Listeria monocytogenes is a bacteria that causes two major illnesses in children: meningitis and a diarrheal illness.  Listeria meningitis affects newborn infants born to infected mothers.  The mother may have no symptoms or a mild flu-like illness.  In older children and adults, Listeria is an occasional cause of diarrhea.  Listeria monocytogenes is found in the environment and is commonly transmitted to humans through undercooked or unwashed food.  Most children who are exposed to Listeria monocytogenes do not develop disease if the immune system is functioning properly.

Diseases

• Listeria meningitis or sepsis - almost entirely in newborn infants in the first month of life
• Listeriosis - typically a mild diarrhea illness

Habitat and Transmission

• Listeria monocytogenes if found throughout the environment, in dirt, and the intestinal tracts of animals
• Transmission to humans typically occurs after eating contaminated foods such as: unpasteurized milk, cheeses, undercooked meats, and unwashed raw vegetables

Weapons and Defenses

• Able to move by flapping flagella
• Can survive without oxygen if necessary
• Can live in the intestinal tracts of many types of animals and birds
• Resistant to the cephalosporin antibiotics

Weaknesses

• Destroyed by appropriate cooking of foods
• Destroyed by pasteurization of milk
• Susceptible to antibiotics such as ampicillin and gentamicin (which work better together than alone)
• Found in the stool of approximately 5% of healthy adults (without causing symptoms)