ACMSF 51st minutes: 18 March 2004

The fifty-first meeting of the Advisory Committee on the Microbiological Safety of Food was held at 10.30 am on Thursday 18 March 2004 in Aviation House, 125 Kingsway, London WC2B 6NH.


Professor D L Georgala

Dr G R Andrews
Professor M J Gasson
Professor T J Humphrey
Professor A M Johnston
Mr A Kyriakides
Mr P Mepham
Dr S J O’Brien
Mr B J Peirce
Mr D J T Piccaver
Dr Q D Sandifer

Mr P J R Gayford (Defra)
Dr J Hilton (FSA)
Dr S Neill (NIDARD)

Mr C R Mylchreest (Administrative Secretary)
Dr P E Cook (Scientific Secretary)
Mrs E A Stretton
Mr G Low

Dr C Little (HPA): agenda item 7
Dr A Belcher (FSA): agenda item 8

1. Chairman's introduction
1.1 The Chairman welcomed ACMSF Members, those making presentations, and members of the public to the Committee’s 51st meeting.

1.2 He explained the format of the meeting and dealt with a number of house keeping matters.

2. Apologies for absence
2.1 The following Members sent apologies for absence – Dr D W G Brown, Ms S Davies, Dr K M Hadley, Dr P R Hunter, Ms E Lewis and Dr T D Wyatt.

2.2 Apologies were also received from the following Departmental Assessors – Dr L Doherty (NIDHSSPS) and Dr G McIlroy (NIDARD), for whom Dr Neill was deputising.

3. Declarations of interests
3.1 Professor Humphrey reported, in connection with agenda items 6-8, that he was an adviser to the British Egg Industry Council and a contractor for one of the research projects.

3.2 Mr Kyriakides reported, in connection with agenda item 6, that some eggs from Sainsbury’s stores had been sampled as part of the FSA’s survey of salmonella contamination of retail eggs.

4. Minutes of the 50th meeting (ACM/MIN/50)
4.1 Members approved ACM/MIN/50 as a correct record of the previous meeting. The Secretariat was asked to arrange for these final minutes to be posted on the Committee’s website.
Action : Secretariat

5. Matters arising ACM/675)
5.1 Members noted Secretariat information paper ACM/675 detailing matters arising from previous meetings.

6. Survey of salmonella contamination of UK-produced shell eggs on retail sale (ACM/676)
6.1 At the invitation of the Chairman, Dr Cook presented ACM/676, a near final draft version of the Report on the Food Standards Agency’s survey of salmonella contamination of UK-produced shell eggs on retail sale.

6.2 Following Dr Cook’s presentation, the Chairman invited Professor Humphrey, Chairman of the Surveillance Working Group, to report on that Group’s consideration of an earlier draft of the surveillance report. By way of introduction, Professor Humphrey said that his oral report reflected the views of the other members of the Surveillance Working Group.

6.3 Professor Humphrey said that the surveillance report was an important piece of work. The Surveillance Working Group had seen the main body of the draft on 19 December 2003 and the annexes on 23 December. The Group had had insufficient time to adequately assess the draft. The Group had nevertheless been very encouraged by the fall in prevalence of salmonella in UK eggs and welcomed the part played by voluntary egg industry controls in bringing about this reduction. The Group regarded vaccination of pullets as the key intervention and was anxious that nothing should be done which served to discourage vaccination. In this connection, the Group was concerned about the danger of the survey data being over-interpreted. While the Group regarded designing the sampling frame to reflect market share as reasonable in relation to the objective of measuring overall production prevalence, members had doubts about some of the inferences drawn when analysing stratified data. The Group had felt that the only safe conclusions to be drawn from the survey were that, compared with earlier surveys, there had been a marked reduction in egg contamination rates, and no egg contents were positive; that salmonella was still present in UK egg production, albeit at a low level; and that because the overall contamination rate was so low, it was not possible to make a reliable comparison of different production types.

6.4 Professor Humphrey said that one of the Surveillance Working Group’s major concerns was the finding of 5 Salmonella dublin-positive eggs, representing 36% of the contaminated eggs found. This gave rise to a number of questions, namely, if the most plausible explanation of the presence of S. dublin was cross-contamination, was there anything to suggest that the procedures applied to the eggs concerned differed from those used for other eggs; what evidence was there that the other salmonella isolates found were not also the result of cross-contamination; had previous egg surveys revealed unexpected salmonella isolates; and what would the FSA have done had the suspect S. dublin isolates been another serovar more usually associated with eggs.

