Identification of Listeria spp. with Antibiotic Resistance in Wastewater from Hospitals in Libreville, Gabon

This study focuses on the use of Gram staining in the identification of Listeria monocytogenes in hospital wastewater in Libreville. The study aims to highlight the presence of this bacterium, which can cause illness and mortality in these wastewater systems. The study was conducted on 27 samples, of which 14 were identified as green colonies and 13 as white colonies after culture and isolation. Gram staining revealed that these were Gram-positive bacteria, with respective prevalence rates of 51.85% and 48.15%. Phenotypic identification of these colonies confirmed that they were Listeria monocytogenes. Antibiotic susceptibility testing showed that these bacteria exhibited an overall resistance rate of 36.4% (59/162) and an overall sensitivity rate of 63.6% (103/162) to the tested antibiotics. Resistance to amoxicillin was the highest at 63.6% (103/162), followed by cefotaxime (37%, 10/27), gentamicin (29.6%, 8/27), kanamycin (25.9%, 7/27), ofloxacin (14.8%, 4/27), and tetracycline (11.11%, 3/27). These results demonstrate that this bacterium, widespread in our environment, requires particular attention due to the risk of epidemics associated with multidrug-resistant Listeria monocytogenes. Hospital wastewater could be a source of human listeriosis resistant to antibiotics. This poses a significant risk to human health, as hospital wastewater can infiltrate the soil and contaminate groundwater. Additionally, it may pollute nearby effluents, thereby exposing human and animal populations that use these waters to potential contamination.