Category Archives: Food Microbiology Research

Research – Anti‐listeria activity and shelf life extension effects of Lactobacillus along with garlic extract in ground beef

Posted on October 14, 2019 by | Leave a comment

Wiley Online

The current study investigates the effect of Lactobacillus reuteri and Lactobacillus plantarum combined with water extract of garlic on microbial growth, chemical changes, and sensory attributes in ground beef samples at refrigeration condition (+4°C) up to 12 days of storage. in vitro study revealed that garlic extract combined with L. reuteri or L. plantarum caused 2.13 and 2.57 log reduction in the Listeria monocytogenes count, respectively. Combination of L. plantarum and 1% garlic extract significantly (p < .05) reduced aerobic mesophilic bacteria (1.64 log cycle) and L. monocytogenes (1.44 log cycle) counts in ground beef. Lipid oxidation was also significantly (p < .05) lower in samples treated with L. plantarum plus garlic extract (1%). Furthermore, higher sensory scores were received by samples treated with Lactobacillus plus garlic extract. In conclusion, the combination of L. plantarum and garlic extract was found to be suitable to use in ground beef by controlling the L. monocytogenes growth and increasing its shelf life.

Practical Applications

Garlic extract not only has an antimicrobial activity but also has a stimulatory effect on the Lactobacillus spp. growth. On the other hand, some Lactobacillus strains can inhibit pathogenic bacteria. Then, the combination of Lactobacillus and garlic extract may be used to produce new bio‐preserved and functional meat products. The current study indicated the potential of Lactobacillus combined with garlic extract to control microbial and chemical changes in ground beef. The combination of Lactobacillus plantarum and garlic extract significantly (p < .05) reduced Listeria monocytogenes counts and lipid oxidation rates and improved the sensory scores in ground beef.

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Posted in Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Technology, lactic acid bacteria, Lactobacillus, Listeria, Listeria monocytogenes, microbial contamination, Microbiology, Research, Technology, Uncategorized

Research – The effect of sucrose-induced osmotic stress on the sensitivity of Escherichia coli to bacteriocins

Posted on October 13, 2019 by | Leave a comment

NRC Research Press

ABSTRACT

Bacteriocins are antimicrobial peptides, produced by Gram-positive bacteria such as lactococci and staphylococci, that have limited bactericidal action against Gram-negative bacteria. The aim of this paper was to study the sensitivity of three strains of Escherichia coli to bacteriocins: nisin (as Nisaplin®) and two staphylococcal peptides (warnerin and hominin) during sucrose-induced osmotic stress. We found that all peptides in a 0.3 g·mL−1 sucrose solution significantly reduced the number of viable E. coli. The most pronounced antibacterial effect was achieved by nisin against E. coli K-12 (3 log reduction). Slightly less bactericidal effects were observed with warnerin (1 mg·mL−1) and hominin (1 mg·mL−1) in sucrose solution. The lytic activity of staphylococcal peptides was detected by decreased optical density and viable cell counts. Moreover, it was confirmed by the increased amount of DNA and protein in the medium and the morphological changes detected by atomic force microscopy after 20 h of treatment. Zymographic analysis revealed the release of lytic enzymes from E. coli cells after treatment with staphylococcal peptides and sucrose. These results indicated that the antimicrobial action of peptides can be extended to Gram-negative bacteria via combination with high concentrations of sucrose.

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Posted in E.coli, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Technology, microbial contamination, Microbiology, Research, Staphylococcus aureus, Uncategorized

Research – Weak spot in pathogenic bacteria

Posted on October 12, 2019 by | Leave a comment

Science Daily mrsa

Antibiotics are still the most important weapon for combatting bacterial infections. But medical science is running out of “ammunition” because of more and more frequently occurring resistances. Scientists from the Technical University of Munich and the Max Planck Institute of Molecular Physiology has now elucidated the structure of the proteolytic complex ClpX-ClpP. This is a key to development of innovative antibiotics which target the degradation process of defective proteins in bacteria.

Almost 700,000 people in Europe suffer from infections every year through antibiotic-resistant pathogens; approximately 33,000 of them die. Despite this enormous and globally increasing danger, very few new antibiotics have been developed and approved in the past few decades.

There is no improvement in sight. That is why it is urgently necessary to find new points of attack in pathogenic bacteria and to develop new antibiotics which exploit these weak spots.

New mechanism of action destroys bacteria

A particularly promising point of attack for antibacterial therapies is the proteolytic enzyme ClpP: on the one hand it plays an important role in bacterial metabolism, and on the other hand it ensures the controlled degradation of defective proteins.

