Stimulation of the growth of cutaneous strains of Peptococcus saccharolyticus by iron, haematin and blood.

The growth of nine strains of Peptococcus saccharolyticus was assessed quantitatively by culture Trypticase Soy/yeast extract/Tween 80 agar (TSY-TW) with and without supplementation with iron or haematin and on blood agar, in aerobic, reduced 02 (3% O2 with 8% CO2, 8% H2 and 81% N2) and anaerobic atmospheres. All strains grew better anaerobically and under reduced O2 conditions than aerobically on supplemented or unsupplemented TSY-TW. Supplementation of TSY-TW with iron or haematin resulted in an average 4.4-fold increase in bacterial count in a reduced O2 atmosphere and an average 4.2-fold increase under anaerobic conditions. Under aerobic conditions the increase in count ranged from O to greater than 5000-fold, as some strains failed to grow on unsupplemented TSY-TW but responded well to the supplements of iron or haematin. The highest bacterial counts were obtained on Columbia blood agar incubated anaerobically. However, P. saccharolyticus failed to grow aerobically on plain or heated Columbia blood agar with or without supplements. TSY-TW blood agar supported the growth of the one strain tested under all three atmospheric conditions. The type strain (ATCC 14953) differed from all others in its failure to grow aerobically or in a reduced O2 atmosphere on supplement or unsupplemented media. Colony size varied greatly on different media, in different atmospheres and from strain to strain, being greatest in a reduced O2 atmosphere on Columbia blood agar. There was no correlation between the viable bacterial count and colony size.