MIRAGLIA AND BERRY 



also was the observation that from a group of 30 non- infected con- 

 trols held at 5° C for 14 days, only 23.3 per cent had liver cultures 

 positive for staphylococci and from none could salmonellae be ob- 

 tained. A similar number of control mice at 25° C had negative liver 

 cultures for both salmonellae and staphylococci. This further sup- 

 ports the contention that animals inthe cold have a decreased capa- 

 city to resist infection. 



Efforts have been made to determine the origin of the staphylo- 

 cocci which appear in the tissues of cold exposed mice. Most of the 

 normal animals (95 per cent or 294 of 308) discharge staphylococci 

 in the feces, but only 1 per cent approximately are coagulase- posi- 

 tive strains. These figures remain essentially unaltered in normal 

 mice exposed to cold. Since coagulase- negative strains do not lend 

 themselves readily to phage typing, a correlation between the staph- 

 ylococci isolated from tissues and those found in feces of the same 

 mouse could not, therefore, be attempted. 



An indirect method was employed, however, using a modification 

 of the technique of Schaedler andDubos(1962) which consists of sub- 

 stituting 0.01 N hydrochloric acid for the drinking water in order to 

 rid the gut of staphylococci. 



Animals have been maintained on hydrochloric acid drinking water 

 for over 40 days without any obvious untoward effects. The appear- 

 ance and behavior of the animals was normal. There was normal 

 weight gain and growth, and the pH and character of the stools was 

 indistinguishable from that of normal controls. 



Effect of acid water treatment on the percent of mice with feces 

 positive for staphylococci . In most experiments five to seven days 

 of acid treatment sufficed to rid the gut completely of culturable 

 staphylococci. In this connection, however, a seasonal effect was 

 noted in experiments conducted during the summer months even 

 though the animals had air-conditioned quarters. At this time of 

 year, additional time on acid treatment was required to free the 

 intestine of staphylococci, as shown in Table IV. Moreover, while 

 studies conducted during the winter consistently yielded coagulase- 

 negative staphylococci from the feces, summe;* studies revealed a 

 low percentage of coagulase-positive strains as well as a high 



282 



