TET - tetracycline; NOR - norfloxacin; CIP - ciprofloxacin; TZ - thioridazine; CPZ - chlorpromazine; RES - reserpine. aparcial data previously published in [21]. EFCATCC - Enterococcus faecalis reference strain; HSEFC – Enterococcus faecalis; HSEFM – Enterococcus faecium. Solutions of TZ and CPZ (Sigma Aldrich, SA, Madrid, Spain) were prepared in deionized water; RES (Sigma Aldrich, SA, Madrid, Spain) was prepared in dimethylsulfoxide. Aliquots of stock solutions of the phenothiazines CPZ and TZ were protected from light and stored at -20ºC. Working solutions were prepared on the day of the experiment. To assure that the efflux inhibitors do not compromise the bacterial viability, each compound was employed at a concentration of1/2 of the MIC. An exception to this is RES, known to affect the cellular viability even at 1/2 of the MIC [30] and in this case the compound was used at a maximum of 20 mg/L (value well below their pre-determined MIC). Values in bold-type correspond to a decrease of 4-fold or higher on the MIC values in comparison to the ones in the absence of inhibitor. Values in parenthesis indicate the MIC decrease relative to the one of the original culture. A reduction in the MIC of at least one-fourth of their original values in the presence of the efflux inhibitor was considered indicative of the presence of efflux activity. All assays were performed in triplicate.