Characterization of the variable region in the class 1 integron of antimicrobial-resistant Escherichia coli isolated from surface water

Abstract Fecal bacteria are considered to be a potential reservoir of antimicrobial resistance genes in the aquatic environment and could horizontally transfer these genes to autochthonous bacteria when carried on transferable and/or mobile genetic elements. Such circulation of resistance genes constitutes a latent public health hazard. The aim of this study was to characterize the variable region of the class 1 integron and relate its genetic content to resistance patterns observed in antimicrobial-resistant Escherichia coli isolated from the surface waters of Patos Lagoon, Southern Brazil. Genetic diversity of the isolates and presence of the qacEΔ1 gene, which confers resistance to quaternary ammonium compounds, were also investigated. A total of 27 isolates were analyzed. The variable region harbored dfrA17, dfrA1 and dfrA12 genes, which confer resistance to trimethoprim, and aadA1, aadA5 and aadA22 genes that encode resistance to streptomycin/spectinomycin. Most of the isolates were considered resistant to quaternary ammonium compounds and all of them carried the qacE Δ1 gene at the 3′ conserved segment of the integron. ERIC-PCR analyses of E. coli isolates that presented the integrons showed great genetic diversity, indicating diverse sources of contamination in this environment. These results suggest that fecal bacteria with class 1 integrons in aquatic environments are potentially important reservoirs of antibiotic-resistance genes and may transfer these elements to other bacteria that are capable of infecting humans.

Characterization of enterocins produced by Enterococcus mundtii isolated from humans feces

The aim of this study was to characterize bacteriocins produced by 70 strains of Enterococcus mundtii.Four strains exhibited antibiotic activity towards Listeria innocua, L. monocytogenes, Lactobacillus plantarum, and Salmonella Enteritidis. They remained active under temperatures of up to 121°C for 20 min, and under pH treatments that varied from 2.0 to 10.0. Antimicrobial activity was maintained during the storage test for 60 days under freezing. The kinetics of production revealed the peak activity of 1600 AU /mL during the logarithmic growth phase and the molecular weight found was approximately 3.0 kDa. The characterization of the products with antimicrobial activity indicated their proteic nature, presenting a typical kinetics of primary metabolite and a molecular weight similar to many purified enterocins.

O objetivo do presente estudo foi caracterizar bacteriocinas produzidas por 70 cepas de Enterococcus mundtii. Estas foram caracterizadas quanto a sua atividade antimicrobiana, sensibilidade ao aquecimento, pH, armazenamento e enzimas proteolíticas. Foi também determinada sua cinética de produção e peso molecular. Entre as 70 cepas analisadas, quatro apresentaram atividade antibiótica contra Listeria innocua, L. monocytogenes, Lactobacillus plantarum, e Salmonella Enteritidis. Esta atividade foi mantida em temperaturas até 121°C por 20 minutos, e sob condições de pH entre 2,0 e 10,0. A atividade antimicrobiana foi mantida nos testes de armazenamento a -20°C, por 60 dias. A cinética de produção revelou picos de atividade de 1600 AU/mL durante a fase logarítmica de crescimento e o peso molecular foi de aproximadamente 3,0 kDa. A caracterização dos produtos com atividade antimicrobiana revelaram suas naturezas protéicas, cinéticas de metabólito primário e peso molecular semelhante aos das enterocinas já purificadas.