Caracterização gênica de linhagens de Escherichia coli isoladas da água do Rio Cuiabá, Mato Grosso

Abstract

Population growth and unplanned urbanization process have impacted water bodies with pollutant loads which can incorporate an enormous amount of disease agents. In the Upper Paraguay River Basin is the Cuiabá River, which is one of its most important affluent and is in deteriorating situation in water quality, with social, environmental, and economic implications, especially on public health. Escherichia coli is an indicator of faecal contamination in water bodies and this work aimed to identify the genetic diversity of E. coli in the water of Cuiabá River between the cities of Cuiabá and Várzea Grande in the State of Mato Grosso. Three sampling were performed in dry season and three sampling during the rainy season. Water samples were collected left bank (1/6 - point P1), main channel (1/2 - point P2) and right bank (5/6 - point P3) of the total width of the river. 299 E. coli strains were isolated by positive chromogenic and fluorogenic culture substrate (Colilert®), grown in nutrient broth and frozen at -20 ° C. Later, 84.6% of the strains were activated in TSB for DNA extraction and amplification using the PCR technique. Data were analyzed by average connection method unweighted grouping in pairs and genetic distances were calculated using arithmetic complement of the Jaccard similarity coefficient. The number of E. coli in water samples collected during the dry season was lower than the density found during the rainy season. The greater density can be attributed in part to runoff due rain events which carry a high number of bacteria to from several sources to the river. The amplification products of PCR of E. coli isolated from water samples on the left bank (P1) of the Cuiabá River showed 97.22% of similar strains having less genetic diversity with 30.61% when comparing the three sampling points. Possibly contamination of this margin is related to domestic effluents corroborating the high bacterial similarity. The PCR amplification products for E. coli isolates from the right bank (P3) generated 98.21% of similar strains and, among the three sampling points, this margin showed higher genetic diversity (36.73%). This greater diversity may be related to affluent receivers of contaminants, as well as agricultural activities, pigs and cattle breeding and pigs, existing upstream of the sampling point in Rio Cuiabá. The main channel of the Cuiaba River in the sampling point P2 had a median value of genetic diversity (32.65%) compared to banks. Even with a high genetic similarity (97.23%) among the 253 bacterial strains activated from the Cuiabá River there was a variety of dissimilar strains, suggesting are possible E. coli virulence genes or even pathogenic E. coli. Thus establishing a potential increase in the risk to the health of population if the efficiencies treatment and launch control domestic sewage, industrial and even diffuse pollution, do not have adequate and ongoing management.