Vanillic acid’s potential to enhance AdeIJK, AdeFGH, and AdeABC efflux pump substrates in Acinetobacter baumannii

This paper focuses on in vitro analysis of the ability of vanillic acid to potentiate representative antibiotics, which are substrates of pumps responsible for antibiotic resistance in Acinetobacter baumannii. To investigate whether vanillic acid can potentiate antibiotics in cells overexpressing the AdeABC, AdeFGH, and AdeIJK efflux pumps, a minimum potentiation concentration determination (MPC4) experiment was performed. Vanillic acid potentiates novobiocin (eightfold) in Acinetobacter baumannii overexpressing AdeIJK. RNA-seq analysis was used to examine the gene-level effects of vanillic acid in AdeIJK-overexpressing cells treated with a sub-MIC concentration of novobiocin. AdeIJK overexpressing cells were cultivated at a sub-MIC concentration of novobiocin alone (1.5625 µg/mL) and at a sub-MIC concentration of novobiocin (1.5625 µg/mL) and vanillic acid (50 µg/mL) together to ascertain the effect of vanillic acid at the transcriptional level. DEG results revealed the upregulation of genes involved in the degradation and transport of aromatic compounds and alcohol metabolism. From the results of the present study, the upregulation of genes related to the degradation of aromatic compounds is regulated by vanillic acid, which is not surprising, and this may also make it possible to increase novobiocin sensitivity, aligning with existing literature. However, it is crucial to validate these findings through experimental studies. ADH genes, known for their involvement in quorum sensing, stress resistance, and virulence were upregulated by vanillic acid treatment. In conclusion, our study highlights the potential regulatory role of vanillic acid, warranting further investigation.