Isolation and Characterization of Variants of Quorum-Sensing Signal Molecules in Clinical Acinetobacter baumannii Isolates.

Acinetobacter baumannii is a multidrug-resistant nosocomial pathogen that poses a significant global health threat. Quorum sensing (QS), a communication system found in this bacterium, is pivotal in biofilm formation, virulence factor production, and its overall survival. This study aimed to detect, quantify, and characterize signaling molecules in representative high biofilm forming clinical isolates of A. baumannii, thereby advancing the chemical understanding of microbial communication signals in this clinically important pathogen and providing a foundation for future investigations into their biological roles. The clinical isolates were screened for QS-associated phenotypes, signal molecule production, and the compounds were extracted, purified, and identified by thin-layer chromatography, mass spectrometry, and nuclear magnetic resonance spectroscopy. The analyses identified the presence of the diketopiperazine cyclo (L-prolyl-L-valine) and the long-chain acyl-homoserine lactone C14:1-HSL in the examined A. baumannii isolates. Based on the available literature, these molecules have not been previously reported in A. baumannii. This variation highlights the diversity of signaling molecules associated with the clinical isolates examined. These findings expand current knowledge of the chemical profiles of signaling molecules produced by high-biofilm-forming A. baumannii isolates and provide a basis for future studies investigating their potential biological significance.