Media used in the detection and enumeration of Staphylococcus aureus

Abstract

Over the years a range of selective and diagnostic media have been developed to assist in the detection and enumeration of Staphylococcus aureus in routine food surveillance programmes and food poisoning investigations and these are reviewed here. Baird-Parker agar remains, however, the medium of choice for direct plating and enumeration of S. aureus in both Europe and the US. This paper also reports on a comparison of the productivity and selectivity of trypticase soy broth with 10% NaCl and 1% sodium pyruvate (PTSBS) with trypticase soy broth (TSB) for the isolation of S. aureus. Using three strains of S. aureus and a strain of S. hyicus the productivity ratio of PTSBS to TSBS ranged from -0.17 to 0.57. In the recovery of heat-injured cells of S. aureus, PTSBS offered little or no improvement over TSB with sodium chloride but no pyruvate in a three-tube MPN assessment. Of the seven other bacterial cultures tested, none grew well on the PTSBS. Selectivity ratios of 4.4-7 were found.