6.5 Professor Humphrey said that he had also raised with the FSA the question of whether the Agency was making best use of the expertise available to it through the Surveillance Working Group in advising on the design of surveillance projects. The Chairman noted that the Group had been set up because in the past there had been a lot of criticism of survey methods generally. The aim of the Group was to provide ACMSF advice to Government in connection with its microbiological food surveillance programme, particularly in relation to the design, methodology, sampling and statistical aspects. It was hoped that this would safeguard against surveillance results being undermined by criticism of the survey methods used.

6.6 In relation specifically to the S. Dublin point, Dr Cook said that the findings of five positive egg samples had been unusual and unexpected. The eggs had been tested at the laboratory on two dates (one positive on 7 April and four on 14 April). The samples had come from four different shops, had five different ‘best before’ dates, and had been packed at four different packing stations. S. Dublin was a cattle-adapted serotype and had been associated, rarely, with chickens only where cattle and poultry were in close proximity to each other on the same farm. Painstaking follow up work on-farm had been undertaken on the S. Dublin positives, in the expectation that, if the results were valid, the serotype would have been seen more widely. However, no S. Dublin was found as a result of this work. Moreover, S. Dublin had not been isolated in previous surveys of UK or imported eggs, including recent surveys by BEIC, two retailers and the HPA (agenda item 7). The last of these was conducted at a similar time to the FSA’s own survey. The other salmonella serotypes found (S. Enteritidis, S. Infantis, and S. Livingstone) had all been found in other similar surveys. There had appeared to be no clear pathway linking the S. Dublin isolates to a common farm, packing station, retail shop or sampler source; samplers and the laboratory appeared to have taken all necessary precautions; and it had not proved possible to identify a specific point in the sample handling and testing regime where S. Dublin contamination might have occurred. Dr Cook said that, given the variation between the samples at retail, packing station and farm, it had been concluded that the most plausible explanation was that cross-contamination had occurred sometime in the handling and/or testing process. However, although the S. Dublin results had been excluded from the main analysis in the Report, a statistical analysis of the egg survey results with the S. Dublin positive samples was contained in an annex to the report.

6.7 Among the points made in the more general discussion of the report which ensued were that:

  • A disadvantage of a retail, as opposed to a packing station-based, survey was that the eggs were subject to an additional step in the distribution process, an advantage was that the results were comparable with previous surveys, which had also been retail-based.
  • If S. Dublin were found in eggs, this would be of concern. However, there was some reassurance to be drawn from the fact that S. Dublin was rarely seen in humans.
  • There had been a significant reduction in the prevalence of Salmonella in UK retail eggs, reflecting the significant resources the UK industry had devoted to tackling Salmonella in eggs.
  • While the absence of contents-positive eggs was welcome, the risk was recognised of cross-contamination from dirty shells. The FSA was likely to revisit its consumer advice on eggs at a later date but, in the context of whether or not this might be relaxed, it was noted that it was already fairly permissive for other than vulnerable groups.

6.8 Mr Gayford said that Defra welcomed the results which it felt reflected the major investment undertaken by the UK industry to improve the salmonella status of eggs. The Agency's conclusions on the S. Dublin results reflected Defra data on the rarity of this serotype in chickens.

6.9 In conclusion, the Committee welcomed the findings of the survey, that, there had been a three-fold reduction in the level of Salmonella contamination since the survey in England in 1995/96. However, it was noted that eggs could still contain salmonella and it was therefore hoped that industry would maintain its efforts to keep on top of the problem. It was noted that salmonella contamination continued to be a problem in relation to some non-UK eggs and that some other Member States could benefit from adopting a similar approach to tackling the problem to that adopted by the UK industry. Members noted that the FSA had already taken steps to make other Member States aware of the problems encountered and were also planning a survey of non-UK eggs.

