Salmonella in reformed frozen chicken products: PHE survey in response to a Salmonella outbreak investigation - Frieda Jorgensen November 2021
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Salmonella in reformed frozen chicken products: PHE survey in response to a Salmonella outbreak investigation Frieda Jorgensen November 2021 UKHSA Food Water and Environmental Microbiology Services
Outbreak reported widely in the media
Salmonella: Chicken products recalled amid outbreak
- BBC News
Nearly 400 people sick from Salmonella in UK;
nearly half are children | Food Safety News
News Articles
October 2020-March 2021
Deadly salmonella outbreak in UK linked to
chicken products | Health | The Guardian
The FSA is reiterating its advice on cooking frozen raw breaded chicken products following link to rising
cases of Salmonella | Food Standards Agency
2
Overview of talk
• Background – outbreak, salmonella WGS/surveillance and regulation
• Initial detection of one outbreak strain in a chicken product
• Reactive survey initiated
• Types and levels of salmonella found in relation to products and plants
• Summary
3
Salmonella Enteritidis associated with frozen reformed chicken products • In the UK during 2020 cases of specific Salmonella Enteritidis clusters were increasinga (S. Enteritidis t5:4833 and S. Enteritidis t25:12 (including t5.590 and t5.12) • Infections more common in children and young adults • Analytical epidemiology (case-case and case- control) detected a significant association with consumption of reconstituted processed chicken products purchased from large chain retail establishments as frozen and ready-to-cook. aEuropean Centre for Disease Prevention and Control, European Food Safety Authority, 2021. Multi-country outbreak of Salmonella Enteritidis sequence type (ST)11 infections linked to poultry products in the EU/EEA and the United Kingdom – 25 February 2021. Stockholm: ECDC/EFSA; 2021. Available from: https://www.efsa.europa.eu/en/efsajournal/pub/en-6486. 4
Whole genome sequencing (WGS) and SNP addresses • WGS is a process that takes the bacteria’s DNA, breaks it into smaller sections and reads the DNA/nucleotide sequences. The reads are compared to reference DNA and any differences are analysed • The analysis allows us to place the bacteria in its family tree and see exactly how closely related it is to its neighbours and can tell us if an isolate is likely to be part of a particular outbreak or not • UKHSA use a so-called SNP address to indicate this - 5
Single Nucleotide Polymorphisms (SNPs) analysis of core genome 6
Salmonella Enteritidis t5.4833
aEuropean Centre for Disease Prevention and
Control, European Food Safety Authority,
2021. Multi-country outbreak of Salmonella
Enteritidis sequence type (ST)11 infections
linked to poultry products in the EU/EEA and
the United Kingdom – 25 February 2021.
Stockholm: ECDC/EFSA; 2021. Available from:
https://www.efsa.europa.eu/en/supporting/p
ub/en-6486. Accessed February 2021
7
Salmonella regulation and surveillance
• The UK the Zoonoses Order 1989 requires the reporting of Salmonella when isolated by laboratories
from a food animal, its environment or feed, or from animal by-products
• The Salmonella 2073 FSC 1.5 for “.. meat preparations made from poultry meat intended to be eaten
cooked” prescribe that any Salmonella must not be present in 25 g in any of 5 sampling units, on the
market during their shelf-life (FSC 1.28 for fresh poultry meat, the FSC prescribes S. Enteritidis and
S. Typhimurium are ‘not detected in 25 g’ on the market during their shelf-life)
• There is considerable targeted surveillance for Salmonella in poultry (broilers and layers)
• In 2019 most human salmonellosis in the EU were due to S. Enteritidis (~ 50%) and S. Typhimurium
(~20%); next most common were S. Infantis (2.4%) and S. Newport (~ 1.1%). From poultry ~ 33% of
reported isolates were S. Infantis and next most common was S. Enteritidis (7.8%)1
1EFSA and ECDC (European Food Safety Authority and European Centre for Disease Prevention and Control), 2021. The European Union One Health 2019 Zoonoses Report.
EFSA Journal 2021;19(2):6406, 286 pp. https://doi.org/10.2903/j.efsa.2021.6406
8
First significant food sample: frozen breaded chicken from freezer of case home collected by Plymouth EHO… 9
Standard culture method for detection of Salmonella
• Day 1: Enrichment in non-selective broth ( ~18 h)
• Day 2: Transfer to selective broths (RV & MKttN) (~ 24 h)
• Day 3: Transfer to selective agar plates (XLD & BGA) (~24 h)
MKttN on XLD
Day 5 - confirmation
RV on XLD
10Initial isolation from frozen breaded chicken – use of serotype specific PCR to identify S. Enteritidis presence in samples ......... 11
Initial isolation from frozen breaded chicken.........
Maybe there is a
way by which we
can isolate it…its
called a Cragie
tube
12Perseverance – S. Enteritidis isolated from product....... 13
Rapid Alert System for Food and Feed
(RASFF) notification
Available from: https://webgate.ec.europa.eu/rasff-window/screen/notification/442438
14aEuropean Centre for Disease Prevention and Control, European Food Safety Authority, 2021. Multi-country outbreak of Salmonella Enteritidis sequence
type (ST)11 infections linked to poultry products in the EU/EEA and the United Kingdom – 25 February 2021. Stockholm: ECDC/EFSA; 2021. Available
from: https://www.efsa.europa.eu/en/supporting/pub/en-6486. Accessed February 2021
15aEuropean Centre for Disease Prevention and
Control, European Food Safety Authority, 2021.
