Biofilms be good protection for bugs

In nature and man-made environments, microorganisms reside in mixed-species biofilms, in which the growth and metabolism of an organism are different from these behaviors in single-species biofilms. Pathogenic microorganisms may be protected against adverse treatments in mixed-species biofilms, leading to health risk for humans. Here, we developed two mixed five-species biofilms that included one or the other of the foodborne pathogens Listeria monocytogenes and Staphylococcus aureus.

The five species, including the pathogen, were isolated from a single food-processing environmental sample, thus mimicking the environmental community. In mature mixed five-species biofilms on stainless steel, the two pathogens remained at a constant level of ∼105 CFU/cm2. The mixed five-species biofilms as well as the pathogens in monospecies biofilms were exposed to biocides to determine any pathogen-protective effect of the mixed biofilm. Both pathogens and their associate microbial communities were reduced by peracetic acid treatments. S. aureus decreased by 4.6 log cycles in monospecies biofilms, but the pathogen was protected in the five-species biofilm and decreased by only 1.1 log cycles. Sessile cells of L. monocytogenes were affected to the same extent when in a monobiofilm or as a member of the mixed-species biofilm, decreasing by 3 log cycles when exposed to 0.0375% peracetic acid. When the pathogen was exchanged in each associated microbial community, S. aureus was eradicated, while there was no significant effect of the biocide on L. monocytogenes or the mixed community. This indicates that particular members or associations in the community offered the protective effect. Further studies are needed to clarify the mechanisms of biocide protection and to identify the species playing the protective role in microbial communities of biofilms.

IMPORTANCE This study demonstrates that foodborne pathogens can be established in mixed-species biofilms and that this can protect them from biocide action. The protection is not due to specific characteristics of the pathogen, here S. aureus and L. monocytogenes, but likely caused by specific members or associations in the mixed-species biofilm. Biocide treatment and resistance are a challenge for many industries, and biocide efficacy should be tested on microorganisms growing in biofilms, preferably mixed systems, mimicking the application environment.

Behavior of foodborne pathogens listeria monocytogenes and staphylococcus aureus in mixed-species biofilms exposed to biocides

Applied and Environmental Microbiology; DOI: 10.1128/AEM.02038-18

Virginie Oxaran, Karen Kiesbye Dittmann, et al

https://aem.asm.org/content/84/24/e02038-18?etoc=

Raw milk convention goerers got sick from raw milk

Katie Burns of JAVMA News writes, what could be more wholesome than chocolate milk from an Amish farm?

In November 2015, the International Raw Milk Symposium in Anaheim, California, brought in unpasteurized chocolate milk from an Amish farm in Pennsylvania. The sale of raw milk is legal in California and Pennsylvania, but the interstate sale of raw milk is illegal. Authorities embargoed the chocolate milk and sent a sample to the Food and Drug Administration—turning up Listeria.

An investigation by the Centers for Disease Control and Prevention and state health departments found that Listeria isolates from the milk seized at the symposium were related to isolates obtained from two people in 2014. One person in California had been hospitalized and the other, a cancer patient in Florida, had died.

The investigation revealed some of the risks of raw milk and some of the complexities of buyers’ clubs, which can be so secretive as to involve drop points and burner phones for temporary use. The AVMA supports laws requiring pasteurization of all milk, but unpasteurized milk has a devoted following despite the safety concerns and varying legality among states.

30+ sick from Listeria linked to Jerusalem Deli meats in Israel

Outbreak News Today reports that Israeli health officials concluded in a report that more than 30 listeriosis cases were reported to the Ministry of Health, some are severe and include invasive infection and fetus mortality, mostly in the southern region among the Bedouin sector settlements.

In food sampling carried out by the Southern District National Food Services according to information emanating in morbidity incidents investigation, Listeria monocytogenes bacterium has been found in “Jerusalem Deli Pastrami” and the “Jerusalem deli smoked salami” products in the 200 and 400 grams packages by Almadain Food Products Ltd. (Madco) Ltd. The manufacturing date of the products is 08/10/2018 and the expiry date is 07/01/2019.

4 sick: Outbreak of listeria infections linked to pork products

The U.S. Centers for Disease Control (CDC) and public health and regulatory officials in several states, and the U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA-FSIS) are investigating a multistate outbreak of Listeria monocytogenes infections linked to pork products produced by 165368 C. Corporation, doing business as Long Phung Food Products.

On November 20, 2018, 165368 C. Corporation, doing business as Long Phung Food Products in Houston, TX recalled ready-to-eat pork products because they might be contaminated with Listeria.

