DNAmacrorestriction analysis of all isolates was conducted by PFGEfollowing the PulseNet protocol with minor modifications. Briefly, agarose plugs containing genomic DNA were prepared from each isolate and digested over night with 24 U of XbaI (Promega). Restriction fragments were separated on 1% agarose gel (Certified Agarose, BioRad) in 0.5× TBE buffer on a CHEFIII system (BioRad); thiourea 50 μM was added to the running buffer to avoid the DNA degradation of some isolates. The settings were: 6 V/cm, included angle 120°, initial switch time 2 s, final switch time 64 s, and run time 22 h. Salmonella Braenderup H9812 XbaI-digested DNA was used as universal molecular reference marker. The different PFGE profiles obtained were compared by GelCompar II 5.0 software (Applied Maths) and analyzed by Dice coefficient and unweighted
pair-group methodwith arithmetic averages (UPGMA),with 1% optimization and 0.5% band position tolerance.
DNAmacrorestriction analysis of all isolates was conducted by PFGEfollowing the PulseNet protocol with minor modifications. Briefly, agarose plugs containing genomic DNA were prepared from each isolate and digested over night with 24 U of XbaI (Promega). Restriction fragments were separated on 1% agarose gel (Certified Agarose, BioRad) in 0.5× TBE buffer on a CHEFIII system (BioRad); thiourea 50 μM was added to the running buffer to avoid the DNA degradation of some isolates. The settings were: 6 V/cm, included angle 120°, initial switch time 2 s, final switch time 64 s, and run time 22 h. Salmonella Braenderup H9812 XbaI-digested DNA was used as universal molecular reference marker. The different PFGE profiles obtained were compared by GelCompar II 5.0 software (Applied Maths) and analyzed by Dice coefficient and unweightedpair-group methodwith arithmetic averages (UPGMA),with 1% optimization and 0.5% band position tolerance.
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