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Bactericidal activity of human peritoneal macrophages from patients undergoing peritoneal dialysis
C A Thomas1, E W Interwies, B L Ziegler
1Department of Internal Medicine, Infectious Diseases, University Hospital, Ulm, FRG.
Abstract:
Peritoneal macrophages (PM) play an essential role in the pathogenesis of bacterial peritonitis, the main complication of peritoneal dialysis (PD). We determined the antibacterial activity of PM from 31 PD patients using gram-positive (Staphylococcus aureus, Staphylococcus epidermidis) and gram-negative (Escherichia coli, Pseudomonas aeruginosa) test organisms. In an 8-hour test assay, PM revealed the highest antibacterial activity against E. coli [median bactericidal index (Bi) = 5.46 representing 0.74 log growth inhibition compared to controls] and the lowest against P. aeruginosa (Bi = 1.63, 0.21 log growth inhibition, p less than 0.05). The antibacterial activity against S. aureus (Bi = 1.99, 0.3 log growth inhibition) and S. epidermidis (Bi = 2.0, 0.31 log growth inhibition) was within this range. When compared to peripheral blood polymorphonuclear leukocytes, PM reached only 4% (S. aureus) and 8.1% (E. coli) of their antibacterial activity (p less than 0.05). Using E. coli as a test organism, PM isolated after a 4-hour dialysis period revealed the highest antibacterial activity when compared to PM isolated after longer dialysis periods (p less than 0.05). Increasing the duration of PD to 6 and 8 h subsequently decreased the antibacterial activity of PM, suggesting that unphysiologic concentrations of toxic metabolites in the peritoneal effluent might have a harmful influence on PM functions.
Insights
Peritoneal macrophages (PM) in dialysis patients show varied antibacterial activity, most effective against E. coli. Prolonged dialysis impairs PM function, potentially due to toxic metabolites in peritoneal fluid.
Area of Science:
- Immunology
- Microbiology
- Nephrology
Background:
- Bacterial peritonitis is a major complication of peritoneal dialysis (PD).
- Peritoneal macrophages (PM) are key immune cells involved in combating peritonitis.
- Understanding PM antibacterial function is crucial for managing PD complications.
Purpose of the Study:
- To assess the antibacterial activity of peritoneal macrophages (PM) from PD patients.
- To compare PM activity against common Gram-positive and Gram-negative bacteria.
- To investigate the impact of dialysis duration on PM antibacterial function.
Main Methods:
- Antibacterial activity of PM from 31 PD patients was tested against Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa.
- Bactericidal index (Bi) was used to quantify bacterial growth inhibition over 8 hours.
- PM activity was compared to peripheral blood polymorphonuclear leukocytes and analyzed based on dialysis duration.
Main Results:
- PM exhibited highest activity against E. coli (Bi=5.46) and lowest against P. aeruginosa (Bi=1.63).
- Activity against S. aureus (Bi=1.99) and S. epidermidis (Bi=2.0) was intermediate.
- PM showed significantly lower antibacterial activity (4-8.1%) compared to peripheral blood leukocytes.
- PM isolated after 4 hours of dialysis demonstrated the highest antibacterial activity, which decreased with longer dialysis durations (6-8 hours).
Conclusions:
- Peritoneal macrophages (PM) possess measurable antibacterial activity, varying by bacterial species.
- PM antibacterial function is inferior to peripheral blood leukocytes.
- Prolonged peritoneal dialysis may impair PM function, possibly due to toxic metabolites in peritoneal effluent.
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