Fidaxomicin Resistance

Fidaxomicin resistance occurs when the antibiotic is not able to treat the infections it is intended to because the bacterial strains causing these infections have developed mechanisms to prevent the drug from functioning. Fidaxomicn is a relatively new drug, having been approved for clinical use in 2011. As a result, there have not been many cases of fidaxomicin resistance. Nevertheless, the main mechanism of resistance involves mutations in the genes encoding RNAP subunits.

Resistance Mechanism(s)

Antibiotic Target Alteration – Mutations

Mutations in the rpoB and rpoC genes which encode the RNAP β and βꞋ­ subunits can confer resistance to fidaxomicin. Examples of amino acid substitutions seen in the β subunit include Y1049F, Q1054E, and Q1054L. Amino acids changes in the βꞋ­ subunit leading to fidaxomicin resistance include R412H, R412E, and D423Y. The locations of these mutations are significant because the residues either directly interact with the drug or are located close to residues that do (Lin et al., 2018).

Learn more about fidoxamicin binding to the bacterial RNA polymerase.

Back to the article on fidaxomicin.

References

Lin, W., Das, K., Degen, D., Mazumder, A., Duchi, D., Wang, D., Ebright, Y. W., Ebright, R. Y., Sineva, E., Gigliotti, M., Srivastava, A., Mandal, S., Jiang, Y., Liu, Y., Yin, R., Zhang, Z., Eng, E. T., Thomas, D., Donadio, S., Zhang, H., Zhang, C., Kapanidis, A. N., & Ebright, R. H. (2018). Structural basis of transcription inhibition by fidaxomicin (lipiarmycin A3). Molecular cell, 70(1), 60–71.e15. https://doi.org/10.1016/j.molcel.2018.02.026