Understanding polymicrobial biofilm dynamics: focus on Escherichia coli and its molecular interactions

Abstract

AIM: To investigate bacterial interactions within dual-species biofilms on biliary stents and their role in stent blockage. BACKGROUND: Polymicrobial biofilms are critical in device-associated infections, including those in biliary stents, which are prone to biofilm formation due to duodenobiliary reflux, leading to stent blockage. This study identifies the microflora of biliary stents and examines their biofilm-forming capabilities to elucidate their role in stent occlusion. METHODS: Biliary stents were collected from patients with biliary obstructions. Microflora were identified using culture techniques and MALDI-TOF. Antimicrobial susceptibility was assessed via disk diffusion, while biofilm formation was measured using the crystal violet assay. Dual-culture biofilms were studied to understand polymicrobial dynamics, and gene expression in biofilms was analyzed at four time points. Statistical analysis was performed using GraphPad Prism 8.0 (p < 0.05). RESULTS: Scanning electron microscopy confirmed biofilms on biliary stents. Microbiological analysis identified 50 species of aerobic, anaerobic bacteria, and fungi. Biofilm formation significantly correlated with multidrug resistance. Based on the abundance, one isolate of E. coli was selected to study the dynamics of dual-species biofilm with K. pneumoniae, E. faecium, P. aeruginosa and S. hominis. Dual-species biofilms differed structurally and quantitatively from mono-species biofilms, influenced by the spatial arrangement of constituent bacteria (Figure 1) CONCLUSION: Delayed adhesion and varied interaction (both cooperatively and competitively) of E. coli with different bacterial species lead to delayed maturation of the biofilm. These interactions bolster bacterial virulence and survival in challenging conditions. Understanding these dynamics is crucial for preventing colonization of indwelling medical devices