But for this purpose it requires the ClpX protein as a starting aid. In the complex with ClpP, ClpX identifies proteins which should be degraded, unfurls them and guides them into its barrel-like degradation chamber.

Scientists in the groups led by Prof. Stephan Sieber, Technical University of Munich (TUM) and Prof. Stefan Raunser, Director at the Max Planck Institute of Molecular Physiology in Dortmund, have now elucidated the three-dimensional structure of the ClpX-ClpP proteolytic complex for the first time and thereby established an important basis for future pharmacological strategies.

A new class of potential antibiotics — the so-called acyldepsipeptide (ADEP) antibiotics — also brings about an uncontrolled degradation through ClpP without the support of ClpX. As a result also vital proteins are destroyed — with lethal consequences for the bacteria.

This unique mechanism of action has considerable innovation potential in the fight against pathogenic bacteria. Whereas common antibiotics act through the inhibition of vital processes, in this case the antibacterial effect is achieved through the activation of a process.

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Posted in Food Micro Blog, Food Microbiology Blog, Food Microbiology Research, Food Pathogen, Food Technology, microbial contamination, Microbiology, Pathogen, pathogenic, Research, Uncategorized

Research – EU – Cryptosporidiosis – Annual Epidemiological Report for 2017

Posted on October 10, 2019 by | Leave a comment

ECDC crypto

Executive summary

Key facts

  • For 2017, 21 EU/EEA countries reported 11 449 cryptosporidiosis cases, of which 11 418 were confirmed.
  • The notification rate was 3.2 confirmed cases per 100 000 population.
  • Germany, the Netherlands and the United Kingdom (UK) accounted for 71% of all confirmed cases, with the United Kingdom alone accounting for 44%.
  • Most of the cases were reported in September 2017, following the seasonal pattern of previous years.
  • Children aged 0–4 years had the highest notification rate of 12.5 cases per 100 000 population.

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Posted in Boil Water Notice, Contaminated water, Cryptosporidium, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, microbial contamination, Microbiology, Research, Uncategorized, Water, water microbiology

Research -Highly virulent listeriosis pathogen discovered

Posted on October 10, 2019 by | Leave a comment

Science Daily

The bacterium Listeria monocytogenes can cause listeriosis, a life-threatening infection in animals and humans. Contaminated food is a frequent source of infection. Elderly people, people with a weakened immune system and pregnant women are particularly at risk with a mortality rate of up to 30 per cent. An international research group led by the Institute of Medical Microbiology at the Justus Liebig University Giessen (JLU) has now discovered the most virulent representatives of this bacterial species to date. They were identified as the cause of serious diseases in sheep in a remote area of the Chinese province Jiangsu.

‘The detection of a completely new form of pathogenic Listeria monocytogenes in China highlights the need for international collaboration’, emphasises Prof. Dr Trinad Chakraborty, Director of the Institute of Medical Microbiology at the JLU and research scientist at the German Center for Infection Research (DZIF). ‘Only by combining resources and expertise can we rapidly identify newly emerging threats to food safety from highly virulent strains worldwide.’

After decoding the genome sequence of these bacteria, the scientists were able to determine the genetic basis for their hypervirulence. They identified the factors that enhance the ability of this Listeria strain to cause severe septic diseases. ‘These isolates are unique in the sense that they combine the virulence characteristics of various highly pathogenic Listeria species that infect animals or humans into a single strain’, says Prof. Chakraborty. ‘Since listeriosis is a food-borne infection, measures to identify such highly virulent strains are extremely urgent.’

Clinical symptoms of listeriosis include fever, blood poisoning (sepsis) and infections of the central nervous system, which can lead to lifelong sequelae. Infections during pregnancy can lead to premature birth, miscarriage or stillbirth. Both raw and processed foods can be contaminated by listeria, especially dairy products, meat, seafood and ready-to-eat products such as pre-packaged salads. Due to the extremely hazardous nature of listeriosis in humans, many countries have set up monitoring systems to quickly identify and recall contaminated food products. Since it can take up to 70 days for a listeria infection to manifest itself with severe symptoms, it can be very difficult to identify the source of contamination and initiate the food recall.

Currently, there are reported listeriosis outbreaks in Germany (Hesse), the Netherlands, Lithuania, Spain, Great Britain, Canada and the United States, posing a particular threat to vulnerable populations. Therefore, considerable efforts are now underway to identify the origin of these pathogens and prevent further outbreaks of listeriosis.

Story Source:

Materials provided by German Center for Infection Research. Note: Content may be edited for style and length.

