Action of the FK-1000 antimicrobial fraction on Escherichia coli STEC: characterization of biological mechanisms

Abstract

Shiga toxins produced by STEC (Shiga toxin-producing Escherichia coli) are responsible for hemorrhagic colitis, abdominal cramps, vomiting, and hemolytic uremic syndrome (HUS), the leading cause of acute kidney injury in children and a significant source of morbidity and mortality among the elderly. The lack of specific treatments worsens this scenanario, as antibiotics are not recommended -they may increase the synthesis and release of Shiga toxin by activating the bacterial SOS response. Thus, supportive care remains the primary option. Moreover, the growing resistance of STEC to antibiotics underscores the urgent need for alternative therapies.MATERIALS AND METHODSThe antimicrobial effect of FK-1000 was evaluated by broth microdilution to determine the MIC. Bacteriostatic activity was measured by optical density (595 nm), and bactericidal activity by CFU counting. Stx1 production was analyzed by ELISA, and Stx2 phage release was assessed using the double-layer agar method with E. coli WG5. Scanning electron microscopy (SEM) was employed to observe biofilm formation and fimbriae in the STEC EDL933 strain. Viability assays (LIVE/DEAD, Thermo Fisher) were used to evaluate membrane damage, and DNA integrity was verified by gel electrophoresis and Nanodrop analysis.CONCLUSIONThe findings demonstrate that FK-1000 exerts microbicidal effects against STEC, with bacterial DNA damage being one of its mechanisms of action.