Abstract
Enteroaggregative Escherichia coli (EAEC) is an emerging pathotype responsible for acute and persistent diarrhea. It can be classified as typical and atypical strains, respectively, based on the presence or absence of the AggR regulon, suggesting a higher virulence for typical EAEC. This study aims to evaluate in the Galleria mellonella model if there are differences in the virulence profiles among clinical strains of typical and atypical EAEC, prototype strains EAEC C1096, 042 and its aggR mutant. The clinical EAEC strains (n = 20) were analyzed for the presence of 22 putative virulence factors of EAEC or extraintestinal E. coli by PCR, as well as phenotypic characteristics of virulence (enzymes, siderophore, and biofilm). The survival of the larvae was analyzed after inoculation of 104–107 CFU/larva; the monitoring of bacterial growth in vivo and hemocyte quantification was determined after inoculation of the prototype strains (105 CFU/larva) at different periods after infection. The strains of typical and atypical EAEC presented the same virulence profile for the larva, regardless of the amount or type of genes and phenotypic aspects of virulence analyzed. In addition, the EAEC 042 aggR mutant strain showed a significant reduction in the mortality of the inoculated larvae compared to the wild-type strain. In conclusion, the results obtained herein demonstrate that the virulence of EAEC seems to be related to the AggR regulon, but not exclusively, and atypical EAEC strains may be as virulent as typical ones in vivo in the G. mellonella model.
Highlights
Enteroaggregative Escherichia coli (EAEC), one of the six diarrheagenic pathotypes of E. coli, has been the most frequent cause of acute and persistent diarrhea in people of all ages in several regions of the world, including Brazil, corresponding to between 21 and 25% of cases (Moreno et al, 2010; Okhuysen and Dupont, 2010; Lozer et al, 2013; Spano et al, 2017)
EAEC was identified by its aggregative adherence pattern in a HEp-2 cell culture; typical and atypical EAEC strains were classified according to the presence or absence of aggR, respectively (Lozer et al, 2013)
Only the atypical strain C1096 was classified as a possible extraintestinal pathogenic E. coli (ExPEC), since it presented four of those virulence markers (Johnson et al, 2003)
Summary
Enteroaggregative Escherichia coli (EAEC), one of the six diarrheagenic pathotypes of E. coli, has been the most frequent cause of acute and persistent diarrhea in people of all ages in several regions of the world, including Brazil, corresponding to between 21 and 25% of cases (Moreno et al, 2010; Okhuysen and Dupont, 2010; Lozer et al, 2013; Spano et al, 2017). EAEC Virulence in Galleria mellonella pathogen that remains misunderstood, has a proposed pathogenesis comprising initial adhesion, biofilm formation, induction of an inflammatory response, and release of toxins; putative virulence factors are not uniformly present in all isolated strains (Okeke et al, 2000, 2010; Navarro-Garcia et al, 2010; Jensen et al, 2014). Presence of AggR regulon distinguishes typical from atypical EAEC, since it regulates both chromosomal and plasmidencoded virulence factors. In this sense, typical EAEC is suggested to be more virulent and more likely to cause diarrhea in humans than atypical EAEC (Sarantuya et al, 2004; Morin et al, 2013). There is still a gap in understanding their virulence aspects and we believe that wellestablished in vivo models may contribute to elucidate a possible difference between these two groups
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