Determinação dos principais patótipos de <i>Escherichia coli</i> isoladas de pacientes com câncer de reto.

Abstract

In Brazil, colon and rectal cancer are increasing and they are considered the gastrointestinal neoplasia most commonly observed in the population. In recent years, national and international literatures have shown a possible correlationship among the presence of microorganisms with the development of cancer; however, no convincing scientific evidence of this interaction has been observed. This study aimed to determine the presence and participation of different pathotypes of Escherichia coli isolated from patients with or without rectal cancer. Fecal samples were collected from patients with rectal cancer and healthy individuals with no signs of cancer (polyps and/or tumor) used as a control. Feces were plated onto agar MacConkey and four strains were randomly selected from each sample. Conventional PCR was used for identification of E. coli and pathotypes, as well as to detect virulence genes in extra-intestinal strains. The molecular characterization of E. coli was performed by ERIC-PCR. Patients with rectal cancer were mean age of 63 years old (P < 0.001). Diarrheogenic E. coli (DEC, 59 strains, 49.17%) were more prevalent than extra-intestinal E. coli (ExPEC, 53 strains, 44.17%). The presence of tEAEC was observed in 44.1% of the DEC strains (59 strains) isolated from patients with rectal cancer and in 12.9% of the DEC strains isolated from the healthy patients (31 strains) (P = 0.003). Atypical enteropathogenic E. coli (aEPEC) strains were isolated in both patient groups (cancer: 22 strains, 37.3%; healthy: 15 strains, 48.4%). The gene afa/dra for adhesin Afa/Dr was observed in higher prevalence in the ExPEC strains (35 strains, 66.0%) isolated from patients with rectal cancer (P < 0.001). E. coli strains showed genetic combinations from 2 to 8 genes, showed 39 and 24 genetic combinations in strains from cancer and healthy patients, respectively. All strains showed high genetic diversity by ERIC-PCR, and some clusters grouped clone strains isolated from the same patient. It was observed presence of eight filogroups and B2 filogroup (55.2%) was the most prevalent. Filogroups D and E were absent in strains from healthy. The results suggest further studies to determine the role of DEC, particularly aEPEC, tEAEC, and ExPEC, individually or in combination, and the synergism and co-infection of different pathotypes in these processes, as well as its presence in the intestinal microbiota in asymptomatic patients with rectal cancer.