Listeria infections: Epidemiology, pathogenesis and treatment

Abstract

Listeria is a motile, Gram-positive, rod-shaped coccobacillus. It is a non-sporeforming, facultatively anaerobic bacterium that can cause a life-threatening disease to both humans and animals known as Listeriosis. Listeria can frequently be isolated from soil, water, food products and vegetation. It is a major food-borne pathogen worldwide, accounting for about 28% of food-related deaths in the USA alone. In 2006, Listeriosis was reported in 23 European Union Member States and it ranked fifth among the most common zoonotic infections in Europe after Campylobacter, Salmonella, Yersinia and Verotoxin-Producing Escherichia coli (VTEC) infections.The most pathogenic species of Listeria is Listeria monocytogenes that often causes food-borne infections in immuno-compromised hosts, including newborns and the elderly. As a facultative intracellular parasitic bacterium, L. monocytogenes invades a variety of host cells, such as hepatocytes, fibroblasts and epithelial cells, multiplying in the cytoplasm of these cells. This pathogen is one of the reasons of meningoencephalitis and abortion in ruminants. In neonates, it is the third most common cause of bacterial meningitis after E. coli and Streptococcus agalactiae.In most Listeria infections cases, the symptoms spontaneously clear in about seven days. However, patients at high risk such as pregnant women require antimicrobial treatment to prevent halt and development of more severe diseases. The duration of antimicrobial treatment depends on the severity of the infection. In Listeriosis treatment, the initial choice of antimicrobials is usually Ampicillin. Some studies also reported a successful treatment using the synergism present in the Trimethoprim-sulfamethoxazole preparations.