Guidance

Audit of official laboratories capabilities and accreditation status in the UK: 2023 results

Updated 22 May 2025

Executive summary

The UK Health Security Agency (UKHSA) provides the UK’s National Reference Laboratory (NRL) for food microbiology for the Food Standards Agency (FSA), as part of the UK’s obligation to adhere to the assimilated Regulation (EU) 2017/625 for official controls. This report details the 2023 results from a survey sent to the Official Laboratories (OLs) from the NRL and comparing results from the three previous surveys since 2013.

Questions used in this survey were predominantly unchanged and thus comparable to previous surveys, in order to draw comparisons over time. The online survey tool, SelectSurvey, was used to send the questions to fourteen UK OLs. Details of Food Examiner (FE) status, schedule of tests performed, participation in proficiency testing (PT) schemes and problem areas that would like support on were requested. All fourteen OLs responded, although individual responses were missing from one or two OLs.

This audit revealed that although the number of laboratories has remained stable since the 2016 audit, numbers of Food Examiners have decreased from 55 to 39 between 2013 and 2023. The distribution of FEs in the OL network vary considerably, and this is reflected in the number of Official Control samples received, as these are also unevenly dispersed between the OLs. Retaining FEs and training others to attain FE status requires resources, as FEs are needed to oversee formal microbiological testing in foods in the UK.

Overall, testing capabilities of the UK OL network has remained stable, according to the EU microbiological criteria (as stipulated in EC 2073/2005). There is good testing capability for Listeria and Salmonella in line with the Food Safety Criteria, with only a few criteria seeing less capability, probably due to low demand in testing of the particular food categories. In addition, there are a few tests where only a small number of laboratories are accredited including Cronobacter in dried products intended for infants below 6 months of age (only 1 of 14 labs holds accreditation) and histamine in fish (4 of 14). Reasons for the low uptake of these tests may include that they are highly specialised tests, and/or rarely requested in the UK. This makes maintaining accreditation and competence in OLs difficult to attain and justify.

Furthermore, there are no OLs capable of detecting the presence of staphylococcal enterotoxins in cheeses, milk powder and whey powder, due to the same reason. In contrast, detection of Shiga toxin producing E.coli (STEC) in sprouts (criterion 1.29) has continued to see good implementation in the OLs, due to the relatively recent addition to the microbiological criteria, and the NRL arranging training workshops to support the OLs. The NRL will support the OLs in implementing tests, especially where there is a demand and need for them.

There is an increase in uptake in PTs by the UK OLs, with participation ranging from 2 to 11 different PT schemes, including the FEPTU European Food Microbiology Legislation (EFL) Scheme. PT participation assures competence and quality when generating laboratory results, which is particularly important for Official Controls and formal samples. The NRL has drafted a protocol on monitoring performance to formalise how the NRL assesses the OLs using the EFL Scheme. At the time of writing, there is no evidence of ongoing issues in performance by any of the OLs.

Other facets of microbiological testing were included in this survey. Only half the OLs perform shelf-life and challenge testing, which has remained stable since 2016. This complex area requires different procedures to microbiology testing of food and thus is difficult for OLs to include in their routine laboratory activities. Detection of viruses and antimicrobial resistant (AMR) bacteria in the food chain are only carried out in a handful of UK laboratories, but as the One Health approach is adopted, testing of these may be required or requested in the future, and the OLs may need to consider these approaches. To continually improve and match the needs of the OLs, the survey included questions regarding NRL activities and support. Six OLs would like to see smaller discussion groups at the annual User Days to facilitate cross-communication. Topics suggested for more support from the NRL include ‘validation/verification of ISOs’, ‘uncertainty of measurement’ and ‘interpretation of EC 2073/2005’, for which the NRL can organise future workshops or small group discussions at the User Days to support the OLs. From this survey, the NRL has identified some issues and a table of recommended actions completes this report.

Introduction

The UK Health Security Agency (UKHSA) has provided the UK’s National Reference Laboratory (NRL) service for food microbiology for the UK’s Competent Authority, the Food Standards Agency (FSA) since 2011. The NRL is responsible for 6 work areas:

• AMR
• Campylobacter
• coagulase-positive staphylococci (CPS)
• Escherichia coli (incl. STEC)
• Listeria monocytogenes
• Salmonella

It provides advice, training and other support to UK Official Laboratories (OLs), as defined in Regulation (EU) 2017/625 (assimilated by UK Statutory Instrument 2019 No. 665).

Three previous audits have been organised by the NRL since 2013 to ascertain the OL’s accreditation status, numbers of Food Examiners (FEs) employed, tests available and membership of proficiency test (PT) schemes. Those audits identified gaps in testing or training areas, which allowed the NRL to direct resources to organise support to the OLs. For example, in 2013, only 3 out of 15 OLs were accredited to perform STEC detection, and an amendment to the EC Regulation 2073/2005 on microbiological criteria for sprouts was added in the same year. Therefore, 2 practical training workshops in STEC detection were organised for OLs in 2013 and 2019, and in the 2019 audit, there were 5 out of 14 OLs accredited, thus increasing the UK’s capability.