7. Microbiological examination of raw shell eggs and their use in catering premises(ACM/677 and corrigendum ACM/677(CORR))
7.1 At the Chairman's invitation, Dr Christine Little (HPA) introduced ACM/677, a report of LACORS/HPA Coordinated Food Liaison Group study on the microbiological examination of raw shell eggs and their use in catering premises. The study had its origins in the epidemiological investigation of the unusually large number of outbreaks in 2002 of Salmonella Enteritidis associated with the use of eggs in catering premises. The objectives of the study, carried out between April and May 2003, were to establish the rate of salmonella contamination in raw shell eggs in catering premises, investigate any correlation between the type of eggs and the presence of particular salmonella sero/phage types, and to examine the use of eggs in catering premises in the UK.

7.2 Dr Little summarised the results. A total of 34,116 (5,686 pooled samples of six) eggs had been collected from 2,104 catering premises. Eighty-seven per cent were UK eggs. Salmonella spp. were isolated from 17 (0.3%) pools of eggs. Fifteen of these were S. enteritidis. Salmonella Livingstone and S. Typhimurium were also isolated. Among the conclusions drawn from the study were that, whilst no egg could be guaranteed salmonella-free, rates of salmonella contamination in UK-produced eggs had decreased significantly when compared with results from a previous study carried out in 1995/96; while no firm conclusion could be drawn when comparing the rate of salmonella contamination of Lion and non-Lion Code eggs, the findings might demonstrate the wider benefit of vaccination to UK egg safety; recent experience suggested that the nature of the catering egg market and the intermittent use of imported eggs may allow the sporadic introduction of highly contaminated eggs.

7.3 Dr Little also summarised the study findings in relation to other important aspects including the use of hazard analysis, awareness of FSA food safety advice by caterers visited, degree of food hygiene training, availability of hand washing facilities, the potential for cross-contamination, the storage and use of eggs and the degree of cooking, and the performance of premises serving vulnerable groups.

7.4 In the ensuing discussion of the report, a number of comments were made, including:

  • Members were unhappy that some premises visited had had no hand washing facilities, and that, even where available, these were not universally used. This was regarded as unacceptable for premises serving food, and contravened legal requirements.
  • Similar remarks applied in relation to HACCP systems.
  • The significant level of lack of awareness of egg safety advice among managers was another cause for concern.
  • Local authority inspection, while of vital importance in encouraging compliance with food hygiene legislation, could not of itself provide a complete solution to existing problems. There was a key role for a continuing programme of advice and education to supplement the inspection and enforcement effort. Members welcomed the efforts being made under the banner of the FSA’s food hygiene campaign, and encouraged the Agency to continue to look for innovative and more effective means of targeting and delivering advice.
  • There was support for a survey of the salmonella status of non-UK eggs, many of which went to catering outlets. In designing such a survey, account needed to be taken of the changing pattern of supplies and the fact that a snapshot survey might not be representative of the pattern of the use of eggs over the longer term.

7.5 The Chairman thanked Dr Little for her presentation of a very interesting report.

8. Egg research (ACM/678)
8.1 At the Chairman’s invitation, Dr Andrea Belcher (FSA) introduced ACM/678 reporting on results from the Agency-funded research sub-programme on eggs. Dr Belcher explained that the programme had been shaped by ACMSF recommendations for further research to improve understanding of the sources of Salmonella enteritidis and possible routes of infection for human disease. The purpose of the paper was to seek the Committee’s views on the findings of the eggs research programme and the need for further work in this area.

8.2 Following her general introduction, Dr Belcher then dealt in greater detail with the individual projects. These were (Project No. B03015) a study to examine the egg-to-egg variations in the growth of salmonella spp in egg contents; (B03016) cross-contamination from the external surface of eggs in relation to the risk of exposure to salmonella; (B03017) a review of commercial egg washing with particular emphasis on the control of salmonella; and (B03018) a pilot study to estimate the nature and extent of adherence to government guidance on safe egg use in the catering industry.

8.3 A number of points emerged from subsequent discussion of the projects, including:

  • B03015: had not investigated the effects of different diets on shell thickness and the rate of transfer of contamination. Birds had received a standard feed. Although shell thickness reduced with age, there was no apparent correlation between bird age and the level of contamination.
  • B03015: as a general rule, when fresh, eggs contained few cells of S. enteritidis. In most cases, at a constant storage temperature of 20°C, there was no significant change in the situation for around 3 weeks. However, it had been found that perhaps 5% of new laid eggs supported rapid early growth of salmonella. That said, no contents-positive eggs had been found in the FSA survey.
  • B03016 and B03017: levels of inoculum used on egg shells were higher than would normally be expected to occur on naturally-contaminated eggs.

