We investigated the antimicrobial resistance profile and the occurrence of Klebsiella pneumoniae carbapenemase (KPC)-producing Gram-negative rods in sewage samples obtained from a Brazilian teaching hospital and from the wastewater treatment plant (WWTP) that receives it for treatment. We identified multidrug-resistant bacteria as well as KPC-2-producing Aeromonas spp. and several Enterobacteriaceae species, including Kluyvera spp., in the hospital effluent and in different sites of the WWTP. Most isolates showed the blaKPC-2 gene harbored on a transposon that was carried by conjugative plasmids. The presence of KPC production among Aeromonas spp., Kluyvera spp., and other Enterobacteriaceae indicates the adaptability of such isolates to aquatic environments, not only in the hospital effluent but also throughout the WWTP. Although secondary treatment seems to decrease the amount of KPC producers in sewage, multidrug-resistant isolates are continually disposed in the urban river. Thus, sewage treatment regulations are urgently needed to decelerate the evolution of antimicrobial resistance beyond hospitals.
The mechanisms involved in the uncommon resistance phenotype, carbapenem resistance and broad-spectrum cephalosporin susceptibility, were investigated in 25 Pseudomonas aeruginosa clinical isolates that exhibited this phenotype, which were recovered from three different hospitals located in São Paulo, Brazil. The antimicrobial susceptibility profile was determined by CLSI broth microdilution. β-lactamase-encoding genes were investigated by PCR followed by DNA sequencing. Carbapenem hydrolysis activity was investigated by spectrophotometer and MALDI-TOF assays. The mRNA transcription level of oprD was assessed by qRT-PCR and the outer membrane proteins profile was evaluated by SDS-PAGE. Genetic relationship among P. aeruginosa isolates was assessed by PFGE. Carbapenems hydrolysis was not detected by carbapenemase assay in the carbapenem-resistant and cephalosporin-susceptible P. aueruginosa clinical isolates. OprD decreased expression was observed in all P. aeruginosa isolates by qRT-PCR. The outer membrane protein profile by SDS-PAGE suggested a change in the expression of the 46kDa porin that could correspond to OprD porin. The isolates were clustered into 17 genotypes without predominance of a specific PFGE pattern. These results emphasize the involvement of multiple chromosomal mechanisms in carbapenem-resistance among clinical isolates of P. aeruginosa, alert for adaptation of P. aeruginosa clinical isolates under antimicrobial selective pressure and make aware of the emergence of an uncommon phenotype among P. aeruginosa clinical isolates.
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