Journal Reference:

  1. Yuelan Yin, Hao Yao, Swapnil Doijad, Suwei Kong, Yang Shen, Xuexue Cai, Weijun Tan, Yuting Wang, Youwei Feng, Zhiting Ling, Guoliang Wang, Yachen Hu, Kai Lian, Xinyu Sun, Yuliang Liu, Chuanbin Wang, Kuhua Jiao, Guoping Liu, Ruilong Song, Xiang Chen, Zhiming Pan, Martin J. Loessner, Trinad Chakraborty, Xin’an Jiao. A hybrid sub-lineage of Listeria monocytogenes comprising hypervirulent isolates. Nature Communications, 2019; 10 (1) DOI: 10.1038/s41467-019-12072-1

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Posted in Food Hygiene, Food Micro Blog, Food Microbiology Blog, Food Microbiology Research, Food Pathogen, Food Safety, Listeria, Listeria monocytogenes, Research, Uncategorized

Research – Fate of Spoilage and Pathogenic Microorganisms in Acidified Cold-Filled Hot Pepper Sauces

Posted on October 8, 2019 by | Leave a comment

Journal of Food Protection

ABSTRACT

Consumption of spicy foods and hot sauces is currently a popular trend worldwide. Shelf-stable acidified sauces are commonly hot-filled to ensure commercial sterility, but cold-fill-hold processes might also be suitable if microbial safety and stability are ensured. For this study, model acidified hot pepper sauces were developed and characterized. The effects of sauce pH and of two different organic acids on the survival of Pichia manshurica and Lactobacillus curvatus isolated from contaminated commercial hot sauces and on pathogenic Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes were assessed. Full factorial designs with three levels for pH (3.2, 3.5, and 3.9) and two for organic acid (citric and acetic) were used to determine the effects of these factors and their interactions on the survival of the microorganisms. Commercially sterile sauces were independently inoculated and kept at ambient temperature. Microbial counts were determined at different sampling times, depending on the treatment evaluated. Sauces acidified to pH 3.2 with citric or acetic acid were inoculated with cocktails of five strains or serotypes of the three pertinent pathogens, and inactivation curves were determined. Trials were performed in triplicate. A greater than 5-log reduction of P. manshurica and L. curvatus was achieved in less than 6 h in sauces adjusted to pH 3.2 with acetic acid. Greater than 5-log reductions of pathogenic bacteria were achieved 0.5 h after inoculation in sauces acidified to pH 3.2 with acetic acid. In contrast, at least 48 h was required to guarantee the same inactivation for the most tolerant pathogen when citric acid was used. Thus, a cold-fill-hold process may be a suitable alternative for acidified hot pepper sauces. Based on survival of the microorganisms evaluated in this study, microbial safety and stability can be achieved by adjusting the pH to 3.2 or less by the addition of acetic acid.

HIGHLIGHTS

  • pH and acidifier influence safety and stability of cold-filled acidified sauces.

  • Safe and stable cold-filled sauces were obtained at pH 3.2 with acetic acid.

  • Results help establish science-based conditions for cold-filled products.

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Posted in E.coli, E.coli O157, E.coli O157:H7, Food Micro Blog, Food Microbiology Blog, Food Microbiology Research, Food Technology, Listeria, Listeria monocytogenes, microbial contamination, Microbiology, Research, Salmonella, Technology, Uncategorized

USA – Four Sick with Scombroid After Eating Mical Seafood Tuna Products

Posted on October 7, 2019 by | Leave a comment

Food Poisoning Bulletin

Four people are sick since 10/01/2019 with scombroid poisoning after eating Mical Seafood tuna. The company is voluntarily recalling frozen, wild-caught yellowfin tuna poke cubes, tuna loins, tuna ground meat, and 6 ounce tuna steaks because they may have elevated histamine levels. This is the third time in about the last month that yellowfin tuna products have been associated with scombroid poisoning.

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Posted in food contamination, Food Hygiene, Food Illness, Food Inspections, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Poisoning, food recall, Food Safety, Food Safety Alert, Food Testing, Food Toxin, Histamine, Scombroid, scombroid poisoning, Uncategorized

Research – Validation of a High-Throughput Sausage Casing Model for the Assessment of Bacterial Inactivation Affected by Salt Concentration, pH, and Temperature

