Category Archives: Research

Research – Microbiological Safety and Shelf-Life of Low-Salt Meat Products—A Review

MDPI

Salt is widely employed in different foods, especially in meat products, due to its very diverse and extended functionality. However, the high intake of sodium chloride in human diet has been under consideration for the last years, because it is related to serious health problems. The meat-processing industry and research institutions are evaluating different strategies to overcome the elevated salt concentrations in products without a quality reduction. Several properties could be directly or indirectly affected by a sodium chloride decrease. Among them, microbial stability could be shifted towards pathogen growth, posing a serious public health threat. Nonetheless, the majority of the literature available focuses attention on the sensorial and technological challenges that salt reduction implies. Thereafter, the need to discuss the consequences for shelf-life and microbial safety should be considered. Hence, this review aims to merge all the available knowledge regarding salt reduction in meat products, providing an assessment on how to obtain low salt products that are sensorily accepted by the consumer, technologically feasible from the perspective of the industry, and, in particular, safe with respect to microbial stability.

USA – USDA Announces Action to Declare Salmonella an Adulterant in Breaded Stuffed Raw Chicken Products

FSIS USDA

The U.S. Department of Agriculture’s (USDA) Food Safety and Inspection Service (FSIS) is announcing that it will be declaring Salmonella an adulterant in breaded and stuffed raw chicken products.

“Food safety is at the heart of everything FSIS does,” said Agriculture Secretary Tom Vilsack. “That mission will guide us as this important first step launches a broader initiative to reduce Salmonella illnesses associated with poultry in the U.S.”

“Today’s announcement is an important moment in U.S. food safety because we are declaring Salmonella an adulterant in a raw poultry product,” said Sandra Eskin, USDA Deputy Under Secretary for Food Safety. “This is just the beginning of our efforts to improve public health.”

By declaring Salmonella an adulterant in these products, FSIS will be able to ensure that highly contaminated products that could make people sick are not sold to consumers. Since 1998, breaded and stuffed raw chicken products have been associated with up to 14 outbreaks and approximately 200 illnesses. Products in this category are found in the freezer section and include some chicken cordon bleu or chicken Kiev products. These products appear cooked, but they are heat-treated only to set the batter or breading and the product contains raw poultry. Continual efforts to improve the product labeling have not been effective at reducing consumer illnesses.

Research – Thermal inactivation of Salmonella enterica and nonpathogenic bacterial surrogates in wheat flour by baking in a household oven 

Journal of Food Protection

Wheat flour has been implicated in recalls and outbreaks linked to Salmonella and pathogenic Escherichia coli. An instructional online video posted on a popular YouTube channel with over 20 million subscribers claimed that safe raw cookie dough could be made from flour baked in a household oven at 177°C (350°F) for 5 min but no evidence in support of that claim was provided. This study was conducted to assess thermal inactivation of two Salmonella strains, as well as Enterobacter aerogenes and Pantoea dispersa in wheat flour during home oven style baking. Wheat flour was inoculated with Salmonella Enteritidis PT 30, Salmonella Typhimurium PT 42 or their potential surrogates at high concentrations (4.8-6.1 log CFU/g) before baking in consumer-style convection oven (toaster oven) at 149, 177, and 204°C (300, 350, or 400°F) for up to 7 min. Flour was heated in aluminum tray with a maximum depth of ~2 cm. Heated wheat flour samples (5 g each) were enumerated in triplicate, and microbial concentration was expressed in log CFU/g. Thermal profiles of the geometric center of the wheat flour pile and air in the oven during the baking were recorded. Water activity of wheat flour samples was also measured before and after baking. Water activity of wheat flour decreased as baking temperature and time increased. Water activity values ranged from 0.30 to 0.06 after 7 min as oven temperature increased from 149 to 204°C. Thermal inactivation kinetics were linear until counts approached the limit of detection for all microorganisms. D-values for Salmonella and potential surrogate strains ranged from 1.86 to 2.13 min at 149°C air temperature, 1.66 to 1.92 min at 177°C air temperature, and 1.12 to 1.38 min at 204°C air temperature. Both Salmonella strains and surrogates showed similar inactivation patterns. Baking of wheat flour in household toaster ovens has potential as an inactivation treatment of pathogenic bacteria in consumer homes, despite its low water activity.

