Thioridazine reduces resistance of methicillin-resistant Staphylococcus aureus by inhibiting a reserpine-sensitive efflux pump

Malthe M. Kristiansen, Clara Leandro, Diane Ordway, Marta Martins, Miguel Viveiros, Teresa Pacheco, Joseph Molnar, Jette E. Kristiansen, Leonard Amaral

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Abstract

Previous studies suggested that the phenothiazine chlorpromazine (CPZ) could reverse or reduce the antibiotic resistance of bacteria. In some areas of the world, the majority of Staphylococcus aureus isolates are now resistant to methicillin, prompting this study to see whether such resistance can be altered by phenothiazine thioridazine (TZ), an agent with equal antibacterial activity, which is free of the severe side-effects associated with chronic administration of CPZ. The results indicated that, whereas methicillin-sensitive strains of Staphylococcus aureus (MSSA) were not rendered more susceptible to oxacillin, resistance to oxacillin by highly-resistant strains (MRSA) could be significantly reduced by sub-inhibitory concentrations of TZ. Reserpine, an inhibitor of efflux pumps, was also shown to reduce the resistance of MRSA strains to oxacillin in a concentration-dependent manner. The phenothiazines have been shown, by others, to inhibit the efflux pumps of bacteria and the mechanism by which MRSA are rendered more susceptible to oxacillin in the presence of TZ is believed to be due to a similar efflux pump.

Original languageEnglish
Pages (from-to)361-366
Number of pages6
JournalIn Vivo
Volume20
Issue number3
Publication statusPublished - May 1 2006

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Keywords

  • Antibiotic resistance
  • Fluoroquinolone resistance
  • Methicillin resistance
  • Phenothiazines
  • Staphylococcus aureus

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Pharmacology

Cite this

Kristiansen, M. M., Leandro, C., Ordway, D., Martins, M., Viveiros, M., Pacheco, T., Molnar, J., Kristiansen, J. E., & Amaral, L. (2006). Thioridazine reduces resistance of methicillin-resistant Staphylococcus aureus by inhibiting a reserpine-sensitive efflux pump. In Vivo, 20(3), 361-366.