Table 1.
Virulence factors of EAEC
| EAEC Virulence Factors | Clinical Attributes and
Biological Characteristics |
2011 Outbreak Straina |
|---|---|---|
| Adhesins and Colonization Factors | ||
| AAF | Contributes to the characteristic
AA phenotype and facilitates adherence, pithelial barrier disruption, and inflammation. AAF I, II, III, and IV are plasmid encoded73–75,105,106 |
+ (AAF/I) |
| Other non-AAF adhesins (eg, Hda) |
Contributes to the characteristic
stackedbrick phenotype107 |
|
| Dispersin (aap) | Promotes penetration of intestinal
mucus and may promote colonization of the epithelium108,109 |
+ |
| Enterotoxins and Hemolysins | ||
| Enteroaggregative
heat-stabile toxin 1 (EAST1, astA) |
Similar to the heat-stabile enterotoxin
of ETEC79 |
|
| Shigella enterotoxin-1 (ShET-1) | Enterotoxin that induces secretion110 | |
| Hemolysin E (hlyE) | A pore-forming hemolysin; the role
in pathogenesis has not been determined, and it is present in pathogenic and nonpathogenic EAEC111 |
|
| Member of SPATE (Serine Protease | Autotransporters of Enterobacteriaceae) | |
| Pet (plasmid encoded toxin) | Enterotoxin with protease and
cytoskeletal altering activities112,113 |
|
| Pic (protein involved
in colonization) |
Modulates immune responses and
induces the secretion and degradation of mucin; may contribute to the mucus-rich biofilm that is characteristic of EAEC mucosal colonization76,114 |
+ |
| SigA | The Shigella flexneri homolog
alters the cytoskeleton in intestinal epithelial cells, similar to Pet77 |
+ |
| SepA | Associated with illness, and the
Shigella flexneri homolog has been shown to contribute to intestinal inflammation and mucosal atrophy78,115 |
+ |
| Transcription Factor | ||
| Transcriptional regulator
AggR (aggR) |
Global regulator of EAEC virulence
genes, including the AAF operons and aap; common to most EAEC; not absolutely required for virulence80,116 |
+ |
| Other | ||
| Flagellin | Highly conserved bacterial
protein required for motility; interaction with basolaterally expressed toll-like receptor 5 on intestinal epithelial cells results in induction of the neutrophil chemoattractant interleukin-8117,118 |
+ |
Abbreviation: AAF, AA fimbriae.
a
+ indicates that the German STEC O104:H4 outbreak strain encodes the virulence factor.