Research – Terpenes Combinations Inhibit Biofilm Formation in Staphyloccocus aureus by Interfering with Initial Adhesion

MDPI

Staph

The biofilm is a conglomerate of cells surrounded by an extracellular matrix, which contributes to the persistence of infections. The difficulty in removing the biofilm drives the research for new therapeutic options. In this work, the effect of terpenes (−)-trans-Caryophyllene, (S)-cis-Verbenol, (S)-(−)-Limonene, (R)-(+)-Limonene, and Linalool was evaluated, individually and in combinations on bacterial growth, by assay with resazurin; the formation of biofilm, by assay with violet crystal; and the expression of associated genes, by real-time PCR, in two clinical isolates of Staphyloccocus aureus, ST30-t019 and ST5-t311, responsible for more than 90% of pediatric infections by this pathogen in Paraguay. All combinations of terpenes can inhibit biofilm formation in more than 50% without affecting bacterial growth. The most effective combination was (−)-trans-Caryophyllene and Linalool at a 500 μg/mL concentration for each, with an inhibition percentage of 88%. This combination decreased the expression levels of the sdrD, spa, agr, and hld genes associated with the initial cell adhesion stage and quorum sensing. At the same time, it increased the expression levels of the cap5B and cap5C genes related to the production of capsular polysaccharides. The combinations of compounds tested are promising alternatives to inhibit biofilm formation in S. aureus. View Full-Text

Research – Listeria monocytogenes Pathogenesis: The Role of Stress Adaptation

MDPI

Adaptive stress tolerance responses are the driving force behind the survival ability of Listeria monocytogenes in different environmental niches, within foods, and ultimately, the ability to cause human infections. Although the bacterial stress adaptive responses are primarily a necessity for survival in foods and the environment, some aspects of the stress responses are linked to bacterial pathogenesis. Food stress-induced adaptive tolerance responses to acid and osmotic stresses can protect the pathogen against similar stresses in the gastrointestinal tract (GIT) and, thus, directly aid its virulence potential. Moreover, once in the GIT, the reprogramming of gene expression from the stress survival-related genes to virulence-related genes allows L. monocytogenes to switch from an avirulent to a virulent state. This transition is controlled by two overlapping and interlinked transcriptional networks for general stress response (regulated by Sigma factor B, (SigB)) and virulence (regulated by the positive regulatory factor A (PrfA)). This review explores the current knowledge on the molecular basis of the connection between stress tolerance responses and the pathogenesis of L. monocytogenes. The review gives a detailed background on the currently known mechanisms of pathogenesis and stress adaptation. Furthermore, the paper looks at the current literature and theories on the overlaps and connections between the regulatory networks for SigB and PrfA.

Research – Peroxyacetic Acid Effectiveness against Salmonella on Raw Poultry Parts is not Affected by Organic Matter

Journal of Food Protection

Organic matter (OM) accumulation is common in chill tanks used to decontaminate raw poultry parts during processing. Organic matter negatively affects the antimicrobial activity of chlorine-based compounds, but its effect on the antimicrobial effectiveness of peroxyacetic acid (PAA) on poultry meat has not been described. Therefore, this study evaluated the effect of OM on the efficacy of PAA solutions in simulated post-chill tanks to reduce Salmonella artificially inoculated onto chicken parts. Chicken thighs were inoculated with a five-strain cocktail of poultry-borne Salmonella enterica serovars at ca. 6 log10CFU/ml. Then, the thighs were immersed for 30 or 45 s in PAA solutions (500 or 1,000 ppm) with chicken slurry to simulate OM accumulation (0, 15 or 30 g/L). The thighs were rinsed with neutralizing buffered peptone water (100 ml) and rinsates were plated onto XLD agar. Experiments were performed in triplicate (3 thighs/treatment/replicate). Chemical oxygen demand (COD), total nitrogen (TN), and pH were measured as the water quality parameters of the PAA solutions before and after use. COD ranged from 2,905 mg/L in unused 500-ppm solutions without added OM to 6,290 mg/Lin used 1,000-ppm solutions with 30 g/L of OM. Initial TN was 42.5 ± 2.0 mg/L and 60.9 ± 8.3 mg/L for 15 and 30 g/L OM, which increased by 27 ± 17 mg/L after use. The pH of solutions ranged from 3.16 ± 0.14 to 3.42 ± 0.09 for the 1,000-ppm solutions and from 3.59 ± 0.06 to 3.96 ± 0.06 for the 500-ppm solutions. Mean Salmonella reductions were 0.9 ± 0.1 log10CFU/ml of rinsate for the 500-ppm PAA treatment and 1.1 ± 0.1 log10CFU/ml of rinsate for 1,000-ppm PAA treatment. Exposure time did not have a significant effect on the logarithmic reductions. There was no significant effect of OM concentration (p>0.05) on the reductions, indicating that the antimicrobial efficacy was not affected and that PAA solutions may continue to be reused as long as the PAA concentration is actively monitored.

