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Interactions of clindamycin with antibacterial defenses of the lung
Abstract:
Clindamycin is speculated to have select advantages in the treatment of certain infections because biologically active antibiotic is internalized by macrophages and PMNs in vitro. By challenging pulmonary host defenses with various bacterial species as probes, we were able to evaluate clindamycin-phagocyte interaction in vivo. A murine model was developed using an implanted mini-osmotic pump to maintain constant clindamycin blood levels at 1/4 MIC (1 microgram/ml). Mice pretreated for 24 h with clindamycin killed a significantly greater percentage of intratracheally inoculated Bacteroides thetaiotaomicron in 4 h than did control animals (37 +/- 2% versus 7 +/- 5%). The enhancing effects of clindamycin on pulmonary defenses could not be duplicated by a 1-h preincubation of B. theta in 1/4 MIC of clindamycin before inoculation into untreated mice. Clindamycin blood levels of 1 microgram/ml did not alter the rate at which Pseudomonas aeruginosa (clindamycin-resistant) was killed by pulmonary defenses, suggesting that clindamycin did not cause nonspecific activation of phagocytic defenses. Both PMNs and alveolar macrophages lavaged from the lungs of clindamycin-treated mice contained bioassayable concentrated intracellular antibiotic. The presence of intracellular antibiotic was further supported by experiments in which the intrapulmonary killing of large numbers of Staphylococcus aureus (sensitive, but not resistant organisms) was significantly enhanced (89 +/- 5 versus 70 +/- 5%) by clindamycin pretreatment. In contrast, phagocytes lavaged from mice with constant 1/4 MIC (4 micrograms/ml) blood levels of penicillin G had no detectable intracellular antibiotic activity and did not augment the intrapulmonary killing of B. theta.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Clindamycin enhances pulmonary defenses by concentrating within immune cells, improving the killing of certain bacteria. This effect was observed in vivo, suggesting a novel therapeutic mechanism for clindamycin in treating infections.
Area of Science:
- Pharmacology
- Immunology
- Microbiology
Background:
- Clindamycin's in vitro internalization by macrophages and neutrophils suggests potential advantages in treating infections.
- Evaluating clindamycin-phagocyte interaction in vivo is crucial for understanding its therapeutic efficacy.
Purpose of the Study:
- To investigate the in vivo interaction of clindamycin with pulmonary phagocytes and its effect on host defense.
- To determine if clindamycin enhances the intrapulmonary killing of bacteria.
Main Methods:
- A murine model was established using mini-osmotic pumps to maintain constant clindamycin blood levels.
- Pulmonary defenses were challenged with intratracheally inoculated bacteria (Bacteroides thetaiotaomicron, Pseudomonas aeruginosa, Staphylococcus aureus).
- Phagocytes were lavaged from lungs of treated and control mice for intracellular antibiotic detection and bacterial killing assays.
Main Results:
- Clindamycin pretreatment significantly increased the killing of Bacteroides thetaiotaomicron by pulmonary defenses.
- Clindamycin did not affect the killing rate of clindamycin-resistant Pseudomonas aeruginosa, indicating specificity.
- Intracellular clindamycin was detected in pulmonary phagocytes (PMNs and alveolar macrophages), correlating with enhanced bacterial killing, particularly of Staphylococcus aureus.
Conclusions:
- Clindamycin is internalized by pulmonary phagocytes in vivo, concentrating the active antibiotic within these cells.
- This intracellular accumulation enhances the host's ability to clear susceptible bacterial infections.
- The findings support clindamycin's role in augmenting innate immune responses against bacterial pathogens.