232 BACTERIOLOGICAL EXAMINATION OF MATERIAL 



nized by their macroscopic appearance. Bacillus pyocyaneus is an 

 occasional incitant of intestinal disturbance. Its colonies upon 

 ordinary agar are surrounded by a yellowish or greenish halo. The 

 same general appearance characterizes its growth upon Endo medium. 

 Among the anaerobic bacilli, the ''gas bacillus" (Bacillus aerogenes 

 capsulatus) is the most important. The organism is present in variable 

 but small numbers in the feces of healthy adults, and occasionally in 

 young children as well. It may occasionally become a very prominent 

 organism among the fecal flora. The isolation and recognition of the 

 gas bacillus from the intestinal contents depends primarily upon the 

 energetic fermentation in milk cultures inoculated with feces and 

 heated to 80 C. for twenty minutes prior to incubation. (See Chapter 

 XXV for details.) Members of the spiral group, including the highly 

 pathogenic cholera vibrio, are readily isolated and identified by the 

 procedure described in the section on Vibrio Cholerse (Chapter XXVI). 



Tubercle bacilli are not infrequently found in the feces of individuals 

 who have advanced pulmonary tuberculosis. It is almost certain 

 that the organisms have been swallowed in a majority of such cases. 

 Occasionally a diagnosis of tuberculosis may be made thus in young 

 children from whom it is difficult or impossible to obtain a satisfactory 

 specimen of sputum. Tubercle bacilli are also found in the feces, 

 derived from tuberculous ulcerations. A diagnosis of tubercle bacillus 

 cannot safely be made from a demonstration of acid-fast organisms in 

 the fecal contents, because acid-fast bacteria other than tubercle 

 bacilli may be present. A guinea-pig furnishes the only reliable 

 method of distinguishing tubercle bacilli from adventitious non-patho- 

 genic acid-fast organisms. 



Examination of Sputum, of Buccal and Pharyngeal Material. 1 

 A sample of sputum suitable for bacteriological examination should be 

 collected with care. The mouth should be clean, the receptacle should 

 be sterile, and the material should be raised by a deep pulmonary 

 cough, not by a superficial effort. Buccal and pharyngeal material 

 for bacteriological examination is usually obtained upon sterile cotton 

 swabs. Bits of membrane may be removed with sterile forceps. 



Examination by Staining. A Gram-stained preparation of sputum, 

 buccal or pharyngeal material usually contains a variety of micro- 

 organisms comprising cocci, spiral forms, and even fungi and yeasts. 

 Many of the organisms may be normal inhabitants of the buccal 



1 An excellent discussion of Infections of the Respiratory Tract and of Sputum as a 

 Means of Diagnosis is that of Leutscher, Arch. Int. Med., 1915, xvi, 657. 



