Sensitivity of an Immunomagnetic-Separation-Based Test for Detecting Escherichia coli O26 in Bovine Feces

• Published in: Applied and Environmental Microbiology 2006-11, Vol.72 (11), p.7260-7263
• Main Authors: Hall, L.M, Evans, J, Smith, A.W, Pearce, M.C, Knight, H.I, Foster, G, Low, J.C, Gunn, G.J
• Format: Article
• Language: English
• Subjects: Animals; Bacteriological Techniques; Bacteriology; Biological and medical sciences; Cattle; Cattle Diseases - microbiology; Colony Count, Microbial; Culture Media; Disease Reservoirs; E coli; Enterobacteriaceae; Escherichia coli; Escherichia coli - classification; Escherichia coli - isolation & purification; Escherichia coli Infections - microbiology; Escherichia coli Infections - veterinary; Feces - microbiology; Fundamental and applied biological sciences. Psychology; Immunomagnetic Separation - methods; Methods; Microbiology; Polymerase Chain Reaction; Sensitivity and Specificity
• ISSN: 0099-2240; 1098-5336
• DOI: 10.1128/AEM.03028-05

The sensitivity of a test for cattle shedding Escherichia coli serogroup O26 was estimated using several fecal pats artificially inoculated at a range of concentrations with different E. coli O26 strains. The test involves the enrichment of fecal microflora in buffered peptone water, the selective concentration of E. coli O26 using antibody-coated immunomagnetic-separation beads, the identification of E. coli colonies on Chromocult tryptone bile X-glucuronide agar, and confirmation of the serogroup with E. coli serogroup O26-specific antisera using slide agglutination. The effective dose of E. coli O26 for an 80% test sensitivity (ED₈₀) was 1.0 x 10⁴ CFU g⁻¹ feces (95% confidence interval, 4.7 x 10³ to 2.4 x 10⁴). Differences in test sensitivity between different E. coli O26 strains and fecal pats were also observed. Individual estimates of ED₈₀ for each strain and fecal pat combination ranged from 4.2 x 10² to 4.8 x 10⁵ CFU g⁻¹. These results suggest that the test is useful for identifying individuals shedding a large number of E. coli O26 organisms or, if an appropriate number of individuals in a herd are sampled, for identifying affected herds. The study also provides a benchmark estimate of sensitivity that can be used to compare alternative tests for E. coli O26 and a methodological approach that can be applied to tests for other pathogenic members of the Enterobacteriaceae and other sample types.