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Streptococcal tetracycline resistance mediated at the level of protein synthesis
Abstract:
The mechanism of tetracycline resistance was examined in strains containing each of the three previously identified resistance determinants in Streptococcus spp. Uptake of tetracycline was measured in tetracycline-sensitive cells as well as in cells containing each of the three resistance determinants. In cells containing tetL, uptake was not observed. However, in sensitive cells and cells containing either tetM or tetN, tetracycline was accumulated approximately 25-fold against a concentration gradient. Furthermore, there was no evidence for modification of intracellular tetracycline recovered from sensitive, tetM, or tetN cells. Protein synthesis in extracts derived from organisms containing tetM or tetN was resistant to tetracycline. In contrast, extracts of sensitive and tetL cells were sensitive to tetracycline.
Insights
Tetracycline resistance in Streptococcus spp. was studied. TetM and TetN determinants confer resistance by preventing tetracycline uptake and maintaining protein synthesis, unlike TetL which blocks uptake but doesn't protect protein synthesis.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Tetracycline resistance is a significant concern in bacterial infections.
- Streptococcus species harbor various resistance determinants, including tetL, tetM, and tetN.
- Understanding the mechanisms of these determinants is crucial for developing effective treatments.
Purpose of the Study:
- To elucidate the specific mechanisms by which tetL, tetM, and tetN confer tetracycline resistance in Streptococcus spp.
- To compare the functional differences between these three resistance determinants at the cellular and molecular levels.
Main Methods:
- Measuring tetracycline uptake in sensitive and resistant Streptococcus strains.
- Analyzing intracellular tetracycline accumulation against a concentration gradient.
- Assessing protein synthesis activity in cell extracts exposed to tetracycline.
Main Results:
- TetL-containing cells showed no tetracycline uptake.
- TetM and TetN conferred resistance by accumulating tetracycline against a gradient and protecting protein synthesis.
- Intracellular tetracycline modification was not observed in any resistant strains.
Conclusions:
- TetM and TetN mediate tetracycline resistance through active accumulation and protection of protein synthesis.
- TetL confers resistance primarily by preventing tetracycline entry into the cell.
- Distinct mechanisms of tetracycline resistance exist among different determinants in Streptococcus spp.