SECONDARY BACTERIAL INFECTION IN MICE 



the conditions of these experiments, be altered experimentally so 

 that a coagulase-positive strain established artificially in the host by 

 eating infected food be subsequently made to invade deep tissue. 



The manner in which infectious agents reach potential victims, 

 enter them and establish themselves with subsequent detriment to 

 the host has been recognized since the "Golden Era of Bacteriology". 

 What needs further elucidation are the mechanisms responsible for 

 the absence of overt disease symptoms in hosts parasitized by 

 virulent pathogens which are known to persist for long periods of 

 time. 



The microorganism possessing the weapons of infectivity and 

 pathogenicity upon entrance into a suitable host need not cause dis- 

 ease. This bespeaks of the complexity of the host- parasite relation- 

 ship. Those studying the infectious process have long been aware 

 that many "normal" animals harbor in their tissues a variety of 

 parasites including viruses and bacteria. There are reports in the 

 literature of a high incidence of the virus of polio and herpes sim- 

 plex and the microbe oftuberculosiSjindicatingthat the ability of the 

 animal to remain free of clinical signs despite invasion exceeds its 

 ability to prevent microbial and viral penetration. Thus, it may not 

 be surprising that staphylococci are found in deep tissues of mice, 

 but why its incidence is increased when the host is stressed by cold 

 or cold and primary infection requires answer. 



There is every reason to believe that there are a number of agents 

 that may parasitize man without his knowledge and are exacerbated 

 only during periods of stress. There are, for example, reports 

 suggesting that herpes simplex expresses its clinical picture during 

 physical and emotional disturbances. Likewise, clinical tuberculosis 

 is manifested in patients stressed by poor nutrition or debilitated by 

 another disease (primary infection). Thus, pathogens or potential 

 pathogens can and in some instances do persist without clinical 

 symptoms. Detection of these elusive agents depends upon adequate 

 procedures and, therefore, come to light only after requisite ad- 

 vances in technology. Recovery of salmonellae from the excreta of 

 individuals with typhoid fever, or from the blood and other tissues 

 during certain stages of the infection, can be accomplished success- 

 fully with present bacteriological methods. However, when the host 



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