Purpose: The current study was conducted to evaluate the ability to recover Salmonella spp. from shell egg contents by culture methods.
Methods: A total of 4,000 eggs were obtained from grading and packing (GP) centers and 200 samples were created by pooling 20 broken eggs. Pooled samples were held at 25°C for 4 days before 25mL aliquots were added to 225 mL of modified trypticase soy broth (mTSB) and incubated at 35°C for 24 h. A loopfulof overnight broth cultures was streaked onto chromogenic Druggan-Forsythe-Iverson (DIF) agar and incubated for 24 h at 37°C. Also, 1mL and 0.1mL of the culture were added to Muller-Kauffmann tetrathionatebroth with novobiocin(MKTTn) and Rappaport-Vassiliadis Soya (RVS) media, which were incubated for 24 h at 37°C and 42°C, respectively. A loopful of the RV and MKTTn enrichment cultures were streaked onto xylose lysine deoxycholate (XLD), bismuth sulfite (BS), and brilliant green (BG) agar plates.
Results: Directly streaking onto DFI agar revealed the presence of Salmonella spp. in 14 of the 200 pooled samples (7%), whereas the combination of RV broth culture and streaking on BG, XLD and BS agar detected the pathogen in only nine (4.5%), seven (3.5%) and three (1.5%) of the pooled samples, respectively. When MKTTn broth was used, Salmonella spp. was detected in seven (3.5%), two (1%) and zero (0%) of the samples when streaked onto BG, XLD and BS, respectively.
Significance: The results of this study indicated that the DFI direct plating method without enrichment is the most suitable for the investigation of Salmonella spp. in raw shell egg contents with a low microbial load.