Do not eat, sell, or serve recalled products from Long Phung Food Products.

The full list of recalled ready-to-eat pork patty rolls is on the USDA-FSIS website.

Recalled products are labeled with establishment number “EST. 13561” inside the USDA mark of inspection.

Recalled pork patty rolls were produced on various dates from May 21, 2018, through Nov. 16, 2018. These items were shipped to distributors and retail locations nationwide.

Return any recalled pork products to the store for a refund or throw them away. Even if some of the product was eaten and no one got sick, do not eat it. If you do not know if the pork product you purchased was recalled, ask the place where you purchased it or throw it away.

Wash and sanitize drawers or shelves in refrigerators and freezers where recalled pork products were stored. Follow these five steps to clean your refrigerator.

Retailers should clean and sanitize deli slicers and other areas where recalled pork products were prepared, stored, or served. Follow the manufacturer’s recommendations for sanitizer strength and application to ensure it is effective.

If you develop symptoms of a Listeria infection  after eating recalled pork products, contact a healthcare provider and tell them you ate recalled pork products. This is especially important if you are pregnant, age 65 or older, or have a weakened immune system.

Four people infected with the outbreak strain of Listeria monocytogenes have been reported from four states.

Listeria specimens from ill people were collected from July 1, 2017, to October 24, 2018.

Four people have been hospitalized. No deaths have been reported.

Epidemiologic and laboratory evidence indicates that pork products from 165368 C. Corporation, doing business as Long Phung Food Products are a likely source of the outbreak.

On November 20, 2018, 165368 C. Corporation, doing business as Long Phung Food Products recalled ready-to-eat pork products because they might be contaminated with Listeria.

This investigation is ongoing, and CDC will provide updates when more information is available.

 

2 dead, 10 sick from Listeria in Switzerland

RTS Info reports that since June, 2018, an unexplained outbreak of listeriosis, has been occurring across Switzerland. The Federal Office of Public Health (FOPH) has identified 12 cases, 2 of which were fatal.

“What is unusual is that it is all cases of the same subtype of bacteria. We counted 12 cases, which is not that much, but 12 of the same type in a short time, it’s not normal,” said Daniel Koch, director of the Division of Communicable Diseases at the FOPH.

Research is being conducted to find the sources of the infection.

“We can talk about an epidemic and this disease can be deadly, but the population is not at risk. These germs benefit from flaws, a decrease in immunity, in the defenses of individuals. This therefore concerns especially pregnant women and the elderly,” Raffaele Malinverni, head of the Department of Medicine at the Neuchatel Hospital, told RTS on its Tuesday 12:45 broadcast.

The FOPH reminds that people at risk should avoid raw vegetables, raw or undercooked meat, raw fish and seafood, soft cheese and unpasteurized milk.
“Our survey is all the more difficult because the cases are spread all over Switzerland; it’s not easy, people have probably been infected with the same food, but it’s a food that had to be distributed in many places,” said Daniel Koch.

In 1987, more than 120 people became ill after eating Vacherin-Mont-d’or, and 30 of them died.

4 dead 8 sick in EU outbreak of Listeria linked to salmon products beginning in 2015

A multi-country outbreak of 12 listeriosis cases caused by Listeria monocytogenes sequence type (ST) 8 has been identified through whole genome sequencing (WGS) analysis in three EU/EEA countries: Denmark (6 cases), Germany (5) and France (1).

Four of these cases have died due to or with the disease. It is likely that the extent of this outbreak has been underestimated since the outbreak was identified through sequencing and only a subset of the EU/EEA countries routinely use this advanced technique to characterise L. monocytogenes isolates.

The first case was sampled in October 2015 in Denmark and the most recent case was reported in May 2018 in Germany. In August 2017, Denmark identified the first cluster of cases, which was investigated and linked to the consumption of ready-to-eat cold-smoked salmon produced in Poland. Control measures were implemented and the Member States and competent authorities were informed.

In October 2017, France reported the identification of a matching L. monocytogenes strain in food isolates from marinated salmon originating from the same Polish processing company as identified in the Danish outbreak investigation. This supports the hypothesis that contamination may have occurred at the processing company in Poland. However, due to the lack of WGS data on the isolates found in the environmental and food samples taken at the Polish processing plant, it is not possible at present to confirm the contamination with the L. monocytogenes ST8 outbreak strain at the suspected Polish plant. Moreover, until detailed information on the Norwegian primary producers of the salmon used in the contaminated batches is reported and assessed, possible contamination at primary production level cannot be excluded either.

