engleski

Dissemination of Listeria monocytogenes

Listeria monocytogenes is a motile gram-positive bacillus capable of growing at a wide range of temperatures, from 1- 45oC. It is beta-hemolytic and exhibits characteristic tumbling motility when viewed with light microscopy. L. monocytogenes is widespread in nature and has been isolated from soil, vegetation, marine sediments and water. The term listeriosis encompasses a wide variety of disease symptoms that are similar in animals and humans. Most infections occur after oral ingestion, with access to the systemic circulation after intestinal penetration. Victims of severe listeriosis are usually immunocompromised. Those at highest risk include cancer patients, individuals taking drugs that affect the body' s immune system, alcoholics, pregnant women, persons with low stomach acidity and individuals with AIDS. Severe listeriosis can cause meningitis, abortions, septicemia and a number of other maladies, some of which may lead to death. In an attempt to obtain a model resembling natural listeriosis, we studied the course of infection in BALB/c mice inoculated by the intragastric (i.g.) route with different doses of EGD strain of L. monocytogenes. The course of infection was monitored using bacteriological and histological methods. Single, high chalenge dose of L. monocytogenes resulted in severe illness and a lethal outcome while repeated i.g. administration of lower doses for three consecutive days significantly reduced the mortality rate. However, dissemination of Listeria to the lungs, kidney, spleen and liver was always achieved, in spite that no bacteria were detected in the small intestines. Repeated lower doses increased the severity of liver infection, resulting in a pronounced necrotizing hepatitis and extreme metabolic liver disfunction according to high levels of serum aminotransferases. In addition, low number of L. monocytogenes was isolated from the brains of all infected mice, even though histological examination revealed only minor lesions. The BALB/c mouse holds promise as a model for further study of host and organism-specific virulence factors mediating the gastrointestinal phase of invasive L. monocytogenes infection, an increasingly important public health problem.

Listeria monocytogenes

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