Genetic and Virulence Profiles of Enteroaggregative Escherichia coli (EAEC) Isolated From Deployed Military Personnel (DMP) With Travelers' Diarrhea

Abstract

To discern if there was a particular genotype associated with clinical enteroaggregative Escherichia coli (EAEC) strains isolated from deployed military personnel (DMP) with travelers' diarrhea (TD), we characterized a collection of EAEC from DMP deployed to Afghanistan, Djibouti, Kenya, or Honduras. Although we did not identify a specific EAEC genotype associated with TD in DMP, we found that EAEC isolated at the first clinic visit were more likely to encode the dispersin gene aap than EAEC collected at follow-up visits. A majority of the EAEC isolates were typical EAEC that adhered to HEp-2 cells, formed biofilms, and harbored genes for aggregative adherence fimbriae (AAF), AggR, and serine protease autotransporters of Enterobacteriaceae (SPATEs). A separate subset of the EAEC had aggR and genes for SPATEs but encoded a gene highly homologous to that for CS22, a fimbriae more commonly found in enterotoxigenic E. coli. None of these CS22-encoding EAEC formed biofilms in vitro or adhered to HEp-2 cells. Whole genome sequence and single nucleotide polymorphism analyses demonstrated that most of the strains were genetically diverse, but that a few were closely related. Isolation of these related strains occurred within days to more than a year apart, a finding that suggests a persistent source and genomic stability. In an ampicillin-treated mouse model we found that an agg4A+ aar-isolate formed a biofilm in the intestine and caused reduced weight gain in mice, whereas a strain that did not form an in vivo biofilm caused no morbidity. Our diverse strain collection from DMP displays the heterogeneity of EAEC strains isolated from human patients, and our mouse model of infection indicated the genotype agg4A+ aar-and/or capacity to form biofilm in vivo may correlate to disease severity.

Molecular Epidemiology of Enteroaggregative Escherichia coli (EAEC) Isolates of Hospitalized Children from Bolivia Reveal High Heterogeneity and Multidrug-Resistance

“…The lack of aggR gene in half of our EAEC isolates coincide with Lima´s findings, and the authors suggested that this gene is not a useful virulence marker for diagnosis in opposite to what was suggested by other studies and that this gene alone is not a sensitive target and much less specific than the aatA gene (2,18). In recent years case-control and epidemiological studies have used several EAEC virulence genes, and aatA, aap, aagR, astA, and aafA were among the most frequently used for EAEC diagnosis (12,20,69). Also, Jenkins, Chart (49) suggested that aaiA, a chromosomal -encoded gene, would improve EAEC diagnosis.…”

“…The aap genes that encode for dispersin was the most prevalent virulence gene among all EAEC isolates; similarly to us, other studies found aap in high proportions (19,31,67). Despite the fact that dispersin was also found among other diarrheagenic E.coli pathotypes and nonpathogenic E.coli (68), several studies focused on EAEC isolates have shown that aap gene was highly prevalent virulent marker and associated with diarrheal cases (56)(57)(58)69). Since the aap gene showed to be a nonexclusive EAEC virulence gene, its addition to the initial detection for EAEC will not improve the identification of EAEC isolates.…”

“…It requires specific laboratory conditions, and it is time-consuming; therefore, molecular techniques such as PCR amplification are a great advantage, particularly in developing settings for extensive epidemiological studies (10). EAEC expresses a heterogeneous array of virulence factors encoded on the bacterial chromosome or the EAEC-specific pAA plasmid, associated with the bacteria's ability to aggregate (AA) (11)(12)(13). Each virulence gene plays a role in the disease, although the pathogenesis of EAEC infection has not been entirely resolved (14).…”

Exploiting Lactoferricin (17–30) as a Potential Antimicrobial and Antibiofilm Candidate Against Multi-Drug-Resistant Enteroaggregative Escherichia coli

“…Further, regarding microbial biofilm, nearly 80% of microbial infections in the living system involve biofilm formation (Batoni et al, 2016). Biofilm constitutes a syntrophic association of microbes enclosed within extracellular polymeric substance matrix that prevents microorganisms from adverse external influences, particularly antimicrobial agents (Lin et al, 2017;Petro et al, 2020). The adhesion of MDR-EAEC strains by MATS in this study was found to be comparatively higher to the tested monopolar solvent, chloroform, than to the apolar solvent, n-hexadecane, which bears almost identical van der Waal's properties.…”

“…Generally, EAEC is regarded as a heterogeneous pathogen; the pathogenicity of EAEC is described initially by its surface adherence to the intestinal mucosa, followed by biofilm formation and toxin release, which often ends up with an inflammatory response (Lima et al, 2018). The biofilm formation by EAEC is correlated well with the persistence of infection and recalcitrance to empirical antimicrobial treatment (Lin et al, 2017;Petro et al, 2020). This persistent colonization of EAEC leads to carrier status, enabling antibiotic pressure, which results in frightening levels of multi-drug resistance.…”