Towards a Unified Theory of Bacterial Persistence and Tolerance in Biofilms Formed on Medical Devices in Nigerian Tertiary Hospital Environments

Bacterial persistence and antibiotic tolerance within medical device biofilms represent a distinct and clinically critical resistance phenotype that transcends conventional heritable resistance mechanisms, yet unified theory integrating persistence dynamics with the specific physico-chemical conditions of Nigerian tertiary hospital medical device surfaces has not been developed. This dissertation constructs and validates a unified theoretical model of bacterial persistence and tolerance in biofilms on medical devices in Nigerian tertiary hospital environments, drawing on empirical data from eight tertiary hospitals across six geopolitical zones. Biofilm samples were recovered from intravenous catheters, urinary catheters, endotracheal tubes, and orthopaedic implant surfaces across hospitals in Lagos, Kano, Enugu, Port Harcourt, Maiduguri, and Ilorin. Transcriptomic profiling of biofilm versus planktonic cells identified persistence-associated gene expression signatures. Quantitative biofilm assays, persister cell frequency counts, and tolerance dose-response modelling were performed for dominant clinical species. The dissertation introduces the Differential Persistence Architecture (DPA) theory, positing that Nigerian hospital biofilm communities exhibit species-specific persistence hierarchies shaped by device surface polymer chemistry, hospital water hardness, and antibiotic concentration gradients in hospital effluents. DPA theory explains the differential eradication responses of Pseudomonas aeruginosa and Staphylococcus aureus biofilms to antibiotic challenge at concentrations achievable in tissue, providing a mechanistic basis for combination dosing strategies. Experimental validation using ex vivo catheter models confirms DPA predictions. Keywords: biofilm, bacterial persistence, medical device, tolerance, Nigerian hospitals