Reducing Listeria contamination from salad vegetable farms Robert Premier Global FS Pty Ltd Project Number: VG07079 VG07079 This report is published by Horticulture Australia Ltd to pass on information concerning horticultural research and development undertaken for the vegetables industry. The research contained in this report was funded by Horticulture Australia Ltd with the financial support of the vegetables industry. All expressions of opinion are not to be regarded as expressing the opinion of Horticulture Australia Ltd or any authority of the Australian Government. The Company and the Australian Government accept no responsibility for any of the opinions or the accuracy of the information contained in this report and readers should rely upon their own enquiries in making decisions concerning their own interests. ISBN 0 7341 2463 5 Published and distributed by: Horticulture Australia Ltd Level 7 179 Elizabeth Street Sydney NSW 2000 Telephone: (02) 8295 2300 Fax: (02) 8295 2399 © Copyright 2010 Reducing Listeria monocytogenes contamination from salad vegetable farms VG07079 Final report for HAL project (July 2010) Robert Premier Global F.S. Pty Ltd Reducing Listeria monocytogenes contamination from salad vegetable farms Final report for HAL project VG07079 By: Robert Premier Project Leader Dr Robert Premier Global F.S. pty ltd Ph: 0418317786 Email: [email protected] Scope of the Report This report presents the key findings and a summary of the work conducted in Victoria and Queensland from September 2008 to June 2010 by the Project team. Funded By: Horticulture Australia Limited and the Australian vegetable industry levy. This publication may be of assistance to you but Global F.S. Pty ltd and its officers do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication. Any recommendations contained in this publication do not necessarily represent current HAL policy. No person should act on the basis of the contents of this publication, whether as to matters of fact or opinion or other content, without first obtaining specific, independent professional advice in respect of the matters set out in this publication. Reducing Listeria monocytogenes contamination from salad vegetable farms Contents 1. Media Summary .................................................................................................................................. 3 2. Technical Summary ............................................................................................................................ 4 3. Key Outcomes and Conclusions ......................................................................................................... 4 4. Introduction ......................................................................................................................................... 5 5. Evaluation of rapid tests for the detection of L. monocytogenes in fresh produce............................. 7 5.1 Introduction: ............................................................................................................................ 7 5.2 Material and methods: ............................................................................................................. 9 5.3 Results: .................................................................................................................................. 10 6. Testing for L. monocytogenes on farms ............................................................................................ 11 6.1 Method: ................................................................................................................................. 11 7. First year testing results (2008-2009) ............................................................................................... 12 7.1 Summer testing: .................................................................................................................... 12 7.2 Discussion of results: ............................................................................................................ 18 7.3 Winter testing: ....................................................................................................................... 18 7.4 Discussion of results: ............................................................................................................ 22 8. Second year testing results (2009-2010) ........................................................................................... 23 8.1 Summer testing: .................................................................................................................... 23 8.2 Discussion of results: ............................................................................................................ 28 8.3 Winter testing: ....................................................................................................................... 29 8.5 Testing of bales of hay (season one and season two): .......................................................... 34 9. General Discussion: .......................................................................................................................... 34 9.1 Rapid testing for L. monocytogenes: ..................................................................................... 34 9.2 L. monocytogenes in vegetable farms ................................................................................... 36 10. Development of best practices for the management of Listeria monocytogenes on farms: ............ 46 12. Project Evaluation ........................................................................................................................... 48 1 13. Conclusions ..................................................................................................................................... 48 14. Key Issues ....................................................................................................................................... 49 15. Recommendations for Future Work ................................................................................................ 49 16. References ....................................................................................................................................... 50 Appendix 1: Results obtained with the three L. monocytogenes tests used .................................. 53 Appendix 2: Results of water testing for L. monocytogenes ......................................................... 56 Appendix 3: Survival of Listeria on the surface of leafy vegetables ............................................ 59 Acknowledgements: The project team would like to acknowledge the support and input from all those that have contributed to the project including the participating growers that wish to remain anonymous. In addition the team would like to acknowledge Dean Harapas, Dr Said Ajlouni from the School of Land and Environment, University of Melbourne, Sandy Clarke from the University of Melbourne statistical consulting centre and Dr Marie-Astrid Ottenhof for reviewing the manuscript. 2 1. Media Summary Listeria monocytogenes (L.monocytogenes) is a bacterium that has been widely detected in the environment and plants, including leafy vegetables. It has the potential to become a human pathogen, affecting young people, older people and pregnant women. Every year in Australia a number of people die as a result of L. monocytogenes infections. Supermarkets displaying due diligence have set very tight specifications that vegetable growers must comply with. This, in turn, has led to growers having to pre-test their products for the presence or absence of L. monocytogenes as a condition of supply to supermarkets. The problem, however, is that with L. monocytogenes testing, there are a number of tests available and often the grower is confused as to which test should be used. More importantly the major problem is that growers have no idea how to reduce the incidence of L. monocytogenes in the field and they have no idea how this bacterium enters farming land to contaminate their crops. What is needed is an information package on this issue for the grower. This project had three aims. The first aim was to understand how L. monocytogenes enters a vegetable farm from the environment. The second aim was to understand if a rapid detection method can be of assistance to the grower and to make recommendations on what method the grower should be asking for when getting produce tested by laboratories. The third aim of this project was to produce an information sheet on testing and on ways to reduce L. monocytogenes issues on farm. In order to understand how L. monocytogenes enters the farm, a number of samples were taken from three vegetable growing sites in Victoria and two vegetable growing sites in Queensland. Samples of produce, soil, water and manures found on farms were taken and tested for the presence or absence of L. monocytogenes, in most cases when positives were detected the numbers of L. monocytogenes were quantified. The results of this project suggest a possible pathway for how L. monocytogenes contamination occurs in vegetable farms. L. monocytogenes was found to be present in high numbers in silage and fermented baled hay, which are both, in turn fed to and ingested by ruminants; this passes through