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Updated: Apr 26, 2026
Production and Visualization of Bacterial Spheroplasts and Protoplasts to Characterize Antimicrobial Peptide Localization
Published on: August 11, 2018
Antimicrobial peptides are highly abundant and active in postoperative pleural drainage fluids
Konrad Hoetzenecker1, Moritz Hochdaninger1, Denise Traxler2
1Department of Thoracic Surgery, Medical University Vienna, Austria.
Background:
The human lung is considered a nonsterile organ, and surgical interventions therefore take place in a more or less contaminated operating field. Nevertheless, infectious complications of the pleural cavity are low after major lung resections. Antimicrobial peptides (AMPs) are part of the innate immunity and display a broad capacity to kill pathogens. We hypothesized that the pleural space must have a high natural antimicrobial barrier and that AMPs might effectively protect the pleural cavity.
Methods:
Pleural effusions were collected after lung operations. Antimicrobial activity of the fluids against gram-positive and gram-negative pathogens was analyzed by microdilution assays. AMPs were determined by enzyme-linked immunosorbent assay (ELISA), polymerase chain reaction (PCR), and immunohistochemical analysis. The impact of proinflammatory triggers on AMP release from pleural mesothelial cells was evaluated.
Results:
Antimicrobial activity assays revealed high bactericidal properties of postoperative pleural drainage fluids. They effectively killed gram-negative pathogens (Escherichia coli, Pseudomonas aeruginosa) as well as gram-positive pathogens (Staphylococcus aureus, Streptococcus pneumoniae, and Streptococcus pyogenes). A variety of AMPs was detected at constantly high concentrations in the pleural fluids. They mainly derived from leukocytes and pleural epithelium. Although proinflammatory cytokine levels were elevated in the postoperative pleural fluids, AMP expression could not be augmented by Toll-like receptor (TLR) triggering or by the proinflammatory cytokines interleukin (IL)-1β and tumor necrosis factor (TNF)α.
Conclusions:
We provide the first evidence of a high abundance of AMPs in postoperative pleural fluids. Our findings might explain the broad protection against infectious complications of the pleural space after major lung operations.
Insights
Postoperative pleural fluids exhibit potent antimicrobial activity, effectively killing diverse bacteria. This suggests that antimicrobial peptides (AMPs) in pleural fluid provide significant protection against infections after lung surgery.
Area of Science:
- Infectious disease
- Immunology
- Thoracic surgery
Background:
- The human lung is a nonsterile organ, making surgical sites susceptible to contamination.
- Despite contamination risk, infectious complications in the pleural cavity post-lung resection are infrequent.
- Antimicrobial peptides (AMPs) are key components of innate immunity, known for their pathogen-killing capabilities.
Purpose of the Study:
- To investigate the hypothesis that the pleural space possesses a robust natural antimicrobial barrier.
- To determine the role of AMPs in protecting the pleural cavity from infection after lung surgery.
Main Methods:
- Collection and analysis of pleural effusions from patients undergoing lung operations.
- Assessment of fluid antimicrobial activity against Gram-positive and Gram-negative bacteria using microdilution assays.
- Quantification of AMPs via ELISA, PCR, and immunohistochemistry; evaluation of AMP release from mesothelial cells under inflammatory conditions.
Main Results:
- Postoperative pleural fluids demonstrated significant bactericidal activity against common Gram-negative (E. coli, P. aeruginosa) and Gram-positive (S. aureus, S. pneumoniae, S. pyogenes) pathogens.
- A diverse array of AMPs was consistently found at high concentrations in pleural fluids, originating primarily from leukocytes and pleural epithelium.
- Elevated proinflammatory cytokine levels did not enhance AMP expression when stimulated by Toll-like receptor (TLR) triggering or by IL-1β and TNFα.
Conclusions:
- This study presents the first evidence of a substantial presence of AMPs in postoperative pleural fluids.
- The high concentration of AMPs in pleural effusions likely contributes to the observed low incidence of infectious complications in the pleural space following major lung resections.
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