Characterization of virulence factors and phylogenetic group determination of Escherichia coli isolated from diarrheic and non-diarrheic calves from Brazil

Abstract

This study aimed to detect virulence factors, pathovars, and phylogenetic groups of Escherichia coli strains obtained from feces of calves with and without diarrhea up to 70 days old and to determine the association between occurrence of diarrhea, phylogenetic groups, and pathovars. Phylo-typing analysis of the 336 E. coli strains isolated from calves with Clermont method showed that 21 (6.25 %) belong to phylogroup A, 228 (67.85 %) to phylogroup B1, 2 (0.6 %) to phylogroup B2, 5 (1.49 %) to phylogroup C, 57 (16.96 %) to phylogroup E, and 3 (0.9 %) to phylogroup F. Phylogroup D was not identified and 20 strains (5.95 %) were assigned as "unknown." The distribution of phylogenetic groups among pathovars showed that NTEC belong to phylogroups B1 (17) and C (4); EPEC to phylogroups B1 (6) and E (8); STEC to phylogroups A (5), B1 (56), B2 (2), C (1), and E (15); EHEC to phylogroups B1 (95) and E (5); and ETEC to phylogroups A (3), B1 (7), and E (10). The EAST-1 strains were phylogroups A (13), B1 (47), E (19), and F (3); E. coli strains of "unknown" phylogroups belonged to pathovars EPEC (1), EHEC (2), STEC (7), and EAST-1 strains (6). ETEC was associated with diarrhea (P = 0.002). Our study did not find association between the phylogenetic background and occurrence of diarrhea (P = 0.164) but did find some relationship in phylogenetic group and pathovar. The study showed that EHEC and STEC are classified as phylogroup B1, EAST-1 phylogroup A, ETEC, and EPEC phylogroup E.

Caution at choosing a particular colony-forming unit from faecal Escherichia coli: it may not represent the sample profile

“…Overall, 65% (126/195) CFUs analysed belonged to commensal phylo-group B1, corresponding to the animals' healthy status. As in the world literature (Son et al, 2009;Tenaillon et al, 2010;Bessalah et al, 2016;Coura et al, 2017;Souto et al, 2017) we also found the predominance of B1 phylo-group (40/65 CFUs; 61Á5%) in calves, followed by E (13/65; 20%). Similarly, B1 (33/65 CFUs; 50Á8%) predominated in foals, followed by E (14/65 CFUs; 21Á5%) and C (10/65 CFUs; 15Á4%), being a profile previously reported in healthy horses (Smati et al, 2015).…”

Distribution of the stx1 and stx2 genes in Escherichia coli isolated from milk cattle according to season, age, and production scale in southwestern region of Goiás, Brazil

“…Similar data were obtained in the study carried from Minas Gerais state, Brazil. Coura et al (2017) demonstrated that STEC and EHEC isolates from healthy and diarrheic calf feces belonged mainly to phylogenetic groups B1 and A.…”

Shiga toxin‐producingEscherichia coliin the animal reservoir and food in Brazil

“…The association of eae‐ positive STEC with animal disease was reported by some authors (Martins et al ; Leomil et al ; Salvadori et al ), whereas many others described similar frequencies both in diarrheic and non‐diarrheic animals (Aidar‐Ugrinovich et al ; Timm et al ; Coura et al ), reinforcing that only some strains are able to cause disease.…”

“…STEC strains are frequently ehxA‐ positive, with frequencies varying from around 35% to as high as 90%, and it is generally similar among strains isolated from either diarrheic or healthy animals and from eae ‐positive or ‐negative STEC strains (Leomil et al ; Salvadori et al ; Vetoratto et al ; Joaquim et al ; Irino et al ; Aidar‐Ugrinovitch et al ; Farah et al ; Oliveira et al ; Pigatto et al ; Beraldo et al ; Maluta et al ; Martins et al ; Gonzalez et al ). However, Coura et al () detected this gene only among eae ‐positive strains isolated from calves, both diarrheic and healthy ones. However, some studies described lower frequencies or even the absence of this gene (Moura et al ; Ferreira et al ; Coura et al ).…”

“…The toxB and efa1 genes are usually encoded by eae‐ positive STEC strains, and also by some aEPEC strains; their presence in eae‐ negative STEC strains is usually rare (Oliveira et al ; Feng et al ; Maluta et al ; Gomes et al ; Coura et al ). The iha and lpf chromosomal genes are usually found in STEC strains.…”