This review was carried out early in the project looking at the microbiological hazards in the vegetable industry.
This review identifies the human microbial pathogens that have been associated with fresh vegetables and which are known to pose a risk or are suspected of doing so.
Three classes of organisms were examined :
A number of different organisms have been isolated from vegetables in random overseas surveys including Listeria monocytogenes. Salmonella spp., Yersinia enterocolitica, Aeromonas spp., Staphylococcus aureus, Cryptosporidium spp. and 61 enteroviruses.
Bacterial contamination was identified as originating from 3 major routes, the soil, manure (faecal material) and contaminated water and handling by an infected individual.
Organisms which can be found in soil and which have caused disease outbreaks in vegetables include Bacillus cereus, Clostridium botulinum and Listeria monocytogenes.
Contaminants that can be spread from faecal matter and contaminated water and which have been associated with vegetable borne disease outbreaks include Salmonella spp., E. coli, enterotoxigenic Escherichia coli and Campylobacter spp.
Yersinia enterocolitica and Aeromonas spp. have been isolated from vegetables but have not been associated with vegetable borne disease outbreaks.
Disease outbreaks caused through direct contamination via an infected food handler have been linked to Shigella spp. and Staphylococcus aureus.
Parasites of concern include : Cryptosporidium, Giardia and Cyclospora.
Cryptosporidium is ubiquitous in the environment and has been responsible for many large waterborne disease outbreaks.
It is possible that it may find it's way onto vegetables via irrigation water or run-off from surface waters.
Giardia has also been the cause of many waterborne outbreaks and has been linked to foodborne outbreaks.
Cyclospora is a newly recognised parasite that may contaminate fresh vegetables and was recently responsible for a large outbreak in the U.S. associated with fresh raspberries as well as some smaller outbreaks involving basil and mesclum mix.
Viral disease is as common in Australia as bacterial disease outbreaks.
Those of concern include hepatitis A, enteroviruses, Norwalk-like viruses and small round shaped viruses.
Detailed data for foodborne disease outbreaks linked to fresh vegetables are severely lacking in Australia.
However, this review has shown that there is enough evidence to suggest that they could be a significant vehicle for disease outbreaks.
Consequently, the vegetable industry needs to adopt good production practices at ail stages of the production and handling chain.
Preharvest practices include :
- the use of properly treated manures
- clean water for irrigation
- provision of suitable facilities for workers, such as toilets and hand washes
Postharvest it encompasses :
- the use of clean equipment (processing and transport)
- adequately sanitised water
- adoption of good personal hygiene practices.
Good food handling practices need to be adopted where appropriate. These include :
- proper protective clothing
- basic knowledge of food safety practices
The Australian vegetable industry needs to be proactive in developing its own food safety guidelines. These are urgently needed to minimise the risk of foodborne disease from vegetables.
We would like to thank John Faragher, Bruce Tomkins and Scott Ledger for their contribution as members of the project management team for the Safe Vegetable Production publication.
As well as the industry team members and those who reviewed the guide, these people are listed in the guide.
In addition, John Faragher for his advice and contribution towards developing the strawberry industry food safety guide.
Peter Franz for his help with the statistical analysis, Janet Tregenza for her technical assistance with the farmgate survey,
Susan Pascoe for her assistance in collection and analysis of the soil samples and the Microbiological Diagnostics Unit for help received in setting up the methodology for the irrigation water analyses.
This project was commissioned by Horticulture Australia Limited with funds frrom the Vegetable R&D levy and the Victorian State Government..
The Australian Government provides matched funding for all HAL's R&D activities.