Last updated: Friday, 24, December, 2010
CausesAppropriate Tests

Sputum - microscopy and culture; blood culture. If indicated: FBC, blood film, differential WCC; electrolytes, creatinine, urea; blood gases. Non-infective processes may also be responsible for radiological changes, eg carcinomatosis, lymphoma, systemic necrotising vasculitis.

Lobar and bronchopneumonia

Occasionally, in severe pneumonia unresponsive to initial therapy, investigations may include bronchial brush, wash; bronchoalveolar lavage, FNAB or endoscopic lung biopsy, including microscopy and culture. Pleural fluid examination may be indicated if pleural effusion is present.

Streptococcus pneumoniae

Legionella pneumophila

See Legionella infection

Haemophilus influenzae

See Haemophilus influenzae infection

Klebsiella pneumoniae

Burkholderia pseudomallei

Aspiration pneumonia

Predisposing conditions include unconsciousness, alcohol intoxication.

Mixed bacterial infection, including anaerobic organisms

'Atypical' pneumonia

The clinical signs are not typical of pneumonia and consolidation appears diffuse or unusual on diagnostic imaging.

Mycoplasma pneumoniae

See Mycoplasma infection

Legionella spp

See Legionella infection

Chlamydia psittaci


Chlamydia antibodies.

Chlamydia pneumoniae

Chlamydia pneumoniae antibodies.

Viral infection

  • Influenza A, B
  • Adenovirus
  • Coronavirus, including SARS agent

Influenza virus antibodies, adenovirus antibodies. Viral culture, detection only indicated for severe pneumonia, eg immunocompromised patients, patients requiring ICU admission, or in an outbreak setting, eg SARS 2003, avian influenza 2004, in defined at-risk patients.

'Opportunistic' pneumonia

Opportunistic infections may occur in immunocompromised or normal hosts and this possibility should be considered when there is failure to respond to initial antibiotic therapy. If appropriate: HIV antibodies, assessment of immune function.

See also Infection (increased susceptibility)

Immunocompromised host

The common pathogens are the most likely cause of pneumonia, but unusual pathogens should be considered early, especially when the illness is severe or when the initial response to therapy is unsatisfactory. Investigation may include: sputum microscopy and culture, bronchial brush, wash; bronchoalveolar lavage, FNAB or endoscopic lung biopsy - microscopy, culture (including mycobacterial and fungal). Open lung biopsy may be required.

Mycobacterial infection

  • Tuberculosis
  • Non-tuberculous mycobacteria

Pneumocystis jiroveci

See Pneumocystis infection

Nocardia spp


See Cytomegalovirus infection

Gram-negative bacilli

Fungal infection

  • Cryptococcus neoformans

See Cryptococcal infection

  • Aspergillus spp

See Aspergillosis


See Neonatal sepsis

Viral pneumonia, especially

  • Respiratory syncytial virus

Virus detection, culture - nasopharyngeal aspirate.

  • Cytomegalovirus

See Cytomegalovirus infection

Chlamydia trachomatis infection

Bacterial pneumonia, especially

  • Staphylococcus aureus

Pneumonia with abscess

Microscopy and culture of pus obtained at bronchoscopy, FNAB.

Aspiration pneumonia, especially

Examination of expectorated sputum may be of little value.

  • Staphylococcal infection

Particularly in infants.

Secondary to bronchial obstruction

  • Tumour
  • Foreign body

Bronchial brushings for cytology; lesion biopsy.

Patients with bronchiectasis and/or cystic fibrosis

See also cough - chronic

Staphylococcus aureus

Pseudomonas aeruginosa

Burkholderia cepacia

Interstitial pneumonia

See Interstitial lung disease