Listeria monocytogenes is the bacterium that causes Listeriosis, a foodborne disease that can become serious, especially in pregnant women, newborns, older adults, and people with weakened immune systems.
Listeria is widely studied in:
• Microbiology
• Food Safety
• Immunology
Because of its ability to move between cells using the host cell’s actin proteins, this bacterium is also an important model organism for studying interactions between pathogens and human cells.
Main characteristics
• Gram-positive, rod-shaped bacterium
• Able to survive in high-salt environments and cold temperatures
• Facultative intracellular pathogen, meaning it can enter and multiply inside human cells
• Commonly found in soil, water, plants, and animals
Common sources of contamination
High-risk foods include:
• Unpasteurized milk
• Soft cheeses
• Processed ready-to-eat meats (ham, sausages, smoked meat)
• Cold-smoked seafood
• Raw vegetables contaminated during handling or farming
• Ready-to-eat foods stored too long in refrigerators
Symptoms of infection
In healthy individuals, symptoms may be mild:
• Fever
• Muscle aches
• Nausea or diarrhea
However, in vulnerable groups, the infection can become severe:
• Sepsis
• Meningitis
• Pregnancy-related infections
• Miscarriage or stillbirth
Groups at highest risk:
• Pregnant women
• Newborn babies
• Elderly people
• Individuals with weakened immune systems
Transmission
Transmission mainly occurs through consumption of contaminated food. Unlike many other bacteria, Listeria can:
• Survive at refrigerator temperatures
• Form biofilms on food-processing equipment
• Contaminate food after cooking
Diagnosis and treatment
Diagnosis is usually made through:
• Blood culture
• Cerebrospinal fluid culture
• Microbiological laboratory testing
Treatment generally involves antibiotics such as:
• Ampicillin
• Penicillin Sometimes combined with gentamicin in severe cases.
Prevention
Important preventive measures include:
• Store refrigerated foods below 4°C
• Reheat ready-to-eat foods thoroughly until steaming hot
• Avoid raw milk products
• Wash fruits and vegetables carefully
• Separate raw and cooked foods