Evaluation of ten commercial blood culture systems to isolate a pyridoxal-dependent streptococcus

This study evaluated the ability of ten commercial blood cultures to support the growth of a nutritional variant Streptococcus mitior (pyridoxal-dependent). The abilities of two established and two new agar formulations are also reported. The dependable isolation of a fastidious streptococcus can best be obtained with fastidious anaerobe broth (FAB) (Lab M Ltd, Ford Lane, Salford) for blood cultures in conjunction with one of the new media. FAB agar with the addition of heated blood was found to support the growth of pyridoxal-dependent Strep mitior and other fastidious organisms.