Although control measures were implemented following the Danish outbreak investigation in September 2017, the identification of the same strain in a salmon product in France and a new human case in Germany suggest that the source of contamination is still active and contaminated products have been distributed to other EU countries than Denmark.

Until the source of infection has been eliminated, new invasive listeriosis cases may still occur. Pregnant women, the elderly and immunocompromised individuals are at increased risk of invasive listeriosis, which is associated with severe clinical course and potentially death.

Bullshit: Australian rockmelon Listeria investigation finds outbreak that killed seven largely caused by dust storm

(thanks to the avid barfblog.com reader who forwarded this)

An investigation into a series of deaths linked to listeria on rockmelons has concluded the contaminated fruit came from a single farm in New South Wales, and the outbreak was largely caused by the weather.

Between January 16 and April 10, 22 cases of listeriosis occurred across New South Wales, Victoria, Queensland and Tasmania, which led to seven deaths and a miscarriage.

Key points:

The investigation found the farm that was the source of the outbreak had hygiene and sanitary procedures on par with or better than most rockmelon-growing operations

Dust storms that covered the farm’s paddocks significantly increased the amount of listeria on the fruit

There were other peripheral issues found in the packing facility that were not considered to be major underlying causes

A report released on Thursday by the NSW Department of Primary Industries confirmed those cases were all linked to consumption of rockmelon packed at Rombola Family Farms in Nericon, NSW.

The report said the farm’s hygiene and sanitary procedures were “on par with or better than most other rockmelon-growing operations across Australia”.

Despite this, heavy rains in December and dust storms that followed covered the farm’s paddocks in dust, and “significantly increased” the amount of listeria on the fruit.

Rockmelons on the farm were washed in a chlorine solution and scrubbed prior to packing.

“The wash water was not recirculated, sanitiser was constantly monitored and applied through an auto-dosing system, and all water coming into the facility was treated and considered potable,” the report said.

“The netted skin of rockmelons makes this fruit particularly hard to clean and sanitise.”

The report said there were other peripheral issues noted in the packing facility during the investigation.

These included some dirty fans that were used to reduce the level of moisture on melons after washing, and some spongy material on packing tables that was not able to be easily cleaned.

These may have been contributing factors to the outbreak but were not considered to be the major underlying causes.

The report said the outbreak highlighted the need for better control measures and awareness of external threats to food safety in the rockmelon indstury.

As more cases of listeriosis emerged, sales of rockmelon plummeted and failed to recover.

Many rockmelon growers called for the farm that was the source of the outbreak to be named, in order to reassure the public that the fruit was safe to eat.

EU study reveals that most Listeria outbreaks remain undetected

More than half of the severe listeriosis cases in the European Union belong to clusters, many of which are not being picked up fast enough by the current surveillance system, suggests a new article published in Eurosurveillance.

The large-scale study looked into listeriosis epidemiology through whole genome sequencing and found that this method, when implemented at EU-level, could lead to faster detection of multi-country outbreaks, saving up to 5 months of the investigations.

The study, coordinated by the European Centre for Disease Prevention and Control (ECDC), analysed 2 726 human Listeria monocytogenes isolates from 27 countries between 2010 and 2015.

It found that slightly under 50% of the cases are isolated whereas the remaining half of cases is clustered together. Around one third of the cases that were identified as part of a cluster affected more than one country, often lasting for several years. However, only two listeriosis outbreaks were reported in the EU in 2016 and five in 2015, which suggests that many of them have gone undetected.

The authors determined that the use of whole genome sequencing to characterise listeriosis cases at EU-level could speed up the detection of clusters by up to five months, when compared to epidemiological investigation at country level. A more timely detection of clusters would potentially limit the occurrence of further cases from the same, common food source.

“This study is a milestone on the way to tackling listeriosis in Europe. With this new collaborative effort with the Member States, we have revealed the related nature of many cases of severe listeriosis. We are now strengthening routine surveillance by introducing the collection and analysis of whole genome sequencing data from all reported human listeriosis cases”, says ECDC’s Chief Scientist Mike Catchpole.

Listeriosis is a relatively rare but potentially severe food-borne disease that has been reported in increasing numbers in the EU/EEA countries since 2008. In 2016, 2 536 cases were reported, including 247 deaths. “Improving our surveillance on Listeria cases will save lives, particularly among vulnerable population groups such as the elderly and also pregnant women, who may pass on the bacteria to the fetus if they consume contaminated food”, Mike Catchpole points out.

The study also defines the most appropriate typing methods for earlier detection and investigation of dispersed cross-border clusters and outbreaks of Listeria monocytogenes.

