Poultry environmental sample testing update

Durda Slavic 

Animal Health Laboratory, University of Guelph, Guelph, ON. 

AHL Newsletter 2024;28(2):19.

In order to provide faster turn-around-time (TAT) for screening of poultry environmental samples for the presence of Salmonella spp., the AHL bacteriology section switched to a new test on May 1, 2024.  This new test involves real-time PCR (qPCR) targeting two Salmonella spp. specific genes.  An internal control (IC) is also included to detect any potential PCR inhibitors.  This screening method is used for all samples previously submitted for testing under ‘hsfe’ and ‘hsfeb’ testing codes, as well as fluff samples for which counts and culture are required.  These 2 test codes are replaced with one ‘hsfepcr’ test code. 
Once received, samples are incubated in buffered peptone water (BPW) overnight, and the screening qPCR test is done the following day (excluding weekends and statutory holidays), providing 24 hr TAT.  Results are reported as either ‘negative’ or ‘culture to follow’.  All ‘culture to follow’ samples undergo routine bacterial culture followed by Salmonella grouping and serotyping, if applicable.   

This screening test was validated using 1630 environmental samples and the summary of test performance is shown in Table 1.  There is almost perfect (0.886 to 0.959) to excellent agreement (0.846) between culture and PCR results.

Table 1.  Diagnostic sensitivity, specificity, agreement between tests, Kappa value, positive predictive value (PPV) and negative predictive value (NPV) shown for the overall PCR results as well as for individual sample types.