Multi-country outbreak of Salmonella Enteritidis
sequence type (ST)11 infections linked to poultry
products in the EU/EEA and the United Kingdom –
25 February 2021. Stockholm: ECDC/EFSA; 2021.
Available from:
https://www.efsa.europa.eu/en/supporting/pub/
en-6486. Accessed February 2021
16No detection of S. Enteritidis reported
from routine monitoring in Company B
aEuropean Centre for Disease Prevention and Control, European Food Safety Authority, 2021. Multi-country outbreak of Salmonella Enteritidis sequence type
(ST)11 infections linked to poultry products in the EU/EEA and the United Kingdom – 25 February 2021. Stockholm: ECDC/EFSA; 2021.
17FW&E, LA & GBRU reactive study 72: Salmonella in
frozen reconstituted chicken and turkey products
• Duration: 3 months, October - December 2020
• Sample types:Frozen reconstituted chicken or turkey products
• Settings: Retail and catering
• Parameters Detection of Salmonella in 25 grams (MPN of positives)
Enumeration (MPN) of Escherichia coli
• Metadata: Ingredients of the sampled product,
Use by Date and Batch Code
Brand, premises name and premises type,
Country of origin and approved premises code
• Confirmation and further typing performed by UKHSA GBRU
18Testing of further batches of initial product type tested........ 19
.. further product types found to contain S. Enteritidis
outbreak strains...
S.E.
S.E. (all three
clusters) and S.
Infantis and S.
Newport
S.E. and S.
Infantis
S.E. and S. S.E. and S.
Infantis Infantis
20…in total three S. Enteritidis outbreak strains and other
salmonellas detected in further batches of initial product tested…..
Three S.E clusters and
S.Infantis and S. Newport
21..fup62 to original RASFF notification 2018.1911 • … • “On 20 November 2020, the food authority in the UK reported in RASFF 2018.1911 that poultry products from Batch O and Batch P had been identified as Salmonella Enteritidis positive.. • “On 1 February 2021, the food authority in the UK reported in RASFF 2018.1911 (fup62) that the British Retail Chain B had recalled all batches, irrespective of the use-by-date, and suspended any further supplies from the Polish Processing Company B… • “..Batch V, Batch U, Batch AL, and all products with use-by-date February 2022 were recalled by the British Retail Chain E on 16 December 2020.” 22
Remaining shelf life and indicator E. coli in relation to
detection of salmonella
% of samples positive for
salmonella
Shelf-life 13-22 (310) 9.7
remaining 7-12 (146) 8.2
(months) 0-6 (32) 0
Not known (4) 0
E. coli levelProblems with co-contaminated
samples
Product Initial test result S. Enteritidis detected
B S. Infantis t5.4833 and t5.590
S. Infantis t5.590
D S. Infantis t5.12 and t5.590
A S. Infantis t5.12
E S. Livingstone t5.590
C S. Infantis t5.590
S. Infantis t5.590
24Salmonella and reconstituted chicken survey summary • Salmonella spp. was detected in 40 of 481 survey samples – but only from chicken products (n = 456; 8.8%) • Survey resulted in much wider source finding (a further 5 affected products were identified) • Detection of Salmonella was confined to just six of 54 production plants recorded • S. Enteritidis was detected in 17 samples and every S. Enteritidis detected belonged to one of the outbreak clusters • Some product were co-contaminated – S. Infantis was up to 100-fold more numerous than S. Enteritidis - risk of missing detection of outbreak strains! • Other salmonellas also detected; most common S. Infantis (24) followed by S. Newport (4) and S. Java, S. Livingstone and S. Senftenberg (one sample each) • Long remaining shelf-life for the majority of the positive products 25
Phylogeny analysis outcomes • Isolates in two of the S. Enteritidis clusters (t5.4833 and t5.12) were only detected in products directly (or indirectly) from one production plant (PL II) • Isolates belonging to the t5.590 cluster were detected in products from two PL plants • Greater level of diversity amongst S. Infantis than S. Enteritidis (despite coming from similar products and time frame and mainly from just two PL plants) • UK population therefore exposed to both S. Enteritidis and S. Infantis from these products – yet very few S. Infantis cases detected • Isolates from only two contemporaneous human cases (2020) and two historical cases (2016 and 2019) in the UK occurring in the same cluster as S. Infantis recovered from one of the samples • Also one case associated with a S. Newport strain detected in one product 26
Previous salmonellosis and raw breaded
chicken products in Canada
• 2015-19, 19 outbreaks, 635 cases
• Associated with chicken strips, nuggets, fries, burgers
• Despite labelling with cooking instructions, concerns that
consumers were unclear on effective cooking
• Simulated domestic cooking showed poor cooking (3-4 log
reductions) for pan frying and toaster oven cooking
Morton et al., Epidemiol Infect 2019;347:e254,1-3.
Rao et al., J Food Prot. 2020;83:1289-95.
27Acknowledgements
Thank you to:
All staff in UKHSA FW&E labs especially Raji from London, Francesca from York and
Kieran&Claire from Porton
Frontline clinical labs and
UKHSA SalmSurv – especially Annie H., Lesley L., Jacqui McC and Lisa B.
GBRU – especially Marie C., Andy L. Amina I., and Amy G. for helping with prompt
reporting to FSA and for Cragie stuff
FES and HPTs especially Trent H
Bioinformatics for fitting the food isolates on the tree alongside the case isolates and
making sense of it all
FSA and local environmental health teams for food tracing, enforcement and sampling
-and thank you Jim and everyone for listening.
Any questions?
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