Media types looking for a sound bite on Listeria in cantaloupes are pulling their hair out tonight.

You couldn’t ask for a more complicated scenario. Advice like “wash your hands” or “cook your foods” or “don’t cross contaminate” is nearly worthless. Here are some troubling facts

Listeria monocytogenes:

  • Psychrophilic, multiplication possible all the way to 29 degrees
  • Ubiquitous, found in almost all environments, terrestrial and aquatic
  • Found in feces of animals
  • Most problematic in ready to eat foods
  • Forms bio films on food prep surfaces that resist sanitizers, nearly impossible to remove once adhesion occurs
  • Incubation period can be days to months
  • Huge dose response curve, from 100 or less cells, to 1,000,000 or more
  • High morbidity and mortality up to 50% of cases
  • Some strains are pathogenic some are not
  • Highly virulent strains may be emerging
  • Targets immune-suppressed victims, fetuses, neonates, pregnant, those on immunosuppressive drugs, those with disorders of the liver, gut, blood
  • Attaches to nervous tissues, systemic infections 


  • Rough netted exterior traps contaminants
  • The rind surfaces of these melons likely can support adhesion as well as colonization by many pathogenic bacteria
  • Melon meat is highly conducive to bacterial multiplication, rich in nutrients and moisture just below the rind
  • Keeps well under refrigeration
  • When cut, surface pathogens are transferred into the meat

Combine the two and you have a marriage made in hell.