Category Archives: Microbiology Investigations

Research – Application of ultra-fine bubble technology to reduce Listeria monocytogenes contamination of fresh produce

Center for Produce Safety

Summary

Water used for washing or hydrocooling can act as a source of produce contamination with Listeria monocytogenes. Since this could lead to human infections, controlling L. monocytogenes in hydrocooling water and produce is critical for food safety. Commercial disinfectants (chlorine, quaternary ammonium compounds) are not completely effective in killing L. monocytogenes in wash water or on produce, especially in presence of organic load.

This proposal aims to investigate the potential of a new technology that employs water containing ultra-fine gas bubbles (size ~ 1 micrometer or less) for washing produce (celery, gala apples, romaine lettuce). We will generate ultra-fine ozone (UFO) bubbles in water using a high energy shear method and test the potential of resulting solution to rapidly kill (in 30 to 60 sec) L. monocytogenes in wash water and on produce surface. In addition, the efficacy of UFO bubble water to synergistically improve the Listeria killing potential of aforementioned commercial disinfectants will be tested. The anti-listerial efficacy of UFO bubble water will also be tested in presence of organic load. Successful completion of this project will provide the produce industry with novel antimicrobial treatment for disinfecting wash water and produce in single pass or re- circulated hydrocooling systems.

Technical Abstract

The widespread distribution of Listeria monocytogenes in agricultural environments such as soil, manure and water results in frequent contamination of food processing areas. Although good agricultural practices partially reduce contamination, however, due to the open nature of farming, it is extremely difficult to completely prevent pathogen influx. Water used for washing or hydrocooling can act as a source of equipment and produce contamination with L. monocytogenes. Since this could lead to human infections, controlling L. monocytogenes in hydrocooling water and on the surface of fresh produce is critical for food safety. Currently used commercial disinfectants (chlorine, peracetic acid, quaternary ammonium compounds) are not completely effective in killing L. monocytogenes in wash water or on the surface of produce, especially in presence of organic load. Moreover, the presence of chemical residues and the formation of harmful organochlorine compounds is an occupational concern due to associated health risks, including cancer. Therefore, there is a need for developing novel strategies that could be employed (either alone or in combination with currently used commercial disinfectants) to control L. monocytogenes in wash water and on surface of fresh produce, vegetables and fruits.

This proposal aims to investigate the potential of a new technology that employs water containing ultra-fine gas bubbles (size ~ 1 micrometer or less) for washing produce (celery, gala apples, romaine lettuce). We will generate ultra-fine ozone (UFO) bubbles in water using a high energy shear method and test the potential of resulting solution to rapidly kill (in 30 to 60 sec) L. monocytogenes in wash water and on produce surface. In addition, the efficacy of UFO bubble water to synergistically improve the Listeria killing potential of aforementioned commercial disinfectants will be tested. The anti-listerial efficacy of UFO bubble water will also be tested in presence of organic load.

Potential impact from anticipated outcomes: Successful completion of this project will provide the produce industry with novel antimicrobial treatment for disinfecting wash water and produce in dump tanks, and single pass or re-circulated hydrocooling systems. This intervention will translate into increased microbiological safety of fresh produce.

Research – Frozen Vegetable Processing Plants Can Harbour Diverse Listeria monocytogenes Populations: Identification of Critical Operations by WGS

MDPI

Frozen vegetables have emerged as a concern due to their association with foodborne outbreaks such as the multi-country outbreak of Listeria monocytogenes serogroup IVb linked to frozen corn. The capacity of L. monocytogenes to colonize food-processing environments is well-known, making the bacteria a real problem for consumers. However, the significance of the processing environment in the contamination of frozen foods is not well established. This study aimed to identify potential contamination niches of L. monocytogenes in a frozen processing plant and characterize the recovered isolates. A frozen vegetable processing plant was monitored before cleaning activities. A total of 78 points were sampled, including frozen vegetables. Environmental samples belonged to food-contact surfaces (FCS); and non-food-contact surfaces (n-FCS). Positive L. monocytogenes samples were found in FCS (n = 4), n-FCS (n = 9), and the final product (n = 1). A whole-genome sequencing (WGS) analysis revealed two clusters belonging to serotypes 1/2a-3a and 1/2b-3b). The genetic characterization revealed the presence of four different sequence types previously detected in the food industry. The isolate obtained from the final product was the same as one isolate found in n-FCS. A multi-virulence-locus sequence typing (MVLST) analysis showed four different virulence types (VT). The results obtained highlight the relevant role that n-FCS such as floors and drains can play in spreading L. monocytogenes contamination to the final product. View Full-Text

