title: Pooled Nucleic Acid Amplification Test for Screening of Stool Specimens for Shiga Toxin-Producing Escherichia coli.
abstract: Shiga toxin-producing Escherichia coli (STEC)-associated enteric illness is attributed to O157 and non-O157 serotypes; however, traditional culture-based methods underdetect non-O157 STEC. Labor and cost of consumables are major barriers to implementation of the CDC recommendation to test all stools for both O157 and non-O157 serotypes. We evaluated the feasibility of a pooled nucleic acid amplification test (NAAT) as an approach for screening stool specimens for STEC. For retrospective evaluation, 300 stool specimens were used to create pools of 10 samples each. The sensitivity was 83% for the preenrichment pooling strategy and 100% for the postenrichment pooling strategy compared with those for individual NAAT results. The difference in cycle threshold (CT) between individual and pooled NAAT results for specimens was significantly lower and more consistent for postenrichment pooling (stx1mean = 3.90, stx2mean = 4.28) than those for preenrichment pooling (excluding undetected specimens; stx1mean = 9.34, stx2mean = 8.96) (P ≤ 0.0013). Cost of consumables and labor time savings of 48 to 81% and 6 to 66%, respectively, were estimated for the testing of 90 specimens by the postenrichment pooled NAAT strategy on the basis of an expected 1 to 2% positivity rate. A 30-day prospective head-to-head clinical trial involving 512 specimens confirmed the sensitivity and labor savings associated with the postenrichment pooled NAAT strategy. The postenrichment pooled NAAT strategy described here is suitable for efficient large-scale surveillance of all STEC serotypes. Comprehensive detection of STEC will result in accurate estimation of STEC burden and, consequently, appropriate public health interventions.
authors: British Columbia Centre for Disease Control Public Health Laboratory, Provincial Health Services Authority, Vancouver, British Columbia, Canada.|Department of Pathology and Laboratory Medicine, The University of British Columbia, Vancouver, British Columbia, Canada.
authors: Agatha N
authors: AN
authors: Jassem
authors: British Columbia Centre for Disease Control Public Health Laboratory, Provincial Health Services Authority, Vancouver, British Columbia, Canada.
authors: Frank Y
authors: FY
authors: Chou
authors: British Columbia Centre for Disease Control Public Health Laboratory, Provincial Health Services Authority, Vancouver, British Columbia, Canada.
authors: Cathevine
authors: C
authors: Yang
authors: British Columbia Centre for Disease Control Public Health Laboratory, Provincial Health Services Authority, Vancouver, British Columbia, Canada.
authors: Matthew A
authors: MA
authors: Croxen
authors: FoodNet Canada, Centre for Food-Borne, Environmental and Zoonotic Infectious Diseases, Public Health Agency of Canada, Ottawa, Ontario, Canada.
authors: Katarina D M
authors: KD
authors: Pintar
authors: British Columbia Centre for Disease Control Public Health Laboratory, Provincial Health Services Authority, Vancouver, British Columbia, Canada.
authors: Ana
authors: A
authors: Paccagnella
authors: British Columbia Centre for Disease Control Public Health Laboratory, Provincial Health Services Authority, Vancouver, British Columbia, Canada.|Department of Pathology and Laboratory Medicine, The University of British Columbia, Vancouver, British Columbia, Canada.
authors: Linda
authors: L
authors: Hoang
authors: British Columbia Centre for Disease Control Public Health Laboratory, Provincial Health Services Authority, Vancouver, British Columbia, Canada natalie.prystajecky@bccdc.ca.|Department of Pathology and Laboratory Medicine, The University of British Columbia, Vancouver, British Columbia, Canada.
authors: Natalie
authors: N
authors: Prystajecky
mesh_terms: D003365:Costs and Cost Analysis; D004927:Escherichia coli Infections / Q000175:diagnosis*; D005243:Feces / Q000382:microbiology*; D006801:Humans; D008403:Mass Screening / Q000191:economics / Q000379:methods*; D021141:Nucleic Acid Amplification Techniques / Q000191:economics / Q000379:methods*; D011446:Prospective Studies; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D054323:Shiga-Toxigenic Escherichia coli / Q000302:isolation & purification*; D013048:Specimen Handling / Q000191:economics / Q000379:methods*