An improved method for the recovery of Salmonella serovars from orange juice using universal preenrichment broth

The relative effectiveness of three methods for the recovery of Salmonella serovars from orange juice was determined. One method, a modified Bacteriol ogical Analytical Manual (BAM) procedure consisted of preenrichment in lact ose broth at 35 degreesC for 24 h, selective enrichment, and selective plat ing. Another method, a National Centers for Disease Control and Prevention (CDC 1) procedure, consisted of direct enrichment in tetrathionate broth at 35 degreesC for 24 and 48 h, followed by selective plating. The third meth od (also from CDC and designated CDC 2) consisted of preenrichment in Unive rsal Preenrichment (UP) broth at 35 degreesC for 24 h, selective enrichment , and selective plating. In 10 experiments encompassing five different Salm onella serovars and 200 test portions per broth, the CDC 1 method recovered 141 Salmonella-positive test portions, the BAM method recovered 151, and t he CDC 2 method recovered 171. In 2 of the 10 experiments, with two differe nt Salmonella serovars, the BAM recovered significantly fewer (P < 0.05) Sa lmonella-positive test portions than did the CDC 2 method. On the basis of the above results, the second phase of this study focused on a comparison o f the effectiveness of the BAM-recommended lactose broth and the CDC 2-reco mmended UP broth as preenrichment media for the recovery of Salmonella sero vars from pasteurized and unpasteurized orange juice. Subsequent culture tr eatment of the two preenrichments was identical so that the effect of other variables (e.g., different selective enrichment media, various incubation temperatures, and different selective plating agars) on the relative perfor mance of these two preenrichment media was excluded. In one of nine experim ents, with pasteurized orange juice, lactose broth recovered significantly fewer (P < 0.05) Salmonella-positive test portions than did UP broth. For t he combined results of the nine pasteurized orange juice experiments (180 t est portions per broth), lactose broth recovered 99 Salmonella-positive tes t portions, and UP broth recovered 116. In three of seven experiments, with unpasteurized orange juice, lactose broth recovered significantly fewer (P < 0.05) Salmonella-positive test portions than did UP broth. For the combi ned results of the seven unpasteurized orange juice experiments (140 test p ortions per broth), lactose broth recovered 73 Salmonella-positive test por tions, and UP broth recovered 117. For both pasteurized and unpasteurized o range juice, the total number of Salmonella-positive test portions recovere d with UP broth was significantly greater than the number recovered with la ctose broth. These results indicate that UP broth is a more effective enric hment broth for the recovery of Salmonella from orange juice than is lactos e broth.