Posted on October 6, 2019 by | Leave a comment

Journal of Food Protection

ABSTRACT

Previous studies have shown the efficacy of high concentrations of salt as the main preservative against vegetative bacteria present on natural sausage casings. These studies were limited in the number of variables and the interactions between these variables that were assessed. To remedy this situation, a MicroCasing high-throughput model was developed and validated to study the inactivation kinetics of various combinations of parameters (salt concentration, pH, and temperature) on eight bacterial isolates of Salmonella enterica, Staphylococcus aureus, Escherichia coli, and Listeria monocytogenes over a prolonged period. A Weibullian power model was the best fit to show the trends in sensitivity of each bacterial isolate to salt, pH, and temperature over time. The inactivation kinetics generated with this novel approach could serve as a predictive model for the required salting period for casings. The actual bacterial contamination of the product can vary with the respective production step during processing from animal intestine into sausage casings (initial level, ∼105 CFU/g; level after salting, <102 CFU/g). Subsequent selection and grading of these casings will require complete removal of all salt, and upon completion of this production step, the casings will be resalted. By determining the actual contamination level before the salting process, the minimum storage period in salt can be calculated and potentially optimized by adjusting the pH and temperature. As a result, a standard holding period of at least 30 days may no longer be necessary to produce salted natural casings in accordance with validated quality and food safety criteria.

HIGHLIGHTS

  • A new model system was developed for analysis of bacterial inactivation kinetics in foods.

  • The novel model allows determination of product-specific bacterial inactivation over time.

  • Effects of time, temperature, pH, and salt on casing preservation can be clarified with the model.

  • Prediction of inactivation parameters allows casing production to meet HACCP criteria.

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Posted in E.coli, Food Microbiology Research, Food Technology, Listeria, Listeria monocytogenes, Research, Staphylococcus aureus, Technology, Uncategorized

Research – Prevalence of Extended-Spectrum β-Lactamase–Producing Bacteria on Fresh Vegetables in Japan

Posted on October 6, 2019 by | Leave a comment

Journal of Food Protection

ABSTRACT

Extended-spectrum β-lactamase (ESBL)–producing bacteria are spreading rapidly, posing a threat to human and animal health. Contamination of vegetables with antimicrobial-resistant bacteria or those harboring antimicrobial resistance genes or a combination of both presents a potential route of transmission to humans. Therefore, the aim of this study was to determine the prevalence of these bacteria in fresh vegetables in Japan. A total of 130 samples of fresh vegetables were collected from seven supermarkets in Japan. The predominant genus detected was Pseudomonas spp., including 10 ESBL-producing strains, isolated from 10 (7.7%) of the vegetable samples. Two ESBL genes were detected, blaTEM-116 (n = 7) and blaSHV-12 (n = 3), and some of these strains were resistant to multiple antibiotics. Because vegetables are often consumed raw, those contaminated with ESBL producers could represent an important route of transmission to humans in Japan. Thus, more stringent hygiene measures and monitoring are required to prevent transmission via this source.

HIGHLIGHTS

  • Retail vegetables in Japan are not as frequently contaminated by animal feces.

  • ESBL-producing bacteria were isolated from vegetables (7.7%).

  • Two ESBL genes (blaTEM-116 and blaSHV-12) were detected in vegetables.

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Posted in ESBL, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, microbial contamination, Microbiology, Research, Uncategorized

USA – Foodborne illness source attribution estimates for 2017 for Salmonella, Escherichia coli O157, Listeria monocytogenes, and Campylobacter using multi-year outbreak surveillance data, United States,

Posted on October 5, 2019 by | Leave a comment

CDC

In an ongoing effort to understand sources of foodborne illness in the United States, the Interagency Food Safety Analytics Collaboration (IFSAC) collects and analyzes outbreak data to produce an annual report with estimates of foods responsible for foodborne illnesses caused by pathogens. The report estimates the degree to which four pathogens – Salmonella, E. coli O157, Listeria monocytogenes, and Campylobacter – and specific foods and food categories are responsible for foodborne illnesses. The Centers for Disease Control and Prevention (CDC) estimates that, together, these four pathogens cause 1.9 million foodborne illnesses in the United States each year. The newest report (PDF), entitled “Foodborne illness source attribution estimates for 2017 for Salmonella, Escherichia coli O157, Listeria monocytogenes, and Campylobacter using multi-year outbreak surveillance data, United States,” can be found on the IFSAC website.

The updated estimates, combined with other data, may help shape agency priorities and inform the creation of targeted interventions that can help to reduce foodborne illnesses caused by these pathogens. As more data become available and methods evolve, attribution estimates may improve. These estimates are intended to inform and engage stakeholders and to improve federal agencies’ abilities to assess whether prevention measures are working.

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Posted in Campylobacter, E.coli, E.coli O157, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Listeria, Listeria monocytogenes, microbial contamination, Microbiology, Research, Salmonella, Uncategorized