162 . STAPHYLOCOCCIC INFECTION 



twenty-four hours old may contain millions of living cocci. In milk 

 there is a slow evolution of acid and coagulation results after about 

 one week. It slowly liquefies gelatin by the formation of a peptonizing 

 ferment This ferment converts proteins into albumoses, peptones, 

 amins and ammonia. 



A temperature of 70 C. (158 F.) continued for five minutes suffices 

 to destroy the organism, and immediate sterilization is secured by 

 boiling. The staphylococcus is highly resistant to drying. Dried pus 

 may contain viable organisms after many months and dust may harbor 

 them and aid in their distribution. Mercuric chlorid in dilution as 

 great as 1 : 10,000 may inhibit growth but does not kill these bacteria. 

 Indeed, they are rather resistant to this germicide, 1 : 1,000 requiring 

 several hours and even 1 : 100 needing from five to ten minutes. 

 Absolute alcohol is without effect but 50 per cent, alcohol is quite 

 efficient in ten minutes. Phenol, from 3 to 5 per cent., kills within 

 five minutes. For disinfecting the hands lysol followed by dilute alco- 

 hol is recommended. 



The staphylococcus is usually found on the skin, the albus most 

 frequently, but the aureus not seldom. It is also present in normal 

 saliva, on the tonsils and walls of the pharynx and in the conjunctival 

 sac. It is frequently present in the normal urethra, both male and 

 female, but rarely in the vagina. It collects on the clothing and makes 

 this a source of infection when carried into wounds. It is often found 

 on cold foods and is a frequent constituent of market milk. The 

 strains showing this wide distribution are generally of low virulence. 



Old filtered bouillon cultures of the staphylococcus have certain 

 well-marked effects. They contain a substance which induces degen- 

 erative and destructive changes in leukocytes and for this reason is 

 known as leukocidin. This substance has not been isolated and its 

 presence is indicated by its effects. It is inactivated at 60 and is sup- 

 posed to be a ferment. When leukocytes are subjected to filtered 

 cultures of the staphylococcus, they soon show degenerative changes 

 and finally lose their nuclei. Leukocytes from different animals vary 

 greatly in susceptibility to this agent. Those from the frog are 

 undisturbed ; from the mice and guinea-pigs, slightly susceptible ; from 

 the dog, more, and from the rabbit, most susceptible. 



