By Malik Altaf Hussain, The Department of Wine, Food and Molecular Biosciences, Lincoln University
The recent outbreak of Listeria in Hawke’s Bay reminds us how important it is to manage food safety constantly and consistently.
This incident claimed three people’s lives. What we are seeing here in New Zealand can also be seen globally. Foodborne illness outbreaks associated with Listeria occur frequently and are reported regularly worldwide. In a Canadian outbreak of Listeria in 2008 that was linked to deli meat, 23 people died and, last year, 32 people who consumed contaminated cantaloupes were victims of this lethal foodborne pathogen in the United States.
Listeria is a dangerous microorganism especially to pregnant women, newborn babies, the frail, elderly and those with compromised immune systems. Listeriosis is the name given to the foodborne illness caused by the bacterium Listeria monocytogenes. This bacterium is associated with a wide range of products including ready-to-eat products such as chicken sandwiches, deli meats and salads, soft cheeses, yoghurt, dairy-based dips and foods with long shelf lives under refrigeration. The FDA considers Listeria as the most important target pathogen to control in ready-to-eat meat and poultry products. Several unique features make this bacterium very dangerous:
- It can multiply quickly under unfavourable conditions, e.g. refrigerators
- Its wide presence in nature
- It can survive during sanitisation treatment
- It has the ability to form biofilms to avoid being killed by antimicrobial agents
- It can invade patient’s immune system rapidly
Although there are fewer than 20-25 cases of listeriosis in New Zealand per year it is the cause of more than 90 percent of deaths due to foodborne illness. In this sense it is matter of great concern. It is serious illness for the immune-compromised groups of society. Generally, healthy people have good recovery rates from this infection and can be treated with antibiotics. Fever, muscle aches, nausea and diarrhoea are the most common symptoms seen in people diagnosed with listeriosis. 
The Hawke’s Bay outbreak was a typical listeriosis case where pre-packed meat products were contaminated with this lethal bacterium and were eaten by people with weakened immune systems. Regardless of the nature of the product carrying this microbe, there is an important lesson to learn here – the existence of Listeria in the food supply can be dangerous at any time. Carol Barnao has discussed several issues to manage Listeria in foods in her article published in NZ FOODtechnology last month. It is clearly stated that effective ways to manage food safety in terms of listeriosis are needed.
Research is the most important tool to understand the spread of Listeria and the physiological mechanisms behind its hardiness. This will allow us to develop better management strategies. Moreover, it is important to prevent contamination at all levels, i.e. the manufacturer, the retailer and the consumer. To create awareness among the public about handling the food to avoid the spread of listeriosis is a key area that needs attention. Postgraduate research students studying food microbiology at Lincoln University are working on different aspects of this food microbe, ranging from evaluation of ready-to-eat foods for the presence of Listeria to understanding the physiological responses of different Listeria food isolates using advanced techniques like proteomics and bioinformatics.
Dr Malik Hussain is a lecturer in food microbiology at Lincoln University. Research students are working on food safety projects under his supervision at Food Microbiology laboratory (the Department of Wine, Food and Molecular Biosciences).
If you are interested in his group research, Email: [email protected]
