EVALUATION OF MEDIA FOR THE ENUMERATION OF FECAL STREPTOCOCCI FROM NATURAL-WATER SAMPLES

The Most Probable Number technique using Azide dextrose broth and Ethyl violet azide dextrose broth, and the membrane filtration technique with the following agars: mEnterococcus, KF, Pfizer selective enterococcus, Kanamycin aesculin azide, Bile-Aesculin, Thallous acetate (Barne's), and Mitis-Salivarius were compared on the basis of their accuracy, specificity, selectivity, precision, and relative recovery efficiency characteristics. The results obtained indicate that none of the above mentioned procedures shows an optimal selectivity. The Most Probable Number technique was a good procedure on the basis of its high recovery efficiency and good selectivity. However, mEnterococcus agar using the membrane filtration technique showed the best performance characteristics of the enumeration media tested, because this method possessed the best recovery efficiency, precision and accuracy, and also a good specificity.