Correlation between in vivo biofilm formation and virulence gene expression in Escherichia coli O104:H4.

ABSTRACT

The emergence of novel pathogens poses a major public health threat causing widespread epidemics in susceptible populations. The Escherichia coli O104H4 strain implicated in a 2011 outbreak in northern Germany caused the highest frequency of hemolytic uremic syndrome (HUS) and death ever recorded in a single E. coli outbreak. Therefore, it has been suggested that this strain is more virulent than other pathogenic E. coli (e.g., E. coli O157H7). The E. coli O104H4 outbreak strain possesses multiple virulence factors from both Shiga toxin (Stx)-producing E. coli (STEC) and enteroaggregative E. coli (EAEC), though the mechanism of pathogenesis is not known. Here, we demonstrate that E. coli O104H4 produces a stable biofilm in vitro and that in vivo virulence gene expression is highest when E. coli O104H4 overexpresses genes required for aggregation and exopolysaccharide production, a characteristic of bacterial cells residing within an established biofilm. Interrupting exopolysaccharide production and biofilm formation may therefore represent effective strategies for combating future E. coli O104H4 infections.