Molecular Regulation of Biofilm Development in Stenotrophomonas maltophilia: Integrating Signal Transduction, Environmental Adaptation, and Antibiotic Resistance

Stenotrophomonas maltophilia is increasingly recognized as a difficult-to-treat healthcare-associated opportunistic pathogen, particularly in critically ill and immunocompromised patients, in whom it causes severe respiratory, bloodstream, and device-associated infections. Its intrinsic resistance to multiple antimicrobial classes, capacity to acquire additional resistance determinants, and ability to establish persistent biofilms substantially limit therapeutic options. This review integrates current knowledge of the structural basis, regulatory circuitry, and ecological interactions governing S. maltophilia biofilm development and examines how these processes converge with antimicrobial resistance. Biofilm formation is driven by coordinated adhesion and motility, extracellular matrix production, quorum sensing, cyclic di-GMP signaling, two-component regulatory systems, and adaptive responses to iron limitation and oxidative stress. Multidrug efflux systems contribute not only to antibiotic extrusion but also to membrane homeostasis, motility, stress adaptation, and biofilm-associated phenotypes, thereby providing a functional link between antimicrobial resistance and bacterial persistence. In polymicrobial communities, interspecies signaling and competitive or cooperative interactions further reshape biofilm architecture and antimicrobial tolerance. Collectively, current evidence indicates that S. maltophilia biofilm formation arises from interconnected regulatory networks rather than isolated molecular determinants. Targeting matrix assembly, signaling pathways, stress adaptation, or resistance-associated physiology may therefore complement conventional antimicrobial therapy. Future studies should prioritize clinically representative isolates, physiologically relevant multispecies models, and in vivo validation to translate mechanistic insights into effective anti-biofilm interventions.