Laboratory diagnosis of Listeriosis caused by Listeria monocytogenes


Listeriosis is a serious infection caused by the bacterium Listeria monocytogenes. It can affect people of all ages, but it is especially dangerous for pregnant women, newborns, elderly people, and people with weakened immune systems. Listeriosis can cause septicemia, meningitis, encephalitis, abortion, stillbirth, and neonatal infection. The mortality rate of listeriosis is about 20-30%, making it one of the most lethal foodborne diseases.

Listeria monocytogenes is a gram-positive, facultative anaerobic rod that can grow at low temperatures (4°C) and high salt concentrations. It is widely distributed in the environment and can be found in soil, water, plants, animals, and food products. The main sources of human infection are contaminated dairy products, meat products, seafood, and fresh produce. Listeria can also be transmitted from mother to fetus through the placenta or from mother to newborn during delivery.

The laboratory diagnosis of listeriosis is based on the isolation and identification of Listeria monocytogenes from clinical specimens such as blood, cerebrospinal fluid (CSF), placenta, fetal tissues, or other normally sterile sites. However, the detection of Listeria monocytogenes can be challenging due to its low numbers in the specimens, its similarity to other gram-positive rods, and its slow growth on conventional media. Therefore, various techniques have been developed to enhance the sensitivity and specificity of the laboratory diagnosis of listeriosis. These techniques include microscopy, culture methods, cold enrichment technique, biochemical tests, carbohydrate fermentation tests, serology, and molecular methods. In this article, we will review these techniques and their applications in the laboratory diagnosis of listeriosis caused by Listeria monocytogenes.