Characterization of potential new adhesion structures in enteroaggregative Escherichia coli (EAEC)

• Grant number: 24/15514-4
• Support Opportunities: Regular Research Grants
• Start date: November 01, 2025
• End date: October 31, 2028
• Field of knowledge: Biological Sciences - Microbiology - Applied Microbiology
• Principal Investigator: Isabel Cristina Affonso Scaletsky
• Grantee: Isabel Cristina Affonso Scaletsky
• Host Institution: Escola Paulista de Medicina (EPM). Universidade Federal de São Paulo (UNIFESP). Campus São Paulo. São Paulo , SP, Brazil

Abstract

Enteroaggregative Escherichia coli (EAEC) is defined by its characteristic aggregative adherence (AA) pattern to HEp-2 cells. The AA phenotype is mediated by plasmid-encoded aggregative adhesion fimbriae (AAF) and regulated by the pAA plasmid-encoded transcriptional activator AggR. Strains containing the AggR regulon are referred to as typical EAEC, in contrast, atypical EAEC strains lack AggR. In a study performed in our laboratory on clinical isolates of atypical EAEC (aggR-), a Q015B AFP-positive (aggregate-forming pilus) strain was identified that exhibited an AA pattern with bacteria adherent primarily to HeLa cells. Using mutagenesis with the mini-Tn5 transposon in strain Q015B, we identified a 5,517-bp ORF (orfHA) encoding a predicted 1,838-amino acid polypeptide that is genetically related to a putative filamentous hemagglutinin identified in E. coli strain 7-233-03_S3_C2. The Q015B¿orfHA mutant strain did not adhere to HeLa cells and had a marked effect on the ability of strain Q015B to kill Galleria mellonella larvae. In an epidemiological study conducted by the Adolfo Lutz Institute, typical EAEC strains (aggR+) belonging to serotypes ONT:H10, O15:H2 and O80:H10 were detected in symptomatic and asymptomatic children, presenting 100% genetic similarity, indicating clonal transmission. Seven isolates belonging to serotype O15:H2 and that did not present genes related to adhesins AAF/I-V, AFP and CS22 were selected to characterize AA adhesins. Preliminary results obtained in our laboratory indicate the presence of plasmids encoding AA adhesion and antimicrobial resistance in three strains. The objective of this project is to characterize the hemagglutinin of strain Q015B and identify the plasmid genes associated with the AA phenotype of strains O15:H2. (AU)