To ascertain the lasting impact of the COVID-19 pandemic and leaving the EU, a fourth audit was organised in 2023 to evaluate whether the UK has adequate capability and capacity for microbiological testing from food. This report describes the data collected and compares to the previous audits in 2016 and 2019 to evaluate the UK OLs capability and capacity. The UK NRL will use this information to support and advise the UK OLs.

Method

Questions from the previous 2 audits in 2016 and 2019 were reviewed and an updated survey was drafted. Correspondingly, Annex 1 of the EC 2073/2005 microbiological criteria (including amendments) was used in this audit to ascertain which test methods the OLs used for which matrices and their accreditation status. This approach was used for the 2016 and 2019 audits, and facilitated data gathering and results could be directly compared with previous audit data. Additional questions collected information on Food Examiner status, capacity and customer base, participation to PT schemes and services from the NRL, such as training and support activities.

Select Survey was used for consistency and to minimise data-entry. The survey was tested internally, before the URL link and amended Annex 1 table was sent to all 14 OL contacts, identified from NRL records and the FSA website, in November 2023. The closing date to submit was 12 January 2024 and responses were downloaded from Select Survey and analysed on a question-by-question basis using Excel. For questions that were identical to previous audits, responses were directly compared. UKAS accreditation schedules were also checked on the UKAS website.

Results

All 14 OLs submitted results, generating a response rate of 100%.

Results are presented in sequential order to the audit. Questions 1, 2 and 6 relate to personal contact details; therefore, these are not included in this report to retain anonymity. Results for question 11 relates to the examinations performed in accordance with the microbiological criteria of EC 2073/2005 (as amended) and are presented as the microorganism in specific food groups. The tables show the 2023 results, and the charts compare these to the 2016 and 2019 audit results.

Comments are found in the Discussion and Conclusion section.

Q3. Do you currently perform microbiology tests in food and feed?

‘Yes’ responses: 14 (100%)

‘No’ responses: 0 (0%)

Q4. Do you currently perform microbiology tests for Official Control purposes in food and feed, including for any other government bodies?

‘Yes’ responses: 13 (93%)

‘No’ responses: 1 (7%)

Q5. How many staff are designated as Food Examiners?

Number of food examiners in 2023	Number of OLs
0	1
1	2
2	6
3	1
4	1
5	1
6	1
7	1

Comparison of number of FEs in the UK between 2013 and 2023

Year	Total number of Food Examiners	Total number of labs
2013	55	17
2016	40	14
2019	45	14
2023	39	14

Q7. How many staff are designated as public analysts (but not Food Examiners) and supervise microbiological testing for Official Control purposes? [note 1]

Number of public analysts	Number of labs
0	11
1	2
6	1

Note 1: two laboratories have interpreted question as having both Food Examiners and Public Analysts.

Q8. On average, how many Official Control samples are submitted for testing every year?

13 OLs responded.

Number of samples: 0; 1; 1; 7; 150; 450; 500; 500; 1,000; 2,000; 2,055; 3,000; 6,400.

Q9. What customer type do you perform microbiological testing for?

Customer type	Number of OLs
Local government	13
Port health authorities	9
Commercial customers (for example, food business operators)	14
Surveillance purposes (for example, local or national surveys)	12
Other, please specify: (hospitals; government organisations, for example, FSA, outbreaks; research projects, for example Food Standards Scotland; private customers)	4

Q10. Do you perform challenge or shelf-life testing for Food Business Operators or otherwise?

‘Yes’ responses: 7

‘No’ responses: 7

Q11. What testing does your laboratory perform, according to the microbiological criteria EC 2073/2005?

Q11 (a)

Listeria in ready-to-eat (RTE) products 2023	Accredited	Not accredited	Not performed
1.1 RTE for infants and for special medical purposes	12	1	1
1.2 RTE supports growth at market	13	1	-
1.2 RTE supports growth at FBO	13	1	-
1.3 RTE unable to support growth	13	1	-

Q.11 (b)

Salmonella in meat products 2023	Accredited	Not accredited	Not performed
1.4 minced meat and other meats eaten raw	12	2	-
1.5 poultry preparations eaten cooked	13	1	-
1.6 meat preparations other than poultry and eaten cooked	13	1	-
1.7 mechanically separated meat	13	1	-
1.8 meats intended to be eaten raw	13	1	-
1.9 poultry meat products intended to be cooked	13	1	-
1.10 gelatine and collagen	7	-	7
1.28 fresh poultry meat	5	3	6
1.30 reptile meat	8	2	4

Q.11 (c)

Salmonella in dairy products, 2023	Accredited	Not accredited	Not performed
1.11 cheese, butter, cream lower heat than pasteur	13	1	-
1.12 milk and whey powder	11	1	2
1.13 ice cream	13	1	-
1.22 dried infant formula and dietary foods less than 6 months	12	1	1
1.23 dried follow-on formula	11	2	1

