THE STAPHYLOCOCCUS GROUP 257 



Acid is produced in dextrose, lactose, saccharose and mannite broths. 

 Milk is coagulated, usually within three days at 37 C.; many strains 

 subsequently partially digest the coagulum. In plain and dextrose 

 broths a turbidity is produced after twelve to fourteen hours' incuba- 

 tion at 37 C.; after forty-eight hours' growth a golden-yellow sedi- 

 ment collects in the bottom of the tubes. t Growth on slanted agar is 

 golden-yellow in color, moist and spreading. Pigment production is 

 especially luxuriant on slanted potato. 



The organisms are aerobic, facultatively anaerobic. The optimum 

 temperature of growth lies between 28 and 38 C.; growth ceases 

 below 8 C. and above 43 C. 



FIG. 32. Staphylococcus. X 1000. 



Staphylococci are among the most resistant of the non-spore-form- 

 ing bacteria to physical agents. An exposure of one hour at 80 C 

 or two hours at 70 C. moist heat is usually fatal. Several minutes' 

 exposure at 100 C. (flowing steam) or twelve hours' exposure to direct 

 sunlight may fail to kill them. Indirect daylight may fail to destroy 

 their vitality even after two weeks; three months' continuous drying 

 (on cloth or paper) is equally ineffective; 0.001 per cent, mercuric 

 chloride and 5 per cent, carbolic acid usually kill the naked germs in 

 about ten minutes. 



Products of Growth. Acids, chiefly lactic, but with demonstrable 

 amounts of propionic, butyric, and valerianic, are formed during the 

 fermentation of ordinary sugars. No gas is produced. The pus of 

 Staphylococcus abscesses is usually acid in reaction; the organisms 

 appear to form limited amounts of acid from protein. 1 Emmering 2 



1 Kendall, Day and Walker, Jour. Am. Chem. Assn., 1913, xxxv, 1246. 



2 Berlin, deut. chem. Gesellsch., 1896, 2721. 

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