Chemical Characteristics of Hospital Wastewater and Their Association with Antibiotic Resistance Patterns in Sabratha, Libya

Abstract

Hospital wastewater is a major source of environmental contamination due to its complex mixture of chemical pollutants and microbial hazards, including pharmaceutical residues, disinfectants, heavy metals, nutrients, and antibiotic-resistant bacteria. This study evaluated the chemical characteristics of wastewater from Sabratha Teaching Hospital and examined their association with bacterial antibiotic resistance patterns. Physicochemical analysis revealed high organic pollution, with elevated chemical oxygen demand (COD = 1975 ± 281 mg/L) and biochemical oxygen demand (BOD₅ = 165.5 ± 20.8 mg/L), alongside markedly increased electrical conductivity and total dissolved solids, while dissolved oxygen levels were very low (DO = 1.40 ± 0.08 mg/L), indicating hypoxic and highly stressed environmental conditions. Multivariate analyses, including principal component analysis (PCA) and canonical correspondence analysis (CCA), demonstrated that organic load and salinity were strongly associated with increased antibiotic resistance. Random forest modeling further identified COD, total dissolved solids (TDS), dissolved oxygen (DO), and electrical conductivity (EC) as the most influential predictors of resistance patterns. Correlation analysis showed that higher COD levels were associated with reduced bacterial antibiotic susceptibility, whereas increased dissolved oxygen was positively associated with susceptibility. Comparative analysis between resistant and sensitive bacterial groups revealed mostly non-significant differences, except for a significant association between salinity and Pseudomonas spp. resistance to imipenem. Overall, the findings indicate that hospital wastewater acts as a reservoir for antibiotic-resistant bacteria, where environmental stressors such as organic pollution, salinity, and oxygen depletion play a more critical role in shaping resistance patterns than antibiotics alone. The study highlights the need for improved wastewater treatment strategies, including reduction of organic load, enhancement of oxygenation, and targeted monitoring of resistance indicators to mitigate environmental and public health risks.