TetB

tetB is a gene that encodes a tetracycline efflux pump, contributing to bacterial resistance to tetracycline antibiotics. It is one of several determinants that enable bacteria to survive in the presence of tetracyclines by actively exporting the drug from the cell, thereby reducing the intracellular concentration that inhibits protein synthesis.

Genetic context and regulation: tetB is typically carried on plasmids or other mobile genetic elements, which facilitates horizontal transfer among bacteria. Its expression is often regulated by a repressor system that senses tetracycline levels; in the absence of the antibiotic, expression is low, while exposure to tetracycline induces transcription of the efflux pump.

Mechanism and family: The TetB protein is a membrane-spanning transporter, generally classified within the major facilitator superfamily. It functions as an energy-dependent efflux pump, commonly using the proton motive force to move substrates, including tetracycline, out of the cell.

Distribution and detection: TetB has been identified in a range of bacterial species, including both Gram-negative and some Gram-positive organisms, though it is less widespread than some other tet genes. It is detected in clinical isolates and environmental samples. Detection methods include molecular assays such as PCR to identify the gene, as well as phenotypic susceptibility testing to observe tetracycline resistance patterns.

Clinical relevance: The presence of tetB reduces bacterial susceptibility to tetracycline antibiotics, contributing to treatment challenges. Because tetB is often located on mobile genetic elements, it can disseminate between strains and species, potentially co-occurring with other resistance determinants and complicating antimicrobial stewardship efforts.