148 BACTERIA 



Habitat. Has been found in soil; sometimes in healthy saliva. 

 Culture Media. Grows luxuriantly on all culture media. 

 On gelatine it grows in roundish elevated colonies that are yel- 

 lowish-white with a slimy lustre, and never liquefies the gelatine. 

 In agar it multiplies even more abundantly with a moister growth. 

 The border of streak cultures is smooth and wavy, and the water 

 of condensation is cloudy. In bouillon the growth is very cloudy 

 with a silvery deposit at the bottom. The 

 bouillon becomes thickened. Milk is not 

 coagulated, and potato yields a luxuriant 

 yellowish, moist shining growth. 



Pathogenesis. It is possible to cause pneu- 

 monia in mice, also septicaemia. Guinea 

 pigs and dogs are susceptible. It may be 



: found in normal mouths ' ^lander's pneu- 

 mococci, showing cap- monia is much less frequent than that due to 

 ' the pneumococcus, but it is very fatal. Ag- 

 glutination takes place with immune serum. 

 This is the most important representative of a group of organisms 

 of moderate pathogenic powers and importance called variously, 

 Bacterium aerogenes, Bacterium mucosus or Aerogenes mucosus 

 group. They all have a luxuriant growth on media; are negative 

 to Gram stain; ferment most of the carbohydrates ; are non-motile 

 and most of them show a capsule when in the animal body. 

 Perkins divides them as follows: 



I. Bacterium aerogenes type ferments all carbohydrates with gas. 



II. Bacterium pneumonias group ferment all carbohydrates but 

 lactose, with gas. 



III. Bacterium lactis aerogenes group ferment all carbodydrates 

 except saccharose, with gas. 



These organisms are important members of the intestinal flora. 



The Bacterium lactis aerogenes group is a very large one and 

 includes nearly all the forms engaged in milk souring. The 

 ordinary B. lactici is very like the colon bacillis, but is non-motile. 

 It forms lactic acid among its principal products. The most 



