First prosecution in the UK involving whole genome sequencing when tracing a Salmonella outbreak results in guilty pleas and fines of £153,000

Experts included food micro biology, epidemiology, environmental health, building pathology specialising in water systems and experts from the UK Agency Gastrointestinal Infections and Food Safety Division.

RICHARD BARRACLOUGH KC leading TAYO DASAOLU instructed by Bolton Council prosecuted the case from the outset.

The long running case involving the 2020/2021 Salmonella outbreak in the United Kingdom has been resolved after the defendant factory based in Bolton pleaded guilty to food safety offences.

On 22.1.26, the factory was fined £153,000 after the Court was informed that they had provided the authorities with considerable assistance in the investigation and had spent considerable sums in remediation works.

The United Kingdom Health Security Agency was created in 2021. It took over the functions of Public Health England. The Agency was created to prevent, prepare for and respond to infectious diseases and environmental hazards in order to save lives. It works with local, national and international agencies to protect the nation’s health. It has its own specialist laboratories.

The Agency, Public Health Scotland, the Food Standards Agencies for England, Scotland, Wales, Northern Ireland and Bolton Council which is the local regulatory agency for the Bolton factory investigated an outbreak of Salmonella dating back to September 2020.

According the Outbreak report “The 2021 outbreak of S. Infantis strain t5:1518 was one of the largest S. Infantis outbreaks on record investigated by UK public health and food safety authorities. However, the magnitude of this outbreak is likely underestimated as the majority of Salmonella infections go under-reported to national surveillance.”

The outbreak report noted “The most commonly reported symptoms were diarrhoea and vomiting but cases also reported fever, abdominal pain and headaches. This is consistent with what would be expected for cases of salmonellosis. Hospitalisation information was available for 35 cases, of which 12 (34%) were admitted to hospital for their illness”.

MANUFACTURING DEFECTS

Tayto manufacture pork scratchings from frozen pork rind and also pork crispy strips and pork crunch from pellets stored at ambient temperature.  Products are sold under the “Mr Porky’s” brand and other brand names including “Jays”.

A number of defects had been allowed to develop over a period some of which resulted in, or contributed to, the serious outbreak of Salmonella Infantis t5:1518, including a failure to segregate the raw from the cooked areas in that the walls separating raw and cooked areas provided no effective isolation of raw from cooked; drains flowing from raw through the cooked area; potential for aerosol contamination; use of high pressure jet washing carrying the risk of aerosolization.

Dr Peter Fox who is a microbiologist and expert in environmental health, water and drainage systems and building pathology described that the drainage system presented a very serious contamination risk.

SAMPLING

A total of 42 formal food samples and environmental swabs were taken. 

6 of the 42 samples / swabs were “presumptive positive” for salmonella.  The positive food samples were the open pork scratchings taken from a gantry conveyor and the packaged pork scratchings sampled from the packing area.  The positive environmental samples were a swab from inside a seasoning drum, a swab from the gantry conveyor, a swab from a red brush used to sweep the product on the floor and a sample of liquor from a floor drain in the ready to eat area of the factory.

PROCESS FOLLOWING DETECTION

The factory stopped production and product recall notices were issued. The FSA notified the INFOSAN ECP of all six countries where the product had been distributed (Canada, Czechia, Hong Kong, Malta, New Zealand and the United Arab Emirates) of the product withdrawal and recall in the UK. Responses were received from all but one. The companies that received the products in the listed countries were contacted by the relevant authorities in each country and reported they were carrying out their own investigations.  Canada, New Zealand and Hong Kong undertook a product recall of Mr Porky’s pork scratchings.

Following the IHR notification posted on the 16 June 2021, responses had been received from five countries (4 EU and one non-EU) indicating that no outbreaks of S. Infantis had been identified and no linked or genetically matching cases had been reported in these countries. The Republic of Ireland reported two cases matched by WGS. The two reported cases had purchased pork scratchings in Northern Ireland.

Production resumed almost one year later. The factory lost £1.9M in relation to the destruction and recall process. They spent almost £1M on remediation works.

