Quantitative evaluation of three commercial blood culture media for growth of anaerobic organisms

The ability of three different commercial blood culture media--brain heart infusion broth (Pfizer), thiol broth (Difco), and PRS-peptone broth (Becton, Dickinson & Co.)--to support the growth of five different anaerobes is described. Inocula of 100 and 1,000 colony-forming units per ml were used to evaluate potential differences in survival, lag time, growth rate, and doubling times of each anaerobe in each medium. In addition, each medium was evaluated for its ability to neutralize the antibacterial effects of whole blood. The results of this study indicate that the PRS-peptone broth is superior to brain heart infusion and thiol broths. Shorter lag times and accelerated generation times and growth rates were noted for more different anaerobes in the PRS-peptone broth. Neither the size of inoculum nor the addition of normal whole blood appeared to alter the survival or growth characteristics of the anaerobes in any medium. However, the addition of normal whole blood did extend the lag time of each anaerobe by approximately 1 to 2 h in each medium.