| Congresso Brasileiro de Microbiologia 2023 | Resumo: 53-1 | ||||
Resumo:Diarrhea remains an important public health problem. One of the main etiological agents of the disease is diarrheagenic Escherichia coli (DEC). The most prevalent DEC pathotypes in Brazil are atypical enteropathogenic E. coli (aEPEC) and enteroaggregative E. coli (EAEC). aEPEC has as its main virulence mechanism the island of chromosomal pathogenicity locus of enterocyte effacement (LEE region), and EAEC harbors the aggregative adherence plasmid (pAA), which plays an important role in adherence and biofilm formation. Recently, our laboratory reported for the first time an outbreak of diarrhea caused by a hybrid isolate of aEPEC/EAEC belonging to serotype O3:H2. In that outbreak, one aEPEC isolate, four EAEC isolates, and three aEPEC/EAEC hybrid E. coli isolates were identified. The objective of the present work is to understand the evolutionary mechanisms of transfer and acquisition of virulence genes, as well as the phylogeny and pathogenic potential of the isolates involved in the outbreak of diarrhea in a comparative genomic scenario, through in silico bioinformatics analyses. Four representative isolates of each pathotype obtained during the outbreak investigation had their complete genome sequenced by short and long reads. The E. coli isolates sequenced were one aEPEC (IAL7254), two EAEC (IAL7250 and IAL7255), and one hybrid aEPEC/EAEC (IAL7252). All sequenced isolates were classified in the O3:H2 in silico serotype, phylogroup A and multilocus sequence type ST8087. The chromosomal pangenome presented 4,723 gene clusters, with 4,157 belonging to the core genome. Among the particularities found in the chromosome of these isolates, we observed that three (aEPEC IAL7254, EAEC IAL7255 and the hybrid aEPEC/EAEC IAL7252) shared 170 gene clusters not presented in the EAEC IAL7250. Among these genes, we can highlight a set of 58 organized in a prophage, harboring genes encoding for important EPEC virulence factors, such as the non-LEE effectors NleB, NleF, and NleH, and an operon with 18 genes encoding for a Type 6 secretion system. On the other hand, the aEPEC IAL7254 and the hybrid aEPEC/EAEC IAL7252 shared a 49.7 kb chromosomal pathogenicity island with a total of 57 genes, where the LEE region (a 35.7 kb region organized in 41 genes) is inserted. Of note, the LEE region belongs to the subtype 8 and is surrounded upstream by a pseudo espS gene and downstream by genes encoding the EspM and NleG non-LEE effectors and 13 genes with high identity to the Sakai prophage-like element (SpLE1). The pAA presented in the EAEC isolates IAL7250 and IAL7255 and in the hybrid IAL7252 exhibited approximately 99.9% of nucleotide sequence identity and harbored important genes associated with the EAEC pathogenesis, such as aatA, aggR, aap, and the operon aggDCBA. Together, our data suggested that all isolates must have emerged from a common ancestral from the O3:H2 serotype that, through several horizontal gene transfer events, allowed the emergence of different pathogenic groups. Moreover, due to the high level of identity found in the chromosome of the aEPEC and the hybrid aEPEC/EAEC, we can suggest that the aEPEC was a receptor for the pAA originating the aEPEC/EAEC hybrid isolate. Palavras-chave: hybrid aEPEC/EAEC, diarrhea, virulence Agência de fomento:São Paulo Research Foundation (FAPESP) | |||||