Expert Team Identifies Chicken Source in Multi-State Listeria Outbreak

A commercial supplier in Sydney is at the root of the outbreak affecting Queensland, New South Wales and Victoria.
Raw chicken breast fillets on a white plate.
October 3, 2023

A skilled team of experts from various fields has found the root of a listeria outbreak that's been affecting people in Queensland, New South Wales and Victoria since mid-August.  The source has been identified as shredded chicken produced by M and J Chickens, a commercial poultry supplier based in Marrickville, Sydney.

Over time, a specialised team consisting of laboratory scientists, epidemiologists and environmental health officers focused on identifying the source of the listeria outbreak. Given that listeria can be especially harmful to high-risk groups such as the elderly, pregnant women and those with chronic illnesses, timely action was important.

A Broad Range of Suspects

Listeria bacteria are notorious for their elusive nature. With an incubation period ranging from a few days to two months, and the ability to hide in a wide variety of foods, pinning down the precise source was challenging. Nine cases across the three states were eventually linked through DNA fingerprinting, confirming a common source of the infection.

Hospital Links Ring Alarm Bells

Five of the nine confirmed cases were tied to two Queensland public hospitals, raising serious concerns. Consultant epidemiologist Russell Stafford cited the importance of swiftly identifying the source, as invasive listeria infections have a mortality rate of about 25%.

Uncovering the Culprit

Rona Roustom, an environmental health officer with Metro South, conducted in-depth interviews with patients and families, which eventually led the team to focus on hospital food menus. Once potential food sources were identified, samples were sent to Queensland Health's Forensic and Scientific Services for testing.

Trudy Graham, a food microbiologist, detected listeria in the shredded chicken samples, sending them off for further DNA fingerprinting. Shortly thereafter, Queensland's chief health officer, Dr. John Gerrard, confirmed the findings in a public news conference.

The Importance of Coordination

"This result is a testament to the extraordinary professional work of our public health teams and laboratory scientists," Dr. Gerrard remarked. The successful resolution was the outcome of seamless cooperation between Queensland Health's communicable diseases branch, Forensic and Scientific Services and the Metro South public health unit.

A Wider Context

Although the COVID-19 pandemic saw a decrease in foodborne pathogens, this outbreak served as a crucial reminder of the ongoing threat posed by bacteria like listeria. Dr. Amy Jennison, FSS chief scientist of public health microbiology, emphasised the variable nature of foodborne disease investigations. In what is described as an "extraordinary piece of detective work," the public health crisis was averted within approximately four weeks. The episode underlines the vital role of scientific investigation in safeguarding public health.

Understanding Listeria

Listeriosis is an infection triggered by Listeria monocytogenes bacteria. These microorganisms are naturally occurring in the environment, commonly found in sources such as water, soil and various animals like cattle and poultry. Foods like unpasteurised dairy items and certain processed goods may also contain listeria.

The Pathways of Listeria Contamination

The most typical way people contract listeria is by ingesting food that has been contaminated. Some of the common culprits in listeria outbreaks include:

  • Uncooked fruits and vegetables
  • Raw or partially cooked meats and fish
  • Milk products that have not been pasteurised
  • Processed deli meats and hot dogs
  • Soft, unpasteurised cheeses like feta, camembert and brie
  • Smoked fish
  • Ready-made salads

Signs, Symptoms and Populations at Risk

After exposure, symptoms might not manifest immediately. They can appear anywhere from a few days to as much as three months later, making it difficult to pinpoint the exact source of contamination. When dealing with an outbreak, quick action from health officials is crucial due to this variable incubation period.

For the general populace, the symptoms may be mild, including:

  • Elevated body temperature
  • Muscle discomfort
  • Gastrointestinal issues like diarrhoea

However, for vulnerable groups such as the elderly, newborns, pregnant women and those with weakened immune systems, the impact can be far more severe, including:

  • Migraines
  • Neck stiffness
  • Disorientation
  • Poor balance
  • Seizures

In extreme cases involving pregnant women, listeriosis can result in miscarriage, stillbirth, or a severe infection in the newborn.

Diagnostic and Treatment

Typically, diagnosing listeriosis involves blood testing and analysis of spinal fluid. The standard treatment, once confirmed, is a course of antibiotics. Early identification and medical intervention are especially important for those in high-risk categories, to mitigate the risk of severe complications.

Preventive Steps Against Listeria

Prevention mainly involves adhering to strict hygiene practices:

  • Always wash fruits and vegetables meticulously
  • Ensure meats are cooked to a safe internal temperature
  • Avoid consuming unpasteurised dairy products
  • Proper kitchen cleanliness is also vital, including the frequent washing of hands, cutting surfaces and cooking utensils that have come in contact with raw produce

Additionally, because listeria can proliferate even in cold environments, maintaining a clean refrigerator and promptly disposing of spoiled or suspect food is crucial.

Food Handler Training Prevents Spread of Illness

The quick containment of the recent listeria outbreak highlights the crucial role that expertise in food handling plays in public health. For business owners in the food industry, ensuring that your employees undergo proper Food Handler training is not just optional; it's essential. The Australian Institute of Food Safety (AIFS) provides comprehensive courses that set the standard in food safety protocols. Contact AIFS today to elevate your team's food safety practices and protect your clientele.