Pandemic ST131 Escherichia coli presenting the UPEC/EAEC and ExPEC/EAEC hybrid pathotypes recovered from extraintestinal infections in a clinical setting of the Brazilian Amazon region.

Background: Escherichia coli is a commensal organism but may become pathogenic by the acquisition of virulence factors involved with intestinal (IPEC) or extraintestinal (ExPEC) infections. Some strains, known as hybrids, may harbour virulence determinants of both IPEC and ExPEC pathotypes, increasing their virulence potential. Reports of hybrid E. coli in Brazil are rare, and the associated lineages were poorly explored.

Objectives: This study characterised ExPEC E. coli strains focusing on the occurrence of hybrid pathotypes.

Methods: Fifteen clinical ExPEC strains were submitted to multilocus sequence typing (MLST), susceptibility test, and polymerase chain reaction (PCR) targeting IEC/ExPEC virulence markers.

Findings: All strains were multidrug-resistant, and 11 STs were determined among the 15 ExPEC strains, including local/new and pandemic lineages, such as ST69 and ST131. Twelve/15 isolates were classified as hybrids, due to the presence of virulence markers of both Enteroaggregative E. coli (EAEC) and ExPEC or UPEC pathotypes. These UPEC/EAEC (n = 10) and ExPEC/EAEC (n = 2) hybrid strains were found among distinct phylogroups and lineages, including new STs. Interestingly, most hybrids belonged to the pandemic ST131 lineage, and this genotype had never been previously reported in the ST131 circulating in Brazil.

Main conclusions: Therefore, this study provides new information on the epidemiological scenario of hybrid E. coli, contributing to a better understanding of the occurrence and pathogenic potential of these organisms.