Susceptibility of some Enterobacteriaceae isolated from 4 different aquatic environments in DR Congo (Central Africa), to Amoxicillin/Clavulanic acid and some 3rd generation Cephalosporins

Abstract

Little is known about the variation of the antibiotic susceptibility of different bacterial strains of the same cells species, isolated from different aquatic environments. The present study aims to evaluate the susceptibility towards some 3rd generation cephalosporins (Ceftriaxon, Ceftazidim and Cefotaxim) and Amoxicillin/Clavulanic acid, of Enterobacteriaceae strains isolated from groundwater, stream, hospital wastewater and slaughterhouse wastewater. Enterobacteria species were isolated on Mac Conkey agar, then identified using enzymatic and MALDI-TOF MS system. The antimicrobial susceptibility was carried out using the disk diffusion method. The antibiotic minimum inhibitory concentrations (MICs) were carried using the VITEK®2 system. Bacterial species mostly identified were Klebsiella pneumoniae, Escherichia coli, Salmonella typhi and Ewingelia americana. The antibiotic inhibition diameters and the MICs varied depending on the antibiotics, bacterial species and type of aquatic environment hosting the microorganism. Relatively lower MICs were recorded with Cefotaxim against different bacteria in slaughterhouse wastewater, in river water and in well water. Antibiotic resistance was noted with all strains from hospital wastewater. Significant differences (P˂0.05) amongst antibiotic inhibition diameter was noted for K. pneumoniae and S. typhi in most cases. The relative variations in the action mechanisms amongst antibiotics and the intrinsic defense potential of each bacterial strain, as well as the potential influence of the physicochemical properties of each water medium, could partly be at the origin of the relative differences observed at the phenotypic level. It seems necessary to explore the diversity, similarities and differences amongst antibiotic resistance genes in these different types of aquatic biotopes.