72 DIFCO MANUAL 



3. Rub the swab slowly and firmly three times over the significant surfaces of 

 the utensil to be examined, reversing the direction of the swab each time. 



The significant surfaces of utensils are generally considered as the upper half 

 inch of the inner and outer rims of glasses and cups and the entire inner and 

 outer surfaces of the bowls of the spoons. In the examination of forks and knives 

 the inner and outer tines of the fork and both sides of the blade of the knife 

 should be swabbed. Plates and bowls should be swabbed on the inner and outer 

 surfaces. 



After swabbing each utensil return the swab to the Neutralizing Buffer solu- 

 tion, rotate well and press free from excess solution, before swabbing the next 

 utensil in the group with the moist swab. 



4. When the last utensil, generally four or more, has been swabbed, replace 

 the swab in the Neutralizing Buffer, and shake vigorously. If separate swabs were 

 used, break ofT each swab in the container under aseptic conditions. 



5. Keep Neutralizing Buffer containing swabs at 0-6°C. until plated in the 

 laboratory. 



6. For procedures requiring a plate count, break the stick of the swab just 

 above the cotton with sterile forceps, if this has not already been done as indi- 

 cated above. Shake the swab in the Neutralizing Buffer thoroughly to disintegrate 

 the cotton swabs. Plate 1 ml. or desired quantity using Bacto-Tryptone Glucose 

 Extract Agar as the plating medium. Incubate at 32 or 35 °C. for 48 hours before 

 making the count. 



If desired, a Visual Sanitation Test may be run by following the above direc- 

 tions through Step 4, except that in Step 4 the swab is not broken but following 

 the swabbing of the last utensil, it is immersed in the Neutralizing Buffer, shaken 

 vigorously, squeezed to remove excess moisture and then smeared directly on 

 the surface of a slant of Bacto-Tryptone Glucose Extract Agar. Inoculation may 

 be made by moving the moist swab across the surface of the slant from top to 

 bottom horizontally and then vertically. The swab is rotated while being streaked 

 across the surface of the medium. The inoculated medium is then incubated as 

 desired. 



To rehydrate Bacto-Neutralizing Buffer, dissolve 5.2 grams in 1000 ml. of cold 

 distilled water. Distribute in screw cap containers and sterilize in the autoclave 

 for 15 minutes at 15 pounds pressure (121°C.). Final reaction will be pH 7.2. 



One hundred grams of Bacto-Neutralizing Buffer will make 19.2 liters. 



1 Standard Methods for the Examination ^ Ann. Year Book 1947-48. Suppl. 



of Dairy Products, 9th Edition: 216: 1948. Am. J. Pub. Health, 5:68:1948. 



3 J. Milk Food Tech., 12:224:1949. 



MEDIA FOR LACTOBACILLI 



The media listed in this section are useful for the cultivation, enumeration and 

 study of Lactobacilli, particularly those concerned with the manufacture of dairy 

 products. 



