Anthropogenic drivers of multidrug resistance: metal-mediated co-selection in Pseudomonas aeruginosa from Orogodo River, Delta State, Nigeria

Abstract

Pseudomonas aeruginosa is a persistent opportunistic pathogen of significant public health concern in freshwater environments, particularly in low- and middle-income countries. This study examined the influence of physicochemical pollution on antibiotic resistance dynamics in P. aeruginosa isolates from the Orogodo River, Delta State, Nigeria. Water samples were collected from upstream (P1), midstream (P2) and downstream (P3) sites along a defined pollution gradient. Isolates were characterized morphologically and biochemically and tested for antibiotic susceptibility alongside comprehensive physicochemical analysis. Although isolates exhibited similar morphological and biochemical profiles, pigment production varied across sites. All isolates demonstrated high resistance to trimethoprim-sulfamethoxazole, amoxicillin, and ciprofloxacin, with no statistically significant differences in resistance profiles among sampling points. Heavily polluted sites showed significantly elevated total suspended solids (TSS; p < 0.001), biochemical oxygen demand (BOD; p < 0.010) and reduced dissolved oxygen (DO; p < 0.001), while chemical oxygen demand (COD; p > 0.567), nitrate (p > 0.432), phosphate (p > 0.177), lead (p > 0.080) and iron (p > 0.085) levels did not vary significantly. Pearson correlation revealed strong positive associations between organic load, nutrients, heavy metals (especially lead, r = 0.93; iron, r = 0.83) and resistance indices, contrasted by strong negative correlations with DO. Regression models confirmed robust predictive relationships in DO (R² = 0.99), lead (R² = 0.98), iron (R² = 0.81) and BOD (R² = 0.66). These results establish the Orogodo River as an anthropogenically driven reservoir of multidrug-resistant P. aeruginosa, highlighting metal-mediated co-selection. The findings therefore emphasize the vital One Health imperatives for enhanced antimicrobial resistance surveillance and stricter wastewater management in this important water sources.