This increased virulence is assumed to be associated with higher amounts of toxin production by fluoroquinolone-resistant strains belonging to PCR ribotype 027, toxinotype III and PFGE NAP1.
Povečana virulenca naj bi bila povezana z večjo količino toksinov, ki jih tvorijo sevi, odporni na fluorokinolon, ki sodijo v PCR-ribotip 027, toksinotip III in PFGE NAP1.