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[Effect of macrolide antibiotics on human serum-bactericidal sensitivity of Pseudomonas aeruginosa S-6]
K Tateda1, N Furuya, Y Hirakata
1Department of Microbiology, Toho University School of Medicine.
Abstract:
It is well known that long-term administration of erythromycin (EM) at a small dose is effective for persistent infections with Pseudomonas aeruginosa in diffuse panbronchiolitis or chronic bronchitis patients. Since EM is less active against P. aeruginosa in vitro, we have been interested in the mechanisms of clinical efficacy of EM in these patients. This study examines the effect of macrolide antibiotics on human serum-bactericidal sensitivity of P. aeruginosa S-6, clinically isolated from the patient with respiratory tract infection. A significant increase in serum-bactericidal sensitivity of P. aeruginosa S-6 was observed on agar containing EM of 10 micrograms/ml after incubation for 36-60 hours (p less than 0.05). The enhancement of serum sensitivity of P. aeruginosa S-6 was apparently observed even at a concentration of EM 1.5 micrograms/ml after the 48 hours incubation (p less than 0.01). Of other macrolide antibiotics used, clarithromycin (CAM) also increased the serum-bactericidal sensitivity of P. aeruginosa S-6 as well as EM, however no change in the sensitivity was found with kitasamycin, josamycin, rokitamycin and oleandomycin. The results suggest that the change of serum-bactericidal sensitivity of P. aeruginosa induced by EM or CAM may, in part, contribute to the clinical efficacy of these antibiotics against persistent pulmonary P. aeruginosa infections.
Insights
Erythromycin (EM) and clarithromycin (CAM) enhance Pseudomonas aeruginosa
Area of Science:
- Microbiology
- Pharmacology
- Immunology
Background:
- Long-term, low-dose erythromycin (EM) is clinically effective for persistent Pseudomonas aeruginosa infections in respiratory diseases.
- In vitro studies show EM has limited activity against P. aeruginosa, suggesting indirect mechanisms for its clinical efficacy.
Purpose of the Study:
- To investigate how macrolide antibiotics affect the serum-bactericidal sensitivity of Pseudomonas aeruginosa.
- To explore the role of enhanced serum sensitivity in the clinical effectiveness of EM and other macrolides against P. aeruginosa.
Main Methods:
- Culturing P. aeruginosa S-6, isolated from a respiratory tract infection patient.
- Assessing the impact of erythromycin (EM) and other macrolides on the serum-bactericidal sensitivity of P. aeruginosa.
- Incubating bacteria on agar containing varying concentrations of EM (1.5 and 10 µg/ml) for 36-60 hours.
Main Results:
- EM significantly increased the serum-bactericidal sensitivity of P. aeruginosa S-6 after 36-60 hours of incubation, even at low concentrations (1.5 µg/ml).
- Clarithromycin (CAM) also enhanced P. aeruginosa's sensitivity to human serum.
- Kitasamycin, josamycin, rokitamycin, and oleandomycin did not alter the bacteria's serum sensitivity.
Conclusions:
- Macrolide antibiotics like EM and CAM can increase the susceptibility of P. aeruginosa to human serum.
- This enhanced serum-bactericidal sensitivity may partially explain the clinical effectiveness of these macrolides in treating persistent pulmonary P. aeruginosa infections.