Research – Dynamics of Salmonella enterica and antimicrobial resistance in the Brazilian poultry industry and global impacts on public health

PLOS One

Non-typhoidal Salmonella enterica is a common cause of diarrhoeal disease; in humans, consumption of contaminated poultry meat is believed to be a major source. Here we determine that Senterica serovars Heidelberg and Minnesota were the most prevalent serovars in Brazilian poultry and in poultry products imported from Brazil into the UK. However, long-term surveillance data collected by the UK Health Security Agency showed no increase in the incidence of Salmonella Heidelberg or Salmonella Minnesota in human cases of clinical disease in the UK following the increase of these two serovars in Brazilian poultry. Salmonella Heidelberg and Salmonella Minnesota clades shared resistance to sulphonamides, tetracyclines and beta-lactams conferred by sul2tetA and blaCMY-2 genes, not widely observed in other co-circulating serovars despite similar selection pressures. The sul2 and tetA genes were concomitantly carried on IncC plasmids, whereas blaCMY-2 was either co-located with the sul2 and tetA genes on IncC plasmids or independently on IncI1 plasmids. These findings suggest that introduction of the Salmonella Enteritidis vaccine, in addition to increasing antimicrobial use, could have resulted in replacement of salmonellae in Brazilian poultry flocks with serovars that are more drug resistant, but less associated with disease in humans in the UK.

Research – Dangerous pathogens lurk in wet areas

Science Daily

Hospitals and homes are havens for germs and disease — but a well-regulated hot water system can prevent the spread of waterborne pathogens, including an emerging infectious disease problem from ‘superbugs’ which can be resistant to most antibiotics.

However, Flinders University experts warn that some drinking water treatment methods may be ineffective against some waterborne pathogens that pose a threat to immune-compromised individuals — and point-of-use devices such as taps and showerheads may create havens for these microorganisms to grow.

The elderly, newborns and those with compromised immune systems are especially vulnerable to waterborne infections. Numbers are rising of people with conditions such as advanced age, cancer and immunodeficiency issues who may be more at risk of ‘opportunistic premise plumbing pathogens’ (OPPP) infection.

Regular changes to tap and outlet filters, hot water service maintenance checks (for heat and pressure) and effective cleaning of shower and tap faucets are recommended for immune-compromised patients receiving healthcare at home or post-surgical management.

Healthcare at home has emerged as an alternative to extensive inpatient hospital stays — especially through the COVID-19 pandemic, to reduce the burden on the healthcare system and to support those with potential long term respiratory side effects.

“These measures can help reduce the risk of waterborne infections in home care, along with quality treatments of mains water to provide safe drinking water,” says lead researcher Claire Hayward, from Flinders University’s College of Science and Engineering.

A new study published in the journal Current Opinion in Infectious Diseases, by environmental health experts at Flinders University, found evidence of hospital water as a source of potential infection and even antimicrobial and multidrug resistant organisms.

“Biofilms formed on taps, showers, drains and other outlets provide an ideal niche to harbour these dangerous antibiotic resistant pathogens originating from the supply water or the human microbiota from washing contaminated hands,” says Ms Hayward.

OPPP infections such as Legionella pneumophila, Pseudomonas aeruginosa and Mycobacterium avium are a group of waterborne pathogens that are slowly receiving increased public health attention in infection control guidelines.

“However, drinking water as a source of healthcare-associated infections continues to be overlooked or underestimated in this monitoring,” Ms Hayward says.

The OPPP waterborne pathogens can be disinfectant resistant and persist in refuges with low nutrients, then form biofilms capable of supporting other clinically relevant pathogens such as Staphylococcus aureus, Enterobacteriaceae, Klebsiella pneumoniae and Escherichia coli.  

