Antibiotics are effective if given promptly. The bacterium Listeria monocytogenes has recently been recognized as an important public health problem in the United States. While less widely know than other foodborne pathogens like Salmonella and E. coli , it is far more deadly. An estimated 2,500 people become seriously ill from Listeria each year in the United States with infections often leading to blood poisoning or meningitis. Most at risk from this pathogen are pregnant women, newborn children, and people with weakened immune systems.
Listeria is found throughout nature, in animals, plants, water, and soil.
Vegetables can become contaminated from the soil or from manure used as fertilizer, and the bacterium can contaminate unpasteurized dairy products such as soft cheese. Ubiquitous in nature and able to thrive in cool environments, this pathogen can easily spread into a processing plant and then contaminate and multiply on the sterile surfaces of processed foods. The long shelf life of processed foods allows time for bacterial populations to grow, increasing the chances of people becoming ill from this pathogen. The development of drug-resistance in Listeria from antibiotic use in farm animals is less of a concern than with other foodborne pathogens. Listeria is also a poor competitor against other human pathogens such as E. coli or Campylobacter and is not likely to build population levels high enough to cause an infection in people.