Heterogeneous antimicrobial activity in broncho-alveolar aspirates from mechanically ventilated intensive care unit
Jolien Seinen1,2, Willem Dieperink3, Solomon A Mekonnen1,4
1Department of Medical Microbiology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
Abstract:
Pneumonia is an infection of the lungs, where the alveoli in the affected area are filled with pus and fluid. Although ventilated patients are at risk, not all ventilated patients develop pneumonia. This suggests that the sputum environment may possess antimicrobial activities. Despite the generally acknowledged importance of antimicrobial activity in protecting the human lung against infections, this has not been systematically assessed to date. Therefore, the objective of the present study was to measure antimicrobial activity in broncho-alveolar aspirate ('sputum") samples from patients in an intensive care unit (ICU) and to correlate the detected antimicrobial activity with antibiotic levels, the sputum microbiome, and the respective patients' characteristics. To this end, clinical metadata and sputum were collected from 53 mechanically ventilated ICU patients. The antimicrobial activity of sputum samples was tested against Streptococcus pneumoniae, Staphylococcus aureus and Streptococcus anginosus. Here we show that sputa collected from different patients presented a high degree of variation in antimicrobial activity, which can be partially attributed to antibiotic therapy. The sputum microbiome, although potentially capable of producing antimicrobial agents, seemed to contribute in a minor way, if any, to the antimicrobial activity of sputum. Remarkably, despite its potentially protective effect, the level of antimicrobial activity in the investigated sputa correlated inversely with patient outcome, most likely because disease severity outweighed the beneficial antimicrobial activities.
Insights
Sputum from intensive care unit (ICU) patients shows varied antimicrobial activity, influenced by antibiotics but not significantly by the microbiome. Higher antimicrobial activity surprisingly correlated with poorer patient outcomes.
Area of Science:
- Pulmonary Medicine
- Infectious Diseases
- Microbiology
Background:
- Pneumonia involves lung alveoli filling with pus and fluid.
- Ventilated patients are at risk, but not all develop pneumonia, suggesting protective factors in sputum.
- The antimicrobial activity of sputum in lung infections is not well-characterized.
Purpose of the Study:
- To quantify antimicrobial activity in broncho-alveolar aspirate (sputum) from intensive care unit (ICU) patients.
- To correlate sputum antimicrobial activity with antibiotic levels, sputum microbiome, and patient characteristics.
- To assess the role of sputum's antimicrobial properties in patient outcomes.
Main Methods:
- Collected clinical metadata and sputum samples from 53 mechanically ventilated ICU patients.
- Assessed sputum antimicrobial activity against *Streptococcus pneumoniae*, *Staphylococcus aureus*, and *Streptococcus anginosus*.
- Analyzed correlations between antimicrobial activity, antibiotic concentrations, microbiome composition, and patient outcomes.
Main Results:
- Significant variation in sputum antimicrobial activity was observed among patients.
- Antibiotic therapy partially explained the observed antimicrobial activity.
- The sputum microbiome's contribution to antimicrobial activity was minimal.
- Antimicrobial activity inversely correlated with patient outcomes, likely due to disease severity.
Conclusions:
- Sputum possesses variable antimicrobial activity in mechanically ventilated ICU patients.
- Antibiotics are a key factor, while the microbiome plays a minor role in sputum's antimicrobial capacity.
- Despite potential protective roles, increased sputum antimicrobial activity was associated with worse patient outcomes in this cohort.
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