Food Safety Talk 162: FST Bolo Ties

The show opens with a bit of discussion about other podcasts, but quickly moves to the main subject at hand: a recent study on the increased isopropanol tolerance of certain bacteria found in hospitals.  The guys weigh in on the strengths and weaknesses of the study, including it’s relevance to food safety, with some help via listener feedback. The next topic is Chipotle’s recent problem with Clostridium perfringens in their beans. The guys introduce a new segment on Canadian foods, before moving to listener feedback on fermented foods, CSPI, and thermometer calibration, times and temperatures, food dehydrators, handwashing, and double gloving. The show ends with a discussion of a recent cookbook recall.

Episode 162 is available on iTunes and here.

Show notes so you can follow along at home:

Thank you, WGS: Listeria linked to smoked salmon in Denmark and France

In Denmark, on 23 August 2017, Statens Serum Institut (SSI) identified a genetic cluster of four human Listeria monocytogenes sequence type (ST) 8 isolates by core genome multilocus sequence typing (cgMLST) [1]. The allele calling was performed in BioNumerics (v7.6.2, Applied Maths, Belgium). We initiated an epidemiological investigation and notified the Danish Central Outbreak Management Group (collaboration between the Danish Veterinary and Food Administration (DVFA), the National Food Institute at the Technical University of Denmark (DTU) and SSI). On 25 August, two additional human isolates were found to belong to the same genetic cluster.

A confirmed case was defined as a person clinically diagnosed with listeriosis after 1 January 2017 with laboratory-confirmed L. monocytogenes ST8 clustering using cgMLST (≤ 5 allelic distance, single linkage). Cases diagnosed before 1 January 2017 with an isolate belonging to this cluster were defined as probable cases.

As of 25 August 2017, the genetic cluster comprised six cases; five confirmed and one probable. The age of the cases ranged from 59 to 96 years (median 80 years) and four were women. All patients had underlying illness and no travel history. One patient died within 30 days of diagnosis. Epidemiological investigations including a standard questionnaire on exposures showed that all five confirmed cases had consumed cold-smoked and/or cured salmon in the 30 days before disease onset. Four cases had bought the salmon in retail chain X. No other food-item was reported as consumed in high frequencies among cases. Epidemiological follow-up for the probable case did not include information on fish consumption.

On 29 August 2017, a comparison between the human outbreak isolates and 16 L. monocytogenes ST8 food- and environmental isolates identified in Denmark from 2014 to August 2017 showed that the human isolates clustered with a food isolate from cold-smoked salmon, cut and packaged at company Y in Poland (zero to two allelic differences using cgMLST). L. monocytogenes had been detected on 31 July 2017 at levels of 110 CFU/g (threshold: 100 CFU/g) at the end of shelf life. The product was widely sold in Denmark and had been sampled by the DVFA in retail chain X, as part of a consumer exposure survey (i.e. analyses project on retail packages). Because the L. monocytogenes concentration had been just above the accepted limit and found at the end of the product shelf life a recall of this batch was not conducted. However, due to the positive finding, follow-up sampling had been performed on the 9 and 10 August 2017 from the central storage unit of retail chain X. L. monocytogenes had been isolated from two batches analysed before end of shelf life. In one sample from the same batches, which was also analysed at the end of the shelf life, on 28 August 2017 a L. monocytogenes level of 240 CFU/g was found. Isolates from the follow-up samples had zero to four allelic differences to the human outbreak isolates using cgMLST.

The human outbreak sequences were also compared to all L. monocytogenes ST8 genomes derived from clinical samples in Denmark from 2012 onwards. Although ST8 genomes from Danish patients in the period 2012–2017 showed high diversity, the outbreak isolates clearly formed a distinct cgMLST cluster with 16 allelic differences to the nearest isolates outside the genetic outbreak cluster and a maximum of nine allelic differences within the cluster (Figure 2a). We investigated the relatedness of outbreak isolates further by single-nucleotide polymorphisms (SNP) analysis performed by both SSI and DTU using two analysis pipelines: Northern Arizona SNP Pipeline (NASP) [2] and CSI Phylogeny version 1.4 from Center for Genomics Epidemiology (CGE), DTU [3] leading to the same conclusion.

On 30 August 2017, DVFA advised retail chain X to recall all cold-smoked salmon produced at company Y. This advice was based on the elevated number of L. monocytogenes (240 CFU/g) found in the product at the end of shelf-life and the link to the outbreak. Retail chain X voluntarily recalled both cold-smoked and cured salmon produced at company Y. As part of the recall procedure, retail chain X informed company Y on the situation. Information from company Y, provided by the Polish food authorities via the European Union Rapid Alert System for Food and Feed (RASFF), showed that the implicated batches were exclusively sold via retail chain X and only in Denmark.

