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Joan Morgan and W. J. Whelan 219 
5. Monitoring of the laboratory work bench, water baths, and centrifuges, 
etc., occasionally revealed detectable numbers of EK1 E. coli K-12. Such organisms 
could be found immediately after performing laboratory procedures such as flaming 
bacteriological loops, replica plating or transferring cultures (even with manual 
pipetting devices). Such contamination was instantaneously sterilized by simple 
disinfectants, including 70% ethanol. Deliberate spills of EK1 E. coli ,K-12 
had become sterile within six hours after drying. Reliable numbers for the 
survival of EK2 hosts in the laboratory are not available to us but survival, 
if any, was much reduced relative to ordinary E. coli. 
6. Individuals working with E. coli K-12 infected mice and calves were not found 
to more likely become colonized with E '. coli K-12 than workers who did only in 
vitro experiments. 
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