Ciprofloxacin Exhibits Synergy with Psychoactive Drug 1-(3-Chlorophenyl)piperazine against Staphylococcus aureus

Staphylococcus aureus is the most frequent isolated pathogen responsible for causing bloodstream infections, pneumonia, and skin/soft tissue infections acquired among community and hospitals that are frequently the cause for mortality worldwide. Ciprofloxacin has been one the most frequently used antibiotics and is so far less effective against S. aureus. Discovery of new drugs that are capable of enhancing current antibiotics are urgently needed. Psychoactive compounds are known to act as an efflux pump inhibitors. The purpose of this study is to investigate the synergy of the psychoactive drug 1-(3-Chlorophenyl) piperazine (mCPP) also known as the recreational drug “ecstasy” with ciprofloxacin (CIP) against S. aureus. A disk diffusion assay was performed to check the interactions between mCPP and CIP at the varying concentrations of 2, 20, 200 μg, and 4 and 5 μg/ml, respectively, with S. aureus 1199B. A synergism test was employed for mCPP and CIP. The Minimal inhibitory concentration (MIC) index values were calculated according to Clinical and Laboratory Standards Institute (CLSI) guidelines. An ethidium bromide (EtBr) accumulation assay was carried out to analyze the interaction between mCPP and CIP.  Reverse transcriptase PCR was performed to identify the expression and regulation of efflux pump genes during treatment with mCPP. The antipsychotic chlorpromazine (CPZ), a known efflux pump inhibitor, was used as the positive control. S. aureus 1199B exhibited a zone of inhibition in the presence of 20 μg of mCPP, with a 2.5 fold increase at 200 μg of mCPP in the presence of 4 or 5 μg/ml of CIP. The minimum inhibitory concentration (MIC) for mCPP was observed to be >512 μg/ml. When CIP was combined with mCPP at 62μg/ml, a 4 fold decrease in the MIC of CIP was observed. Interactions between mCPP and CIP were found to be synergistic with FIC 0.50 ± 0.04. Treatment of S. aureus 1199B with mCPP at 40 μg/ml significantly increased EtBr accumulation (P<0.0001). Treatment of S. aureus 1199B with 40 μg/ml of mCPP for one hour increased the expression level of the efflux pump mdeA gene. mCPP exerts synergistic antimicrobial activity in the presence of CIP against S. aureus 1199B. Our results showed that mCPP could be used to overcome resistance against CIP in S. aureus. This interdisciplinary research integrates the knowledge on the neuro-pharmacological properties, the cell physiology of a bacterium, and the biochemical mechanism of resistance to an antibiotic.