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.

Contaminación fecal del agua superficial de la microcuenca del río Purires, Costa Rica, 2010-2011 / Fecal contamination of the superficial water of the microbasin of Rio Purires, Costa Rica, 2010-2011

La contaminación fecal de las aguas superficiales es un problema importante para la salud pública, dada la transmisión de microorganismos patógenos. Se estima que las poblaciones ubicadas cerca de costas, ríos o lagos con elevada contaminación fecal, tienen mayor riesgo de desarrollar enfermedades infecciosas gastrointestinales. En esta investigación se analizó durante un año, la contaminación fecal en las aguas superficiales de la microcuenca del río Purires, ubicada en una zona de alta densidad poblacional en Costa Rica. En el 100% de las muestras se detectó contaminación fecal, siendo el punto de muestreo 3 el que mostró los niveles más altos, en promedio 2,2 x 10(4) Número Más Probable(NMP)/100()mL. Aunque los puntos 1 y 2 presentaron menor contaminación fecal, en promedio 6,4 x 10² NMP/100 mL y 6,3 x 10³ NMP/100 mL respectivamente, estos valores indican también mala calidad de las aguas. Con estos resultados se pretende llamar la atención sobre la problemática ambiental de alta contaminación fecal en las aguas superficiales de esta microcuenca. Esta información es un insumo para desarrollar acciones de control sobre las fuentes de contaminación que afectan la calidad de las aguas y por ende, la salud de las poblaciones ubicadas en su cercanía.

Fecal contamination of the superficial waters is an important public health problem due to the presence of pathogenic microorganisms- It has been estimated that populations located close to coasts, rivers of lakes with an elevated fecal contamination have a higher risk of developing communicable gastrointestinal diseases. This investigation analyzed the fecal contamination of the superficial waters of the microbasin of the Rio Purires, located in a highly populated area of Costa Rica. Fecal contamination was detected in 100% of the samples, and sample point 3 was the one that showed the highest levels, with an average of 2.2 x 10(4) Most Probable Number (MPN)/100mL. Even thought points 1 and 2 presented a lower fecal contamination, an average of 6.4 x 10² MPN/100mL and 6.3 x 10³ MPN/100mL, respectively, these values also indicate low quality water. With these results we intend to alert regarding the problem of a high fecal contamination of superficial waters of this microbasin. This information is an input for developing control actions over the contamination sources which compromise the quality of water and, therefore, the health of the populations located in its vicinity.