Research – Microbiome of Lettuce Might Hold Secret to Better Food Safety

Growing Produce

Eurofins Food Testing UK

Researchers at the University of Georgia Center for Food Safety are preparing to launch a study on E. coli colonization from a new angle: the microbiome of lettuce.

By studying the interactions between EcO157 and the lettuce microbiome — the entire community of microorganisms like bacteria that live on the surface of lettuce — researchers hope to better understand how the microbiome may affect the pathogen’s fate during produce processing.

Center for Food Safety Professor Xiangyu Deng, lead researcher on the project, says, “We want to really figure out the interactions between the pathogen and potential biocontrol organisms indigenous to lettuce.”

In other words, how does E. coli interact with other microorganisms on lettuce, and how can we use those interactions to control foodborne outbreaks?

The focus of the research, to start this year, will be how the microbiome interacts with EcO157. The team will use a new microscopic approach to create a biogeographic map of the microbiome.

“Clearly the microbiome interacts with EcO157, and that interaction has an implication for food safety,” Deng adds. “We want to understand the mechanism behind this interaction.”

Finland – Large Salmonella outbreak dominates Finnish figures

Food Safety News

A Salmonella outbreak affected more than 700 people in Finland in 2021, according to new information from the Finnish Food Authority (Ruokavirasto).

The implicated food was a salad with iceberg lettuce, cucumber and peas served in several kindergartens. It was previously known that almost 450 people, mostly children, had been ill.

Officials in the city of Jyväskylä investigated the incident with the help of the National Institute for Health and Welfare (THL).

Overall, 46 foodborne outbreaks were recorded in Finland this past year affecting almost 1,400 people. In 2020, 34 outbreaks were reported involving 543 people.

Seven Salmonella outbreaks sickened 824 people compared to three outbreaks with 21 sick in 2020.

The most common pathogen was norovirus with nine outbreaks and 260 cases. One of the main factors that contributed to foodborne norovirus incidents was an infected kitchen worker.

Read More at the link above.

Research – Temperature, Time, and Type, Oh My! Key Environmental Factors Impacting the Recovery of Salmonella Typhimurium, Listeria monocytogenes, and Tulane Virus from Surfaces 

Journal of Food Protection

Environmental monitoring (EM) programs are designed to detect the presence of pathogens in food manufacturing environments with the goal of preventing microbial contamination of food. Nevertheless, limited knowledge exists regarding the influence of environmental conditions on microbial recovery during EM. This study utilizes a commercially-available polyurethane foam (PUF) EM tool to determine the influence of environmental factors on the recovery of foodborne pathogens. The specific objectives of this study were to determine if environmental conditions and surface composition impact the recovery of sought-after microorganisms found in food processing environments. These data are compared across 1) microorganism type, 2) surface type, 3) environmental temperature and relative humidity, and 4) exposure time. Two bacteria ( Listeria monocytogenes , Salmonella Typhimurium) and one human norovirus surrogate (Tulane virus [TV]) were inoculated onto three non-porous surfaces (polypropylene, stainless steel, neoprene). Surfaces were held in an environmental chamber for 24 or 72 h at 30°C/30%, 6°C/85%, and 30°C/85% relative humidity (RH). Data indicate that microbial recovery from environmental surfaces significantly (p ≤ 0.05) varies by microorganism type, environmental conditions, and exposure time. For instance, all microorganisms were significantly different from each other, with the greatest mean log reduction being TV and the lesser reduction being L. monocytogenes at 4.94 ± 1.75 log 10 PFU/surface and 2.54 ± 0.91 log 10 CFU/surface, respectively. Overall, these data can be used to improve the effectiveness of EM programs and underscores the need to better comprehend how EM test results are impacted by food manufacturing environmental conditions.

