Hospital effluents as sources of antibiotics residues, resistant bacteria and heavy metals in Benin

This study aims to evaluate the bacteriological, chemical, and toxicological quality of hospital effluents in Benin. Eighteen (18) samples were collected from the south and north of Benin, and poles were set up. Bacteriological analysis was carried out according to the French National Organization for Standardization (AFNOR) standard. Identification of the bacterial species isolated was performed using the API 20E gallery and specific biochemical tests. Antibiotic residues were searched by following ELISA kit instructions. 109 bacterial isolates were obtained, with a predominance of non-enterobacteria (37.7%) and Acinetobacter spp. (24.6%), followed by Klebsiella spp. (11.48%); S. aureus and Coagulase-negative staphylococci (CoNS) were isolated at the same frequency (6.5%). Physico-chemical and toxicological parameter analyses showed that they were in conformity with the standards of discharge into the environment. The pH, temperature, electrical conductivity, total solids below, P-redox and suspended solids measured were, on average, 6.83, 27.21 °C, 693.68 µS/cm, 693.68 mg/l, 1.68 mV and 0.15 mg/l, respectively. For heavy metals, cadmium was most prevalent (0.22 mg/l), followed by nickel (0.18 mg/l) and lead (0.03 mg/l). The average antibiotic residue concentrations ranged from 0.043 to 7.65 µg/l. Ciprofloxacin, metronidazole and sulfamethoxazole had the highest residue concentrations of 7.65 ± 2.272 µg/l, 6.61 ± 0.051 µg/l and 3.88 ± 3.088 µg/l, respectively. The heavy metal concentrations obtained were below those required by Benin standards. These effluents therefore present health and environmental risks. It is then more than necessary to develop treatment methods for them before their rejection into the natural environment.