Listeriosis.

Listeria monocytogenes, a small, facultative anaerobic, Gram-positive motile bacillus, is an important cause of foodborne illness which disproportionately affects pregnant women and their newborns. Listeria infects many types of animals and contaminates numerous foods including vegetables, milk, chicken and beef. This organism has a unique proclivity to infect the fetoplacental unit with the ability to invade cells, multiply intracellularly and be transmitted cell-to-cell. The organism possesses several virulence factors, including internalin A and internalin B, which facilitate the direct invasion of cells. Cell-to-cell transmission is promoted by the bacterial surface protein ActA which is regulated by a transcriptional activator known as positive regulatory factor A. Both innate and adaptive immune responses enable the host to eliminate this pathogen. Clinical manifestations of infection in the newborn fall into the traditional categories of early- and late-onset sepsis. Therapeutic recommendations include ampicillin and gentamicin for 14-21 days.