Effects of antibiotics on Shiga toxin-producing Escherichia coli biofilms

ANGEL VILLEGAS N; ALBESA I; ETCHEVERRÍA AI; BECERRA MC; PADOLA NL; PARAJE MG

Córdoba

Otro; RICiFa 3° Reunión Internacional de Ciencias Farmacéuticas.; 2014

Dpto. Farmacia. Fac. Ciencias Químicas-UNC y la Univ. Nac. de Rosario.

Effects of antibiotics on Shiga toxin-producing Escherichia coli biofilms Angel Villegas N, Albesa I, Etcheverría A, Becerra MC, Padola NL, Paraje MG The use of antibiotics in the treatment of enterohemorrhagic Escherichia coli (EHEC) infections is controversial since they are capable of triggering hemolytic uremic syndrome (HUS) by increasing Shiga toxin (Stx) production. In the present study, three antibiotics (ciprofloxacin, fosfomycin and rifaximin) at different concentrations were evaluated on Shiga toxin-producing Escherichia coli (STEC) biofilms to determine the relationships among biofilms, cellular stress and release of Stx. With this purpose, reference and clinical strains associated with HUS were used, and biofilm formation was determined using crystal violet stain. In these biofilms, the reactive oxygen species (ROS) and the reactive nitrogen intermediates (RNI) were detected by the reduction of nitro blue tetrazolium and the Griess assays, respectively. In addition, the activities of the two antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT) were studied. The effect of an exogenous antioxidant (tiron) was also studied, and the Stx release of STEC biofilms was evaluated by cytotoxic assays using Vero cells. It was found that ciprofloxacin significantly altered the prooxidant-antioxidant balance, with an increase of antioxidant enzyme activity (SOD and CAT) and a high-level of Stx production. However, this effect was reverted by the addition of tiron. In contrast, fosfomycin and rifaximin produced less alteration to the oxidative cellular balance (antioxidant enzymes/oxidative metabolites) than controls, with minimal cytotoxic effects in Vero cells being observed. The disturbance in the prooxidant-antioxidant balance induced by different antibiotics provoked oxidative stress in biofilms, and concomitantly had an effect on the production and release of Stx. Consequently this effect might play an important role in the pathogenesis of infections caused by STEC. In future, an improved understanding of the mechanisms involved in the release of toxins during biofilm formation would contribute to a better understanding of the pathogenesis of HUS. Keywords: Biofilms; Escherichia coli O157:H7; antibiotic; Shiga toxin