The use of transoligosaccharide (TOS) propionate agar medium with mupirocin for selective enumeration of bifidobacteria in dairy cultures and in fermented dairy products.

摘要

Transoligosaccharide propionate agar medium (TOS) with mupirocin was studied for selective enumeration of bifidobacteria from dairy cultures and dairy products, including kefir cultures and kefir beverages. The sensitivity of 9 bifidobacteria strains and 20 lactic acid bacteria (LAB) strains to mupirocin was tested in TOS medium. TOS with addition of mupirocin (50 micro g/ml) was successfully used to enumerate bifidobacteria in dairy cultures and in dairy products. The recovery of bifidobacteria was >95%. Bifidobacteria formed colonies >1 mm in diameter, in contrary, growth of LAB was suppressed, or they formed colonies <0.5 mm in diameter and could be readily distinguished. Bifidobacteria showed resistance to high level of mupirocin (MIC >300 micro g/ml), whereas Leuconostoc, Lactococcus, Streptococcus and Lactobacillus strains were sensitive (MIC <100 micro g/ml for most of the strains). The results confirmed the usefulness of TOS medium modified by addition of mupirocin (50 micro g/ml) proposed by IDF for the enumeration of bifidobacteria in wide range of dairy cultures and dairy products.