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

Abstract Objectives : Many laboratories use culture-independent diagnostic tests for bacterial gastroenteritis (ie. 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 we 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 E. 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 negative clinical stools were greater than 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, stx2f was detected by only 1 of 4 assays. Of note, no assay could detect Yersinia non-enterocolitica and C. upsaliensis. Conclusions : Depending on the prevalence of certain stx sub-types, Yersinia and Campylobacter species in a laboratory's jurisdiction, culture methods remain critical for the detection of these pathogens without further improvement in PCR assays.