8.4 In conclusion, the Committee did not identify any major gaps in the research programme. In relation to the individual research topics, it concluded that:

  • (B03015) poultry genomics might provide some helpful insights into the behaviour of Salmonella. It was noted that Defra was supporting work in this area.
  • B03016: the findings from this project were unsurprising. Defra was funding research in this area too and would keep ACMSF informed of developments.
  • B03017: as the question of commercial egg washing was now being considered by the EU, a need for further research might be identified; particularly as salmonella grows more rapidly in washed eggs.
  • B03018: no further work seemed necessary.

8.5 The Chairman thanked Dr Belcher for her presentation. She in turn said that the Committee’s comments would be fed into the planned review of the egg research sub-programme when this took place later in the year.
Action: FSA

9. Horizon scanning: changing social habits (ACM/679)
9.1 At the Chairman’s invitation, Dr Andrews, in his capacity as Chairman of the Ad Hoc Group on Changing Social Habits, presented ACM/679, his report on the Group’s work. This contained a number of recommendations for follow-up action. Dr Andrews expressed his gratitude to the other members of the Group (Mr Peirce, Mrs Jefford and Professor Humphrey) for their assistance and also expressed his appreciation of the help provided by Mr Richard Campbell of the FSA’s Economics and Analytical Division.

9.2 Following Dr Andrews’ presentation Members discussed his Group’s report. Among the comments were that:

  • The report was consistent with what Members had heard earlier in the meeting and with their own professional experiences. Links had been usefully demonstrated between a number of inter-related factors, including the decline in food hygiene skills, obesity, changing eating habits, and the loss of food preparation skills, particularly among younger members of society.
  • The use in the report of HIV data as a proxy for immunocompromised groups was interesting. However HIV was not a surrogate for all types of immunocompromise. Members wondered whether the HPA could obtain further information on illness in the immuncompromised. The difficulties in linking laboratory data to databases containing patient information were noted. HPA had established links with public health observatories to try to do this and some progress had been made in relation to listeria data.
  • Data were collected centrally on travel-associated illness.
  • The elderly with IID were less likely to consult their GPs so the data might be skewed towards illness in children.
  • Good leadership was seen as very important in ensuring proper standards of hygiene in the catering sector. Literacy skills were often not well developed and staff were thus more likely to follow the example of their managers. It was, of course, important that managers were sending the right messages to staff.

9.3 The Chairman suggested that, as none of the recommendations in the report were directed at further ACMSF work, it might be sensible to allow the FSA to consider these in the light of the initiatives it was already taking. The Agency could then return to the Committee at a later date to develop particular points, as appropriate. This suggestion was accepted.
Action: FSA (as appropriate)

10. Campylobacter Working Group
10.1 The Chairman reported that the draft of the Committee’s Second Report on Campylobacter had been submitted to the Chairman of the FSA in January and the Agency had asked that the draft should now go to public consultation. Arrangements were in hand.

10.2 The Chairman reminded Members that, since the report had focused on helping the FSA to develop its campylobacter reduction strategy, the longer-term research opportunities and gaps had not been addressed in the report. However, the Campylobacter Working Group had held a further meeting to identify where further information would have been helpful in identifying ways of controlling campylobacter. He explained that the output of that meeting had been incorporated into a Memorandum on Research (ACM/680) which, it was intended, should supplement the full report when it went to public consultation. The Chairman drew particular attention to the caveat contained in the final paragraph of the Memorandum, that implementation of the practical measures contained in the draft Report should not be delayed until the results of the further research or surveillance identified were available. The Chairman sought Members’ comments on the Memorandum and the action proposed.

