Risk Profiling Listeria in Ready-to-Eat Foods

Project start date: 1 December 2014
Project status: Completed
Project type: Food safety
Discipline: Microbiology and food hygiene
Author/s: Dr Nicolae Corcionivoschi & Dr Robert Madden (retired in April 2016), Agri-Food & Biosciences Institute
Collaborator/s: Dr Kieran Jordan, Teagasc

Research objective

This project aimed to conduct a comprehensive risk profiling of Listeria monocytogenes in ready-to-eat (RTE) foods and determine effective control strategies and practical interventions for food processors in Northern Ireland. Building on an equivalent project from the Republic of Ireland under the Food Institutional Research Measure (FIRM) translational research programme, the study benefited from the experiences of Irish researchers. The objectives were to monitor the occurrence and persistence of Listeria in food and processing environments, understand the routes of contamination, evaluate the effectiveness of control measures, and identify potential risk factors to improve food safety practices across Northern Ireland's food processing industry.

Outputs

Research report

Title: Risk profiling Listeria in ready-to-eat foods
Publication date: 12 July 2018
Summary: This study focused on risk profiling Listeria monocytogenes in ready-to-eat (RTE) foods and determining control strategies for food processors in Northern Ireland. The research complemented a similar study in the Republic of Ireland, with collaboration ensuring the sharing of expertise and methodologies.
Findings:
1. Sampling and analysis:
- The study conducted approximately 2,250 analyses and examinations.
- Participants swabbed six specific sites in their premises and sent these, along with two samples of final food products, for Listeria analysis.
- Isolates of Listeria monocytogenes underwent pulsed-field gel electrophoresis and whole genome sequencing for detailed analysis.
2. Incidence and contamination:
- Listeria monocytogenes was found in 4.6% of food samples and 6.3% of environmental swab samples.
- Half of the food businesses submitted samples with no detected Listeria.
- Two meat products exceeded the legal limit of 100 colony-forming units per gram.
- Contamination was predominantly found in premises handling processed mushrooms, cooked meats, or sandwiches.
3. Environmental findings:
- Floors, drains, trolley wheels, boots, and chill surfaces were primary contamination sites, yielding 81% of the isolates.
- Higher contamination rates were observed during warmer months, although no specific cause was identified.
4. Growth and resistance:
- Analysis showed 111 out of 130 food samples could support Listeria growth at refrigeration temperature, with significant growth at abuse temperatures.
- All isolates carried genes associated with pathogenicity (inlA and actA), and 71% carried the qacH gene, indicating resistance to common sanitisers.
5. Cross-Contamination and Persistence:
- Multilocus sequence typing revealed recurrence of specific bacterial strains over extended periods and evidence of cross-contamination within facilities.
- Northern Ireland isolates shared similarities with those from the Republic of Ireland, including clinical cases.
6. Control measures:
- A questionnaire assessing control strategies was returned by 54% of participants, but the data was insufficient for concrete recommendations.
- On-site audits were suggested to identify effective control practices and address the persistence of Listeria.
Recommendations:
1. Enhanced control efforts:
- Strengthen control strategies, particularly in facilities producing high-risk products like cooked meats and sandwiches.
- Implement regular environmental monitoring and rigorous sanitation practices.
2. Training and awareness:
- Increase training for food business operators on effective control measures and the importance of maintaining the cold chain.
- Provide guidance on preventing cross-contamination and managing sanitisers' resistance.
3. Further research:
- Conduct detailed on-site audits to identify effective interventions.
- Continue collaboration with Republic of Ireland researchers to leverage shared insights and improve food safety across both regions.
You can download the report below.

Risk profiling Listeria in ready-to-eat foods

Other outputs

Peer reviewed articles

Robert H. Madden, Mike Hutchison, Kieran Jordan, Vincenzo Pennone, Ozan Gundogdu, Nicolae Corcionivoschi. Prevalence and persistence of Listeria monocytogenes in premises and products of small food business operators in Northern Ireland, Food Control, Volume 87, 2018, Pages 70-78, ISSN 0956-7135,
https://doi.org/10.1016/j.foodcont.2017.12.020.