The effect of a biological containment system in Escherichia coli based on the stochastic induction o f a lethal gene, hok,* was investigated in the gastrointestinal system of 33 germ-free rats. E. coli BJ16, identical to E. coli BJ4 originally isolated from a rat, but containing a plasmid pPKLlOO with the hok gene, was given to germ-free rats. In these rats a plasmid-free and a plasmid-containing population was formed and co-existed in the gut. When given to gnotobiotic rats which had been initially monoassociated with E. coli BJ4, the E. coli BJ16 (hok+) was eliminated at a faster rate than E. coli BJI 7, identical to E. coli BJ4 but carrying a plasmid pMG33 without the hok gene. Expressed as T,,, the time used for a 90 per cent reduction of the bacterial concentration, the mean elimination for E. coli BJ16 (hok') was 2.8 d and for E. coli BJ17 (hok-) was 5.3 d, indicating an effect of the hok gene in a competition situation.
Die Frage, welche Urinkeime bei entzündlichen Erkrankungen der Harnwege pathogenetische Bedeutung haben, ist seit der Anwendung der antibiotischen Therapie besonders dringlidi geworden. War die Antwort früher fast nur von theore-
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