Related Experiment Videos
Antibiotic uptake by alveolar macrophages
Abstract:
Optimal therapy of infections caused by bacteria able to survive within phagocytes requires the use of antibiotics which inactivate these intracellular organisms. To define characteristics that determine entry of antimicrobial agents into phagocytes, we studied the uptake of 14 radiolabeled antibiotics by rabbit AM. Cell-antibiotic mixtures were incubated for 2 hr, and at intervals antibiotic uptake was determined by velocity-gradient centrifugation (separation of cells from extracellular antibiotic). Many drugs failed to penetrate AM readily. Cellular concentrations of penicillin G and three cephalosporin antibiotics were much lower than extracellular levels (C/E = less than 0.1 to 0.4). Gentamicin, isoniazid, and tetracycline attained C/E values of 0.5 to 0.8. The more lipid-soluble antibiotics, refampin, lincomycin, and chloramphenicol, were concentrated approximately twofold (C/E = 2) in AM. Ethambutol (C/E = 7) and two erythromycin preparations (C/E = greater than 20) were markedly accumulated by macrophages. In comparison with other antibiotics tested, the uptake of clindamycin was both massive and rapid (C/E = 50 by 30 min). Ethambutol, erythromycin and clindamycin uptakes by AM are dependent upon oxidative metabolic processes. Detailed characterization of clindamycin uptake confirmed that the drug is accumulated by an active transport system. These findings, in association with studies of antibiotic-mediated influence on phagocytes, should provide information useful in establishing guidelines for optimal antibiotic usage.
Insights
Certain antibiotics, like clindamycin and erythromycin, are highly concentrated within phagocytes, indicating effective intracellular bacterial infection treatment. This research explores antibiotic uptake mechanisms for improved therapy guidelines.
Area of Science:
- Pharmacology
- Microbiology
- Cell Biology
Background:
- Intracellular bacteria require antibiotics that penetrate phagocytic cells.
- Understanding antibiotic uptake by phagocytes is crucial for effective treatment.
Purpose of the Study:
- To investigate the characteristics of antibiotic entry into phagocytes.
- To identify antibiotics with significant intracellular accumulation.
Main Methods:
- Studied uptake of 14 radiolabeled antibiotics by rabbit alveolar macrophages (AM).
- Used velocity-gradient centrifugation to quantify antibiotic concentrations within cells.
- Assessed the impact of metabolic processes on antibiotic uptake.
Main Results:
- Most antibiotics showed limited penetration into AM.
- Lipid-soluble antibiotics like rifampin and chloramphenicol showed moderate uptake (C/E ≈ 2).
- Ethambutol, erythromycin, and clindamycin demonstrated significant accumulation (C/E > 20), with clindamycin uptake being rapid and massive (C/E = 50).
- Uptake of ethambutol, erythromycin, and clindamycin depends on oxidative metabolism, with clindamycin accumulation via active transport.
Conclusions:
- Antibiotic uptake by phagocytes varies significantly.
- Clindamycin, erythromycin, and ethambutol show high intracellular concentrations, suggesting potential for treating intracellular infections.
- Findings inform guidelines for optimal antibiotic selection and usage against intracellular pathogens.