INFLUENCE OF MILK ON THE GROWTH OF COAGULASE-NEGATIVE STAPHYLOCOCCI ON TELLURITE GLYCINE AGAR MEDIUM1

N. Joshi, A. C. Blackwood, D. G. Dale
1963 Journal of Bacteriology  
During studies involving quantitative determination of coagulase-positive staphylococci in mastitic milk, discrepancies occurred between counts obtained on the tellurite glycine (TG) agar medium (Difco) of Zebovitz, Evans, and Niven (J. Bacteriol. 70:686, 1955) and on the Staphylococcus Medium No. 110 (Difco) of Chapman (J. Bacteriol. 51:409, 1946). This suggested that the milk itself might have an effect on the growth of staphylococci in certain selective media. Accordingly, an experiment was
more » ... an experiment was conducted to study the influence of milk on the growth of staphylococci on TG agar medium. Ten coagulase-negative isolates were used. The organisms were grown in Brain Heart Infusion (BHI) broth (Difco) for 18 hr at 37 C, and 0.1-ml samples of a 104 saline dilution of each organism were inoculated into separate tubes containing 5 ml of sterile whole milk and also into doubling dilutions of milk in saline (1: 64). Tubes containing 5 ml of sterile saline were also inoculated with a 0.1-ml sample of a 104 saline dilution of each organism; these served as controls. Five plates were made with 0.1-ml samples from these tubes on TG agar medium and BHI agar by spreading the inoculum with the aid of a bent glass rod. After incubation at 37 C for 24 hr, the colonies were counted. The results indicated that 61 to 95% (average, 82%) of the organisms which grew on BHI agar also grew on TG agar medium in the presence of whole milk. In contrast, no growth took place on
doi:10.1128/jb.86.5.1119-1119.1963 fatcat:hjdddthwwvbg5jt4pmeotfiz2a