ACID FAST BACILLI 77 



f Colonies more flat and moist. 

 Nonacid-fast. Corynebactermm. < _.. 



( Like other bacteria. 



I. Do not stain by Gram's method. 



i. B. mallei (Glanders). Characteristic culture is that on potato. Growth 

 like layer of honey by third day. Becomes darker in color, until on eighth 

 day is reddish-brown or opaque with greenish-yellow margin. 



II. Gram positive. 



1. Very luxuriant growth on ordinary media. Colonies often yellow to brown- 

 ish. B. pseudodiphtheriae. Shorter, thicker and stain uniformly. 



2. Moderate growth on ordinary media. B. diphtheriae. Best media are 

 blood-serum (Loffler's) or glycerine agar. Has metachromatic granules at 

 poles. 



3. Scanty and slow growth on nutrient media. B. xerosis. 



THE GROUP or ACID-FAST BRANCHING BACILLI. 



There is a large and ever-increasing number of organisms which 

 have the same staining reactions as the tubercle bacilli, but which differ 

 in four important essentials of: 



1. Growing readily on any media. 



2. Showing more or less abundant growth or colonies in twenty- 

 four hours. 



3. Having no pathogenic power for guinea-pigs when inoculated 

 subcutaneously. 



4. Not requiring body temperature for development, but growing 

 at room temperature. 



Many of these organisms, if injected intraperitoneally into guinea-pigs will pro- 

 duce a peritonitis with false membrane. Some also produce granulation tissue 

 nodules which may be confused with true tubercles. For this reason it is well to 

 study the lesions in experimental tuberculosis in the guinea-pig. Injected subcuta- 

 neously, on either or both sides of the posterior abdomen with the needle pointing 

 toward the inguinal glands, we may have caseation and ulceration at the site of 

 inoculation. The glands in relation enlarge and caseate. Smears from these show 

 T. B. The marked and characteristic change is the enormous enlargement of the 

 spleen, which is studded with grayish and yellow tubercles. Make smears and cul- 

 tures from the spleen. The death of the guinea-pig usually occurs in about two 

 months. The lesions may be looked for at three to five weeks. 



These nonpathogenic acid-fast bacilli are of greatest importance by reason of 

 their possible confusion with the true tubercle bacilli. Their colonies correspond 

 more or less with different types of tubercle bacilli colonies, being either dry and wrint 

 kled like human, or moist and irregularly flat as avian. Eventually the mois- 

 colonies become dry and wrinkled. They have been isolated from: 



1. Butter and milk. 



2. From grasses, especially in timothy grass infusion. 



