Category Archives: Listeria

Research – Evaluation of sodium hypochlorite and peroxyacetic acid to prevent transfer of surface‐attached Listeria monocytogenes to produce

Wiley Online


Sporadic contamination of produce with Listeria monocytogenes (Lm) is a recurrent problem. Ways for contamination to occur include transfer of the pathogen to produce from processing surfaces or soil particles to which it has become attached. Since it is known that surface‐attached Lm is less susceptible to antimicrobials than Lm grown in liquid culture, the goal of the current study was to determine if Lm grown on surfaces and released into water retained its higher tolerance of antimicrobials. In addition, transfer of Lm from surfaces or soil particles to blueberries, mung beans and spinach leaves in the presence of the antimicrobials, sodium hypochlorite (NaOCl) adjusted to pH 6.8 and peroxyacetic acid (PAA), was studied. The experiments were carried out with a cocktail of six Lm strains and strains obtained from produce processing plants. Results indicated that Lm released from surfaces was as susceptible to the two antimicrobials as Lm grown in liquid culture and was inactivated within seconds by an initial concentration of 100 ppm of NaOCl or PAA. Transfer of Lm grown on stainless steel coupons to blueberries in wash water was not observed at NaOCl concentrations as low as 20 ppm. In contrast, transfer of Lm from washed soil particles (COD = 1.7 ± 0.89 mg/l) in contact with mung beans was observed even at initial NaOCl or PAA concentrations of 250 ppm. Lm released from washed soil particles to which it was attached to spinach leaves could be detected in the presences of 20 ppm of NaOCl and PAA and occasionally even in the presence of 100 and 250 ppm of the antimicrobials.

USA – Publix Steam in Bag Products Recalled For Possible Listeria

Food Poisoning Bulletin

Publix Steam in Bag products are being recalled for possible Listeria monocytogenes contamination because they contain a specific butternut squash ingredient that has been recalled for the same reason. Pero Family Farms, the supplier of the butternut squash, has issued the recall. No illnesses have been reported to date in connection with this issue.

The recalled items include Publix Steam in Bag Green Beans Butternut Squash, with GTIN number 002-24887-00000. This item was sold from 01/03/2021 to 01/14/2021. Also recalled is Publix Steam in Bag Season Butternut Medley, with GTIN number 002-25399-00000 printed on the label. This item was sold between 01/03/2021 and 01/14/2021. Finally, Publix Steam in Bag Butternut Brussel Pecan is recalled. That item has the GTIN number 002-25677-00000 on the package. It was sold between 01/03/2021 to 01/14/2021. You can see pictures of product packages at the Publix web site.

If you purchased any of these items, do not eat them, even if you are going to cook them first.

USA – Pero Family Farms Butternut Squash Trays Recalled For Possible Listeria

Food Poisoning Bulletin

Pero Family Farms Butternut Squash Trays are being recalled for possible Listeria monocytogenes contamination, according to a notice posted on the Publix web site. No illnesses have been reported to date in connection with this problem.

The recall was triggered when Race West Company, a supplier of butternut squash to Pero Family Farms, notified them about the possible contamination. Production of these items has been halted as an investigation has bene launched.

The recalled items include Pero Family Farms Butternut Squash Cubed Tray. The GTIN number on the package is 8 74896 00977 1. The lot number/expiration dates are 01/15/2021 to 01/20/2021. Also recalled is Pero Family Farms Butternut Squash Veggie Spirals Tray. The GTIN number on that product label is 8 74896 00975 7. And the lot number/expiration dates for that variety range from 01/15/2021 to 01/20/2021. You can see pictures of product packages at the Publix web site.

RASFF Alerts – Listeria monocytogenes – Blanched maize Kernels – Swett Chilli Chicken Wraps – Chilled Cheese

European Food Alerts


Listeria monocytogenes (present /25g) in frozen blanched sweet maize kernels from Hungary in Switzerland


Listeria monocytogenes (in 2 out of 5 samples /25g) in chilled sweet chilli chicken wraps from the Netherlands in the Netherlands


Listeria monocytogenes (<10 CFU/g) in chilled cheese from the Netherlands in France

Ireland – Recall of Tesco Finest Taleggio PDO Italian Cheese Due to the Presence of Listeria monocytogenes


Category 1: For Action
Alert Notification: 2021.05
Product: Tesco Finest Taleggio PDO Italian Cheese; pack size: 200 g
Batch Code: Use-by date: 25.01.2021
Country Of Origin: Italy


Tesco Ireland is recalling Tesco Finest Taleggio PDO Italian Cheese with the use by date of 25th January 2021, due to the detection of Listeria monocytogenes. Point-of-sale recall notices will be displayed in all Tesco stores.

Nature Of Danger:

Symptoms of Listeria monocytogenes infection can include vomiting, nausea, persistent fever, muscle aches, severe headache and neck stiffness.  In rare cases, the infection can be more severe, causing serious complications. Some people are more vulnerable to Listeria monocytogenes infections, including pregnant women, babies, and people with weakened immune systems, including the elderly.  The incubation period (time between initial infection and first symptoms appearing) is on average 3 weeks but can range between 3 and 70 days.

