University of Tehran

Simultaneous effects of shaking and temperature on verotoxin1 phage induction from verotoxigenic escherichia coli strains

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Verotoxin producing Escherichia coli (VTEC) are responsible for sporadic cases of diarrhea and have occurring world wide by ingestion of humburgers. (Paton et al., 1998) VTEC causes severe clinical manifestations such as haemorrhagic colitis and haemolytic uremic syndromes. These strains produce shiga like toxins. Verotoxin genes in VTEC are encoded by lambdoid bacteriophage family , that could be induced by factors such as irradiation and mitomycin C. Subinhibitory concentrations of selective antimicrobials for treatment of VTEC outbreaks (Quinolones and macrolides ) also could induce verotoxin genes in VTEC strains. Induction of this genes in turn could be increase verotoxin1 titer in culture or natural environments of bacteria(Yoh et al., 1999 ). Muniesa and Jofre reported that free phages carring verotoxin genes are present in sewage. This phages lysogenized E.coli ATCC (43888, O157: H7, slt) and produced Verotoxin (Muniesa et al.,1998). Muniesa reported that VTEC bacteriophages are more resistant to chlorination and pasteurization, survive better in water than their bacterial hosts. Therfore free living phage particles are potential factors in the spreading and transmission of verotoxin genes among diverse groups of E.coli and related bacteria (Muniesa et al.,1999). Presence of free infectious phage particles in the environment and potential risk of horizontal transmission to other related bacteria, alerts health care authorities and professionals about risks of VTEC caused disease(Schmidt et al., 1999). These facts indicate that in natural habitates some factors may be help to the induction and spreading of phage particles to other bacterial hosts. In this study we investigate the effects of tow environmental factors shaking and temperature on the induction of verotoxin1 bacteriophage from a VTEC.

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