Performance of four commercial real-time PCR assays for the detection of bacterial enteric pathogens in clinical samples

Objectives Many laboratories use culture-independent diagnostic tests for bacterial gastroenteritis (i.e. real-time polymerase chain reaction, RT-PCR) instead of culture because of better sensitivity, automation, and faster turnaround times. To address some gaps in initial evaluations and lack of intraassay comparisons for many commercial RT-PCRs, this study compared the ability of four commercially available RT-PCR tests (Ridagene, Fast Track Diagnostics, BD Max, and Prodesse Progastro) to detect five major bacterial enteric pathogens: Campylobacter, Salmonella , Shiga-toxin producing Escherichia coli (STEC), Shigella , and Yersinia. Methods Clinical stool specimens and contrived samples comprising commonly circulating species, serotypes, biovars, and/or toxin subtypes were used for the comparison. Results Concordance rates for RT-PCR and culture using culture-positive and culture-negative clinical stools were >90% for Campylobacter (97.5-100%), Salmonella (97.5-100%), Shigella (100%), and STEC (90-100%). However, the agreement between RT-PCR and culture for Y. enteroccolitica ranged from 70-90%. For the contrived sample set, stx 2f was detected by one of four assays. Of note, no assay could detect Yersinia non- enterocolitica and Campylobacter upsaliensis. Conclusions Depending on the prevalence of certain stx sub-types, Yersinia species, and Campylobacter species in a laboratory's jurisdiction, without further improvement in culture-independent tests, culture methods remain critical for the detection of these pathogens.