Evaluation and comparison of selective media for recovery of fecal streptococci and enterococci from environmental waters
Emken, Nancy J.
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Three selective media, KF Streptococcus Agar (KFSA), mE and EIA(esculin in situ agar), and modified mE, were evaluated for the recovery of streptococci utilizing pure cultures and environmental water. Fecal streptococci (FS) were recovered on KFSA, and the enterococci, a subgroup of FS, were recovered on both mE/EIA and modified mE agars. KFSA, compared to mE/EIA agar, recovered strains of E. faecalis and E. faecium without significant differences. Comparison of mE/EIA to the modified mE media employing log and stationary phase E. faecalis and E. faecium resulted in both media recovering statistically equal numbers of organisms. Utilizing environmental water, KFSA recovered an average 89.0% enterococci. The mE/EIA method revealed 88.7% true positives with a 12.5% false negative rate. Modified mE easily identified enterococci correctly at the 100% level. Both KFSA and mE/EIA were considerably more cost efficient compared to modified mE. However, the added indicator to modified mE allowed for easier and more accurate identification in half of the incubation time with less media preparation and labor involvement, suggesting that modified mE may be a useful media when accuracy and time are important parameters to consider.