Q.11 (d)

Salmonella in miscellaneous products, 2023	Accredited	Not accredited	Not performed
1.14 egg products	13	1	-
1.15 RTE foods containing raw eggs	13	1	-
1.16 cooked crustaceans and molluscs	11	1	2
1.17 live shellfish	9	1	4
1.18 sprouted seeds	13	1	-
1.19 precut fruit and vegetables	13	1	-
1.20 unpasteurised fruit and vegetables juices	13	1	-

Q.11 (e)

Miscellaneous in food safety criteria, 2023	Accredited	Not accredited	Not performed	Notes
1.21 Staph tox in cheese and milk or whey powder	-	-	14	No OLs in the UK performs this test
1.24 Cronobacter in dried products intended for less than 6 months	1	1	12	-
1.25 E.coli in live shellfish	9	1	4
1.26 Histamine in fish associated with high histidine	4	1	9	5 OLs use method according to ISO
1.27 Histamine in brined fish associated with high histidine	4	-	10	5 OLs use method according to ISO
1.27a Histamine in fermented fish sauce	5	-	9	1 OL uses ISO method
1.29 STEC in sprouts	6	-	8	Accredited OLs use ISO method

Q.11 (f)

ACCs in meat products, 2023	Accredited	Not accredited	Not performed
2.1.1 cattle, sheep, goat and horse carcases	4	5	5
2.1.2 pig carcases	4	5	5
2.1.6 minced meat	10	3	1
2.1.7 mechanically separated meat	10	3	1

Q.11 (g)

Enterobacteriaceae in process hygiene, 2023	Accredited	Not accredited	Not performed
2.1.1 cattle, sheep, goat and horse carcases	5	4	5
2.1.2 pig carcases	6	3	5
2.2.1 pasteurised milk and other liquid dairy	12	1	1
2.2.7 milk powder and whey powder	12	1	1
2.2.8 ice cream and frozen dairy products	13	1	-
2.2.9 dried infant formula and dietary foods less than 6 months	5	2	7
2.2.10 dried follow-on formula	5	2	7
2.3.1 egg products	13	1	-

Q.11 (h)

Salmonella in meat products, process hygiene, 2023	Accredited	Not accredited	Not performed
2.1.3 cattle, sheep, goat and horse carcases	5	4	5
2.1.4 pig carcases	5	4	5
2.1.5 broiler and turkey carcases	5	4	5

Q.11 (i)

Campylobacter in broiler carcases, process hygiene, 2023	Accredited	Not accredited	Not performed
2.1.9 broiler carcases, 2023	4	3	7
2.1.9 broiler carcases, 2019	5	2	6
Before criteria in place, 2016	3	2	9

Q.11 (j)

E. coli in process hygiene, 2023	Accredited	Not accredited	Not performed
2.1.6 minced meat	12	1	1
2.1.7 mechanically separated meat	12	1	1
2.1.8 meat preparations	12	1	1
2.2.2 cheese from heat treated milk or whey	13	1	-
2.2.6 butter, cream and milk lower heat than pasteur	11	1	2
2.4.1 shelled or shucked cooked shellfish	10	1	3
2.5.1 precut fruit and vegetables (RTE)	13	1	-
2.5.2 unpasteurised fruit and vegetables juices	12	1	1

Q.11 (k)

CPS in dairy and cooked shellfish, 2023	Accredited	Not accredited	Not performed
2.2.3 cheese from raw milk	10	1	3
2.2.4 cheese from <pasteur and ripened cheese pasteur	12	1	1
2.2.5 unripened cheese from pasteurised milk or whey	12	1	1
2.2.7 milk and whey powder	12	1	1
2.4.1 shelled or shucked cooked shellfish	10	1	3

Q.11 (l)

Bacillus cereus in infant formula, 2.2.11, 2023	Accredited	Not accredited	Not performed
2023	11	1	2
2019	9	-	5
2016	10	-	4

Q12. Does your laboratory perform testing for viral detection or AMR bacteria in food?

Test category	Number of OLs [note 1]
Viruses	0
AMR	2
Neither	11

Note 1: one OL did not enter data for this question.

Q13. What methods would you be interested in adding to your testing repertoire?

Response, test or method	Number of OLs
Real-time PCR for pathogens [general]	5
AMR screening of E.coli	4
Real-time PCR for Salmonella from enrichment broth	4
STEC PCR	2
Listeria identification using MALDI-ToF	2
Chromogenic agar for Salmonella and STEC	1
Virus detection	1
Nothing at the moment	1

Q14. What support would you need to implement these methods?

Type of support	Number of OLs
National SOP	9
Validation or verification advice	7
Practical training in method	9
Other: equipment	1
Other: funding	1
Not needed	1

Q15. Are there any food matrices that your laboratory has difficulty in classifying, processing and/or interpreting results for any target organism?

‘Yes’ responses: 2

‘No’ responses: 11

No reply: 1

Q16. If yes, which matrices cause problems?

