Special Issue "Bacterial Biofilms and Its Eradication in Food Industry"

A special issue of Microorganisms (ISSN 2076-2607). This special issue belongs to the section "Biofilm".

Deadline for manuscript submissions: closed (30 November 2020).

Special Issue Editors

Prof. Dr. Giuseppe Comi
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Guest Editor
Department of Food Science, University of Udine, Via Sondrio, 2/a, 33100 Udine, Italy
Interests: food microorganisms; spoilage; safety; hygiene; natural antimicrobial compounds; starters; food bioprotection and improvement; fermented foods and beverages; microbial ecology; toxin and mycotoxin; biomolecular methods
Special Issues and Collections in MDPI journals
Dr. Krzysztof Skowron
E-Mail
Guest Editor
Ludwik Rydygier Collegium Medicum in Bydgoszcz, Bydgoszcz, Poland
Dr. Joanna Kwiecińska-Piróg
E-Mail
Guest Editor
Ludwik Rydygier Collegium Medicum in Bydgoszcz, Bydgoszcz, Poland

Special Issue Information

Dear Colleagues,

In recent years, there has been observed an increase in the number of foodborne infections caused by various microorganisms, including Campylobacter spp., Salmonella spp., Listeria monocytogenes, and many others. This phenomenon may be explained by the microbiological contamination of food, including the primary contamination of the raw materials and the secondary contamination of the final product during its preparation in food plants. One of the main problems in food production is the formation of biofilm by various species of bacteria and fungi.

Many pathogenic microorganisms are able to multiply and then form a biofilm on the surface of food products and within the infrastructure of the food industry. These pathogens are capable of forming biofilm structures on various abiotic surfaces common in the food industry, such as stainless steel, polyethylene, wood, glass, polypropylene, rubber, etc. As a consequence, food products that have contact with such surfaces become a source of pathogens posing a serious threat to the consumer health. Microorganisms whose biofilms constitute the largest and most common problem in food processing plants are, among others, Bacillus cereus, Escherichia coli, Listeria monocytogenes, Salmonella enterica, and Staphylococcus aureus.

Biofilms are complex microbial ecosystems formed by one or more species immersed in the extracellular matrix, with different compositions depending on the type of production environment and colonizing species. The presence of more than one species of bacteria in the biofilm structure significantly affects the increased adhesion of the biofilm to the surface. Mixed biofilms are also characterized by higher resistance to disinfectants, such as quaternary ammonium compounds and other biocides.

The main goal of eradication processes is to reduce the population of microorganisms to the level safe for humans. Sanitization of production equipment is essential to prevent cross-contamination between food batches. Many methods have been developed to prevent and eliminate biofilms in food processing plants, including quorum-sensing inhibition strategies; chemical disinfection; enzymatic degradation strategies of the biofilm structure; non-thermal plasma treatments; and the use of bacteriophages, bacteriocins, biosurfactants, and plant essential oils. Nevertheless, the complex structure of the biofilm results in high resistance of the microorganisms, and thereby it becomes a challenge for scientists to search for new eradication methods that are safe for future consumers and the environment.

For this reason, I believe that there is a need to prepare a Special Issue focused mainly (but not only) on the following:

  • Bacterial single and multi-species biofilms in food processing plants;
  • The impact of environmental conditions in food processing on the formation of biofilms;
  • Physical, chemical, and biological methods of biofilms eradication;
  • Resistance of microrganisms in the biofilm to antimicrobial effects and pheno- and genotypic aspects;
  • The impact of biofilms on the functioning of devices used in food processing plants;
  • The role of biofilms in the spread of microorganisms in food plants;
  • Quorum sensing in biofilms;
  • The mechanism of biofilm formation.

I would like to invite you to submit your most recent contributions to this Special Issue on bacterial biofilms and their eradication in the food industry.

Prof. Giuseppe Comi
Dr. Krzysztof Skowron
Dr. Joanna Kwiecińska-Piróg
Guest Editors

Manuscript Submission Information

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Published Papers (7 papers)

