Listeria Guidance

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Listeria Guidance Part 1

• Sally Hasell

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Purpose of Guide 1

• Gives an overview of the issues why controls
  are needed and why this need is becoming greater
  than ever
• Identifies how Listeria gets into food via the
  environment, contaminated surfaces, ingredients
  and equipment
• Explains why there must be a focus on RTE foods
  that support the growth of Listeria
• Discusses microbiological limits and how they are
  applied
• Describes how to setup, document and implement a
  Listeria Management Programme

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What makes Listeria special?

• Grows at low temperatures i.e. during
  refrigerated storage of food and in chillers
• Grows in most types of packaging vacuum packing
  does not inhibit it
• Is everywhere in the environment, so can
  potentially be re-introduced into clean areas at
  any time
• Is able to invade the cells of people with poor
  immune systems and cause very severe often fatal
  illness

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Why Listeria needs to be controlled

• Cases are few (20 a year) but high mortality rate
  (25) and includes babies
• If a large quantity of highly contaminated food
  got into the market, many could be hospitalised
  and die
• Vulnerable consumers such as the elderly and
  those with poor immune systems are an increasing
  group
• Food preferences are increasing the volume and
  types of RTE foods that Listeria can survive and
  grow in

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Listeria sp.

• Only Listeria monocytogenes is a significant
  human pathogen
• Other members e.g. L.innocua are rarely harmful
  but share other characteristics with
  L.monocytogenes
• This means finding any type of Listeria in food
  or somewhere it should not be, means that control
  is needed or has failed

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Growth in food as a critical factor

• Small numbers of Listeria are unlikely to be a
  problem for healthy adults but as numbers
  increase, the potential for illness increases
• When number get really high, even healthy adults
  can become ill.
• If Listeria can grow in a food, over time a small
  number can quickly become a large number,
  especially if temperature control not good
• HIGHEST RISK FOOD ARE THOSE THAT SUPPORT THE
  GROWTH OF LISTERIA AND ARE STORED CHILLED FOR
  MORE THAN 3 DAYS

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Control strategies

• Listeria present are destroyed or removed -
  apply a listericidal step, wash, incoming
  ingredient specs
• Limit the potential for growth in the food e.g.
  low pH (lt4.4), water activity lt0.92, combinations
  of pH and water activity and other hurdles,
  freeze, some packaging
• Prevent/protect from recontamination, especially
  after a listericidal step

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Preventing recontamination

• A major problem is when food gets contaminated
  after a listericidal step e.g. cook the ham and
  then slice and package
• Need to make sure that cannot get contaminated
  slicers, conveyor belts, aerosols, condensation
  drips, work flow, people
• Focus cleaning and sanitation on this part of the
  process i.e create a high care hygiene area and
  monitor effectiveness

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How many is too many?

• Healthy consumers can tolerate small numbers of
  Listeria in their food but vulnerable consumers
  may not.
• Thus important that Listeria should not be
  detected in food intended for these consumers
  e.g. infants.
• Foods that are consumed regularly by all
  consumers should also be Listeria free e.g.
  spreads, butter, milk
• Foods like salads need to make sure fresh and
  washed to keep numbers as low as possible

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How many Listeria is too many?

• Food should never have more than 100cfu/g of
  Listeria monocytogenes present.
• When counts are gt100cfu/g it is obvious that
  Listeria controls have failed -
• Incoming ingredients
• Processing control steps failed
• Contamination from equipment, environment

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Listeria limits and Regulators

• Zero limits typically set to support strategies
  to reduce the incidence of listeriosis and for
  foods known to be problematic Std 1.6.1 for
  example
• Now international agreement that the focus is on
  not letting numbers get above 100cfu/g and this
  most often is because of contamination during
  processing and then growth during chilled storage

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Microbiological targets
Product risk group Characteristics of the food and processing L. monocytogenes level targets L. monocytogenes level targets
Product risk group Characteristics of the food and processing At the end of processing At the end of shelf life
High Processed RTE foods in which growth can occur (during storage in final packaging) and the food stored refrigerated for gt 3 days Absent in 25g Absent in 25g
Medium Processed RTE foods in which growth will not occur Absent in 25g Not more than 100cfu/g
Low Products where the occurrence and/or survival is highly unlikely L. monocytogenes not a pathogen of concern Testing not usually required. Not more than 100cfu/g
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Microbiological limits

• Regulatory limits that may apply to a product
• Food Standards Code Std 1.6.1
• Product safety limits for dairy products (DPC1)
• Operator defined limits
• Customers
• Countries to which exporting food

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Listeria Management Programmes

• A record of how a business manages Listeria -
• What controls are in place e.g. specifications,
  cleaning/ sanitation, training, monitoring,
  responding to failures, new products and
  processes reviewed
• How they are done e.g. new staff get trained,
  pasteurisation failures responded to, out of spec
  ingredients rejected, lab results acted on, new
  equipment checked

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Listeria Management Programmes

• Provides an overview of the Listeria control
  system so that everyone (management, auditor,
  regulator, customer) knows what is being done,
  their role and how to see and know when it is
  failing

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Critical aspects of a LMP

• It is written down
• Everyone who needs to be involved is
• It truly reflects what is happening in the
  processing environment
• Observations made are responded to
• It is a living document
• It is focussed on the key factors that could be
  the source of contamination