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[Influence of low level antibiotics on Pseudomonas aeruginosa]
Abstract:
Erythromycine (EM) and chrolamphenicol (CP), the inhibitors of protein synthesis, were quantitatively examined for the growth of Pseudomonas aeruginosa EA83 and its production of extracellular proteins. The minimal inhibitory concentration (MIC) of EM for the strain was higher than 100 micrograms/ml and that of CP was 100 micrograms/ml. The growth curve of EA83 was not influenced by adding 5 micrograms/ml of EM to the broth culture, but proteolytic activity and the total protein in the culture supernate went down to 60% of the control. Number of organisms in 20 hour culture was almost constant regardless of EM concentration ranging from 0 to 50 micrograms/ml, however, the suppression of proteolytic activity and total protein in the culture supernate was seen even at 1 micrograms/ml of EM concentration. The degree of suppression was inversely proportional to EM concentration. This phenomenon was also seen in the substitution of CP for EM. All extracellular proteins separated on SDS-PAGE decreased the amount as increasing EM in the culture media. These results suggested that EM inhibited the production of not only protease including elastase, but also any other extracellular proteins including well known pathogenic factors such as exotoxin A and phospholipase C.
Insights
Erythromycin (EM) and chloramphenicol (CP) significantly reduced Pseudomonas aeruginosa
Area of Science:
- Microbiology
- Molecular Biology
- Bacterial Pathogenesis
Background:
- Pseudomonas aeruginosa is an opportunistic pathogen known for producing various extracellular virulence factors.
- Protein synthesis inhibitors like erythromycin (EM) and chloramphenicol (CP) are used clinically, but their specific effects on P. aeruginosa virulence factor production require detailed investigation.
Purpose of the Study:
- To quantitatively assess the impact of erythromycin (EM) and chloramphenicol (CP) on the growth and extracellular protein production of Pseudomonas aeruginosa EA83.
- To determine the dose-dependent effects of EM on protease activity and the production of other key extracellular virulence factors.
Main Methods:
- Quantitative analysis of Pseudomonas aeruginosa EA83 growth curves in the presence of varying concentrations of EM and CP.
- Measurement of proteolytic activity and total extracellular protein concentration in culture supernatants.
- Separation and visualization of extracellular proteins using SDS-PAGE.
Main Results:
- The minimal inhibitory concentrations (MICs) for EM and CP were determined to be >100 µg/ml and 100 µg/ml, respectively.
- EM at 5 µg/ml did not affect bacterial growth but reduced proteolytic activity and total extracellular protein by 60%.
- Suppression of proteolytic activity and total protein was observed even at 1 µg/ml EM, with effects inversely proportional to EM concentration. Similar effects were noted with CP.
- SDS-PAGE analysis revealed decreased amounts of all separated extracellular proteins with increasing EM concentrations, including elastase, exotoxin A, and phospholipase C.
Conclusions:
- Erythromycin (EM) and chloramphenicol (CP) effectively inhibit the production of multiple extracellular proteins in Pseudomonas aeruginosa EA83, including critical virulence factors.
- The study demonstrates that EM suppresses the production of not only proteases like elastase but also other secreted virulence factors such as exotoxin A and phospholipase C, even at sub-inhibitory concentrations.