USA – Food Safety Belongs on the Grill

USDA

Meat on the grill

There’s nothing better than gathering around the grill to prepare a good meal. Don’t forget the rules of food safety this grilling season.

Wash Your Hands

USDA recommends washing your hands for at least 20 seconds with warm, soapy water. In our recent consumer research study (PDF, 49 KB), 97% of participants who attempted to wash their hands failed to wash them properly. Additionally, 56% of participants didn’t attempt to wash their hands at all during meal preparation. Most participants in this study claimed that they always wash their hands before preparing food; but in reality, most failed to wash their hands properly when observed.

Use a Food Thermometer

You can’t see, smell, or taste germs that can cause foodborne illness. USDA doesn’t recommend tasting food to check if it’s fully cooked. Using a food thermometer is the only way to ensure that your food is fully cooked to a safe minimum internal temperature. When grilling ground meats (beef, pork, veal or lamb), make sure they reach an internal temperature of 160 F on a food thermometer. Ground poultry is safe to eat once it has reached an internal temperature of 165 F.

Avoid Cross Contamination

Cross contamination is one of the main causes of foodborne illness. Here are some tips:

  • Use separate cutting boards—one for raw meat and poultry, and the other for fruits and vegetables.
  • USDA recommends not washing meat products, because bacteria can spread from the meat onto your sink and kitchen surfaces.
  • Use separate plates while grilling—one for bringing raw meat and poultry to the grill, and the other for removing cooked meat and poultry off the grill.

For more information, call the USDA Meat and Poultry Hotline at 1-888-MPHotline (1-888-674-6854) or email MPHotline@usda.gov to reach a food safety expert or chat live at ask.usda.gov from 10 a.m. to 6 p.m. Eastern Time, Monday through Friday.

USA – Waterville Country Club’s Nineteen 16 Restaurant link in Hepatitis A scare

Food Poison Journal

The state  of Maine CDC is warning of a possible hepatitis A exposure at an Oakland restaurant.

It says a food service worker had the virus, which can spread through contaminated food or water.

The worker at Waterville Country Club’s Nineteen 16 Restaurant was infectious from April 26-May 17.

If you ate or bought food from the restaurant, you could be at risk.

The state says there is no evidence linking this to a recently confirmed case of hepatitis at the Skowhegan Walmart.

UK – More than 80 Brits got food poisoning from hotel with faeces in the pool

Metro

Dozens of British tourists have been handed compensation after falling ill on a ‘nightmare’ holiday.

Families were among 89 people who stayed at the all-inclusive Holiday Village on Lanzarote when they suffered from acute gastrointestinal infections, nausea, diarrhoea and cramps in summer 2019.

Representing some victims in a legal battle with Tui, barrister Charles Crow said: ‘Fresh food was added to older food, food appeared to be recycled/re-presented at later meals.

‘Maggots were reported in the milk, which was sometimes curdled. Food, restaurant and general hygiene standards were poor.

India – 20 train passengers hospitalised due to food poisoning in Kerala

The Hindu

As many as 20 train passengers, including children, were admitted to the Thrissur General Hospital on Tuesday with symptoms of food poisoning. They were travelling in Maveli Express from Mookambika to Thiruvananthapuam. All were discharged after receiving treatment.

The passengers, belonging to one family, were returning after a dance arangettam programme at Mookambika. According to the passengers, they had consumed food bought from the Mangalore railway station.

India – 200 people contract food poisoning after having dinner at Gujarat wedding

India Tv News

At least 200 people got food poisoning in Gujarat’s Katargam, after they had dinner at a wedding in the area. One day after the function, 200 out of 200 guests complained of fever, and vomiting. Out of the 200, at least 9 people were admitted to a hospital nearby.

The wedding took place at Nityanand Dham, and the menu consisted of grapes, and Bengali sweets named Oreo Sake, Angoor Rabri and Kesar Kumkum. The ones who were admitted to the hospital, also said that they had a problem walking.