STREPTOCOCCUS 927 



Genus Diplococcus Weichselbaum, 1886, emendavit Winslow 

 and Rogers, 1905. 



Definition, — Streptococceae usually in encapsulated pairs, forming 

 acid in glucose, lactose, saccharose, and inulin. Haemolysis usually 

 absent. Characteristic group serum reactions. Soluble in bile salts. 

 Undergo autolysis in cultures and in emulsions of physiological saline. 



Type Species. — Diplococcus pneumonice Weichselbaum, 1886. 



Remarks. — The genus contains the organisms associated with 

 pneumonia, of which there are many strains separable by serum 

 reactions. The genus requires further study before a definite 

 classification can be given. 



Two groups are recognized — viz. , those which exhibit a diplococcal 

 form and are usually oval or lanceolate in shape (Pneumoniae group), 

 and those which are in chains and rounded in form (Mucosus group). 

 These groups can be further differentiated by seriological tests and 

 by complement fixation. 



Genus Streptococcus Rosenbach, 1884, emendavit Winslow 

 and Rogers, 1905. 



Definition. — Streptococcese parasitic in short or long chains or pairs, 

 forming a large quantity of acid in fermented sugars. Haemolysis 

 present or absent. Without characteristic group serum reactions. 



Type Species. — Streptococcus erysipelatos Fehleisen, 1883. 



Remarks. — Streptoccoci are frequently found in disease in the 

 tropics, as primary agents causing the pathological changes, and 

 as secondary or terminal infections in the course of illnesses due to 

 other causes. 



They are responsible for several types of puerperal fever, of 

 abscesses, of septicaemias and of skin diseases. 



Natural Habitat. — Most streptococci are found as parasites (or 

 saprophytes) of the nose, nasopharynx, and alimentary canal of 

 vertebrate animals, but they can also be found in the alimentary 

 tract of the invertebrata, and apparently also, but to a less extent, 

 living on or in plants. 



From these natural homes they may pass to air, soil, milk, or 

 water, and so may be conveyed from one animal to another, as they 

 are extremely resistant against heat and drought. 



Thus 5. salivarius Andrewes and Horder, 1906, lives in normal 

 human saliva; S. bovinus Broadhurst, 1915, in bovine faeces, and 

 is found in the cow-dung plastered on walls and floors of native 

 huts; while S. versatilis Broadhurst, 1915, is found in equine and 

 bovine faeces. 



Researches with regard to certain human passages have shown 

 how quickly these become infected with streptococci after birth. 



It would appear that man quickly obtained his normal strepto- 

 coccal flora from the animals by which he is surrounded, and that 

 so long as they abide in their natural habitats they do no harm, but 

 if they depart therefrom they become pathogenic. 



