title: Colistin inhibits E. coli O157:H7 Shiga-like toxin release, binds endotoxins and protects Vero cells.
abstract: The role of antibiotics in the treatment of Shiga-like toxin (Stx)-producing E. coli infection is still controversial. This study investigated the effects of colistin on Vero cell cytotoxicity caused by the enterohemorrhagic EC O157:H7, and the effects of colistin on Stx and endotoxin release by EC O157:H7. Vero cells were incubated with supernatant collected from EC O157:H7 cultured for 18 h without (control) or with various concentrations of colistin. In the absence of colistin, Vero cell viability after 48 h was 29.1±6.5%. Under the same conditions, the overnight presence of colistin reduced cytotoxicity to Vero cells (viability: 97±3.5 to 56.5±14.4% for colistin concentrations ≥MIC). Sub-MIC concentrations of colistin also provided partial protection (viability: 38.8±12.5 to 36.6±14% for 0.125 and 0.06 mcg/ml colistin, respectively). Endotoxins contributed to the cytotoxic effects on Vero cells since lower but still significant protection was observed when colistin was added directly to the supernatant collected from cultures of untreated EC O157:H7. Colistin reduced Stx release in a concentration-dependent manner, also at sub-MIC concentrations. Coincubation of the supernatant from EC O157:H7 cultures with colistin markedly reduced the endotoxin concentration at all doses investigated. In conclusion, colistin protects Vero cells from EC O157:H7 at supra- and sub-MIC concentrations by inhibiting Stx release and binding endotoxins. Colistin might be a valuable treatment for clinically severe forms of EC O157:H7 infection.
authors.affiliation: Microbiology and Virology Department.
authors.forename: Elena
authors.initials: E
authors.lastname: Percivalle
authors.affiliation: Microbiology and Virology Department.
authors.forename: Vincenzina
authors.initials: V
authors.lastname: Monzillo
authors.affiliation: Charles River Laboratories, Ecuilly, France.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Pauletto
authors.affiliation: Microbiology and Virology Department.
authors.forename: Piero
authors.initials: P
authors.lastname: Marone
authors.affiliation: Phase I Clinical Trial Unit and Experimental Therapy, Fondazione IRCCS Policlinico S. Matteo, Pavia, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Imberti
mesh_terms: D000818:Animals; D002470:Cell Survival / Q000187:drug effects*; D002522:Chlorocebus aethiops; D003091:Colistin / Q000737:chemistry / Q000494:pharmacology*; D004731:Endotoxins / Q000737:chemistry*; D019453:Escherichia coli O157 / Q000187:drug effects* / Q000378:metabolism; D022603:Shiga Toxins / Q000235:genetics / Q000378:metabolism*; D014709:Vero Cells
chemical_list: D004731:Endotoxins; D022603:Shiga Toxins; D003091:Colistin
keywords: Colistin; EC O157:H7; Enterohemorrhagic colitis; HUS; Hemolytic uremic syndrome; Shiga-like toxin