Growth of Peptococcus and Peptostreptococcus: effect of variations of culture media on efficiency of recovery.

Reference strains and clinical isolates of Peptococcus and Peptostreptococcus spp. were evaluated for their growth response in supplemented thioglycolate-yeast extract media. Supplements used included various combinations of hemin, menadione, sodium bicarbonate, and Tween 80. Parallel studies were done to compare the efficiency of recovery of viable cells grown in thioglycolate-based media and Wilkins-Chalgren broth and agar. In addition, the effects of age of the medium and medium storage on viable cell yields for reference strains were determined. Reference strains grown in freshly prepared thioglycolate-yeast extract medium supplemented with sodium bicarbonate produced a 10-fold greater increase in the number of viable cells recovered after 24 h of incubation than did the same organisms cultivated in Wilkins-Chalgren medium. The efficiency of recovery of organisms when either mid-logarithmic- or mid-stationary-phase cells were used to prepare standardized inocula was similar. The results suggest that thioglycolate-yeast extract medium supplemented with sodium bicarbonate is more productive than Wilkins-Chalgren medium for the cultivation of anaerobic gram-positive cocci and may represent a suitable alternative for antimicrobial susceptibility testing of these organisms.