| Summary: | Background: In the last decade, the importance of hetero-pathogenic enteroaggregative Shiga-toxin-producing <i>E. coli</i> for public health has increased. Recently, we described the genetic background of the EAHEC O181:H4 strain of ST678 carrying the <i>stx2</i> gene in prophage and five plasmids, including the plasmid-carrying <i>aggR</i> and <i>aaiC</i> genes. Here, we present the morphological and enzymatic characteristics of this strain, as well as susceptibility to antimicrobials, biofilm formation, etc. Methods: Bacterial morphology was studied using an electron microscope. Susceptibility to antimicrobials was determined using the microdilution method. Cytotoxicity was estimated in Vero cells. Virulence was studied on mice. Results: The morphological and enzymatic properties of the hetero-pathogenic EAHEC strain were typical for <i>E. coli</i>; electron microscopy revealed the specific flagella. The strain was susceptible to most antibiotics and disinfectants but resistant to ampicillin and ciprofloxacin and showed a high degree of biofilm formation. Cytotoxicity towards Vero cells was estimated as 80%. Conclusions: The emergence of a new O181:H4 EAHEC strain poses a potential threat to humans because of the virulence potential that must be taken into account in the epidemiological analysis of outbreaks and sporadic cases of foodborne infections associated with hemolytic–uremic syndrome.
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