Once these biofilms are established on plumbing surfaces, there are many ways for contamination and transmission. The design of outlet devices that result in splashing and aerosolising of water can also increase the risk of contaminating nearby areas.

“The rise of these resistant pathogens has been identified by the World Health Organization and US Centers for Disease Control and Prevention as one of the most significant threats to global public health,” says research co-author, Flinders University microbiology expert Professor Melissa Brown.

“While the COVID-19 pandemic has increased the use of disinfectants and sanitisers, particularly in healthcare facilities, these antiseptic soaps do not tackle what’s going on behind the scenes in the water supply pipes and faucets,” she says.

The researchers recommend broad, universal surveillance guidelines to understand the role of drinking water and water-related devices to reduce healthcare associated infections and the rise of possible antimicrobial resistance that poses a threat to at risk individuals in residential and healthcare settings.

USA – FDA Is Focusing on Safety of Frozen Berries

Food Safety Tech

From 1983 to 2018, there were 50 outbreaks globally that were attributed to frozen berries: 36 caused by Norovirus and 14 by Hepatitis A.

On July 22, the FDA announced that it is developing a food safety prevention strategy to enhance the safety of fresh and frozen berries. The move comes in response to multiple hepatitis A (HAV) and norovirus (NoV) outbreaks linked to the consumption of both fresh and frozen berries.

The FDA reports that there have been four HAV outbreaks and three NoV outbreaks linked to frozen berries from 1990 to 2016 in the U.S., and since 2011, there have been three HAV outbreaks linked to fresh berries, including a current outbreak linked to fresh organic strawberries.

In addition, from 1983 to 2018, there were 50 outbreaks globally that were attributed to frozen berries: 36 caused by NoV and 14 by HAV. The FDA noted that although freezing preserves berries it generally does not inactivate viruses that may be introduced at various points in the supply chain, such as by infected workers, contaminated water or contaminated food contact surfaces. In addition, fresh berries are generally eaten raw without a kill-step that could eliminate pathogens.

In August, the FDA plans to resume an assignment to collect and test frozen berries that it paused at the start of the COVID-19 pandemic. The assignment seeks to estimate the prevalence of HAV and NoV in frozen strawberries, raspberries and blackberries and help the FDA identify sites where practices or conditions may exist that constitute safety vulnerabilities.

The FDA also plans to work collaboratively with industry, academia and regulatory partners in the development of a food safety prevention strategy to identify measures that can be taken to limit or prevent contamination from occurring throughout the berry supply chain, approaches to re-enforce control measures and their application as well as areas where additional research is needed.

Research – From chicken to salad: Cooking salt as a potential vehicle of Salmonella spp. and Listeria monocytogenes cross-contamination

PubMed

Epidemiological studies show that improper food handling practices at home account for a significant portion of foodborne illness cases. Mishandling of raw meat during meal preparation is one of the most frequent hazardous behaviours reported in observational research studies that potentially contributes to illness occurrence, particularly through the transfer of microbial pathogens from the raw meat to ready-to-eat (RTE) foods. This study evaluated the transfer of two major foodborne pathogens, Salmonella enterica and Listeria monocytogenes, from artificially contaminated chicken meat to lettuce via cooking salt (used for seasoning) during simulated domestic handling practices. Pieces of chicken breast fillets were spiked with five different loads (from ca. 1 to 5 Log CFU/g) of a multi-strain cocktail of either S. enterica or L. monocytogenes. Hands of volunteers (gloved) contaminated by handling the chicken, stirred the cooking salt that was further used to season lettuce leaves. A total of 15 events of cross-contamination (three volunteers and five bacterial loads) were tested for each pathogen. Immediately after the events, S. enterica was isolated from all the cooking salt samples (n = 15) and from 12 samples of seasoned lettuce; whereas L. monocytogenes was isolated from 13 salt samples and from all the seasoned lettuce samples (n = 15). In addition, S. enterica and L. monocytogenes were able to survive in artificially contaminated salt (with a water activity of 0.49) for, at least, 146 days and 126 days, respectively. The ability of these foodborne pathogens to survive for a long time in cooking salt, make it a good vehicle for transmission and cross-contamination if consumers do not adopt good hygiene practices when preparing meals.