Influence of freezing-thawing and refrigeration on R-plasmid (pRPJ24) stability in Enterobacter cloacae 94R.
The effect of twenty freezing (-20 degrees C) and thawing cycles of Enterobacter cloacae 94R cells containing the R-plasmid pRPJ24 inoculated into broth and ground beef meat samples revealed no loss of resistance due to plasmid instability. In addition, low temperature storage at 4 degrees C did not produce any significant loss of the tetracycline and kanamycin resistances encoded on the pRPJ24 plasmid. The results of this study indicated that indigenous R-plasmids like pRPJ24 are stable in resident recipients like E. cloacae 94R in ground beef. However, the proportion of viable cells containing the pRPJ24 plasmid decreased significantly after 20 freezing-thawing cycles over 14 days incubation at 4 degrees C.
Jayaratne
A H
AH
Department of Environmental Biology, University of Guelph, Ontario, Canada.
Collins-Thompson
D L
DL
Trevors
J T
JT
D000818:Animals; D002417:Cattle; D003080:Cold Temperature; D003470:Culture Media; D004754:Enterobacter / Q000187:drug effects / Q000235:genetics*; D005516:Food Microbiology; D005615:Freezing; D007613:Kanamycin Resistance / Q000235:genetics; D008460:Meat; D011815:R Factors; D012034:Refrigeration; D013753:Tetracycline Resistance / Q000235:genetics
D003470:Culture Media