• products with melted cheese on top
• fresh fruit smoothies
• those where it is not clear whether they are specifically ready-to-eat or not (for example, cook chill)

Q17. Do you have any further comments or problems regarding microbiological testing of food?

• very few official control samples received
• Bacillus spp. common in black bean, spiced and garlic products but not accounted for in the HPA guidelines

‘No’ responses: 6

No response entered: 5

Q18. Do you participate in any PTs/EQAs other than the European Food Law scheme for food microbiology? If so, please list (multiple answers)

PT/EQA Scheme	2023	2019	2016
FEPTU Standard	10	7	7
FEPTU Environmental Swab	7	4	2
FEPTU Non-Pathogen	6	4	3
FEPTU Pathogenic Vibrio	4	2	1
FEPTU STEC	5	3	2
FEPTU/CEFAS Shellfish scheme	9	5	5
FEPTU Campylobacter scheme	not available	2	not available
FEPTU Norovirus and hepatitis A virus	1	-	-
LGC Standard	3	3	3
LGC Dairy Chemistry (pH and phosphatase)	6	1	1
LGC Food Chemistry (Aw)	5	1	1
LGC Vet	-	-	1
APHA Pet Food	1	-	-
FAPAS Standard	3	1	1
Don Whitley (spiral plater)	3	1	1
Eurofins PT schemes	1	-	-
Eurofins Bacterial Endotoxin Testing/LAL	-	1	-
Charles River endotoxin	1	-	-
Did not answer	-	-	1

Q19. Do you perform trending data on your EQA/IQA enumeration results, to monitor trends and bias?

‘Yes’ responses: 13

‘No’ responses: 0

No reply: 1

Q20. If you have attended an OL user day, would you like to see smaller discussion groups?

‘Yes’ responses: 6

‘No’ responses: 7

Not answered: 1

Q21. If yes, what topics would you like to discuss?

• emerging trends, insider knowledge
• microbiology of novel food products
• about the methods themselves
• EQA performance
• auditing
• IQC assessment
• UoM assessment training

Q22. What topics would you like the NRL to cover in future trainings as either practical or Teams sessions? Please choose any that apply

Topic	Number selected
Campylobacter enumeration	5
PCR techniques (focus on STEC)	9
Uncertainty of measurement	10
Validation or verification of ISOs	9
Trend analysis and monitoring bias in QC data	10
Impact assessment of ISOs	7
Interpretation of EC 2073/2005	9
Other	2

Q23. If other, please state

• interpretation of Feeding Stuffs including raw pet foods
• general microbiology training, practical and theory for new members of staff, and refreshers for existing staff

Q24. Have you any other comments or suggestions for the NRL’s service?

• ensure notifications of new legislation, ISOs and SOPs
• when courses are proposed if they could be more central, as travel often extends courses for us by several days
• I would just like to say that I have enjoyed the training days held by the NRL, always well presented and contain a lot of interesting areas and lots to learn from each session, thank you

Discussion and conclusions

Microbiology testing and capacity: Q3 to Q10, Q12 to Q14, Q19

Similar to the 2019 audit, all 14 OLs currently perform microbiological testing in food and feed (Q3). However, one OL stated they did not test Official Control (OC) samples collected by public bodies (Q4). The remaining 13 OLs test samples from Local Government, Port Health Authorities and commercial customers, for surveillance or outbreak investigations via local or national surveys and UKHSA/FSA, respectively (Q9). Overall, the number of laboratories has remained relatively stable for microbiological testing for the UK, allowing continued support of surveys, outbreak investigations and imported food monitoring in line with the Border Target Operating Model (BTOM) which was introduced on 31 January 2024.

When asked, 13 OLs submitted data on the average number of OC samples received annually, but these varied significantly, from no samples received to 6,400 (Q8). This difference largely relates to the size of regions or customer groups served by each laboratory. However, the numbers may also be impacted by uneven rates of OC sampling across the UK and government agencies and the different repertoire of testing offered in each OL. There may also be some difference in the way this question was interpreted by different respondents (see Q11).

The histogram and table for Q5 reveals the fluctuations of food examiners (FEs) working in UK OLs over a 10-year period. Six OLs each had 2 FEs in 2023, with a decrease in OLs having only one FE. Despite 5 OLs having 3 or more FEs, within a decade there has been a gradual reduction of FEs in the UK; from 55 FEs in 2013 to 39 in 2023. In addition, one OL reported having no FEs, although this OL has 6 Public Analysts supervising microbiological testing (Q7), and 2 OLs have both Food Examiners and Public Analysts. Official microbiological testing in the UK requires the availability of FEs to oversee the process, due to legislative requirements, and this audit suggests that retention seems to be difficult for these highly trained staff. Additional resources may be necessary to train and retain competent staff as FEs to ensure adequate ongoing capability for microbiological testing in the UK, and support may be needed by NRLs and the Competent Authority.

