High Prevalence of Multidrug-Resistant Pseudomonas aeruginosa in Pre-Treated Pharmaceutical Wastewater: Evidence of Treatment Failure in Nigerian Manufacturing Facilities

Pharmaceutical wastewater treatment plants are intended to mitigate environmental contamination, yet their efficacy against critical priority pathogens like Pseudomonas aeruginosa in low- resource settings remains unverified. This study isolated P. aeruginosa exclusively from pre-treated effluents across three Nigerian pharmaceutical facilities to assess treatment performance and compare inter-facility resistance patterns. About 150 pre-treated effluent samples (50 each from Companies A, B, C) in Ogun State, Nigeria, were cultured on cetrimide agar. Antibiotic susceptibility testing against 12 antipseudomonal agents followed CLSI 2022 guidelines. Inter-facility resistance differences were analyzed using chi-square and one-way ANOVA with post-hoc Tukey tests; p ≤ 0.05 was considered significant. P. aeruginosa was isolated from 21.3% (32/150) of pre-treated samples, yielding 41 total isolates. Overall MDR prevalence was 78.0%, with pan-drug resistance detected in 19.5% of isolates. Significant inter- facility disparities in resistance to meropenem (p=0.008), imipenem (p=0.011), ciprofloxacin (p=0.005), gentamicin (p=0.028), and amikacin (p=0.025) were documented. P. aeruginosa Company C exhibited the highest resistance across all drug classes. Current pre-treatment methods at Nigerian pharmaceutical facilities fail to eradicate P. aeruginosa, discharging MDR and PDR strains into the environment. Significant inter-facility variability underscores the need for enhanced tertiary treatment technologies and routine national effluent surveillance against WHO critical priority pathogens.