Multidrug-resistant Enterobacter spp. in wastewater and surface water: Molecular characterization of & beta;-lactam resistance and metal tolerance genes

Among the ESKAPE group pathogens, Enterobacter spp. is an opportunistic Gram-negative bacillus, widely dispersed in the environment, that causes infections. In the present study, samples of hospital wastewater, raw and treated urban wastewater, as well as surface receiving water, were collected to assess the occurrence of multidrug-resistant (MDR) Enterobacter spp. A molecular characterization of & beta;-lactam antibiotic resistance and metal tolerance genes was performed. According to identification by MALDI-TOF MS, 14 isolates were obtained: 7 E. bugandensis, 5 E. kobei, and 2 E. cloacae. The isolates showed resistance mainly to & beta;-lactam antibiotics, including those used to treat infections caused by MDR bacteria. Multiple antibiotic resistance index was calculated for all isolates. It allowed verify whether sampling points showed a high risk due to antibiotic resistant Enterobacter spp., as well as to determine if the isolates have been in environments with a frequent antibiotic use. Twelve isolates showed & beta;-lactam antibiotic resistance gene, being the blaKPC widely detected. Regarding metal tolerance, 13 isolates showed at least two genes that encode metal tolerance mechanisms. Overall, metal tolerance mechanisms to silver, copper, mercury, arsenic and tellurium were found. New data on metal tolerance mechanisms dispersion and antibiotic-resistance characterization of the E. bugandensis and E. kobei species were here provided. The occurrence of MDR Enterobacter spp. in analyzed samples draws attention to an urgent need to put control measures into practice. It also evidences waterborne spread of clinically important antibioticresistant bacteria recognized as critical priority pathogens.

Automated summary

In this study, the occurrence of multidrug-resistant Enterobacter spp. in different water sources was investigated. The isolates showed resistance mainly to β-lactam antibiotics and harbored β-lactam antibiotic resistance genes, with blaKPC being widely detected. Metal tolerance genes were also found in the isolates. These findings highlight the urgent need for control measures to prevent the spread of antibiotic-resistant Enterobacter spp. and emphasize the waterborne transmission of clinically important antibiotic-resistant bacteria.