Shelf-life and challenge testing of food requires expertise, knowledge of the food matrix, the behaviour of pathogenic and spoilage micro-organisms, interpretation of legislation, and the resources to perform testing. The OLs receive queries about potential work in this area from local authorities and food business operators (FBOs); however, only half the OLs perform challenge or shelf-life testing (7 out of 14), which has not changed from the 2016 and 2019 audits (Q10). This is despite the NRL organising a one-day workshop for OLs in October 2017 to equip OLs with the background and knowledge necessary to address queries in this area. In addition, there is a need for separate work areas for the routine examination of food samples and the intentional introduction of pathogens for challenging testing, which makes it difficult for OLs to support this complex area of food microbiology. This area of work also requires procedures which are different to the main testing work carried out by OLs and their personnel. However, there is provision for this type of work within commercial laboratories, but availability is likely to be relatively limited.

Detection of viruses in food, such as norovirus and hepatitis A, has up until recently been limited to one or 2 laboratories in the UK and focused on testing shellfish and fruit and vegetables, due to complex extraction techniques that are not standard practice for OLs predominantly detecting bacteria. However, with both norovirus and Hepatitis A being seen in association with soft fruit, salad and other fresh produce, there may be a demand for testing from customers. Therefore, the OLs were asked if they performed viral detection, with results indicating that no OL laboratories offer these tests (Q12). While viruses do not fall within the remit of the NRL for Food Microbiology, this survey indicates that a review of resources may be needed in the future to enable OLs to investigate potential sources of viral foodborne incidents.

The OLs were also asked if antimicrobial resistance testing was performed on bacterial isolates from food as, under a One Health approach, there is a need to understand the relationship between antimicrobial-resistant (AMR) bacteria in people, animals, food and the environment. Only 2 OLs perform AMR testing on food (Q12) and this is limited to screening for the presence of AMR bacteria, where presumptive isolates are subsequently referred to other laboratories to detect resistance genes via whole genome sequencing and perform phenotypic sensitivity tests to ascertain the isolates’ resistance to specific antimicrobials. There have been recent FSA-funded studies into AMR prevalence in food commodities, which has enabled a few OLs to trial screening of AMR bacteria. In 2024, the NRL supported the drafting of a national SOP on this topic and a training session is planned for 2025 to improve awareness amongst OLs of this method and the steps required to screen food for the presence of AMR bacteria.

Twelve of the 14 OLs would be interested in adding new methods to their testing repertoire (Q13), which included using real-time PCR, either in general, to screen for Salmonella or for STEC detection. Related to the previous question, 4 OLs would like to introduce AMR screening of E. coli and one OL would be interested in detecting viruses. This reveals an appetite to expand and update testing from the OLs, although current demand for this testing is likely to be geographically variable, depending on the location of food businesses and the requirements of Local Authorities and FSA. Eleven of these OLs would find support useful to implement these methods (Q14), including a reference to a national SOP, advice on validation or verification and to attend practical training. The NRL will explore further with the OLs to ensure support can be given in the appropriate way.

To ensure there is no shift or drift in the accuracy of enumeration data, trend analysis of quality control results is recommended, as is looking for bias over time. The NRL uses the FEPTU EFL PT scheme to monitor OL testing performance and has recently produced a ‘Monitoring Performance’ protocol to set out what would happen if OLs reported erroneous results in the EFL scheme and the expectation to perform root cause analysis with support from the NRL. Thirteen OLs perform trend analysis on their EQA and IQA data, which ensures that enumeration methods employed by the OLs are checked regularly to minimise deviations that could impact on routine sample results.

Testing according to EC 2073/2005 microbiological criteria: Q11

To directly compare with previous audits in 2016 and 2019, data was gathered in the same way from the OLs according to the annexes in the microbiological criteria, EC 2073/2005. Therefore, the charts in the results section can reveal differences over time in the OLs’ testing provision. Additional questions were asked regarding whether alternative methods were used in place of the reference ISO methods stipulated in EC 2073/2005. The microbiological criteria annexes are split into 2 chapters; Chapter 1. Food Safety Criteria and Chapter 2. Process Hygiene Criteria (PHC). The Food Safety Criteria are discussed first.

There has been a general increase in attaining accreditation for detection and enumeration of Listeria monocytogenes in the different ready-to-eat (RTE) food categories (1.1 to 1.3) for all OLs. This reflects the increase in listeriosis cases in the UK and subsequent investigations in food and, although RTE foods cover a broad range of food matrices, an increased capacity ensures the UK are in good stead to detect and enumerate this organism.

Capacity for Salmonella detection has also increased in general and covers a wide variety of matrices. At least 12 OLs are accredited to test 6 of the 9 meat-based food categories (1.4 to 1.9 inclusive), whereas for testing in gelatine and collagen (1.10), there has been a drop to 7 OLs and for fresh poultry meat (1.28), 5 OLs are accredited. The relatively low number of OLs processing these matrices is likely to be due to a lack of demand from enforcement officers and FBOs. Moreover, for fresh poultry meat, there is a specific requirement to detect Salmonella Typhimurium and Salmonella Enteritidis. This requires the serotyping of Salmonella isolates using the White-Kauffmann-Le Minor scheme or whole genome sequencing (as a validated alternative method), which OLs may not have the capacity to undertake. However, the Gastrointestinal Bacteria Reference Unit at UKHSA Colindale and the Scottish Salmonella Reference Laboratory can identify Salmonella species and the OLs are invited to submit their presumptive isolates for confirmation. Reptile meat is the most recent criterion added to EU 2073/2005 and whilst 8 OLs have stated they are accredited for Salmonella testing, in practice, many OLs will not have received this specialised meat product for examination.

