tetAC

tetAC is a tetracycline resistance determinant found in bacteria, typically representing a tandem arrangement of the tetA and tetC genes or a mosaic variant such as tetA(C). These genes encode membrane-associated efflux pumps that reduce intracellular concentrations of tetracycline, enabling bacterial survival in the presence of the antibiotic.

Function and gene products: TetA and TetC encode proteins that belong to the major facilitator superfamily. They act as efflux pumps, often functioning as proton motive force–driven antiporters to export tetracycline from the cell. In strains carrying both genes in an operon or linked arrangement (tetAC), the combined activity can broaden resistance or enhance pump expression.

Regulation: Expression of tetracycline resistance genes is commonly controlled by TetR family repressors. In the absence of tetracycline, TetR binds to operator regions and represses transcription. When tetracycline or related compounds are present, TetR releases from the operator, leading to de-repression and increased pump production.

Genetic context and mobility: tetAC is frequently located on plasmids or transposons, facilitating horizontal transfer among bacteria, including various Gram-negative species. The existence of mosaic tetA(C) sequences reflects recombination events between tetA- and tetC-derived alleles and can contribute to diversity in resistance determinants.

Clinical significance: The presence of tetAC contributes to tetracycline resistance in pathogenic bacteria, potentially limiting treatment options. Detection methods include molecular assays targeting tetA, tetC, or tetA(C) sequences, complemented by phenotypic susceptibility testing.

See also: Tetracycline resistance, tetA, tetC, TetR.