Two Improved Media for Isolating and Enumerating Enterococci in Certain Frozen Foods

SUMMARY A direct plating method was employed in a comparison of two newly modified selective media, Tween‐carbonate (TC) and thallous acetate‐citrate (TAC) agars, and 4 other selective media, M‐enterococcus (ME) thallous acetate (TA), KF‐streptococcus (KF) and citrate‐azide (CA) agars, for enumerating enterococci in some frozen foods. Pure cultures of enterococci yielded comparable counts on TC, TAC, TA, KF and CA agars. When frozen food samples were plated, enterococcal counts on TA agar were generally higher than counts obtained on TAC, ME, TA or KF agars; TC and TAC agars were more selective than the other media tested. The TC agar at pH 6 inhibited enterococcal growth in the absence of bicarbonate. TC and TAC agars were the most suitable for isolating the interococci both qualitatively and quantitatively.