CHAPTER VIII 



STUDY AND IDENTIFICATION OF BACTERIA. GRAM- 

 NEGATIVE BACILLI. KEY AND NOTES 



KEY to the recognition of nonspore-bearing, nonchromogenic, non- 

 Gram-staining, nonbranching bacilli. 



(NOTE. Some books say that the proteus group is Gram-positive. It is, how- 

 ever, usually negative.) 

 Do not grow on ordinary media. Require blood agar (haemophilia bacteria), serum 



agar, or blood-serum. 



Minute dewdrop colonies. 



1. Influenza bacillus. Requires blood media. 



2. Koch- Weeks bacillus (conjunctivitis). Serum agar best medium. Many, 

 however, regard haemoglobin as necessary for growth. 



3. Muller's bacillus of trachoma. Like Koch- Weeks bacillus, but easier to 

 ^cultivate. 



4. Morax diplobacillus of conjunctivitis. Grows well and produces little pits 

 of liquefaction in Loffler's blood-serum. 



5. Bordet-Gengou bacillus of whooping-cough. Does not grow on LofBer's 

 serum. Requires blood or ascitic fluid agar. Original isolation should be on 

 glycerine potato agar. 



6. Ducrey's bacillus (soft chancre). Requires media rich in blood or serum. 

 Forms chains. 



Grow well on ordinary media. 



I. Cultures in litmus milk. PINK. 



A. Nonmotile. 



Lactis aerogenes group. B. lactis aerogenes. 



Produce gas in glucose, lactose, and saccharose. No liquefaction of gelatin. 

 Short, stubby bacteria, often showing capsules. Intermediate between the 

 colon and Friedlander group. 



B. Motile. 



1. Nonliquef action of gelatin. 



(a) B. coli group. Coagulation of milk. No subsequent peptonization. 

 Gas in glucose and lactose, none in saccharose. Indol produced. 

 Neutral red reduced. 



2. Liquefaction of gelatin. 



(a) B. cloaca? group. Gas in glucose, slight in lactose. Slow coagulation 

 of milk. Subsequent peptonization. 

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