SHIGA TOXIN-PRODUCING Escherichia coli ISOLATION AND CHARACTERIZATION IN DRINKING WATER

The drinking water sources, when contaminated with animal feces, may contain pathogenic organisms and its monitoring is relevant to public health. Shiga toxin-producing Escherichia coli (STEC) stands out as an important enteropathogen involved to diarrhea, with the possibility of progressing to hemorrhagic colitis and Uremic Hemolytic Syndrome (UHS), being related to gastroenteritis outbreaks associated with food and waterborne worldwide. In this study, we investigated the prevalence of STEC in untreated water sources to human ingestion from mines and shallow wells in northern of Paraná, Brazil in 2017, as well as its phenotypic and genotypic characteristics. To detection of total coliforms and E. coli was used Colilert® chromogenic substrate, with subsequent biochemical characterization by MacConkey, EPM, MILi and Simmons Citrate media. PCR (Polymerase Chain Reaction) was used to detect STEC (toxins genes stx1, stx2, and eae gene) and characterization in phylogenetic groups A, B1, B2, C, D, E, F. Serotypes were determined by plaque micro-agglutination technique and to phenotypic characterization, biofilm formation tests, cytotoxicity in Vero cell and HEp-2 cell adhesion tests were performed. Among 210 water samples studied, 153 (72.9%) had total coliforms and 96 (45.7%), E. coli. STEC were identified in 13 (6,19%) samples. Among them, 12 (92.3%) presented stx2 gene and one (7.69%) stx1. The eae gene was not detected in any one. In relation to phylogenetic group, eight (61.53%) strains belonged to B1, two (15.38%) to C, two to E (15.38%) and one (7.69%) to B2. The identified serotypes were: O103: H7, O185: H16, O4: H12, O73: H12, O103: H16, O139: H7, O91: H10, O150: H8, O49: H49, O6: H49, O91: H21, O64474:H12, O107: HNT. All 13 STEC strains produced cytotoxic effect on Vero cells and were biofilm forming. In HEp-2 cells, 11 (84.6%) were detected as adherent and two (15.4%) as non-adherent. Among the adherents, nine (82%) presented aggregate adhesion pattern, one (9%) not characterized and one (9%) diffuse adhesion pattern. This study shows relevant evidence to encourage increased monitoring of water to human ingestion once it may be a source of pathogenic microorganisms and preventive measures should be taken to avoid such contamination. The intention of this research is also to contribute to a better understanding of STEC epidemiology.