Von Holy Consulting hosted the second of their one day Listeria Workshops to highlight this organism and inform delegates about how it can be controlled and managed in South African food businesses. Nicola Brook reports back after the event, which was held in Johannesburg.
Listeria species are bacteria commonly found in many environments including soil, animals, humans, agricultural irrigation sources, equipment, packing sheds and refrigerators. There are six distinct species and some are harmless and others can, but rarely cause illness. Listeria monocytogenes causes Listeriosis and is the most dangerous member of the genus.
Listeriosis can be serious especially to those with compromised immune systems. In pregnant women, the disease can be transferred to the foetus or newborn before or during delivery and can be fatal. SA has a high percentage of the population susceptible to food borne diseases, however we have little reliable data or statistics the incidencse. Cases of food boren illnesses, it is reported, have doubled in some developed countries in recent years.
We live in the age of having global food supplies, and so, global pathogens and it would be unlikely if SA was not affected. Recent withdrawals due to Listeria have involved raw coleslaw salads, cold smoked trout, butter, ready prepared sandwiches, hot dogs, sliced deli meats, soft cheeses (e.g. camembert and queso fresco.) A recent outbreak earlier this year in Austria and Germany proved that the spread of this pathogen via food can be difficult to trace and so in turn prevent. New guidlines regarding Listeria have been developed by Codex Alimantarius (the international food law body).
Emiritus Professor Chris Griffith from the University of Wales Institute Cardiff and editor of the British Food Journal was the guest presenter at thie workshop. Also a member of the International Life Sciences Institute working group on ‘Achieving Continuous Improvement in Reductions in Foodborne Listeriosis- A Risk Based Approach’, Griffith added a wealth of knowledge and practical experience describing strategies for preventing contamination of food coupled with preventing its growth in food if it is present. He highlighted the increased attention given to environmental monitoring of cleanliness as a proactive approach with specific information on environmental monitoring for Listeria. The presence of other species of Listeria in the environment can indicate the potential for Listeria monocytogenes.
A company needs to prevent or minimise entry of the organism into a food business by designing the receiving area and limiting the inflow of dirty crates or pallets.The raw material suppliers need to work on good agricultural practices as the organism is widespread in fields and pastures where animals live and feed. Plant design and construction can also be critical, especially drains, floors, footbaths conveyors and refrigeration units. These are places which can become Listeria reservoirs. Cleaning needs to be managed and part of this involves surface testing.
Griffith advocated an integrated approach using visual, ATP and microbiological testing. Records need to be monitored for trends - are organisms detected at certain times, after certain procedures, or at particular sites? This microbiological detective work can clarify the problem, whether the organism is transient or resident, and leads to short and longer term solutions.
Griffith advised that when searching for pathogens, the use of sponges is generally more sensitive than more conventional swab tests and he advised the use of Petrifilms, dip slides or contact plates for more routine surface colony counts. Equipment such as slicers need to be dismantled and given adequate contact time with the appropriate cleaning/disinfecting chemicals. He stressed that ‘no pathogen exploits the food processing environment better than Listeria’. This organism thrives in cool, wet conditions; is common in biofilms and can grow in a wide range of temperatures and acidities; and tolerates salt.
The environmental monitoring needs to be sytematic and then documented and if Listeria is found then it is time for a ‘seek and destroy’ strategy. The latter can be difficult and costly as Griffith explained, ‘Listeria has been shown to be resident many years even after routine cleaning and disinfection, for example seven years in an ice-cream plant in Finland and up to 12 years in a poultry plant’ says Griffith. Genotyping of the isolates showed the persistence of the strains over time, and that environmental contamination led to food contamination.
Listeria is widespread and could even be found in domestic refrigerators! Controlling it effectively is a major challenge for the food industry. Whilst much information is available from overseas, local data is the best data. We need to be proactive before a major outbreak occurs and causes a crisis in one or more sectors of the food industry.
Is Listeria monocytogenes (Lm) a concern to your factory or product?
If you answer YES to any of these questions then you need to evaluate your facility for presence and survival of this organism. Prevention and knowledge is the best solution.
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