Liver abscess due to Listeria monocytogenes

Autolysin amidase of Listeria monocytogenes promotes efficient colonization of mouse hepatocytes and enhances host immune response

Listeria monocytogenes is an intracellularly growing pathogen which is able to infect and to spread from cells to cells. It produces several virulence factors required for invasion and intracellular niche colonization. Endogenous peptidoglycan hydrolases which are important for survival of bacteria have been shown to be involved in pathogenesis. An autolysin amidase (Ami)-deficient mutant of L. monocytogenes (Δami) is attenuated in virulence as evidenced by a reduction in mortality of infected mice. We showed that Ami is not essential for bacterial growth and protein secretion. Histopathological analysis suggests that Ami promotes bacterial colonization of hepatocytes. By using cultured eukaryotic cells, we present evidence that a critical function of Ami in pathogenesis is to promote an efficient listerial adherence and internalization into mouse hepatocytes. Simultaneously, the peptidoglycan hydrolase activity of Ami linked to the release of immunologically active cell wall components enhances production of tumor necrosis factor (TNF)-α and interleukin 6. In the early phase of infection, interferon-γ and TNF-α production of Δami-infected mice is significantly less than that of wild-type controls, suggesting a contribution of Ami to enhance the host innate immune response to listerial infection.

Clinical features of liver involvement in adult patients with listeriosis. Review of the literature

Clinical features of liver involvement due to Listeria monocytogenes infection in adults are rarely reported in literature. This is surprising, regarding the current opinion that the portal system is extensively involved in the first stages of pathogenesis in invasive L. monocytogenes disease. A literature search in the PubMed and Embase database revealed 34 cases with clinical features of hepatic involvement due to listeriosis. We systematically analyzed all case reports with respect to clinical manifestations, treatment and outcome. In addition, we added clinical information on a patient diagnosed with a solitary liver abscess due to L. monocytogenes, who was seen at our institution. This review describes the different presentations of liver-involvement reported in listeriosis; solitary liver abscess, multiple liver abscesses and diffuse or granulomatous hepatitis. Distinction between these different forms of liver involvement is clinically relevant as they have a different outcome. We delve into the different pathogenic events leading to different forms of liver involvement. In addition, diagnostic modalities and possible treatments are reviewed.

Update on Listeria monocytogenes infection

Listeria monocytogenes is a gram-positive bacillus that causes meningitis, encephalitis, bacteremia, and febrile gastroenteritis. Most disease occurs in immunosuppressed individuals. Recent seroepidemiologic studies show that the infection is foodborne. Due to the increasing number of immunosuppressed individuals at risk for listeriosis, as well as the persistence of substantial foodborne outbreaks, L. monocytogenes has gained worldwide attention as an important pathogen. Heightened surveillance and quality control by the food industry have been instituted, leading to a reduction in the number of cases and deaths from this infection in the past decade. However, due to the ubiquity of the organism in the environment, outbreaks and sporadic disease continue to occur. The standard therapy for listeriosis is a combination of ampicillin and gentamicin or, for patients who are intolerant of b-lactam agents, trimethoprim-sulfamethazole. Despite the availability of therapy, the mortality rate remains high in those with T-cell immunodeficiencies.