Crystal Diagnostics Xpress^™ LM Kit for the Rapid Detection of Listeria monocytogenes from Environmental Surfaces

The Crystal Diagnostics (CDx) Xpress™ LM kit is used for rapid screening of low concentrations of Listeria monocytogenes on environmental surfaces such as stainless steel, plastic, and ceramic tile. In addition to the Xpress LM kit, the CDx Xpress System comprises an automatic Xpress Reader, a BioCassette™ that incorporates antibody-coupled microspheres, and liquid crystal for selective identification of the intended microbe. All 56 of the 56 tested L. monocytogenes strains evaluated were detected, and 50 of the 50 nontarget bacterial strains were excluded when the test was conducted under the described kit conditions. Shelf-life testing of the antibody-coated microspheres and other CDx consumables indicated that all materials were stable for a minimum of 6 months (ongoing), and lot-to-lot testing demonstrated no significant differences among lots. The internal and independent laboratory tests on stainless steel, plastic, and ceramic tile surfaces demonstrated that the method is equivalent to the U.S. Department of Agriculture (USDA) reference method, and there were no significant differences between the CDx Xpress LM kit presumptive and confirmed results for any of the matrixes. Overall, the CDx Xpress LM kit is one of the fastest to provide the sensitivity and specificity equivalent to the USDA reference method in screening low levels of L. monocytogenes surface contamination and, when combined with chromogenic culturing of presumptive positives, provides a streamlined confirmation process to rapidly and accurately differentiate L. monocytogenes from other microbes.