Phenotypic characterization and molecular identification of multidrug-resistant bacteria in untreated effluent from a hospital in Brazil

In recent years, Enterobacteriaceae bacteria have become increasingly significant in hospital infections due to their prevalence and high antimicrobial resistance, particularly in carbapenemase-producing strains, which are associated with higher mortality rates. This resistance, driven by carbapenemase production, is a global concern as it facilitates the spread of resistance genes. This study aimed to characterize phenotypically and genetically carbapenemase-producing enterobacteria in untreated hospital effluents. Samples were collected seasonally from 2019, excluding rainy days. Phenotypic analysis identified 30 strains, with five species distributed among eight strains expressing extended-spectrum β-lactamases (ESBLs). Of these, four strains carried the blaKPC resistance gene. Genotypic analysis via PCR confirmed one strain of K. pneumoniae in the fall with ESBL-positive phenotype, while a summer strain of K. pneumoniae showed carbapenem resistance due to the blaKPC gene. Additionally, Enterobacter cloacae in the fall and strains of Klebsiella oxytoca and Escherichia coli in the winter were resistant to carbapenems, all linked to the blaKPC gene. The study revealed that blaKPC is present in various enterobacteria species and may be co-transported with other resistance genes, complicating hospital treatments. These findings highlight the need for understanding the dissemination of multidrug-resistant bacteria and the potential role of untreated hospital sewage as a reservoir of clinically significant pathogens, posing risks to both human and animal health.