Protein antigens expressed on the surface of all strains of Listeria monocytogenes and absent from nonpathogenic Listeria spp. are presumably useful targets for pathogen identification, detection, and isolation using specific antibodies (Abs). To seek such surface proteins expressed in various strains of L. monocytogenes for diagnostic applications, we focused on a set of surface proteins known to be involved or putatively involved in L. monocytogenes virulence and identified Listeria adhesion protein B ( T he Gram-positive bacterium Listeria monocytogenes is an intracellular pathogen that can cause a severe and life-threatening illness referred to as listeriosis in humans (1). This organism is ubiquitous in nature, is commonly found in water, soil, and vegetation, and can survive in harsh environments (2), making foods vulnerable to pathogen contamination during harvesting and/or processing. Consumption of contaminated foods is the most common route of transmission of L. monocytogenes to humans, posing an extremely high risk to newborns, the elderly, pregnant women, and immunocompromised individuals. Although the incidence of listeriosis is low, its high mortality rate of up to 50% (3,4,5,6) continues to make L. monocytogenes a serious foodborne pathogen. Recent outbreaks of listeriosis in Canada, linked to contaminated ready-to-eat meat products resulting in 22 deaths (http: //news.gc.ca/web/article-en.do?nidϭ468909), and in the United States, attributed to cantaloupes causing 33 deaths (http://www .cdc.gov/listeria/outbreaks/cantaloupes-jensen-farms/082712 /index.html), highlight the importance of enhancing the capability to detect and identify this pathogen in food chains.L. monocytogenes belongs to the genus of Listeria, in which 17 species are recognized (7)