In 2023, there were at least 11 OLs accredited to detect Salmonella in all 5 dairy food categories related to the Food Safety Criteria (1.11 to 1.13, 1.22 and 1.23). Eggs, shellfish, and fruit and vegetables have been grouped as ‘miscellaneous products’ (1.14 to 1.20, inclusive) and have relatively high testing capability, with at least 11 OLs accredited to detect Salmonella, except for one, live shellfish (1.17).

The remaining Food Safety Criteria in Chapter 1 cover a variety of matrices and analytes, and either require specialised methodology or relate to low demand food products. Consequently, there is little capability in the UK for these remaining criteria and since 2019, there have been minor fluctuations in the number of OLs able to test these. One outlier is E.coli testing in live shellfish (1.25), where 10 OLs have been able to perform this since 2016. This contrasts with the detection of staphylococcal enterotoxins in cheeses, milk powder and whey powder (1.21), where no OLs perform this highly specialised test. This test is only a statutory requirement after ≥10⁵ colony-forming units per gram (cfu/g) of coagulase positive staphylococci are detected in specific food products as specified in process hygiene criteria. In addition, the UK has experienced very low referrals for this testing, and as such, the NRL has an agreement with a designated official laboratory in the EU that performs this test, where the UK last sent them an official sample in 2017 for testing.

Capacity for Cronobacter testing (1.24) remains the same since the 2019 audit, where only one OL performs as an accredited test and another performs the test but is not accredited. The requirement for this criterion is dependent on the outcome of Enterobacteriaceae testing for the same matrix, according to process hygiene criterion, 2.2.9. As the Enterobacteriaceae procedure is a simpler test and is seen as a precursor to Cronobacter detection, with subsequent Cronobacter testing rarely required in practice, this could explain why so few OLs test for Cronobacter spp.

Histamine testing (1.26, 1.27 and 1.27a) has seen a slight increase in capability from the 2019 survey, as there was a dip in the number of OLs testing from the 2016 survey. This may be partly due to the stipulated method being standardised in EU 2073/2005 to ISO 19343 in 2019 and OLs having to change their approach for testing fish products. However, only about a third of UK OLs adopt this method and can test these matrices, and this may be because the detection and quantification of histamine does not employ conventional microbiological methods.

Detection of Shiga toxin producing E.coli (STEC) in sprouts (1.29) has seen a steady increase in UK capability since it was added to EU 2073/2005 in 2013, from 2 OLs accredited for this test in 2013, to 6 OLs in 2023. This increased capability was encouraged by 2 practical training workshops that the NRL organised in 2013 and 2019, which focused on detection of STEC using PCR and according to the reference method TS/ISO 13136:2012. A similar workshop was run in 2024 to further support OLs to adopt this method. However, it is acknowledged that there are practical and infrastructure hurdles that can impede laboratories, as handling STEC requires a Schedule 5 licence (according to the Anti-terrorism, Crime and Security Act 2001) and the provision of Containment Level 3 (CL3) facilities for isolation of the organism. The NRL offers support to OLs wishing to implement STEC testing in their accreditation schedule.

Within the process hygiene chapter of EC 2073/2005 (as amended), testing animal carcases for aerobic colony counts, Enterobacteriaceae and/or Salmonella (2.1.1 to 2.1.5) has seen a slight decline in capability, with only 4 to 6 food microbiology OLs accredited. Testing carcases can be performed by either food or veterinary OLs; however, food microbiology OLs receive carcase swabs infrequently. The recent process hygiene criterion for enumeration of Campylobacter in broiler carcases (2.1.9) has seen a slower adoption by the OLs compared to the STEC testing in beansprouts. Between the 2 surveys in 2019 and 2023, there has been no change in 7 OLs capable of performing Campylobacter enumeration, although the OLs’ schedules of accreditation record that 9 OLs are accredited for Campylobacter detection, which assures the UK’s capability in detecting this pathogen. The UK NRL has supported the UK OLs by delivering practical training for Campylobacter testing in 2013 and 2017 but may need to organise further training to expand Campylobacter enumeration capacity in the UK.

