Restraining the multidrug efflux transporter STY4874 of Salmonella Typhi by reserpine and plant extracts

Abstract

Efflux‐mediated multidrug resistance is a well‐known phenomenon facilitated by multidrug resistant (MDR) transporters. One of the approaches to counteract efflux‐mediated resistance is the use of MDR pump inhibitors, and thus be used in combination with the conventional antibiotics to treat deadly diseases like typhoid fever. We have previously reported that STY4874, an efflux transporter of Salmonella serotype Typhi, exhibited promising characteristics as MDR pump. In this study, we aimed to get an insight into possible STY4874 inhibitors of plant origin. STY4874 was overexpressed in Escherichia coli and extracts from pomegranate peel, milk thistle seeds and reserpine, a synthetic plant alkaloid, were screened for inhibition of ciprofloxacin efflux. The extracts of milk thistle seeds and reserpine when incubated with ciprofloxacin showed statistically significant STY4874‐mediated inhibitory activity, rendering the efflux pump inactive and hence early growth inhibition of host cells compared with cells expressing efflux pump and incubated only with ciprofloxacin. This efflux pump inhibitory activity was further confirmed by time‐kill experiments. This study is the first to report on efflux pump inhibition of S. Typhi STY4874 and results can be extended towards its close homologues such as MdfA and MdtM from E. coli. Significance and Impact of the Study Understanding and combating resistance governed by multidrug efflux transporters is an ongoing research intensive area, affecting treatment of various nosocomial and endemic/epidemic infections. Confronting drug resistance requires that inhibitors debilitating the underlying mechanisms should be included in combination therapy. One such example is the prescription of clavulanic acid as combination therapy with amoxicillin, collectively called as co‐amoxiclav to combat β‐lactamase‐mediated resistance. However, research related to finding the inhibitors of efflux transporters, the resistance mechanism distinct from β‐lactamase mediated resistance is at an early stage. The current study finds that plant‐derived inhibitors can be an option towards restraining efflux‐mediated resistance.

Xanthones Active against Multidrug Resistance and Virulence Mechanisms of Bacteria

“…The biofilm inhibition, presented in percentages (%), was calculated based on the mean of absorbance units. Reserpine was used as the control in both strains, as it has been shown to inhibit not only the formation of biofilm in S. aureus strains [ 39 ], but also bacterial efflux activity [ 40 , 41 , 42 ]. The results obtained concerning the biofilm inhibition assay are presented in Table 3 .…”

Elucidation of Phytochemical Content of Cupressus macrocarpa Leaves: In Vitro and In Vivo Antibacterial Effect against Methicillin-Resistant Staphylococcus aureus Clinical Isolates

“…A nonsignificant change in the expression level of the nor C gene was observed after treatment. Many researchers have focused on the detection of efflux pump inhibitors from plant sources [ 38 , 40 , 41 , 42 ]. Such efflux inhibitors from a natural source can be used to decrease antibiotic resistance among pathogenic bacteria [ 38 ].…”

Naturally-Occurring Alkaloids of Plant Origin as Potential Antimicrobials against Antibiotic-Resistant Infections

“…The evidences of the disk diffusion assay were confirmed by other experiments suggesting that reserpine when tested in combination with ciprofloxacin exerted significant STY4874-mediated inhibitory activity leading to the accumulation of ciprofloxacin inside the cell. These results could be also extended towards STY4874 close homologues, MdfA and MdtM from E. coli making this study an important starting point to further develop potent inhibitors of these efflux pumps [73]. Nevertheless, the potential of reserpine as EPI limits its usage due to the toxic effect to humans at the concentration needed for inhibition.…”