Evaluation of culture media for detection of salmonellae in composted biosolids

Although US EPA sewage sludge regulations include monitoring for salmonellae, the relative efficiency of various culture methods for detecting salmonellae in composted biosolids is not well established. In this study, four enrichment and three plating media were compared in terms of their ability to detect salmonellae from composted biosolids. Rappaport-Vassiliadis broth was more efficient than strontium chloride B, tetrathionate and mannitol selenite enrichment broths. There were no statistical differences between the salmonellae isolation rates on xylose lysine deoxycholate, bismuth sulphite and lysine mannitol glycerol agars. Attempts were also made to improve the performance of selenite enrichment broth by altering its composition. Optimal isolation media identified in this research represent a significant departure from the media recommended by the US EPA.