Evaluation of the intrinsic antibacterial and antibiotic potentiating activity against antibiotic resistance in Staphylococcus aureus and inhibition of the NorA and MepA efflux pumps by a hydrazone derivative of isoniazid.

Hydrazones are organic compounds with promising antimicrobial properties, particularly in the fight against resistant microorganisms. The aim of this study was to synthesize and evaluate the antibacterial activity of the hydrazone derivative of isoniazid N'-[[4-({[(pyridin-4-yl)formamido]imino] methyl)phenyl]methylidene]pyridine-4 carbohydrazide (BISHDZHI) against Staphylococcus aureus overexpressing NorA and MepA efflux pumps. The broth microdilution methodology was used in the microbiological tests to evaluate the antibacterial potential of the BISHDZHI compound and its ability to inhibit efflux pump resistance mechanisms. To elucidate the mechanism of action, molecular docking simulations were conducted to assess the binding affinity of BISHDZHI to the NorA and MepA efflux pumps. Minimum inhibitory concentration (MIC) tests showed that BISHDZHI in association with norfloxacin moderately reduced the MIC of the antibiotic, indicating the enhancement of its efficacy. However, an antagonistic effect was observed in combination with ethidium bromide, suggesting that the compound does not directly inhibit bacterial efflux pumps, but may act on other intracellular targets, such as the enzyme topoisomerase IV. The docking studies revealed strong interactions between BISHDZHI and key amino acid residues within the efflux pumps, particularly Tyr225, Val302, and Phe306 in NorA and Leu59, Phe280, and Tyr276 in MepA. The docking scores indicated favorable binding energies, suggesting potential inhibitory effects on efflux activity. This study highlights the potential of the hydrazone BISHDZHI as a promising candidate for treating infections caused by the bacterium Staphylococcus aureus.