Citrobacter spp. and Enterobacter spp. as reservoirs of carbapenemase blaNDM and blaKPC resistance genes in hospital wastewater.

Antibiotic resistance has emerged as a global threat to public health, generating a growing interest in investigating the presence of antibiotic-resistant bacteria in environments influenced by anthropogenic activities. Wastewater treatment plants in hospital serve as significant reservoirs of antimicrobial-resistant bacteria, where a favorable environment is established, promoting the proliferation and transfer of resistance genes among different bacterial species. In our study, we isolated a total of 243 strains from 5 hospital wastewater sites in Mexico, belonging to 21 distinct Gram-negative bacterial species. The presence of ß-lactamase was detected in 46.9% (114/243) of the isolates, which belonging to the Enterobacteriaceae family. We identified a total of 169 ß-lactamase genes; blaTEM in 33.1%, blaCTX-M in 25.4%, blaKPC in 25.4%, blaNDM 8.8%, blaSHV in 5.3%, and blaOXA-48 in 1.1% distributed in 12 different bacteria species. Among the 114 of the isolates, 50.8% were found to harbor at least one carbapenemase and were discharged into the environment. The carbapenemase blaKPC was found in six Citrobacter spp. and E. coli, while blaNDM was detected in two distinct Enterobacter spp. and E. coli. Notably, blaNDM-1 was identified in a 110 Kb IncFII conjugative plasmid in E. cloacae, E. xiangfangensis, and E. coli within the same hospital wastewater. In conclusion, hospital wastewater showed the presence of Enterobacteriaceae carrying a high frequency of carbapenemase blaKPC and blaNDM. We propose that hospital wastewater serves as reservoirs for resistance mechanism within bacterial communities and creates an optimal environment for the exchange of this resistance mechanism among different bacterial strains. IMPORTANCE: The significance of this study lies in its findings regarding the prevalence and diversity of antibiotic-resistant bacteria and genes identified in hospital wastewater in Mexico. The research underscores the urgent need for enhanced surveillance and prevention strategies to tackle the escalating challenge of antibiotic resistance, particularly evident through the elevated frequencies of carbapenemase genes such as blaKPC and blaNDM within the Enterobacteriaceae family. Moreover, the identification of these resistance genes on conjugative plasmids highlights the potential for widespread transmission via horizontal gene transfer. Understanding the mechanisms of antibiotic resistance in hospital wastewater is crucial for developing targeted interventions aimed at reducing transmission, thereby safeguarding public health and preserving the efficacy of antimicrobial therapies.

Molecular and genome characterization of colistin-resistant Escherichia coli isolates from wild sea lions (Zalophus californianus).

Using molecular and whole-genome sequencing tools, we investigated colistin-resistant Escherichia coli isolates from wild sea lions. Two unrelated E. coli colistin-resistant isolates, ST8259 and ST4218, were identified, both belonging to the B2 phylogroup and different serotypes. Polymorphisms in PmrA, PmrB, and PhoQ proteins were identified, and the role of PmrB and PhoQ in contributing to colistin resistance was determined by complementation assays. However, the mutations characterized in the present study are not involved in colistin resistance, which have been described in E. coli isolates from clinical settings. Therefore, the acquired mutations in pmrB and phoQ genes in resistance to colistin in bacteria related to marine environment animals are different. This work contributes to the surveillance and characterization of colistin resistance in Escherichia coli obtained from animals from aquatic environments.