A foodborne bacterium that most people shrug off but that can cause severe illness in pregnancy, newborns and older adults. Explore its illustrative 3D model, human context, and sources.
PHAC describes L. monocytogenes as a Gram-positive, non-spore forming, rod-shaped coccobacillus measuring 0.5 to 2 micrometres long and 0.5 micrometres in diameter, able to reproduce at temperatures between 1 and 45 degrees Celsius and across pH values from 4.3 to 9.6 — which is why refrigeration does not stop it. CDC estimates that 1,250 people are infected with Listeria and 172 people die from the infection each year in the United States, and describes it as the fourth leading cause of death from foodborne illness there. CDC also states that people outside the higher-risk groups can be infected but rarely become seriously ill, so the same organism produces very different outcomes depending on who eats it.
CDC identifies pregnant women, newborns, adults aged 65 or older and people with weakened immune systems as the groups at higher risk, and states that other people can be infected but rarely become seriously ill. PHAC reports mortality approaching 50% in human cases and neonatal mortality of 20 to 30%; those figures describe diagnosed invasive cases, which are a small and severe subset of all exposures, not the chance that any one meal makes a person ill.
Listeria monocytogenes · A short rounded rod. This view omits temperature-variable flagella and does not depict a spore. This is a species-informed teaching diagram; colours, proportions, envelope spacing and internal detail are illustrative. The model uses muted illustrative colours; stains, colony pigments and microscopy colourization are not natural cell colours. Anatomy is enlarged for phone viewing. Morphology reference: Listeria monocytogenes · pathogen safety data sheet.
Source check: 2026-09-20. Educational content; independent scientific review remains pending.