Abstract
Enteroaggregative Escherichia coli (EAEC) is an important agent of acute and persistent diarrhea in children and adults worldwide. Here we report a characterization of 220 EAEC isolates, 88.2% (194/220) of which were typical and 11.8% (26/220) were atypical, obtained from diarrheal patients during seven years (2010-2016) of epidemiological surveillance in Brazil. The majority of the isolates were assigned to phylogroups A (44.1%, 97/220) or B1 (21.4%, 47/220). The aggregative adherence (AA) pattern was detected in 92.7% (204/220) of the isolates, with six of them exhibiting AA concomitantly with a chain-like adherence pattern; and agg5A and agg4A were the most common adhesin-encoding genes, which were equally detected in 14.5% (32/220) of the isolates. Each of 12 virulence factor-encoding genes (agg4A, agg5A, pic, aap, aaiA, aaiC, aaiG, orf3, aar, air, capU, and shf) were statistically associated with typical EAEC (P < 0.05). The genes encoding the newly described aggregate-forming pili (AFP) searched (afpB, afpD, afpP, and afpA2), and/or its regulator (afpR), were exclusively detected in atypical EAEC (57.7%, 15/26), and showed a significant association with this subgroup of EAEC (P < 0.001). In conclusion, we presented an extensive characterization of the EAEC circulating in the Brazilian settings and identified the afp genes as putative markers for increasing the efficiency of atypical EAEC diagnosis.
Highlights
Enteroaggregative Escherichia coli (EAEC) is one of the six diarrheagenic E. coli (DEC) pathotypes, which is defined as E. coli isolates that produce the aggregative adherence pattern (AA) on cultured epithelial cells (HeLa and/or HEp-2) in vitro (Nataro and Kaper, 1998; Kaper et al, 2004; Croxen et al, 2013)
In the 17 remaining EAEC isolates, obtained during the year of 2010, the O and H antigens were determined by standard agglutination tests, with O (O1–O181) and H (H1–H56) antisera produced at Instituto Adolfo Lutz, São Paulo, Brazil (Ewing, 1986)
The majority of the diarrheal patients, from which the EAEC isolates were obtained, were children up to five-years-old (62.7%, 138/220) and from the São Paulo State (66.8%, 147/220), besides EAEC isolates that were obtained from other Brazilian States, such as Minas Gerais (18.6%, 41/220) and Santa Catarina (14.5%, 32/220) (Table S2)
Summary
Enteroaggregative Escherichia coli (EAEC) is one of the six diarrheagenic E. coli (DEC) pathotypes, which is defined as E. coli isolates that produce the aggregative adherence pattern (AA) on cultured epithelial cells (HeLa and/or HEp-2) in vitro (Nataro and Kaper, 1998; Kaper et al, 2004; Croxen et al, 2013). A type IV pilus, termed aggregate-forming pili (AFP), encoded by genes located in the afp operon, was identified to be responsible for the establishment of the AA pattern by a hybrid EAEC/STEC (Shiga-toxin producing E. coli) isolate of serotype O23:H8, that lacks the AAFs described so far (Lang et al, 2018)
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