The remaining food categories in the process hygiene criteria are more likely to be tested by the food microbiology OLs, which include meat and meat products. Testing capability for ACCs and E.coli in meat (2.1.6 to 2.1.8) has remained stable in general since the 2016 audit. The dairy food criteria 2.2.1 to 2.2.7 also have good testing capability from the OLs for Enterobacteriaceae, E.coli and coagulase-positive staphylococci; between 10 and 13 OLs are accredited. However, capability for testing of Enterobacteriaceae in dried infant and follow-on formula (PHCs 2.2.9 and 2.2.10) has dipped back to the same level as seen in the 2016 audit of only 7 OLs testing these categories. This decrease may reflect the fact that the procedure for detection (rather than enumeration) of Enterobacteriacae is unique to this food commodity which, in practice, is rarely submitted to OLs for testing. Therefore, the justification for maintaining the method is low for the majority of laboratories. The change may also be in part due to criterion 2.2.9 requiring parallel testing of Cronobacter spp. which is the food safety criterion 1.24 and is a more specialised procedure (see above for more detail). In contrast, there is good capability for testing dried infant formula and other dietary foods for infants below 6 months of age (2.2.11) for Bacillus cereus and this has been generally stable since the 2016 audit: 11 OLs were accredited in 2023.

The remaining categories, egg products, shelled and shucked shellfish and fruit and vegetable products (2.3.1, 2.4.1 and 2.5.1 to 2.5.2, respectively) have also remained stable in terms of capability and are tested by between 11 and 14 OLs for Enterobacteriacae, E.coli and CPS.

As some of these criteria rely on either specialised methods or challenging matrices (for example, staphylococcal enterotoxins in dairy products, Cronobacter in dried foods intended for infants below 6 months of age), this has resulted in a lower number of OLs able to process these. The NRL will therefore hold an OL list of any microbiological criteria where 4 or less OLs are capable of testing, which can be referred to by the NRL or FSA if testing is required.

Challenges in microbiological testing: Q15 to Q17

Similar to the 2019 audit, only 2 of 14 OLs noted that they experience difficulties in classifying, processing and/or interpreting results when testing certain food matrices (Q15). However, specific concerns were raised, which related to products with melted cheese, fresh fruit smoothies and products that were ambiguous (for example, RTE or cook chill product; Q16).

Further comments (Q17) included that very few OC samples were received by one laboratory. Across the UK, there is an uneven distribution of OC sampling undertaken by the local authorities and Port Health Authorities and often the nearest OL will be in receipt of the samples. This is inherent and difficult to change due to geography and funding, and consequently, some OLs may find their testing capability and competence to be a challenge to retain. The other comment was that Bacillus spp. is common in black bean, spiced and garlic products but not accounted for in the HPA guidelines. The revised Ready-to-eat guidelines was published after the survey was sent and describes investigating elevated Bacillus levels in herbs and spices. The UKHSA FWEMS food sample testing algorithm has also been added to the guidelines to inform others of the decision process, which includes testing for Bacillus spp. in specific product types.

Participation in Proficiency Test schemes: Q18

The NRL uses FEPTU’s EFL Scheme, which is agreed by UKHSA and FSA, to allow direct comparisons of performance to be made between OLs. Since 2014, participation in the EFL Scheme has been successful, with between 11 and 14 OLs (73% and 100%) registering on an annual basis. The NRL has monitored results and after a slight decline in OL performance in 2022 to 2023, the NRL has produced a ‘Monitoring Performance’ protocol, which has a tiered approach to remedial action and supports the OL if corrective steps are to be taken. At the time of writing, OL performance has improved, and previous issues were rectified by all OLs.

There has been a general increase in uptake of PT schemes when comparing the results in the 2016, 2019 and 2023 audits. There are various PT schemes available from several PT providers, and this caters for the OLs’ needs and the schedule of tests of the individual laboratories. Seven additional FEPTU schemes other than the EFL scheme were selected by OLs according to the 2023 audit, including the Standard Scheme for food methods (N=10 OLs), the Environmental Swab Scheme (N=7), and the non-pathogen scheme (N=6). Four schemes run by the provider, LGC, were also used, as well as the APHA Pet Food Scheme, the FAPAS Food Microbiology Scheme, the Don Whitley (spiral plater) scheme and a Eurofins PT scheme. Whilst one OL did not respond to this question, excluding the EFL scheme, OLs are participating in between one and 10 other PT schemes, with an average of 5 PT schemes per OL.

Provision of National Reference Laboratory services: Q20 to Q24

In order to ascertain and improve the needs of the OLs, several questions regarding NRL activities were included in the survey. In 2023, when asked about the format of the OL User Days, which the NRL organises annually to inform OLs of relevant topics, 6 would like to see smaller discussion groups introduced. This is an increase compared to only 3 of the 14 OLs in 2019. Topics suggested included emerging trends, the microbiology of novel food products, methodologies, EQA performance and IQC assessment, auditing and measurement uncertainty (MU) assessment training. As there is more interest in using smaller discussion groups, the NRL will look to reformat the next User Day and select particular topics for group discussion to help further support UK’s microbiological capability.

