Abstract
Diarrheagenic Escherichia coli is the major bacterial etiological agent of severe diarrhea and a major concern of public health. These pathogens have acquired genetic characteristics from other pathotypes, leading to unusual and singular genetic combinations, known as hybrid strains and may be more virulent due to a set of virulence factors from more than one pathotype. One of the possible combinations is with extraintestinal E. coli (ExPEC), a leading cause of urinary tract infection, often lethal after entering the bloodstream and atypical enteropathogenic E. coli (aEPEC), responsible for death of thousands of people every year, mainly children under five years old. Here we report the draft genome of a strain originally classified as aEPEC (BA1250) isolated from feces of a child with acute diarrhea. Phylogenetic analysis indicates that BA1250 genome content is genetically closer to E. coli strains that cause extraintestinal infections, other than intestinal infections. A deeper analysis showed that in fact this is a hybrid strain, due to the presence of a set of genes typically characteristic of ExPEC. These genomic findings expand our knowledge about aEPEC heterogeneity allowing further studies concerning E. coli pathogenicity and may be a source for future comparative studies, virulence characteristics, and evolutionary biology.
Highlights
Diarrhea is the second leading cause of death in children under five years of age, leading approximately 525,000 children to death annually
We report the sequencing, assembly, and annotation of the genome of a strain previously classified as atypical enteropathogenic E. coli (aEPEC), BA1250 [17], according to this pathotype genetic markers, as the presence of genes that comprise the pathogenicity island called Locus of enterocyte effacement (LEE) [32]
These results indicate that, it has its particularities, the assembled genome is similar to a reference genome, which suggests that the sequencing and the assembly step could generate material with a good representation of the genomic content of the BA1250 strain
Summary
Diarrhea is the second leading cause of death in children under five years of age, leading approximately 525,000 children to death annually. Despite the presence of specific virulence factors in each pathogroup, E. coli has great genomic plasticity, which has led to the identification of isolates with a combination of virulence characteristics from different pathotypes These isolates are considered potentially more virulent and are called hybrid pathogenic strains [4,7], as the strain responsible for a large diarrhea outbreak in Germany in 2011 [8,9,10]. Phylogenetic analysis showed a more recent relationship among BA1250 with E. coli strains responsible for urinary infection than with other aEPEC strains This strain genome presents a set of genes characteristic of ExPEC, which allows its classification as a hybrid strain. The genome of BA1250 aEPEC/ExPEC strain will be useful for comparative studies as a genomic reference to allow analyses of singular virulence factors and for studies of molecular and evolutionary biology
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