CHAPTER XV 



THE BACTERIOLOGY OF FOODS 



The relation of bacteria to foods is an important one and should 

 be as thoroughly understood as possible by both the profession and 

 the laity. The relationship may be expressed thus: 



I. Foods serve as vehicles by which infectious agents are con- 

 veyed to the body. 



II. Foods are chemically changed and made unfit for use by the 

 bacteria. 



I. Foods as Fomites.' — In animal food the first source of infection 

 is the animal ItseK, danger of infection always accompanying the 

 employment of foods derived from diseased animals. Thus, milk 

 apparently normal in appearance has been found to contain danger- 

 ous pathogenic bacteria. The tubercle bacillus is one of the most 

 important of these, and at the present time the consensus of opinion 

 inclines toward the view that the great prevalence of tuberculosis 

 among human beings depends partly upon the ingestion of tubercle 

 bacilU ia milk. It does not appear necessary that the udder of the 

 cow be diseased in order that the organisms enter the milk, as they 

 seem to have been found in milks derived from cows whose udders 

 were entirely free from demonstrable tuberculosis. It is, therefore, 

 imperative to retain only healthy cows in the dairy, and careful 

 legislation shotdd provide for the detection and destruction of all 

 tuberculous animals. The detection of tubercle bacilli in milk can 

 only be certainly accomplished by the injection of a few cubic centi- 

 meters of the fluid into guinea-pigs and noting the results. 



In addition to the tubercle bacillus, pyogenic strq)tococci. have 

 been observed in enormous quantities and almost pture culture in 

 milk drawn from cows suffering from mastitis. Stokes * has observed 

 a remarkable case of this kind in which the milk contained so much 

 pus that it floated upon the top like cream. Such seriously in- 

 fected milk could not be used with safety to the consumer. 



In market milk one occasionally finds pathogenic organisms, such 

 as the diphtheria bacillus, tj^hoid bacillus, streptococcus, etc., de- 

 rived from human sources. Such polluted milks have been known 

 to spread epidemics of the respective diseases whose inicro-organisms 

 are present. Bacteria may enter milk from careless handling, from 

 water used to wash the cans or to dilute the milk, or from dust; and 

 as milk is an excellent medium for the growth of bacteria, it should 



* "Maryland Medical Journal," Jan. 9, 1897. 



2SI 



