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Abnormal sputum
Enterococcus histological pneumonia 01.png
Cocci-shaped Enterococcus sp. bacteria taken from a pneumonia patient.
Classification and external resources
Specialty Pulmonology
ICD-10 R09.3
ICD-9-CM 786.4

Sputum ['spju.təm] is mucus that is coughed up from the lower airways. This process is known as sputilization. [1] In medicine, sputum samples are usually used for microbiological investigations of respiratory infections and cytological investigations of respiratory systems.

The best sputum samples contain very little saliva,[2] as saliva contaminates the sample with oral bacteria. This event is assessed by the clinical microbiologist by examining a Gram stain of the sputum. More than 25 squamous epithelial cells at low enlargement indicates salivary contamination.[citation needed]

When a sputum specimen is plated out, it is best to get the portion of the sample that most looks like pus onto the swab. If there is any blood in the sputum, this should also be on the swab.[citation needed]

Microbiological sputum samples are usually used to look for infections by Moraxella catarrhalis, Mycobacterium tuberculosis, Streptococcus pneumoniae, and Haemophilus influenzae. Other pathogens can also be found.

Purulent sputum[3] contains pus, composed of white blood cells, cellular debris, dead tissue, serous fluid, and viscous liquid (mucus). Purulent sputum is typically yellow or green. It is seen in cases of bronchiectasis, lung abscess, an advanced stage of bronchitis, or acute upper respiratory tract infection (common cold, laryngitis).

Sputum can be:

  1. Bloody[4] (hemoptysis)
    1. Blood-streaked sputum – inflammation of throat, bronchi; lung cancer;
    2. Pink sputum – sputum evenly mixed with blood, from alveoli, small bronchi;
    3. Massive blood – cavitary tuberculosis of lung, lung abscess, bronchiectasis, infarction, embolism.
  2. Rust colored – usually caused by pneumococcal bacteria (in pneumonia)
  3. Purulent – containing pus. The sputum colour of patients with acute cough and no underlying chronic lung disease does not imply therapeutic consequences such as prescription of antibiotics.[5] The colour can provide hints as to effective treatment in chronic bronchitis patients:[6]
    1. A yellow-greenish (mucopurulent) color suggests that treatment with antibiotics can reduce symptoms. Green color is caused by Neutrophil Myeloperoxidase.
    2. A white, milky, or opaque (mucoid) appearance often means that antibiotics will be ineffective in treating symptoms. This information may correlate with the presence of bacterial or viral infections, but current research does not support that generalization.
  4. Foamy white – may come from obstruction or even edema.
  5. Frothy pink – pulmonary edema.

See also[edit]

  • Sputilization - the process of producing sputum: Word origin - group 5
  • Phlegm – the mucus produced by the respiratory system that is called sputum after it is expelled by coughing


  1. ^ Sputum definition – Medical Dictionary definitions of popular medical terms easily defined on MedTerms
  2. ^ Clinical Microbiology procedures handbook, American Society for Microbiology 2nd Ed. 2007 update
  3. ^ Richard F.LeBlond. Diagnostics_expectoration. US: McGraw-Hill Companies, Inc. ISBN 0-07-140923-8. 
  4. ^ Richard F.LeBlond. Diagnostics_expectoration. US: McGraw-Hill Companies, Inc. ISBN 0-07-140923-8. 
  5. ^ Sputum colour for diagnosis of a bacterial infection in patients with acute cough
  6. ^ Sputum Color is the Key to Treating Acute COPD Exacerbations

External links[edit]