The contaminated products were being disseminated widely within the UK over a period of time, as well as internationally. Following the implementation by Tayto and food safety authorities of risk management and risk communication measures, a significant reduction in the number of reported cases associated with the outbreak was observed. Recalls of the pork scratchings were also carried out in at least three other countries.

Human disease outbreak case reporting continued beyond the date when risk management measures were implemented. Incomplete recall of all contaminated product was considered likely to be the main reason for ongoing reporting of cases in late 2021 and early 2022 but this, despite known lack of adherence to best before date usage may not be a plausible reason alone.  Other vehicles of infection associated with the imported pork supply chain could not be ruled out. 

THE PLEAS

TAYTO GROUP LIMITED pleaded guilty to two counts:

• Between September 2020 and August 2021 placed an unsafe food on the market in that food namely pork scratchings produced by them at their site in Westhoughton, Bolton was contaminated with Salmonella Infantis and whole Genome Sequencing of Salmonella isolates from the said pork scratchings showed that they were genetically related to isolates  obtained in an outbreak of the Salmonella Infantis between September 2020 and  July 2022 in England, Wales, Northern Ireland and Jersey (Article 14 of Regulation (EC) 178/2002 and Regulation 19 of the Food Safety and Hygiene (England) Regulations 2013) and

• Failing to ensure that food was protected against contamination likely to render food unfit for human consumption, injurious to health etc (Regulation 852/2004).

The pleas related to the period June to August 2021. The outbreak continued into 2022.

DEVELOPENT OF THE OUTBREAK

The outbreak report describes a “marked escalation in case reporting in June 2021” and “The first Salmonella Infantis case falling into the specific 5- single nucleotide polymorphism (5-SNP) cluster, eBurst Group (eBG) 31, SNP address 1.1.775.1129.1477.1518.% (t5.1518) was reported by the GBRU reference laboratory in October 2020 followed by a further five cases reported by 31 December 2020. Ongoing intermittent reporting of cases continued in January and February 2021 (eight reported cases each month) and the cluster was continually assessed until an escalation in reporting was detected with 18 cases reported in March 2021”.

The distribution of cases was high in the South East, Wales, Yorkshire, West Midlands, the South West and North West. There was a number of cases in Scotland and one in Northern Ireland.

Samples were taken from a number of consumers who ate the product. They were linked with samples taken from the defendant’s factory.

WHOLE GENOME SEQUENCING

Whole genome sequencing is a means of determining the DNA in all the genetic information of a substance. WGS enables the genomes of Salmonella bacteria to be analysed down to differences between individual DNA bases (Single Nucleotide Polymorphisms [SNPs]).

The microbiological investigation records “UKHSA is accredited …for whole genome sequencing and application of this methodology to microbiological characterisation of human and non-human sequence data. Phylogenetic analyses of the WGS data indicated very limited genetic diversity between outbreak cases and food and environmental samples, with all confirmed (according to the agreed case definition) outbreak cases’ isolates falling within a 5-SNP cluster and indicating that all isolates were highly likely to originate from a common source of contamination, with the majority being genetically indistinguishable. This provided strong microbiological evidence, in conjunction with the strong epidemiological evidence (in line with internationally accepted guidance on strength of evidence), that consumption of pork scratchings was associated with developing illness, with product manufactured by the Tayto company as the vehicle of infection”.

The microbiological evidence noted “The 586- patient S Infantis isolates fell into the same t5_1518 single linkage cluster…This level of diversity is consistent with a point source outbreak of Salmonella gastroenteritis and indicates all cases have likely been exposed to the same vehicle of infection…”

The outbreak report noted “Phylogenetic analyses of WGS data indicated very limited genetic diversity between outbreak cases and the 2021 food and environmental sample isolates – with the majority being genetically indistinguishable and indicating that all isolates were highly likely to originate from a common source”.

Interestingly, the outbreak was at its highest at a time of major football and other sporting events and “overall, a total of 587 confirmed outbreak associated cases were identified up to the point investigations were de-escalated in early 2022. In total, just over half (51%) of all cases were male and over a third (38%) were aged 60+ years”.

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