10.3 One Member suggested the addition of a paragraph on functional genomics. This apart, Members were content with the draft and for it to go to public consultation along with the draft report itself. The Secretariat was asked to make the necessary changes to the draft Memorandum to accommodate the functional genomics reference.
Action : Secretariat

11. Ad Hoc Group on Infant Botulism
11.1 At the Chairman’s invitation, Dr O’Brien, Chair of the Ad Hoc Group on Infant Botulism, reported that the Group had held its first meeting on 11 February 2004. She reminded Members that the Group’s terms of reference were to consider the potential human health risk associated with the consumption of chilled or frozen, puréed baby foods, particularly in relation to Clostridium botulinum and infant botulism, in order to inform the development of ACMSF advice to the FSA. Dr O’Brien said that, at its first meeting, the Group had considered information from:

  • a manufacturer of a range of baby foods, on the processing and food safety systems in place to produce safe frozen baby food
  • the R&D Department of a company, designed to help assess the risk of infant botulism from non-sterilised baby foods. Material provided covered hazard characterisation and modelling of the distribution and numbers of spores in raw materials and the environment
  • a trade association, on the possible risks from minimally-processed baby foods
  • a retailer, about the steps taken by the company to assure the safety of the baby foods it sells

11.2 Dr O’Brien said that the Group had to date received offers from three further manufacturers of baby foods to provide evidence of their operations. They would provide this over the course of the next two meetings of the Group which had been set for 16 April and 24 May. Invitations to provide evidence had been sent to trade associations in November 2003 but had produced a very poor response. The Secretariat was therefore directly approaching individual companies involved in the manufacture and sales of minimally-processed baby foods to invite evidence. The Group would also be seeking to establish the extent to which minimally-processed baby foods were manufactured and sold elsewhere in Europe and outside the EU.

11.3 In response to Members’ questions, Dr O’Brien confirmed that there had been no cases of infant botulism in the UK linked to minimally-processed baby foods, and that there was no cause for concern on the basis of what the Ad Hoc Group had seen to date, although it was in the very early stages of its work.

11.4 The Chairman thanked Dr O’Brien for her report which was duly noted.

12. Membership and Secretariat changes
12.1 At the Chairman’s invitation, the Administrative Secretary reported on impending changes in ACMSF membership and Secretariat changes. He said that the final day of Professor Georgala’s chairmanship would be 31 March 2004. An appointments panel had interviewed candidates on 4 February and the Chairman of the FSA would be meeting them shortly before reaching his final decision. Dr Hadley, Professor Hunter and Dr Sandifer had been appointed for further terms from 1 April 2004. A formal announcement would be made in due course. Dr Andrews was leaving the food industry and was therefore resigning from the Committee. The vacancy thus created would be advertised in the usual way. The Secretary said that the final day of the terms of appointment of Professor Johnston and Dr Wyatt would be 31 March 2004. An appointments panel had interviewed candidates to fill the veterinary and medical microbiology posts arising from these retirements on 9 and 17 March.

12.2 The Secretary said that once the Chairman of the FSA had decided on the candidates to be appointed to fill the vacant positions, he would consult UK Health Ministers on his proposals, as he was required to do under the Food Standards Act 1999. Appointments would follow once Ministers’ views had been received and considered. Finally, the Secretary reported that Dr Lucy Foster would become Administrative Secretary to the Committee after the Easter holiday.

12.3 The Chairman thanked the departing members for their friendship and their contribution to the work of the Committee and its Working Groups over the years. He greatly valued the quality of their work and their commitment. The Chairman also thanked the Secretary for his excellent contribution to the work of the Committee. This was echoed by Mr Kyriakides on behalf of the Members. Professor Johnston expressed the Committee’s thanks and good wishes to the Chairman for the way he had led and represented ACMSF over many years. Expressions of good wishes had been received from Ms Davies, Dr Hadley, Ms Lewis and Dr Wyatt and had been circulated at the meeting.

13. Dates of future meetings (ACM/681)
13.1 The Chairman drew Members’ attention to ACM/681 which gave details of the meetings for the remainder of 2004. He drew particular attention to the final meeting, the date of which had been moved from 2 to 1 December.

14. Any other business
14.1 Mr Gayford reported that Defra would that day be announcing an outbreak of brucellosis in a beef herd in Cornwall. This was the first outbreak in England for a considerable number of years. The disease could be spread via food, but was more likely to be transmitted through direct contact with infected cattle. In practice, the risk to humans through food chain exposure pathways was likely to be very low.

15. Public questions and answers
15.1 The Chairman invited members of the public present to ask any questions they might have on the work of the Committee, or to make any statements.

