230 BACTERIOLOGICAL EXAMINATION OF MATERIAL 



diagnosis. Streptococci and pneumococci produce distinctive changes 

 in the hemoglobin of blood a'gar plates. Their final identification 

 is discussed in the section devoted to these organisms. Bacillus coli 

 and Bacillus proteus are common incitants of cystitis; they grow readily 

 upon ordinary media and their recognition depends upon the changes 

 pure cultures induce in artificial media. (See table, page 316.) 



Bacillus typhosus and members of the Paratyphoid Group are occa- 

 sionally found in the urine of patients and convalescents. The organ- 

 isms are readily obtained in pure culture by plating upon nutrient 

 agar, or, better, upon Endo medium (see page 201). Their cultural 

 characteristics and agglutination with specific sera establish their 

 identity. Tubercle bacilli may be found in the urine; the only satis- 

 factory and trustworthy diagnosis is made by injecting the sediment 

 of a twenty-four-hour sample of urine subcutaneously into a guinea- 

 pig. The animal will succumb to infection if tubercle bacilli are 

 present, but will fail to react to smegma bacilli, which are acid-fast 

 and resemble tubercle bacilli morphologically. 



Examination of Feces. (See also Special Section, Bacteriology of 

 the Feces.) The isolation and identification of pathogenic microorgan- 

 isms from the feces is frequently a difficult task because the normal 

 intestinal bacteria preponderate even in severe infections. Never- 

 theless, the use of special media has greatly reduced the difficulties 

 and a search for specific microorganisms is now possible with a very 

 favorable outlook for success. 



For convenience, intestinal infections may be divided into those 

 caused by cocci, by bacilli, and spiral organisms. Of the spherical 

 organisms or cocci, the streptococcus is by far the most common 

 pathogenic organism encountered in intestinal infections, although an 

 overgrowth of Micrococcus ovalis may be associated with a distinct 

 symptomatology. The streptococcus is a common inhabitant of the 

 intestinal tract, and for this reason streptococcus infection of the 

 alimentary canal is denied by many observers. The streptococcus is 

 frequently an important secondary invader of the intestinal mucosa 

 in bacillary dysentery, and possibly in typhoid and paratyphoid infec- 

 tions as well. It is also frequently associated with an overgrowth of 

 the ''gas bacillus' 5 (Bacillus aerogenes capsulatus) in intestinal infec- 

 tion with the latter organism. The occasional acute enteritis observed 

 both sporadically and epidemically among young children is also 

 incited by streptococci. The distinction, if any exists, between the 

 intestinal streptococcus and Streptococcus pyogenes is not clearly 



