280 Microbes and You 



lining to help retain the natural color of foods during processing. 

 There is not sufficient evidence to warrant the statement that illness 

 is more likely to occur from foods preserved in cans with a thin 

 coating of tin. 



Because foods may contain heat-resistant, spore-forming bacteria 

 prior to processing, some spoilage must be expected in the finished 

 product, since spores frequently survive this heat treatment. A 

 leaky can or one having bulged ends due to gas pressures built up 

 within the container obviously should be discarded. Any cans 

 with distinct off-odors should also be thrown away. Oftentimes 

 an off-odor does not become apparent until heat is applied to the 

 food. 



MILK AND DAIRY PRODUCTS 



Because milk is one of nature's most nearly perfect foods, 

 microorganisms thrive in it when the temperature is raised much 

 above that found in a properly functioning refrigerator. Serious 

 milk-borne outbreaks have occurred in the past due to pathogenic 

 organisms which have gained entrance to the milk either directly 

 from infected persons and from healthy carriers, or indirectly from 

 milk-producing animals which have served as carriers when man 

 has contaminated their udders. There are still other diseases 

 which can be transmitted to man directly from infected animals, 

 and tuberculosis and undulant fever fall into this group. 



TUBERCULOSIS 



Pulmonary (lung) tuberculosis is usually transmitted from one 

 infected person to another through the agency of discharges con- 

 taining the bacteria Mycobacterium tuberculosis. The protective 

 capsule surrounding these organisms allows them to withstand 

 considerable periods of drying and a relatively long contact with 

 sunlight and chemical agents before the cell succumbs. Viable 

 tuberculosis organisms have been isolated from house dust many 

 months after a patient has left the area. 



Once the leading cause of death in the United States, tubercu- 

 losis—formerly called the white plague— has dropped far down the 

 list of diseases affecting man. This reduction is largelv the result 



