Influence of the Time lapse in Bacterial Inoculation upon the Experimental Mixed Infection of Staphylococcus aureus and Escherichia coli

Recent investigations on mixed microbial infections have shown increasing incidence with unclarified pathogenesis, although various factors including time lapse in microbial inoculation into body tissue have been discussed in part. The authors pximary interest in the phenomenon of persistence of both staphylococcus and colon bacillus in the body led to comparative studies on the time lapse upon the experimental mixed infection. With the possibility that observation on the time lapse in bacterial introduction into circulation might lead to significant influences on the blood stream and urinary bacterial aspects, Staphylococcus aureus and Escherichia coli, being cultured in the Brain-Heart Infusion Broth aerobically at 37℃, were inoculated into the ear vein of rabbit simultaneously, or with a time lapse of one hour, 24 hours or 72 hours. Heart blood and bladder urine were collected aseptically and viable units of both microbial species were correlated with time sequence. Results were summarized as follows: 1 Following the inoculation of mixed suspensions of Staph. aureus and E. coli intravenously; a. the viable units of staphylococci in the blood stream decreased rapidly with recovery in small number of cocci during the period from 3 hours to the third day, but disappeared from the blood stream thereafter. b. the viable units of staphylococci in bladder urine increased to the peak on the third day. c. only small number of colon bacilli were recovered from the blood stream but viable units of colon bacilli in urine showed gradual increase until the 7th day and decreased later on. 2 Following the inoculation of colon bacilli, one hour after the introduction of staphylococci; a. Population curve patterns of both microbial species were almost same as those of the simultaneous inoculation group. 3. Following inoculation of colon bacilli, 24 hours after introduction of staphylococci; a. staphylococci in the blood stream were rapidly cleared out, but reappeared following inoculation of colon bacilli. b. staphylococci in urine increased rapidly until the third day and decreased thereafter. c. colon bacilli in the blood stream were removed rapidly whereas in urine, they revealed a slight increase until for the first 24 hours, a sharp fall on the second day, and a gradual increase again from the 4th day This was a significant difference compared with the other groups that we have observed. 4. Following inoculation of colon bacilli, 72 hours after introduction of staphylococci; a. the viable units of staphylococci decreased in the blood stream until the third day, but increased in atypical curve until the 7th day, and decreased again later on. b. staphylococci in urine revealed almost an identical pattern as the group of 24 hours after inoculation. c. colon bacilli in the blood stream demonstrated a transient increasing pattern, different from other groups, but urinary colon bacilli showed gradual increase without any evidence of significant decrease.