The tet genes (e.g. tet(A), tet(B), tet(M)) encode either tetracycline efflux pumps or ribosomal protection proteins, conferring resistance to tetracyclines. These genes are widespread in both Gram-negative and Gram-positive pathogens. Detection of a tet gene indicates that tetracycline antibiotics (doxycycline, minocycline) will not be effective, and often correlates with multidrug-resistant plasmids. Clinically, this finding leads to avoiding tetracyclines and choosing other agents (such as fluoroquinolones or β-lactams) for treatment (Chopra& Roberts 2001, Grossman 2016).
Grossman T. H. (2016). Tetracycline Antibiotics and Resistance. Cold Spring Harbor perspectives in medicine, 6(4), a025387. https://doi.org/10.1101/cshperspect.a025387
Chopra, I., & Roberts, M. (2001). Tetracycline: mode of action, applications, molecular biology, and epidemiology of bacterial resistance. Microbiology and molecular biology reviews : MMBR, 65(2), 232–260. https://doi.org/10.1128/MMBR.65.2.232-260.2001
