Proposal of an easy method to improve routine sputum bacteriology

Area of Science:

• Microbiology
• Pulmonology
• Infectious Diseases

Background:

• Accurate bacterial flora analysis of the lower respiratory tract is crucial for diagnosing pulmonary infections and guiding therapy.
• Sputum contamination by upper airway bacteria presents a significant methodologic challenge in respiratory specimen analysis.

Purpose of the Study:

• To introduce an improved procedure for reducing upper airway bacterial contamination in sputum specimens.
• To compare the diagnostic accuracy of qualitative and quantitative cultures of spit versus sputum.
• To evaluate the utility of bronchial lavage aspirate (BLA) cultures as a control.

Main Methods:

• A preliminary mouthwash procedure was implemented to minimize oral flora contamination.
• Qualitative and quantitative cultures of spit and sputum were compared.
• Bronchial lavage aspirate (BLA) cultures served as a control for bacterial contamination.
• Both definite and random sequence sampling procedures were employed.

Main Results:

• The preliminary mouthwash significantly decreased mean contaminant concentrations in sputum (p < 0.001).
• When sputum preceded spit, bacterial counts were not significantly different, highlighting the importance of collection sequence.
• Oral contaminants were infrequently found in BLA (12.5%) in correctly treated patients.
• Bacteria found in BLA but absent in spit/sputum were rare (4.8%).

Conclusions:

• A preliminary mouthwash effectively reduces sputum contamination by upper airway bacteria.
• Comparing spit and sputum cultures, particularly with a correct collection sequence, is sufficient for microbiologic examination in most cases, including chronic obstructive lung disease (COLD) patients.
• BLA cultures are rarely needed when proper specimen collection and processing are employed.