Action Required:


Consumers are advised not to eat the implicated batch.


UK – Tesco recalls Tesco Finest Taleggio because of contamination with Listeria monocytogenes


Tesco is recalling Tesco Finest Taleggio 200g because it contains Listeria monocytogenes.

Product details

Tesco Finest Taleggio
Pack size 200g
Batch code all
Use by 25 January 2021

Risk statement

The presence of Listeria monocytogenes in the product listed above.

Symptoms caused by this organism can be similar to flu and include high temperature, muscle ache or pain, chills, feeling or being sick and diarrhoea.

Some people are more vulnerable to listeria infections, including those over 65 years of age, pregnant women and their unborn babies, babies less than one month old and people with weakened immune systems.

Action taken by the company

Tesco is recalling the above product. Product recall notices will be issued to explain to customers why the product is being recalled and tell them what to do if they have bought the product. Please see attached notice.

Our advice to consumers

If you have bought the above product do not eat it. Instead, return it to the store from where it was bought for a full refund.

About product recalls and withdrawals

If there is a problem with a food product that means it should not be sold, then it might be ‘withdrawn’ (taken off the shelves) or ‘recalled’ (when customers are asked to return the product). The FSA issues Product Withdrawal Information Notices and Product Recall Information Notices to let consumers and local authorities know about problems associated with food. In some cases, a ‘Food Alert for Action’ is issued. This provides local authorities with details of specific action to be taken on behalf of consumers.

Ref: FSA-PRIN-02-2021

Research – Possibility, duration, and molecular predictors of sanitizer tolerance in Listeria monocytogenes

Centre For Produce Safety


Due to concerns over bacterial tolerance to sanitizers, FDA and FSIS recommend rotating sanitizers in RTE food processing facilities to better control foodborne pathogens, in particular, Listeria monocytogenes (Lm). These recommendations are nonbinding; whether Lm develops tolerance to common sanitizers remains
inconclusive and debated. Even if Lm develops tolerance through sub-lethal exposure to sanitizers, how long and how strong the tolerance can last should be considered in determining whether sanitizer rotation is needed and how often it should be applied. Lack of consensus and quantitative data on possibility and duration of sanitizer tolerance creates confusions and dilemmas, especially when sanitizer rotation presents considerable challenges in training, compliance, and cost control to the industry. This proposal describes studies to help settle the debate and fill critical knowledge gaps regarding Lm tolerance to chlorine and quaternary ammonium compounds. We will measure residual sanitizer levels in produce processing facilities. We will perform laboratory assays to investigate tolerance development and persistence. We will explore machine-learning-aided tolerance prediction and identify evolutionary signals (or lack thereof) of tolerance development from whole genome sequencing data. Our results will provide the industry and regulators with scientific evidence for substantiating, better implementing, or justifiably shelving sanitizer rotational programs.

Technical Abstract

There is still no scientific consensus on whether Listeria monocytogenes (Lm) develops sanitizer tolerance. We hypothesize that development of two types of sanitizer tolerance may occur in Lm. First, short-term adaptation to sub-lethal levels of sanitizers induces acquired tolerance, which is transient and not hereditary. Second, long- term selection by sanitizers causes intrinsic tolerance, which is established in Lm populations by evolutionary changes to Lm genomes. To help settle the debate, we will test our hypothesis by distinguishing and investigating both types of tolerance in Lm using chlorine and a quaternary ammonium compound as example sanitizers.

In this study, we will survey residual sanitizer levels in a leafy green and a tomato processing facilities to evaluate if laboratory-derived sanitizer levels optimal for tolerance development are relevant to produce processors. We will assess the possibility of acquired tolerance by measuring the difference in minimum inhibition concentrations (MIC) before and after sanitizer adaptation. We will study how different sanitizer levels and exposure time affect the development of acquired tolerance, including how long the tolerance can last after exposure to sanitizers. We will explore the mechanisms behind the development of acquired sanitizer tolerance by characterizing temporal shifts in Lm transcriptome throughout the duration of the tolerance.

We will assess intrinsic tolerance in a collection of 200-300 strategically selected Lm strains using high-throughput growth kinetics assays. We will search for evolutionary evidence that suggests the development of intrinsic tolerance in recent history by analyzing whole genome sequencing (WGS) data of these strains. We
will build a machine-learning classifier to predict tolerance levels and identify key tolerance predictors from WGS.

This research will provide valuable prerequisite information for determining if sanitizer rotation is necessary for preventing the development of Lm tolerance to sanitizers. Scientific data from the project will also help optimize sanitation practices to mitigate tolerance development and determine frequency for sanitizer rotation if rotation is needed.

