Listeria monocytogenes

Introduction

Listeria monocytogenes is a bacterium that can cause the disease listeriosis. It is a series disease, especially for pregnant women, people with a weakened immune system, and adults over the age of 65. It causes a variety of symptoms depending on the location the bacterium is affecting. Basic symptoms include fever and diarrhea. However, if the bacteria travels further than the gut, the symptoms depend on if the person is pregnant. If it is a woman who is pregnant, symptoms are usually flu like, however, the infection may lead to miscarriages or life-threatening infections to the newborn. If the people are not pregnant, symptoms can include headaches, stick neck, loss of balance, and convulsions.

Hosts

Humans. Especially pregnant women, newborn infants, immunocompromised individuals, patients with cancer and other diseases, and the elderly.

Transmission / Exposure Route

Listeria monocytogenes is transmitted in food, person to person spread, direct contact, and in utero. The bacteria is found in dairy, raw and cooked poultry, all types of raw meats, and raw and smoked fish. It can also spread from person to person contact, for example, in a nursery setting. The bacteria can also infect someone if there is a cut on their hand, and they come into contact with an environment filled with L. monocytogenes. Lastly, L. monocytogenes can be transmitted to the fetus through an infected mother during her pregnancy.

Case Fatality Ratio

Of the 1,600 people that get listeriosis each year, about 260 die. When listeriosis occurs during pregnancy, it can cause miscarriage, stillbirth, or newborn death. Fetal loss can occur in about 20% of the cases, and newborn death in about 3% of cases.

Incubation Period

Ranges from 2 to 70 days, with the median period being three weeks.

Microbiology

Listeria monocytogenes is a Gram-positive, non-spore forming motile rod shaped bacteria.

Enviromental Survival

It can survive in an environment with or without oxygen. It is motile at room temperature, but not at body temperature.