MEDIA FOR ENUMERATING STAPHYLOCOCCUS AUREUS TREATED WITH HYDROGEN PEROXIDE IN MILK1

Abstract
Summary Several media were compared with plate count agar (PCA) for determining numbers of Staphylococcus aureus 196E (ATCC 13565) surviving hydrogen peroxide-catalase treatment in milk at 54.4 C. Time intervals required for 90, 99, 99.9, and. 99.99% destruction of S. aureus were determined from survivor curves obtained with each medium. Statistical analyses were made of the intervals for 90 and 99.9% destruction. The time required for 99.9% destruction was significantly longer when survivors were enumerated on PCA than when enumeration was made on Staphylococcus medium 110 (SM110), Staphylococcus medium 110-Egg Yolk agar (SM110-Ey), tryptic soy agar, or trypticase soy agar (TSA). SM110-Ey was the only medium which inhibited growth of survivors sufficiently to give significantly shorter time for 90% destruction than PCA. Heart infusion agar (HIA) did not differ significantly from PCA in ability to support growth of survivors.

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