Although Listeria has been known for at least 60 years, it has only been linked to foodborne disease since the early 1980s. Since then, the pathogen has become recognised as an important food poisoning bacterium.
While healthy individuals can become infected with Listeria, the most at-risk are the elderly, the young, pregnant women, and those with a compromised immune system.
Despite the fact that there are a number of other pathogens that affect the food manufacturing industry, Listeria is perhaps one of the most dangerous.
This is because the foodborne bacterium - when present in food - shows no difference in taste, smell or appearance; leading people into a false sense of security that the contaminated item is, in fact, safe to eat.
With its unique ability to thrive and survive in even refrigerated conditions, ranging from below 1°c up to 44°c, Listeria is an organism that can fast become a lethal liability for food manufacturing industries if floor-staff are not properly educated on the dangers of an outbreak.
So far there have only been two major recorded outbreaks of Listeriosis in Australia, reports Meat and Livestock Australia (MLA). Once in 1990, when six stillborns, following an autopsy, were discovered to have all been infected with the same subtype of Listeria, found in a particular brand of Pate.
The next episode occurred in 1991, after three people who ingested the same brand of smoke mussels became violently ill. An unopened packet of mussels was subsequently tested and was found to contain 107 listeria cells per gram - despite industry-dictated ‘safe’ levels sitting at less than 10 cells per gram.
Sporadic cases still occur in Australia, with around 40 being reported per year. The numbers overseas, however, are significantly higher and the outbreaks much more severe.