Relative abundance and diversity of extended-spectrum beta-lactamase-producing Enterobacteria in some aquatic environments in an urbanized area in DR Congo

ESBL-producing enterobacteria have a significant impact on public health as they provide antibiotic resistance. Little is known about the relative diversity in various types of biotopes in the same geographical area. This study aimed to determine their diversity and abundance in 3 different aquatic environments. Samples from wells, river water, and hospital wastewater were analyzed. ESBL-producing enterobacteria isolated were identified using double-disk synergy test method based on enzymatic tests. Results showed that the abundance of total enterobacteria in log (CFU/100 µL) varied from 0.60 to 2.10 in wells, from 0.79 to 5.73 in rivers, and from 1.58 to 6.52 in hospital wastewater. That of ESBL-producing enterobacteria reached 6.23 in hospital wastewater, 3.08 in river samples and 2.04 in wells. Their relative abundances compared to all of the isolated enterobacteria varied from 0.34 to 4.55% in wells, from 0 to 97.5% in rivers and from 0.73 to 61.29% in hospital wastewater. Their abundances and diversity varied significantly between hospital wastewater and the 2 other types of samples analyzed (P<0.05). ESBL-producing enterobacteria identified included Escherichia coli, Ewingelia americana, Erwina spp, Citrobacter freundii, Edwarsiella spp, Klebsiella ozaenae, Shigella spp, Enterobacter aerogenes, E. agglomerans, Citrobacter diviersys, Proteus mirabilis, Serratia fonticola, Serratia ficana, Moellerella wisconsensis, Klebsiella rhinoscleromatis and Providencia rettgeri. Among these, 12 were identified in hospital wastewater, 6 in river water and 4 in wells. The Shannon and Weaver diversity index showed an uneven distribution of ESBL-producing enterobacteria species and the dominance of a few species. Most species in wells and rivers were identified in hospital wastewater.