Salmonella contamination of meat and bone meal

The production of meat and bone meal from 8 rendering plants was examined for the presence of salmonellas. Of 164 samples of final product 114 (69.5%) were contaminated with salmonellas. Of 65 samples, collected at various points from the production line 35 (53.8%), and of 95 samples collected from the processing environment 79 (83.1%) were found to be contaminated with salmonellas. A total of 41 serotypes were found with S. havana, S. eimsbuettel, S. ohio and S. singapore being the most frequently isolated. Pre-enrichment of 25g samples in buffered peptone water, followed by enrichment in mannitol selenite cystine broth at 42 degrees C and Muller-Kauffmann Tetrathionate Broth at 37 degrees C and plating on Bismuth Sulphite Agar was found to yield 98.5% of the salmonella-positive samples.