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Listeriosis tragedy ‘breakthrough’ evidence makes ‘overwhelming’ case Tiger Brands was responsible - lawyers

Manqoba, Zanele, Zwane, Welcome and Portia Zwane in their family home in Soweto. Their mother, Nomvula Zwane, died after contracting listeriosis during the outbreak in 2017/18. (Photo: Thom Pierce)

By Tamsin Metelerkamp

8 Sep 2024

The legal team behind a class action lawsuit representing more than 1,000 claimants who suffered due to the outbreak of listeriosis in 2017/18 claim that ‘breakthrough’ evidence that emerged this year makes an ‘overwhelming’ case that food producer Tiger Brands was responsible for the outbreak in its entirety. Listeriosis was transmitted mostly via contaminated polony.

Six years on from the listeriosis outbreak that killed more than 200 people in South Africa, individuals and families who were affected by the outbreak have yet to receive any compensation for their suffering. The legal team representing claimants in a class action lawsuit against food producer Tiger Brands alleges that “breakthrough” evidence has come to light, further linking the surge in listeriosis infections to an Enterprise Foods factory in Polokwane, Limpopo. Tiger Brands was the parent organisation for Enterprise Foods.

The legal team is made up of Richard Spoor Incorporated (RSI) Attorneys and LHL Attorneys. Zeenat Emmamally, an associate at RSI Attorneys, said they received two important pieces of evidence related to the outbreak from the National Health Laboratory Service (NHLS) this year. The NHLS is a national public entity that provides health laboratory services in South Africa.

“We’ve received confirmation from them that the strain that was predominantly responsible for the outbreak, the sequence type 6 (ST6) strain, was not found in any other facility or location apart from Tiger Brands’ Enterprise facility in Polokwane,” said Emmamally.

The NHLS also provided DNA sequence data. In January 2024, the National Institute for Communicable Diseases (NICD), a division of the NHLS, provided public access to sequence data via the National Center for Biotechnology Information (NCBI) database for 403 ST6 isolates (a culture of microorganisms isolated for study) from the listeriosis outbreak. These isolates were derived from samples collected from human patients, food products and environmental samples from the factory in Polokwane, sequenced by NICD and analysed by multiple methods, including multilocus sequence typing (MLST) and core genome MLST.

Tiger Brands has had access to the sequence data since January, giving its experts the opportunity to perform independent analyses of the data, according to RSI Attorneys.

However, “Tiger Brands … have done absolutely nothing with this new evidence,” Emmamally claimed.

“These two pieces of evidence in conjunction make it a very overwhelming case that Tiger Brands was responsible, not only for the ST6 cases, but for the outbreak in its entirety.”

Manqoba, Zanele, Zwane, Welcome and Portia Zwane in their family home in Soweto. Their mother, Nomvula Zwane, died after contracting listeriosis during the outbreak in 2017/18. (Photo: Thom Pierce)

What is sequence type 6 strain?

Listeriosis is an infectious disease of the blood or brain caused by Listeria bacteria. It primarily affects people with impaired immune systems due to factors like pregnancy, extremes of age, underlying malignant conditions, human immunodeficiency virus (HIV) infection or chronic disease.

The species of bacteria that causes listeriosis, Listeria monocytogenes, can be broken up into different strain types. Multilocus sequence typing can be used to establish strain types, according to John Besser, an independent contractor and former deputy chief of the Enteric Diseases Laboratory Branch at the Centers for Disease Control and Prevention in the US.

When the NICD was investigating the listeriosis outbreak in South Africa, it initially included all Listeria monocytogenes infections in its case definition. The case definition establishes the criteria used to determine which ill persons will be classified as part of the outbreak.

Read more: ‘I wouldn’t wish for anyone to experience this’ — the listeriosis outbreak and a mother’s heartbreak

Read more: Tiger Brands on the hook as lawyers build case for listeriosis victims

Read more: Life After Listeriosis: Photo Essay

However, sequence typing of Listeria monocytogenes isolates from patients showed that 93% of cases had a single sequence type, ST6. The case definition was therefore refined to include ST6 cases only.

“[The NICD] used the classification strains to help them zero in on the problem. The reason that this is important is that there’s always a few listeria cases around even if there’s no outbreak, and those cases might be caused by something entirely different. The sequence typing is used to group together cases that are most likely to all have the same exposure, such as a food,” explained Besser.

“By doing that, it makes it possible for the researchers to zoom in on the cause of the outbreak quickly, because it’s not confused by cases that are less likely to be related.”

What is core genome multilocus sequence typing?

In addition to MLST, researchers further confirmed that the cases likely had a common source using core genome MLST.

Core genome MLST is a globally recognised method for precisely identifying individual bacterial strains. The process showed that about 382 of the 403 ST6 isolates that were sequenced and analysed had no more than four allelic differences, which meant they were closely related and shared a common origin, according to Thamsanqa Malusi, an RSI senior attorney.

When the outbreak strain was found at the facility identified in the trace-back investigation – as was the case with the Enterprise Foods factory in Polokwane – it’s considered a ‘smoking gun’.

Researchers tend to suspect a “common-source outbreak” when a cluster of cases show seven or fewer allelic differences in the letters of their genetic code. There are 2.5 to three million letters of the genetic code in listeria, according to Besser. However, a core genome MLST doesn’t look at all the letters, but rather focuses on regions of DNA that are shared by all strains of the species, which contain about 30% to 40% of the total genetic code. This provides a stable basis for comparison of isolates.

“Bacteria are different from people in that… they produce much more rapidly. For listeria, it can be in as little as 50 minutes, whereas for us, it takes 20 to 30 years,” said Besser.

