INVESTIGATING BIOFILM FORMATION AND QUORUM SENSING IN UROPATHOGENIC E. COLI UNDER STRESS CONDITIONS

Abstract

Biofilm formation and quorum sensing represent critical survival strategies for uropathogenic Escherichia coli (UPEC), especially under environmental stress. This study investigated the effects of oxidative stress, nutrient limitation, and sub-inhibitory antibiotic exposure on biofilm development and quorum sensing activity in clinical UPEC isolates. Quantitative assays demonstrated a significant increase in biofilm biomass under all stress conditions, with ciprofloxacin-induced stress producing the most pronounced effect. AI-2 production, a central quorum sensing signal, was markedly elevated across stress environments, indicating enhanced bacterial communication and coordination. Gene expression analysis revealed substantial upregulation of key quorum sensing (luxS, sdiA, tnaA) and biofilm-associated genes (csgA, bssS, fimH), further affirming the activation of these virulence pathways under duress. Examination of structures under a confocal microscope and scanning electron microscope demonstrated that the biofilms in stressed samples were thicker and more complex than those in unstressed samples. Interestingly, the highest concentration of each antibiotic needed to stop cell growth was much greater for biofilm-forming cells. The viability test showed biofilms helped cells remain intact far more than planktonic cells when subjected to the same stress. The discovery demonstrates that UPEC can respond to stress by sticking around, becoming tougher and making treatment harder. By disrupting how chronic biofilms are maintained and how their matrix is formed, we may reduce antibiotic resistance and infections in the urinary tract.