[Study on the resistance of Escherichia coli O157:H7 to disinfectants in relationship with its plasmid pO157 and chromosome DNA].

OBJECTIVE

To study the change of Escherichia coli O157:H7 resistance to disinfectants in continuous disinfection and the relationship between the resistance and pO157, chromosome DNA.

METHODS

Using 4 disinfectants in a separate manner to disinfect 5 Escherichia coli O157:H7 50 generations continuously, we made a before-after comparison of their resistibility and analyzed the change of the structure of pO157 and chromosome DNA.

RESULTS

After the 50-generation-continuous disinfection, the bacteria resistance to sodium dichloroisocyanurate, iodophor and quaternary ammonium increased, but the resistance to chlorhexidiniacetas did not any change; the maps Cal I and Rsr II cutting pO157 revealed some changed after disinfection by sodium dichloroisocyanurate and quaternary ammonium, but the maps showed no change after disinfection by iodophor and chlorhexidiniacetas; the chromosome DNA PFGE maps change considerably after 50 generations of disinfection by sodium dichloroisocyanurate, iodophor and quaternary ammonium, but the chromosome DNA PFGE maps were similar after 50 generation of disinfection by chlorhexidiniacetas.

CONCLUSION

The Escherichia coli O157:H7 resistance to disinfectants will increase after the 50-generation-continuous disinfection by sodium dichloroisocyanurate, iodophor and quaternary ammonium. There may be genes both in chromosome DNA and in pO157 which resist sodium dichloroisocyanurate and quaternary ammonium, the reason for increase of resistance may be related with the change of chromosome DNA and pO157. There may be genes in chromosome DNA which resist iodophor, the reason for increase of resistance to iodophor may be related with the change of chromosome DNA, but not related with pO157.