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The in vitro effect of three antibiotics on alveolar macrophages
Abstract:
The effects of 3 antibiotics, azlocillin, ticarcillin and tobramycin, on rat alveolar macrophage function has been examined. These antibiotics are used in the treatment of Pseudomonas aeruginosa lung infections in cystic fibrosis patients. In this study low concentrations of the antibiotics were used, similar to the low levels found in the lungs of these patients. Tobramycin, a highly active aminoglycoside, inhibited the phagocytosis of opsonized Pseudomonas aeruginosa and enhanced the binding of sheep erythrocytes sensitized with IgG2b, when pre-incubated with macrophage monolayers for 30 min. Inhibition of both phagocytosis and binding of sensitized sheep erythrocytes was observed when tobramycin was co-incubated with the macrophage monolayers and indicator cells. Azlocillin, a semi-synthetic penicillin, caused inhibition of phagocytosis of opsonized bacteria and binding of sensitized sheep erythrocytes when added with the indicator cells. However, no effect was found if the macrophages were pre-incubated with azlocillin for 30 min. Ticarcillin, a semi-synthetic penicillin which is less active in vitro as an antimicrobial agent than azlocillin, had no effect on alveolar macrophages at the concentrations used in these assays. It is postulated that if these in vitro findings with rat alveolar macrophages are reflected in the in vivo situation in humans, the effect of antibiotics on host defence may be of clinical importance.
Insights
Tobramycin and azlocillin antibiotics impaired rat alveolar macrophage function, affecting bacterial phagocytosis and immune cell binding. Ticarcillin showed no impact at tested concentrations, suggesting potential clinical relevance for host defense during Pseudomonas aeruginosa infections.
Area of Science:
- Immunology
- Pharmacology
- Microbiology
Background:
- Pseudomonas aeruginosa lung infections are common in cystic fibrosis patients.
- Azlocillin, ticarcillin, and tobramycin are antibiotics used to treat these infections.
- Therapeutic antibiotic concentrations in cystic fibrosis lungs are often low.
Purpose of the Study:
- To investigate the effects of azlocillin, ticarcillin, and tobramycin on rat alveolar macrophage function.
- To determine if low antibiotic concentrations impact macrophage phagocytosis and immune cell binding.
Main Methods:
- Rat alveolar macrophages were incubated with varying concentrations of azlocillin, ticarcillin, and tobramycin.
- Macrophage phagocytosis of opsonized Pseudomonas aeruginosa was assessed.
- Binding of sensitized sheep erythrocytes (IgG2b) to macrophages was measured.
Main Results:
- Tobramycin inhibited phagocytosis and enhanced erythrocyte binding when pre-incubated, and inhibited both when co-incubated.
- Azlocillin inhibited phagocytosis and binding when co-incubated but not when pre-incubated.
- Ticarcillin had no significant effect on macrophage function at the tested concentrations.
Conclusions:
- Low concentrations of tobramycin and azlocillin can impair alveolar macrophage functions crucial for host defense.
- These in vitro findings suggest potential clinical implications for antibiotic treatment strategies in cystic fibrosis patients.
- Further in vivo studies are warranted to confirm the clinical relevance of these observed effects on host defense mechanisms.
