Usefulness of pyridoxal-containing blood agar as a primary plating medium to enhance recovery of nutritionally deficient streptococci.

We evaluated the use of horse blood agar containing 0.0005% pyridoxal hydrochloride (HBAP) mainly for use as a primary plating medium for blood cultures, other sterile fluids, wounds, and abscesses in order to facilitate the isolation of nutritionally deficient streptococci (NDS). Our results showed that the addition of pyridoxal hydrochloride (pxl) permitted good growth of NDS within 24 h and did not inhibit or significantly alter the colony morphology of 34 different species of microorganisms and 296 isolates of beta hemolytic streptococci presumptively identified as Group A streptococci. The use of pxl-supplemented blood agar such as HBAP is recommended for primary plating as well as subculturing of blood cultures, and may also increase recovery of NDS from wounds and abscesses.