A SELECTIVE MEDIUM FOR THE ISOLATION AND ENUMERATION OF ORAL LACTOBACILLI

¹ National Institute of Dental Research, National Institutes of Health, Bethesda, Md.

A new, easily prepared, inexpensive, and reproducible medium is presented for the selective isolation and enumeration of oral lactobacilli from human and animal samples. In the comparative study of 122 human salivary specimens and 156 oral hamster samples in the new SL agar and on the modified Hadley TJ agar, it was found that SL agar was almost completely specific for lactobacilli and produced counts which compared favorably witih those obtained from TJ agar. Except for the very infrequent presence of yeasts in greatly reduced numbers, all of the organisms other than lactobacilli found on TJ agar, such as micrococci or staphylococci, streptococci. molds, spore-forming bacteria, and gram-negative rods, are eliminated in SL agar.