Research – Growth and Survival of Attached Listeria on Lettuce and Stainless Steel Varies by Strain and Surface Type


The foodborne pathogen Listeria monocytogenes lives as a saprophyte in nature and can adhere to and grows on surfaces as diverse as leaves, sediment, and stainless steel. To discern the mechanisms used by L. monocytogenes for attachment and growth on various surfaces, we studied interactions between the pathogen on lettuce and stainless steel. A panel of 24 strains (23 of Listeria monocytogenes and 1 L. innocua ) was screened for attachment and growth on lettuce at 4 o C and 25 o C and on stainless steel at 10 o C and 37 o C. Overnight growth of attached cells resulted in a 0 – 3 log increase on lettuce, depending on the strain and the temperature. Among the worst performing strains on lettuce were two from a large cantaloupe outbreak, indicating that factors important for interactions with cantaloupe may be different from those required on lettuce tissue. Strains that grew the best on lettuce belonged to serotypes 1/2a, 1/2b, and 4b and were from cheese, potatoes, and water/sediment near produce fields. Confocal microscopy of L. monocytogenes tagged with constitutively expressed green fluorescent protein indicated associations with the cut edges and veins of lettuce leaves. On stainless steel coupons, there was a 5 – 7 log increase at 10 o C after 7 d and a 4 – 7 log increase at 37 o C after 40 h. Statistically, surface growth on stainless steel was better for serotype 1/2a than for serotype 4b strains, even though certain serotype 4b strains grew well on the coupons. The latter included strains that originated from produce and water/sediment. Some strains were fit in both environments, while others showed variability between the two different surfaces. Further analysis of these strains should reveal molecular factors needed for adherence and surface growth of L. monocytogenes on different biotic and abiotic surfaces.

Australia – Bellarine Smokehouse — Smoked Barramundi Pâté 150g and Smoked Salmon Pâté 150g – Listeria monocytogenes

Product Safety Australia

Photograph of Ballarine Smokehouse Pate

What are the defects?

The recall is due to microbial (Listeria monocytogenes) contamination.

What are the hazards?

Listeria may cause illness in pregnant women and their unborn babies, the elderly and people with low immune systems.

What should consumers do?

Any consumers concerned about their health should seek medical advice and should return the products to the place of purchase for a full refund.

For more information, consumers can contact Bellarine Smokehouse on 0434 229 680.

Traders who sold this product

Independent food retailers including IGAs and direct to consumers from Bellarine Smokehouse

Where the product was sold
Dates available for sale
  • 11 January 2021 – 12 January 2021

Recall advertisements and supporting documentation

Coordinating agency

Food Standards Australia New Zealand is the coordinating agency for this recall.

Norway – The Norwegian Food Safety Authority with an inspection campaign on Listeria measures in salmon slaughterhouses


In 2021, the Norwegian Food Safety Authority will carry out an inspection campaign in all salmon slaughterhouses where we will investigate measures and routines to prevent the fish from becoming contaminated with the listeria bacterium.

Listeria monocytogenes can cause listeriosis. Most of us do not get sick from the bacterium, but pregnant women, children, the elderly and people with weakened immune systems are vulnerable. Listeria multiplies at cooling temperature, survives freezing, salting and smoking, but is killed by adequate heat treatment.

– Since salmon and aura are largely eaten without heat treatment and used for ready-to-eat products such as sushi, sashimi, smoked and digged fish, it is important that producers have effective measures against Listeria, says Elisabeth Wilmann, director of fish and seafood at the Norwegian Food Safety Authority.

Several listeriosis outbreaks in EU countries a few years ago

In 2018 and 2019, there were serious outbreaks of listeriosis in several EU countries related to the consumption of smoked, grated and marinated fish products. The raw materials were Norwegian salmon and aura. The product was traced back to processing plants in Poland and Estonia, but one could not rule out that the raw materials from Norway were contaminated.

– The fact that Norwegian salmon and aura have been linked to serious disease outbreaks is one of the reasons why the Norwegian Food Safety Authority is carrying out the inspection campaign. Another reason is that more and more countries are making demands with regard to Listeria in Norwegian fish, Wilmann says.

The Norwegian Food Safety Authority’s experience is that Norwegian salmon slaughterhouses generally have good knowledge of microbiological hazards in fish, and that targeted work has been done on measures against Listeria.

– At the same time, we know that Listeria is regularly detected in the production environment in Norwegian slaughterhouses, says Wilmann.

The Norwegian Food Safety Authority will guide, clarify responsibilities and get an overview

In the campaign, the Norwegian Food Safety Authority will examine the slaughterhouse’s measures, sampling and routines for non-conformance treatment.

– We emphasize guidance. In addition, we will clarify the regulations and the responsibility of the slaughterhouse to prevent unsafe products from entering the market, says Wilmann.

The aim is to control all salmon slaughterhouses and vessels that slaughter salmonids. The campaign period is 15 January to 1 September, and the final report will be published towards the end of 2021. It may be relevant to carry out some of the inspections digitally due to coronary restrictions.

In 2020-2021, the Norwegian Food Safety Authority will also implement a monitoring and mapping program to map the status of Listeria.

– By obtaining a better overview of the status of Listeria in salmonids, we will be in a better position to contribute to the clarification of any future disease outbreaks, Wilmann concludes.

Read more on the website for the supervision campaign