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Survival of Streptococcus pneumoniae in sputum from patients with pneumonia
Abstract:
The isolation rate of Streptococcus pneumoniae in sputum cultures from patients with pneumococcal pneumonia is low. An investigation was made to determine whether this low yield might be due to loss of pneumocci and/or overgrowth by pharyngeal flora before the specimen is plated. Pneumococcal survival times and pharyngeal overgrowth at 4 degrees C and at room temperature were determined in sputum obtained from 42 patients with pneumococcal pneumonia. It was found that pneumococci survived for long periods in sputum--2.2 +/- 1.4 days at room temperature and 9.5 +/- 3.6 days at 4 degrees C. Overgrowth by pharyngeal flora occurred in only 6 of 42 specimens kept at 4 degrees C and 31 of 42 specimens kept at room temperature. The low yield of S. pneumoniae in sputum from patients with pneumococcal pneumonia is not explained by decreased viability of the organism.
Insights
The isolation of Streptococcus pneumoniae from pneumonia patients is often low. This study found that pneumococci survive well in sputum, even at room temperature, suggesting viability is not the cause of low isolation rates.
Area of Science:
- Microbiology
- Clinical Diagnostics
Background:
- The isolation rate of Streptococcus pneumoniae in sputum cultures from patients with pneumococcal pneumonia is frequently low.
- This low yield may be attributed to pre-plating specimen handling, such as pneumococcal loss or overgrowth by pharyngeal flora.
Purpose of the Study:
- To investigate whether decreased viability or overgrowth by pharyngeal flora contributes to the low isolation rate of Streptococcus pneumoniae in sputum samples.
- To determine pneumococcal survival times and the extent of pharyngeal flora overgrowth in sputum specimens under different storage conditions.
Main Methods:
- Sputum samples were collected from 42 patients diagnosed with pneumococcal pneumonia.
- Pneumococcal survival and pharyngeal flora overgrowth were assessed at 4 degrees C and room temperature.
- Viability was monitored over time to establish survival rates and overgrowth patterns.
Main Results:
- Streptococcus pneumoniae demonstrated prolonged survival in sputum: an average of 2.2 days at room temperature and 9.5 days at 4 degrees C.
- Pharyngeal flora overgrowth was minimal at 4 degrees C (6/42 specimens) but significant at room temperature (31/42 specimens).
- The organism's viability remained high, indicating it is not the primary factor for low isolation rates.
Conclusions:
- The decreased viability of Streptococcus pneumoniae is not the reason for the low isolation rates observed in sputum cultures from patients with pneumococcal pneumonia.
- Storage conditions significantly impact pharyngeal flora overgrowth, with refrigeration at 4 degrees C being more effective in preventing it.
- Further research should focus on other factors that may influence the low diagnostic yield of sputum cultures for pneumococcal pneumonia.