Microorganisms, known as flora or microbiota, naturally inhabit various parts of the human body. These communities of bacteria, fungi, and viruses are a normal aspect of human biology. One such area where they thrive is the oropharynx, and their presence can be noted in substances like sputum.
Understanding Oropharyngeal Flora
The oropharyngeal flora is the diverse community of microorganisms living within the mouth and throat. This ecosystem includes bacteria like Streptococci Viridans, Staphylococci, Neisseria species, and Haemophilus species, and fungi and viruses. These microorganisms form a stable community that typically does not cause disease in healthy individuals. They contribute to local immunity and help prevent harmful pathogens from colonizing by competing for resources.
Understanding Sputum
Sputum is a thick mucus material expelled from the lower respiratory tract, which includes the lungs, bronchi, and trachea, typically through coughing. It is distinct from saliva, which is produced in the mouth and primarily aids in digestion. Sputum is composed of mucus, cells, and other debris, and its primary function is to trap and remove inhaled foreign particles, pathogens, and irritants from the airways.
Why Flora Appears in Sputum
When sputum is expelled, it travels from the lower respiratory tract through the mouth and throat. During this passage, the sputum picks up normal microorganisms residing in the oropharynx. Therefore, the presence of oropharyngeal flora in a sputum sample is common and expected. It is considered a form of contamination, as these organisms originate from the upper respiratory tract rather than indicating a lung infection.
Clinical Significance of Sputum Flora
The presence of oropharyngeal flora in a sputum sample is clinically significant. Laboratories differentiate between normal contaminants and potential pathogens from the lower respiratory tract by assessing the quantity and type of organisms present. For example, a sputum culture showing “normal respiratory flora” indicates harmless bacteria like Streptococcus viridans or Neisseria species, which typically do not require antibiotic treatment. However, predominant growth of pathogenic bacteria, such as Streptococcus pneumoniae or Haemophilus influenzae, can indicate a lower respiratory tract infection like pneumonia or bronchitis. Identifying these organisms guides the selection of appropriate antimicrobial therapy.
When Sputum Samples Are Analyzed
Sputum samples are often analyzed when a healthcare provider suspects a lower respiratory tract infection. Conditions include pneumonia, bronchitis, or tuberculosis. Symptoms that might prompt a sputum analysis include a persistent cough, fever, chills, shortness of breath, or chest pain. The analysis helps identify the specific microorganism causing the infection, which guides appropriate treatment with antibiotics or other medications. Sputum cultures can also monitor the effectiveness of ongoing treatment for chronic respiratory conditions.