Comparison of fluorescent gentamicin-thallous-carbonate and KF streptococcal agars to enumerate enterococci and fecal streptococci in meats

Abstract

Two selective and differential media were compared for their abilities to enumerate enterococci and fecal streptococci in pork, beef, and poultry products. Counts obtained on KF streptococcal (KF) agar were compared with counts obtained on fluorescent gentamicin-thallous-carbonate (fGTC) agar. Reactions of 13 known enterococcal species were also observed. All 13 species of enterococci as well as Streptococcus bovis and Streptococcus equinus grew equally well on fGTC agar. KF streptococcal medium allowed growth of most species of enterococci but not S. bovis and S. equinus. Quantitative comparisons between the two media inoculated with pure cultures of known species of enterococci revealed equivalent plate counts following incubation. However, when meat samples were plated, counts on fGTC agar were consistently and significantly higher than counts on KF agar for all sample sources.