cultures.
The CURB-65 score is a validated method of assessing the severity and prognosis of community-acquired pneumonia. It is simple to perform and should be done routinely as part of the admission procedure. It consists of five points.
• Confusion: new disorientation in time, place, and person or an abbreviated mental test score ≤8.
• Urea >7 mmol/L.
• Respiratory rate >30 breaths/minute.
• Blood pressure: DBP <60 mmHg or SBP <90 mmHg.
• Age >65 years.
• 0–1: low risk of death, has non-severe pneumonia, and may be suitable for outpatient care.
• 2: recommend a short hospital stay and IV antibiotics.
• >3: patient at high risk of death and should be treated as severe pneumonia in hospital.
• ≥4: critical care involvement should be considered.
The choice of initial antibiotic is guided by the severity of the pneumonia, the treatment setting, the ability of the patient to take penicillin and local antibiotic sensitivities, and prescribing practices. Current BTS recommendations for empirical therapy in CAP are shown in Table 27.1.
Table 27.1 BTS recommendations for empirical therapy in CAP
Severity of pneumonia
Non-severe: community treatment
Amoxicillin 500 mg to 1 g tds po
Eythromycin 500 mg qds po or clarithromycin 500 mg bd po
Non-severe: hospital treatment, oral
Amoxicillin 500 mg to 1 g tds po
PLUS Eythromycin 500 mg qds po or clarithromycin 500 mg bd po
Eythromycin 500 mg qds po or clarithromycin 500 mg bd po
OR Levofloxacin 500 mg od po or moxifloxacin 400 mg od po
Non-severe: hospital treatment, IV therapy
Ampicillin 500 mg qds IV or benzylpenicillin 1.2 g qds IV
PLUS Erythromycin 500 mg qds IV or clarithro mycin 500 mg bd IV
Fluoroquinolone with enhanced pneumococcal activity, e.g. Levofloxacin 500 mg od po
Co-amoxiclav 1.2 g tds IV or cefuroxime 1.5 g tds IV or ceftriaxone 2 g od IV
PLUS Erythromycin 500 mg qds IV or cefotaxime 1 g tds or clarithromycin 500 mg bd IV (± rifampicin 600 mg od)
Fluoroquinolone with enhanced pneumococcal activity, e.g. levofloxacin 500 mg bd IV PLUS benzylpencillin 1.2 g qds IV
Hospital-acquired pneumonia (HAP), also known as nosocomial pneumonia, is recognized as pneumonia developing at least 48 hours after hospital admission. It accounts for 10–20% of hospital-acquired infections. Some people use the phrase ‘healthcare-associated pneumonia’ to encompass both HAP and pneumonia occurring in those living in long-term care environments for whom traditional CAP bacteriology and therapy do not apply. HAP has a poor prognosis, with a mortality of up to 50%. Failure to improve should prompt a search for pleural infection or lung abscess. ICU care should be sought early if appropriate.
Include impaired host defences, impaired conscious levels and aspiration, reduced gastric pH from medications, and broad-spectrum antibiotic usage.
In contrast with CAP:
• Mixed infection is common.
• Aerobes commonly include S.aureus and Gram-negative rods (Pseudomonas, Klebsiella, coliforms).
• Anaerobes are important pathogens.
• Multiresistant organisms, including MRSA, should always be considered.
Antibiotics should be given intravenously initially and cover the above organisms. Possible regimens include:
• Cefuroxime (750–1500 mg tds) and metronidazole (500 mg tds).
• To cover Pseudomonas infection consider piperacillin/tazobactam 4.5 g tds, ceftazidime 1–2 g tds, gentamicin 3–5 mg/kg od, or meropenem 500–1000 mg tds.
• Vancomycin 1 g bd or teicoplanin 400 mg od are required to cover MRSA.
Occurs due to aspiration of material from the upper airways or GI tract into the lower airways. Risk factors include a reduced level of consciousness, gastro-oesophageal reflux, dysphagia, and recent upper GI surgery.
Aspiration may cause a bacterial pneumonia or a chemical pneumonitis.
Caused by pathogens which usually inhabit the upper respiratory or GI tract.
• Classically affects the dependent lung segments, e.g. usually right lower lobe or posterior segment right upper lobe on lying flat.
• Antibiotics which include cover of anaerobic organisms are traditional although this is debated by some.
• Cefuroxime (750–1500 mg) tds and metronidazole (500 mg) tds IV.
• Co-amoxiclav (1.0 g) tds IV.
The aspiration of substances into the lower airways causing a rapid inflammatory process to develop in the lung. It is not caused by bacteria.
• Care is supportive.
• Antibiotics for pneumonia are often given as it may be hard to separate the two diagnoses and secondary infection of pneumonitis is common.
• Steroids occasionally used with little evidence of benefit.
Ventilator-associated pneumonia (VAP) is the combination of symptoms and signs of pneumonia with new consolidation on CXR, developing at least 48 hours after endotracheal intubation. It is thought to be a consequence of repeated aspiration of upper airways secretions into the lower airway. A cuffed endotracheal tube or tracheostomy may reduce aspiration but will not eliminate it. The normal pulmonary clearance mechanisms are then unable to clear the lower airways.
• A respiratory physician may be asked to perform a bronchoscopic BAL to obtain a sample for microbiologic analysis. Some units use a non-directed BAL using a suction catheter to obtain repeated samples.
• Antibiotics are broad spectrum (e.g. meropenem or piperacillin/tazobactam) to cover HAP and should be discussed with the microbiologist.
Complications/failure to improve
The presence of either an empyema or complicated parapneumonic effusion implies an infected pleural space and further therapy is indicated.
• Pleural infection should be suspected in any patient with pneumonia who is failing to improve as predicted.
• It should be investigated with CXR, thoracic ultrasound, or CT scanning if atypical features on CXR, and pleural sampling to guide definitive management ( Chapter 25).
• If pleural infection is confirmed advice from a respiratory physician should be sought.
This is necrosis of the lung parenchyma. It is usually the consequence of aspiration pneumonia and therefore the risk factors are the same.
• Classic features include a cough productive of foul sputum if the cavity communicates with an airway. Cavities seen on CXR may have air–fluid levels.
• Pulmonary abscess formation in IV drug users should prompt a search for right heart infective endocarditis.
• Klebsiella, S.aureus, anaerobes, and TB are the most common bacteria to cause cavitation.
• Empirical antibiotic therapy with cefuroxime 1.5 g tds IV, metronidazole 500 mg tds IV ± flucloxacillin 1 g qds IV.
• Consider radiologically guided percutaneous drainage in those who fail to respond to antibiotics and supportive treatment.
1. Macfarlane JT et al. (2001). BTS guidelines on the management of community acquired pneumonia in adults. Thorax, 56 (Suppl 4), 1–64.
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3. Bacterial respiratory infection, Chapter 20, OHRM.