The French National Reference Centre (NRC) for Listeria (Institut Pasteur, Paris), compared the sequences of the Danish human isolates against its database, using cgMLST as previously described [1,4]. A human isolate from a French resident belonged to the same cluster (L2-SL8-ST8-CT771) as the Danish isolates. This French probable case, a female patient in her mid-80s, was diagnosed in June 2016. Epidemiological investigations carried out by Santé Publique France were inconclusive, since food consumption history was not available at the time of diagnosis nor could information on travel to Denmark be retrieved, as the person had since died.

On 6 September 2017, an official control by the Ministry of Economy was carried out at a French retailer where a kosher chilled cured salmon was sampled for analysis. The sample was contaminated with L. monocytogenes at the level of 460 CFU/g and the salmon producer was company Y. An isolate was sent to the French NRC for typing and showed to belong to the same cgMLST type as the Danish outbreak. Further investigations on the food product confirmed that it had not been further processed after production in Poland. The product was recalled and no human cases were linked to its consumption as of beginning of December 2017.

The other nine countries that replied to the EPIS-FWD UI-426 notification (Austria, Finland, Germany, Luxembourg, the Netherlands, Norway, Slovenia, Sweden, United Kingdom) did not report any human or food isolates linked to the Danish outbreak. However, after submission of this report, at the end of November, we were informed through EPIS about three genetically linked human isolates in Germany.

Discussion

Here we report on a listeriosis outbreak and highlight the value of rapidly comparing the genomes of human and food/environmental isolates at the national and international levels.

The fact that the contaminated salmon products identified in Denmark and France were from different batches suggests environmental contamination possibly at the production facility at company Y. It is too early to assess whether any measures taken at company Y have been effective in controlling the outbreak. However, experiences from previous investigations suggest that once L. monocytogenes is detected in one product, the whole production site should be subject to a thorough inspection, and sampling with special attention to all the possible contamination/cross contamination issues before implementing corrective measures [5,6]. Moreover, the risk for L. monocytogenes persistent strains in the production environment requires the close monitoring for several years to ensure the elimination of these [7,8].

Since WGS was introduced for routine surveillance in Denmark, a number of listeriosis outbreaks have been detected and solved, including outbreaks involving cold-smoked ready-to-eat sliced fish products [5]. The present investigation further reinforces the suspicion that ready-to-eat fish products are important sources of L. monocytogenes infections in Denmark, as well as in other countries.

Though only involving a low number of isolates, WGS L. monocytogenes surveillance and communication between countries allowed us to detect and rapidly solve this salmon-associated outbreak, leading to food product recall in two European countries. Compared with previous typing methods, WGS has a higher discriminatory power and the ability to determine genetic distance between isolates. The introduction of WGS for surveillance of food-borne infections has shown that it improves outbreak detection and facilitates outbreak investigations and likely helps reduce the number of infections [4,9-16]. The EPIS-FWD communication platforms allowed for the communication to link cases across borders. However, currently cross-border outbreaks are only detected when case numbers in at least one country exceed normal levels and are notified internationally. Therefore, a possible future system for easy exchange of and comparison of WGS data, e.g. by the use of an agreed cgMLST nomenclature, across borders will enable the identification of more dispersed outbreaks as well as cross-border links between food samples and human infections. This report highlights that by the application of cross-disciplinary and real-time cross-border comparison of WGS data, L. monocytogenes infections can be prevented and thereby providing safer food for at-risk groups such as the elderly, immunodeficient individuals and pregnant women.

Cross-border outbreak of listeriosis caused by cold-smoked salmon, revealed by integrated surveillance and whole genome sequencing (WGS), Denmark and France, 2015 to 2017

Schjørring Susanne, Gillesberg Lassen Sofie , Jensen Tenna, Moura Alexandra, Kjeldgaard Jette S, Müller Luise, Thielke Stine, Leclercq Alexandre, Maury Mylene M, Tourdjman Mathieu, Donguy Marie-Pierre, Lecuit Marc, Ethelberg Steen, Nielsen Eva M. Cross-border outbreak of listeriosis caused by cold-smoked salmon, revealed by integrated surveillance and whole genome sequencing (WGS), Denmark and France, 2015 to 2017. Euro Surveill. 2017;22(50):pii=17-00762. https://doi.org/10.2807/1560-7917.ES.2017.22.50.17-00762

https://eurosurveillance.org/content/10.2807/1560-7917.ES.2017.22.50.17-00762