18 A BACTERIOLOGICAL STUDY OF EGGS. 



METHODS USED IN THE BACTERIOLOGICAL EXAMINATION OF 



EGGS. 



STERILIZATION. 



All glassware and utensils should be thoroughly cleansed and steri- 

 lized before use. Sterilization may be accomplished by the use of dry 

 heat or live steam. An exposure to dry heat at 160 C. for one hour, 

 or until the cotton plugs become slightly brown, is deemed sufficient. 

 Live steam under 15 pounds pressure for 30 minutes usually destroys 

 all organisms. 



CULTURE MEDIA. 



All culture media are prepared according to the approved methods 

 recommended by the American Public Health Association. 1 Special 

 media not mentioned by this association should be described in detail. 



SAMPLING. 



In removing samples from the original containers proper care 

 should be exercised to prevent extraneous contamination. Only 

 sterile instruments and containers should be used for this purpose. 

 Representative portions should be removed from solid substances and 

 liquid samples should be well shaken before sampling. Eggs should 

 be examined at once when this is practicable, or be properly iced if 

 in the shell, or frozen if out of it, to prevent bacterial increase until 

 such examinations are made. 



RECORDS. 



The proper records and means of identification must be observed 

 with each sample. 



TECHNIQUE OF EXAMINATION. 



Solid substances should be examined on the gram basis ; liquid sub- 

 stances on the cubic centimeter basis. Dilutions of solid substances 

 are made by weighing definite quantities of the sample (about 5 

 grams) in sterile glass-stoppered flasks. To the weighed amount 

 9 times tha quantity of sterile water is added to the sample to make 

 a dilution of 1 to 10. The addition of sterile glass beads to the flask 

 before agitation facilitates the disintegration of solid substances. 



i Report of the Committee on Standard Methods of Water Analysis to the Laboratory Section of the 

 American PublicHealth Association; presented at the Havana meeting, January 9, 1905, reprinted from 

 the Journal of Infectious Diseases, May, 1905, Supplement No. 1; also Progress Report of the Committee on 

 Standard Methods for Bacterial Examination of Water and Sewage, reprinted from the Amer. J. Public 

 Hygiene, 1908, vol. 18, No. 4; also Second Progress Report of the Committee on Standard Methods for the 

 Bacterial Examination of Water and Sewage, reprinted from the Amer. J. Public Hygiene, August, 1910, 

 vol. 20, No. 3. The last report of this committee under date of December 19, 1910, has been issued for con- 

 sideration, but has not been finally approved. 



