Molecular and Phenotypic Characterization of Escherichia coli O26:H8 among Diarrheagenic E. coli O26 Strains Isolated in Brazil

Abstract

f Escherichia coli strains of serogroup O26 comprise two distinct groups of pathogens, characterized as enteropathogenic E. coli (EPEC) and enterohemorrhagic E. coli (EHEC). Among the several genes related to type III secretion system-secreted effector proteins, espK was found to be highly specific for EHEC O26:H11 and its stx-negative derivative strains isolated in European countries. E. coli O26 strains isolated in Brazil from infant diarrhea, foods, and the environment have consistently been shown to lack stx genes and are thus considered atypical EPEC. However, no further information related to their genetic background is known. Therefore, in this study, we aimed to discriminate and characterize these Brazilian O26 stx-negative strains by phenotypic, genetic, and biochemical approaches. Among 44 isolates confirmed to be O26 isolates, most displayed flagellar antigen H11 or H32. Out of the 13 nonmotile isolates, 2 tested positive for fliC H11 , and 11 were fliC H8 positive. The identification of genetic markers showed that several O26:H11 and all O26:H8 strains tested positive for espK and could therefore be discriminated as EHEC derivatives. The presence of H8 among EHEC O26 and its stx-negative derivative isolates is described for the first time. The interaction of three isolates with polarized Caco-2 cells and with intestinal biopsy specimen fragments ex vivo confirmed the ability of the O26 strains analyzed to cause attaching-and-effacing (A/E) lesions. The O26:H32 strains, isolated mostly from meat, were considered nonvirulent. Knowledge of the virulence content of stx-negative O26 isolates within the same serotype helped to avoid misclassification of isolates, which certainly has important implications for public health surveillance.

Flagellin and GroEL mediates in vitro binding of an atypical enteropathogenic Escherichia coli to cellular fibronectin

“…Atypical EPEC (aEPEC) strains BA2103 (serotype O26:H11) and 2271-1/85 (serotype O26:HNM, where NM indicates nonmotile) were previously characterized by the eae +/EAF-/ bfpA - genetic profile, lack of production of BFP and production of the localized adherence-like (LAL) pattern on HEp-2 cells [ 5 , 6 , 39 ]. Molecular typing of fliC defined the H type of 2271-1/85 strain as H11 [ 39 ]. Binding ability to ECM of supernatant proteins from BA2103 was described elsewhere [ 7 ].…”

“…A non-pathogenic K12 E. coli DH5α was included as a control strain [ 40 ]. Also, twenty O26:H11 aEPEC strains were employed in the fibronectin binding screening [ 5 , 39 ]. This study does not involve humans, human data or animals, since all strains employed herein belong to the Bacteriology Laboratory bacterial collection of Butantan Institute, São Paulo, SP, Brazil.…”

Genetic Diversity and Pathogenic Potential of Attaching and Effacing Escherichia coli O26:H11 Strains Recovered from Bovine Feces in the United States

“…The aim of this work was to investigate the distribution of E. coli O26 genotypes within bovine feces and identify the pathogenic potential of Shiga toxin-negative and eae-positive strains that belong to the AEEC pathogroup. Recent findings in Brazil of E. coli O26 containing the H8 antigen belonging to EHEC and stx-negative strains led to the inclusion of this antigen in this study (45). Furthermore, antigen H11 and nonpathogenic antigen H32, commonly isolated in food products, were also tested (18,(45)(46)(47).…”

“…Recent findings in Brazil of E. coli O26 containing the H8 antigen belonging to EHEC and stx-negative strains led to the inclusion of this antigen in this study (45). Furthermore, antigen H11 and nonpathogenic antigen H32, commonly isolated in food products, were also tested (18,(45)(46)(47). Investigation of the H antigen revealed that all strains were positive for fliC H11 .…”

Papel da proteína EspFU em <i>Escherichia coli</i> enteropatogênica atípica.

“…Cepas de aEPEC podem apresentar um repertório de virulência bastante heterogêneo, especialmente devido à plasticidade de seus genomas que permitem a aquisição de genes de virulência derivados de outros patotipos de E. coli diarreiogênicas ou que causam doenças extra-intestinas (ExPEC) (BANDO et al, 2009;HERNANDES et al, 2009). Deste modo, aEPEC pode carregar genes que codificam adesinas fimbriais e afimbriais (AFSET et al, 2006;GOMES et al, 2011;HERNANDES et al, 2011;SCALETSKY et al, 2009), enterotoxinas (DUTTA et al, 2015;HAZEN et al, 2017a;SILVA et al, 2014), hemolisinas (MAGALHÃES et al, 2011MURASE et al, 2012;PIAZZA et al, 2013) e uma série de proteínas autotransportadoras (ABREU et al, 2013;ABREU et al, 2016;RUIZ et al, 2014).…”