Xylose lysine tergitol 4 agar xlt 4

Alongside positive (Salmonella Typhimurium ATCC 14028) and negative (E. coli ATCC 25922) controls, feces and sponge swab washings were each dispensed into Tetrathionate (TT; BD Canada, Mississauga, ON, Canada) and Rappaport-Vassiliadis (RV; EMD Millipore, Etobicoke, ON, Canada) broths and incubated at 42 °C for 20–24 h. Tetrathionate enrichments were streaked onto Xylose Lysine Tergitol 4 agar (XLT-4; BD Canada, Mississauga, ON, Canada) and RV enrichments were transferred to modified semisolid RV (MSRV) agar plates and incubated at 37 °C for 24 h. A loop of MSRV culture from the edge of opaque zones was streaked onto modified Brilliant Green agar (MBGA; Hardy Diagnostics, Santa Maria, CA, USA) and incubated overnight at 37 °C for 24 h. Up to three colonies per XLT-4 and MBGA plate were sub-cultured to fresh XLT-4 plates and incubated at 37 °C for 24 h. Presumptive Salmonella isolates were tested for agglutination with Poly A-I + Vi antiserum (BD Canada, Mississauga, ON, Canada).

Upon arrival to the laboratory, 10 g of each faecal sample, or the entire swab, were placed into 90 mL Tryptic Soy Broth (TSB) (BD, Sparks, MD) and incubated at 25 °C for 2 h followed by 42 °C for 8 h, then held at 6 °C (Eppendorf, Hauppauge, NY). From this TSB enrichment, 1 mL was transferred into 9 mL Buffered Peptone Water (BPW) (Hardy Diagnostics, Santa Maria, CA) and incubated at 37 °C for 24 h. Then, 100 µL of BPW enrichment was incubated in 10 mL Rappaport Vassiliadis (RV) broth (BD, Sparks, MD) at 42 °C for 24 h followed by plating onto Xylose lysine tergitol 4 agar (XLT4) (BD, Sparks, MD) and incubation at 37 °C for 24 h [26 (link)]. Presumptive positive colonies were confirmed using traditional polymerase chain reaction (PCR) [27 (link)].