From a multiple-choice list, OLs selected a range of topics they would like the NRL to cover in future training sessions either as practical laboratory training or online sessions. Comparing over time, there are some repeating topics that continue to be a challenge for OLs, and there are some new topics which are different to previous years. Nine OLs selected ‘validation/verification of ISOs’, which also scored highly in 2019 (N=10 OLs). The NRL ran a workshop in 2022 to launch the National Verification/Validation SOP, which introduced the OLs to the ISO 16140 series in order for them to apply these approaches to their methods. However, there are many parts to this ISO with further parts still to be finalised, therefore the NRL will consider arranging another workshop to support the OLs in due course.

Other repeating topics from 2019 were ‘uncertainty of measurement’, ‘interpretation of EC 2073/2005’, ‘PCR techniques’, ‘impact assessment of ISOs’ and ‘Campylobacter enumeration’ where several OLs are still interested in support. The NRL can organise future workshops or small group discussions at the User Days to facilitate this. Ten OLs were also interested in a ‘trend analysis and monitoring bias in QC data’ workshop, which can also be considered, as the NRL has produced a ‘Monitoring Performance’ protocol in 2024 to help assess the OL’s EFL results, in line with the retained Official Control Regulations, EU 2017/625.

Two additional topics were suggested by OLs: ‘Interpretation of Feeding Stuffs including raw pet foods’ and ‘General microbiology training, practical and theory for new members of staff, and refreshers for existing staff’. These suggestions can be added to future feedback surveys to the OLs to gauge interest and need.

Regarding the NRL’s service, OLs gave free text comments and suggestions. These included: to ensure notifications of new legislation, ISOs and SOPs; when courses are proposed if they could be more central, as travel often extends course by several days. These comments can be considered by the NRL when carrying out activities. The following positive feedback was included: ‘I would just like to say that I have enjoyed the training days held by the NRL, always well-presented and contain a lot of interesting areas and lots to learn from each session, thank you’.

Issues identified and recommended actions

The following issues from the 2019 report are shown below, with appropriate action that has helped resolve them. Some issues are unresolved, and the NRL will investigate further as to whether they are still a concern.

Table 1. Previous issues identified and recommended actions

Issue identified	Recommended action	Action implemented
Shelf-life testing a knowledge gap for OLs despite NRL holding a one day workshop in October 2017	Further training or workshops are required	Workshop or training not yet arranged: 2023 audit indicates that this may still be a knowledge gap – low priority
Challenge testing performed in 7 out of 14 OLs (requiring separate work areas and different expertise)	Assess capability in OLs and other UK food laboratories against the demand from FBOs and local authorities	Difficulty in gathering appropriate information from FBOs and local authorities
Detection of STEC testing in 5 out of 14 OLs	NRL to organise laboratory training for OLs to implement method	NRL organised workshop in March 2024
Enumeration of Campylobacter testing in 7 out of 14 OLs	NRL to organise laboratory training for OLs to implement method	Workshop not yet arranged: 2023 audit indicates 5 out of 14 OLs are interested, which indicates that this is a lower priority than other topics – low priority
Interpreting novel vegan foods identified as challenging	Conduct a survey to assess appropriate testing for vegan foods	UKHSA FWEMS performed survey in 2022 to 2023, with findings published in: Willis C and others (2024) ‘Microbiological quality of vegan alternatives to dairy and meat products in England during 2022-2023’ Journal of Applied Microbiology 135: lxae245
Interpretation of STEC results and isolation of organism is challenging	Training to be given to OLs to improve capability	NRL organised workshop in March 2024
Training sought for ‘rapid confirmation methods, for example, PCR, MALDI-ToF	NRL to arrange training for OLs	NRL organised PCR workshop in March 2024
Continued evaluation of UK OLs capability and capacity	NRL to organise a repeat survey in 2023 to 2024	Completed: 2023 audit report

Further issues were identified from this 2023 audit, which are shown below.

Table 2. Further issues identified in 2023 audit

Issue identified	Recommended action	Action implemented
Numbers of FEs are decreasing in the UK over time	Additional resources necessary to train and retain competent staff as FEs
No OLs have capability to detect hepatitis A or norovirus from food	Liaise with NRL for foodborne viruses regarding support for implementation of virus detection testing in OLs	Development work undertaken within UKHSA in 2024, but no routine method used to date
Only 2 OLs can perform AMR screening	Support implementation of AMR screening in OLs	NRL to arrange a training session to introduce AMR SOP – medium priority
Low number of OLs are capable of doing specialised methods or challenging matrices	To collate a list of OLs able to offer specialist tests
Half of OLs would like to see smaller discussion groups used in User Days	NRL to organise next User Day to include smaller discussion groups – planned for September to October 2025
Nine OLs selected ‘validation/verification of ISOs’ as a training need	NRL to organise a workshop to further support OLs – high priority
Ten OLs selected ‘trend analysis and monitoring bias in QC data’ as a training need	NRL to organise workshops to support OLs – high priority

This audit has produced qualitative data concerning the capabilities and capacity of the OLs and reveals that the OLs needs are continually evolving. The NRL will support the OLs on the areas identified and a repeat survey will be performed to ensure the NRL can efficiently support the UK OL food microbiology network.