It has been reported that the clinical cases of mixed infection due to Es. coli and Ps. aeruginosa are not uncommon. However, the mechanisms concerning the esta-blishment of mixed infection state of these organisms has not been studied expermentally.
The normal habitate of Es. coli is the intestinal canal of animals and Ps. aeruginosa may be reco￢vered from either the intestine or the natural sources such as sewages, swimming pool, soil, etc. It is, therefore, conceivable that Es. coli enter the host tissues together with Ps. aeruginosa either from the intestine or from the natural sources and establish the state of mixed infection.
Thus, (10±1.5)X10" viable units each of Es. coli grown at 37°C. and Ps. aeruginosa grown at 37° C. or 22° C. were inoculated into the ear vein of rabbits singly or together with and the viable units populations in the rabbits blood and urine were followed.
The result of observation may be summarized as follows;
1) In the group inoculated with Es. coli or Ps. aeruginosa grown at 37´C. : Either organisms appeared to be removed rapidly from the blood stream and the viable units population in the rabbits urine showed a kind of persistence after initial increase for few days.
2) In the group inoculated with Ps. aeruginosa grown at 22°C.: The organisms appeared to be cleared rapidly from both blood stream and urinary tract without sign of increase.
3) In the group inoculated with Es. coli and Ps. aeruginosa grown at 37´C. : Both organisms appeared to be removed rapidly from the blood stream and the viable units populations of both organisms in the urine showed more prolonged and significant increase for several days.
4) In the group inoculated with Es. coli and Ps. aeruginosa grown at 22´C. : The viable units populations of both organisms showed about the same pattern as the group inoculated with the bacterial suspensions of single speces.
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