“So, they’re changing at a very fast rate compared to people and they’re also picking up DNA from the environment and different germs. They change quickly. We expect there to be some differences. But when they’re very close, like we find in this outbreak, it’s almost certain that this represents a common exposure… in all the cases.”

Trace-back and environmental investigations

Once MLST has been used to establish a case definition for a listeriosis outbreak, the people who meet that case definition are usually interviewed to find out what they’ve eaten and where they’ve been, according to Besser.

“Once a possible common food is identified, this is called a hypothesis. Analyses such as case-control studies are conducted and a trace-back investigation is initiated to see if the common foods they ate have a common origin,” he explained.

“As we know in South Africa, the trace-back investigations for polony did converge on one facility. But then, once the facility is identified and microbiology testing happens at the facility, core genome MLST is used once again, to compare what’s found in the facility and the food to what’s found in the patients.”

Besser noted that in some outbreaks, the listeriosis strain responsible for the surge in cases was not found at the facility where the contaminated food originated. This could be because the contamination was a one-time event, or because the facility was cleaned up quickly once an outbreak was detected.

However, he said that when the outbreak strain was found at the facility identified in the trace-back investigation – as was the case with the Enterprise Foods factory in Polokwane – it’s considered a “smoking gun”.

“If it’s found in an unopened package of food and in the patients, it’s very, very strong evidence,” he said.

This case has been a travesty of justice… While Tiger Brands continues to make money, these children are suffering.

In a journal article on the NICD-led investigation into the South African listeriosis outbreak, published in The New England Journal of Medicine, the factory identified as the producer of the contaminated polony was referred to only as “Facility A”. It was noted that Listeria monocytogenes was isolated from 47 of the 317 environmental samples (15%) collected at Facility A.

“A total of 34 of the 47 typed isolates (72%) were identified as ST6. These isolates originated from samples collected at several facility sections (precooking and postcooking), including from food-contact surfaces, non-food contact surfaces, and chilling brine. L. monocytogenes ST6 was detected in two of 13 samples of unopened polony loaves collected at the facility,” the article stated.

The article concluded that contaminated polony produced at the facility was the cause of the national outbreak of listeriosis. Evidence supporting this included:

A strong association between eating polony and ST6 infection;

The detection of ST6 isolates in unopened polony loaves collected at the facility;

The detection of ST6 isolates in environmental samples collected from the facility; and

The fact that outbreak-associated ST6 isolates from patients, as well as food and environmental isolates from the facility, were shown to be very closely related using core genome MLST.

It was also noted that a recall of all ready-to-eat processed meat products from the facility was “associated with a rapid decline in the incidence of L. monocytogenes ST6 infections”.

“This is a classic, textbook investigation… This is, to my mind, an open-and-shut case. And once the product was recalled, the cases rapidly declined, which by itself wouldn’t be important, but given all of the other facts of the case, is a very powerful finding. I would like to add that I thought the NICD did a very excellent job under very difficult circumstances,” Besser said.

Daily Maverick asked the NICD about the investigation but they declined to comment.

‘Travesty of justice’

The Enterprise Foods factory in Polokwane has since shut down. However, RSI Attorneys claims that Tiger Brands has continued to use “every legal loophole available” to delay paying compensation to the victims of the outbreak.

The listeriosis outbreak in South Africa between 2017 and 2018 was the largest recorded listeriosis outbreak in history, resulting in more than 1,000 infections and claiming 218 lives, according to RSI Attorneys. It was declared to be over in September 2018.

Those affected by the outbreak include children who were infected with listeriosis in utero, some of whom are still struggling with health complications such as hydrocephalus and cerebral palsy.

“This case has been a travesty of justice. If there’s no immediate intervention, the condition of these victims is going to worsen,” said Malusi. “While Tiger Brands continues to make money, these children are suffering.”

Tiger Brands responds

Daily Maverick asked Tiger Brands about the claims made by the legal team representing claimants in the class action lawsuit. It responded that it was “saddened” by the impact that listeriosis has had and continues to have on the lives of the victims and those who lost loved ones due to the outbreak.

“We reiterate our commitment to ensure a resolution of the listeriosis class action lawsuit is reached in the shortest possible time, in the interest of all parties, particularly the victims of listeriosis,” Tiger Brands said.

“As part of the overall endeavours to expedite a resolution, Tiger Brands’ legal team and the plaintiffs’ attorneys jointly approached the National Institute of Communicable Diseases for access to their records relevant to the listeriosis outbreak. These records are vital to a determination of the class action.”

According to Tiger Brands, the NICD provided the FASTQ files (a text-based format for storing a biological/nucleotide sequence and corresponding data) relating to their investigation of the outbreak to the plaintiffs’ attorneys in the class action in February this year.

“These FASTQ files were shared with the attorneys representing the company’s insurers for review by their appointed experts. The experts’ review of the files remains ongoing,” Tiger Brands said.

“Tiger Brands’ legal team and the attorneys representing the plaintiffs in the class action continue to attend to pre-trial preparations to get the matter ready for trial, where liability will be determined by the Court. The Court will allocate a trial date once all necessary pre-trial procedures have been attended to and the matter is ready to proceed to trial.

“As the lawsuit is currently pending before the Courts, Tiger Brands is not in a position to comment further.” DM

Daily Maverick will this week run a series of articles and interviews with families who have lost loved ones or have been impacted by having to care for disabled children and adults.

Read more: ‘We want justice for our mother’ — family struggles to pick up pieces six years after deadly listeriosis outbreak

There will also be a webinar on Tuesday at 6pm interviewing the lawyers and activists.

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