Inhibitory Effects of Curcumin on the Expression of NorA Efflux Pump and Reduce Antibiotic Resistance in Staphylococcus aureus

The Impact of Plant-Derived Polyphenols on Combating Efflux-Mediated Antibiotic Resistance

The global healthcare system is increasingly challenged by the rising prevalence of multidrug-resistant bacteria and the limited therapeutic options for related infections. Efflux-mediated antibiotic resistance represents a significant obstacle, primarily due to the absence of drugs specifically designed to target bacterial efflux pumps. Recent research has identified polyphenols, a broad class of plant-derived organic compounds, as potential inhibitors of efflux pump activity. This review consolidates data on the inhibitory properties of eight widely distributed polyphenols: curcumin, quercetin, luteolin, tannic acid, naringenin, epigallocatechin-3-gallate, ellagic acid, and resveratrol. These compounds have demonstrated the capacity to inhibit efflux pumps, either through direct interference with bacterial protein function or by downregulating the expression of genes encoding pump subunits. Importantly, several polyphenols exhibit synergistic interactions with antibiotics, including colistin, ciprofloxacin, and tetracycline. For instance, quercetin has shown inhibitory potency comparable to that of established efflux pump inhibitors such as verapamil and reserpine. These findings suggest that polyphenols represent promising candidates for the development of novel efflux pump inhibitors. However, further research is required to validate their efficacy and safety and facilitate their translation into clinical applications for combating antibiotic resistance.

New insights on antibacterial mode of action of blue-light photoactivated berberine and curcumin-antibiotic combinations against Staphylococcus aureus

Antimicrobial photodynamic inactivation (aPDI), using photosensitisers in combination with antibiotics, is a promising multi-target strategy to address antibiotic resistance, particularly in wound infections. This study aimed to elucidate the antibacterial mode of action of combinations of berberine (Ber) or curcumin (Cur) with selected antibiotics (Ber-Ab or Cur-Ab) under blue light irradiation (420 nm) against Staphylococcus aureus, including methicillin-resistant (MRSA) and methicillin-susceptible (MSSA) strains. Multiple physiological parameters were assessed using complementary assays (fluorometry, epifluorescence microscopy, flame emission and atomic absorption spectroscopy, zeta potential, flow cytometry, and the plate agar method) to examine the effect on ROS production, membrane integrity, DNA damage, motility and virulence factors of S. aureus. Results indicated that blue light photoactivated Ber-Ab and Cur-Ab combinations led to substantial ROS generation, even at low concentrations, causing oxidative stress that severely impacted bacterial membrane integrity (approximately 90 % in MRSA and 40 % in MSSA). Membrane destabilization was further confirmed by elevated intercellular potassium release (≈ 2.00 and 2.40 µg/mL in MRSA and MSSA, respectively). Furthermore, significant DNA damage was observed in both strains (≈ 50 %). aPDI treatment with blue light also reduced S. aureus pathogenicity by impairing motility and inhibiting key virulence factors such as proteases, lipases, and gelatinases, all of which play key roles in the infectious process. Overall, Ber-Ab combinations demonstrated the highest efficacy across all parameters tested, highlighting for the first time the multi-target therapeutic potential of this phytochemical-based aPDI strategy to combat antibiotic-resistant S. aureus infections and improve wound infection treatment outcomes.

Antibacterial activity of curcumin and its essential nanoformulations against some clinically important bacterial pathogens: A comprehensive review

Multidrug-resistant bacterial infections can kill 700,000 individuals globally each year and is considered among the top 10 global health threats faced by humanity as the arsenal of antibiotics is becoming dry and alternate antibacterial molecule is in demand. Nanoparticles of curcumin exhibit appreciable broad-spectrum antibacterial activity using unique and novel mechanisms and thus the process deserves to be reviewed and further researched to clearly understand the mechanisms. Based on the antibiotic resistance, infection, and virulence potential, a list of clinically important bacteria was prepared after extensive literature survey and all recent reports on the antibacterial activity of curcumin and its nanoformulations as well as their mechanism of antibacterial action have been reviewed. Curcumin, nanocurcumin, and its nanocomposites with improved aqueous solubility and bioavailability are very potential, reliable, safe, and sustainable antibacterial molecule against clinically important bacterial species that uses multitarget mechanism such as inactivation of antioxidant enzyme, reactive oxygen species-mediated cellular damage, and inhibition of acyl-homoserine-lactone synthase necessary for quorum sensing and biofilm formation, thereby bypassing the mechanisms of bacterial antibiotic resistance. Nanoformulations of curcumin can thus be considered as a potential and sustainable antibacterial drug candidate to address the issue of antibiotic resistance.