Asiatic acid disrupts biofilm formation and shows additive effect with antibiotic against Acinetobacter baumannii

Abstract

Asiatic acid, a bioactive pentacyclic triterpenoid derived from Centella asiatica, has been widely used against infectious wounds and inflammation. Recently, this natural compound has also drawn attention to interfering with bacterial biofilms, a major phenotypic strategy that enables bacteria to survive under stress or antibiotic pressure. Acinetobacter baumannii, a nosocomial pathogen, is well known for its remarkable ability to form biofilms that promote chronic infections and contribute to conventional antibiotic resistance. The present study investigated the inhibitory effect of asiatic acid during the early stages of A. baumannii biofilm development. Despite exhibiting indirect antimicrobial activity, asiatic acid significantly reduced biofilm production in both drug-resistant clinical isolates and A. baumannii ATCC 19606 reference strain. Confocal microscopic evaluations supported the visual attenuation of biofilm structure following treatment. Molecular analyses revealed that asiatic acid downregulated the expression of critical biofilm-associated adhesion genes, csuE and bap. By suppressing these genes, this natural compound may prevent bacteria from surface attachment and interfere with the subsequent maturation of biofilms. Furthermore, asiatic acid additively contributed to antimicrobial activity of standard antibiotics against A. baumannii. These findings support the potential of asiatic acid as an adjunctive agent for the control of biofilm-associated infections caused by A. baumannii, particularly in the context of rising multidrug resistance. Continued investigation into its mechanisms and synergistic combinations may inform the development of novel anti-biofilm therapeutic strategies.