ABSTRACT
The genus Listeria comprises six closely related, Gram-positive bacterial species (i.e., L. monocytogenes, L. ivanovii, L. seeligeri, L. innocua, L. welshimeri, and L. grayi), which share many similar morphological, biochemical, and molecular characteristics.1-4 Listeria species are ubiquitously distributed in the environment and frequently found in various manufactured food products; L. monocytogenes strains are remarkably tolerant to a broad spectrum of external stresses (including wide pH, osmolarity, and temperature ranges)5 and are capable of causing especially severe illness to vulnerable human population groups (e.g., infants, pregnant women, the elderly, and immunocompromised individuals),4 and listeriosis often produces nonspecic initial clinical manifestations (e.g., u-like symptoms and gastroenteritis) with potentially fatal consequences (e.g., meningitis, encephalitis, septicemia, and occasional death).3 Thus, it is imperative that specic, sensitive, and speedy laboratory procedures are available for prompt detection and accurate identi-cation of L. monocytogenes from nonpathogenic Listeria and other contaminating bacteria. This is essential to the timely implementation of antibiotic therapy, thus preventing an otherwise easily treated malaise from developing into a life-threatening disease.
