SECONDARY BACTERIAL INFECTION IN MICE 



Duration of Per cent of mice Per cent Per cent 



HCL treatment with fecal coagulase coagulase 



(Days) staphylococci negative positive 



95 95 



(308) 



6 67 67 



(15) 



10 11 11 



(27) 



12 5 5 



(20) 



28 40 30 10 



(20) 



Table IV. Staphylococci recovered from the feces of mice after various periods 

 of hydrochloric acid treatment. Number of mice tested shown in parentheses. 



percentage of coagulase-negative strains. When no staphylococci 

 could be cultured from the feces after a period of acid treatment, 

 the digestive tract was then recolonized with strain Giorgio, a 

 coagulase- positive staphylococcus, and for about a week thereafter 

 the stool cultures contained only coagulase-positive strains. While 

 mice continued to shed these strains for at least several additional 

 weeks, they also began to discharge coagulase-negative strains by 

 the 14th day. This occurred in animals maintained at 25° C and 5° C. 



Although the gut can be made free of staphylococci by treat- 

 ment with hydrochloric acid, these organisms became reestab- 

 lished in approximately 50 per cent of the animals within several 

 days after tap water was substituted for the acid. In fact, in 

 animals autopsied after the usual experimental period of 14 days, 

 coagulase-negative staphylococci were found in nearly all stool 

 cultures. This too was independent of the environmental tempera- 

 ture at which the mice were kept. 



Effect of acid water treatment on the per cent of mice with 

 tissues positive for staphylococci. Deep tissue invasion has, 

 with only a few exceptions, consisted of coagulase-negative 



283 