15.2 Dr Bob Mitchell (HPA) said that some caterers were still failing to observe good hygiene practice, and noted that education could have an important influence on behaviour. However, he wondered about the role of enforcement and how important the Committee considered that to be.

15.3 Mr Mepham said that effective enforcement was essential but was only one of a mix of necessary tools. In addition to enforcement and education, the mix should include, eg. good measures of the effectiveness of any steps taken, and robust investigation of any failures. Enforcement was important in ensuring that hygiene standards were not allowed to slip, although it was not easy to quantify its effect on levels of food poisoning.

15.4 Dr Norman Simmons expressed reservations about the way the FSA had treated the Salmonella dublin results in its survey of UK eggs at retail. He did not regard it as reasonable to exclude these results simply because it was not normally seen in chickens. He was concerned that FSA research and surveillance outputs were not subject to in-depth peer review. He also pointed to the confusion about advice on keeping eggs in the fridge once they reached the domestic environment. He cited three celebrity chefs who were recently asked the reason for this advice and none of whom had been clear about it. Finally, Dr Simmons suggested that, if the ACMSF and the FSA were persuaded by the circumstantial evidence that eggs from vaccinated flocks were safer than eggs from unvaccinated flocks, they should be advising vulnerable groups only to eat eggs from vaccinated flocks.

15.5 In response, Dr Hilton said that the ACMSF was free to take a view on whether it was appropriate to change existing guidance, and to advise the FSA accordingly. However, it was clear that salmonella did appear from time to time in vaccinated flocks, and the success in tackling salmonella was thought to be not solely due to vaccination, important though it was, but to a suite of measures.

15.6 The Chairman said that the ACMSF had reached a similar conclusion, namely that the reduction in salmonella in chickens and in humans reflected a wide range of measures put in place by the poultry industry, of which vaccination was probably the most important. However, the Committee’s advice in relation to vulnerable groups was centred on cooking advice rather than seeking to differentiate between eggs from vaccinated and unvaccinated flocks.

15.7 Mr Kyriakides regretted that the egg industry had felt unable to cooperate in a survey centred on packing stations, as this might have enabled the most effective interventions to be identified. In terms of changing advice, he suggested that it would also be important to have data available from a survey of non-UK eggs.

15.8 Responding to the former point, Mr Mark Williams (BEIC) said that, while the egg industry would have welcomed a survey centred on packing stations, there had been concerns over animal rights activists and possible action against the caged sector, because the FSA was unable to provide assurances that names and addresses would not be made public. Dr Hilton said that the Agency would have had to reveal company names but had agreed to withhold information about addresses.

15.9 Dr Thomas Quigley (Food Safety Promotion Board of Ireland) said that there was a ban in the Republic of Ireland on vaccinating layers against salmonella, and a prohibition on the importation of eggs from vaccinated flocks. However, research was being undertaken on the effectiveness of vaccination and researchers in the Republic were keen to share the results of this work with the FSA, HPA and LACORS. Current data gave no grounds for believing that salmonella contamination was more of a problem in the Republic in eggs from unvaccinated flocks.

15.10 Dr Barbara Lund (IFR) asked, in connection with the proposed survey of non-UK eggs, whether it would be possible to determine whether or not eggs sampled were from vaccinated flocks. She also asked to what extent the occurrence of salmonella in vaccinated flocks was feed-associated, and whether there was any information available about the extent to which flocks were vaccinated against salmonella.

15.11 Dr Cook said that the FSA had called for expressions of interest in relation to the non-UK egg survey. The aim of the survey would be to gather as much information as possible but it was not yet clear whether it would be possible to distinguish between eggs from vaccinated and unvaccinated flocks. Dr Cook said that he did not have up-to-date information about vaccine usage, although some information was contained in the ACMSF's Second Report on Salmonella in Eggs.

15.12 In response to Dr Lund’s request for clarification of two points in connection with ACM/679, it was confirmed that the reference to the incidence of foodborne outbreaks having declined sharply in the period 1992-2002 related to outbreaks of salmonella in England and Wales; and that the data in the sentence 'In this period, a mean of 177 cases per annum……for the 65 years and over group' in paragraph 30 were rates per 100,000 population.