Invasive Species Compendium

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Abstract

Improvements to the immunoassay for detection of Rathayibacter toxicus in hay.

Abstract

An improved protocol for the previously described enzyme-linked immunosorbent assay for Rathayibacter toxicus in hay is described. The improvements were driven mainly by the export hay industry requirement of same-day turnaround for testing of hay extracts. The preparation of hay extracts was shortened by 8 h. The time for adding samples to the enzyme-linked immunosorbent assay plates was shortened by the use of sample tubes with penetrable stoppers combined with specially designed racks. The monoclonal antibody used in the original protocol was purified and conjugated to horseradish peroxidase. This eliminated the need for a secondary step with an anti-mouse horseradish peroxidase conjugate and thereby shortened the assay by over 1 h. Results: with the improved assay protocol showed a very high correlation with results obtained with the original protocol (r=0.98). The assay is still sensitive enough to detect antigen equivalent to less than 1 average gall per kg of hay. These cost-effective changes have streamlined the testing of large numbers of samples for the presence of R. toxicus, in support of the hay export industry.