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Research

Open AccessArticle
The Occurrence of Aflatoxins in Nuts and Dry Nuts Packed in Four Different Plastic Packaging from the Romanian Market
Microorganisms 2021, 9(1), 61; https://doi.org/10.3390/microorganisms9010061 - 28 Dec 2020
Viewed by 756
Abstract
Mycotoxins are secondary metabolites produced by various fungi. A very important category of mycotoxins are aflatoxins, considered to be the most dangerous in humans. Aflatoxin B1, well known as a favorable factor in the occurrence of hepatocellular carcinoma in humans, is [...] Read more.
Mycotoxins are secondary metabolites produced by various fungi. A very important category of mycotoxins are aflatoxins, considered to be the most dangerous in humans. Aflatoxin B1, well known as a favorable factor in the occurrence of hepatocellular carcinoma in humans, is the most controversial of all mycotoxins. Aflatoxins, found in naturally contaminated food, are resistant to degradation by heat. Current food processing practices and conventional storage conditions do not completely eliminate aflatoxin contamination from the food supply chain. Long storage food products—such as peanuts, pistachio, nuts in general, and dried fruits—are susceptible to aflatoxins contamination. The type of plastic material can influence the concentration of aflatoxins during storage due to the permeability to gas and moisture exchange with the external milieu. Nuts in general and dried fruits are consumed in large quantities worldwide. Therefore, herein we investigated the effect of plastic material on the total aflatoxins and aflatoxin B1 content in 64 samples of nuts and dried fruits packed and stored in low-density polyethylene (LDPE), polypropylene (PP), polyethylene (PE), and polyethylene terephthalate (PET). The method consisted in a cleanup procedure using immunoaffinity columns coupled with RIDASCREEN FAST immunoenzymatic competitive assays based on the ELISA technique. Collected data were subjected to statistical analysis and multiple comparisons tests were applied. From the total analyzed samples, 14.06% exceeded the maximum admitted European levels for total aflatoxins. The highest concentrations of total aflatoxins were obtained from samples packed in LDPE, followed by PP, PE, and PET. Aflatoxin B1 was detected in all samples packed in LDPE, PP, and PE. Most of the samples packed in PET had concentrations <1 µg/kg. These results indicate that nuts in general packed and stored in LDPE are more prone to contamination with aflatoxins, while PET is more suitable for maintaining the quality and safety of these products. Full article
(This article belongs to the Special Issue Bacterial Biofilms and Its Eradication in Food Industry)
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Open AccessArticle
Influence of Selected Factors on Biofilm Formation by Salmonella enterica Strains
Microorganisms 2021, 9(1), 43; https://doi.org/10.3390/microorganisms9010043 - 25 Dec 2020
Viewed by 467
Abstract
Biofilm formed by S. enterica on the surface of gallstones or biomaterials promotes the development and spread of chronic infection. The aim of the study was to assess biofilm formation on the surface of polystyrene depending on nutritional conditions and the effect of [...] Read more.
Biofilm formed by S. enterica on the surface of gallstones or biomaterials promotes the development and spread of chronic infection. The aim of the study was to assess biofilm formation on the surface of polystyrene depending on nutritional conditions and the effect of 0.5, 1.0, and 2.0% glucose and 3.0% bile and sub-inhibitory concentrations of ampicillin on biofilm formation of S. enterica. Sixty-nine clinical strains of S. enterica isolated from feces (92.8%) and blood (7.2%) collected from patients (66.7%) and carriers (33.3%) were used in the study. Assessment of forming 24-h biofilm by these strains was performed on the surface of polystyrene 96-well plates at 37 °C. In this study, it was indicated that 1.0% glucose and 3.0% bovine bile inhibit biofilm formation. Biofilm formation was inhibited in all examined sub-MIC of ampicillin. Biofilm formation is varied in different conditions, depending on the serovar. Full article
(This article belongs to the Special Issue Bacterial Biofilms and Its Eradication in Food Industry)
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Open AccessArticle
Biofilm Eradication by Symmetrical Selenoesters for Food-Borne Pathogens
Microorganisms 2020, 8(4), 566; https://doi.org/10.3390/microorganisms8040566 - 15 Apr 2020
Cited by 1 | Viewed by 897
Abstract
Infections caused by Salmonella species and Staphylococcus aureus represent major health and food industry problems. Bacteria have developed many strategies to resist the antibacterial activity of antibiotics, leading to multidrug resistance (MDR). The over-expression of drug efflux pumps and the formation of biofilms [...] Read more.
Infections caused by Salmonella species and Staphylococcus aureus represent major health and food industry problems. Bacteria have developed many strategies to resist the antibacterial activity of antibiotics, leading to multidrug resistance (MDR). The over-expression of drug efflux pumps and the formation of biofilms based on quorum sensing (QS) can contribute the emergence of MDR. For this reason, the development of novel effective compounds to overcome resistance is urgently needed. This study focused on the antibacterial activity of nine symmetrical selenoesters (Se-esters) containing additional functional groups including oxygen esters, ketones, and nitriles against Gram-positive and Gram-negative bacteria. Firstly, the minimum inhibitory concentrations of the compounds were determined. Secondly, the interaction of compounds with reference antibiotics was examined. The efflux pump (EP) inhibitory properties of the compounds were assessed using real-time fluorimetry. Finally, the anti-biofilm and quorum sensing inhibiting effects of selenocompounds were determined. The methylketone and methyloxycarbonyl selenoesters were the more effective antibacterials compared to cyano selenoesters. The methyloxycarbonyl selenoesters (Se-E2 and Se-E3) showed significant biofilm and efflux pump inhibition, and a methyloxycarbonyl selenoester (Se-E1) exerted strong QS inhibiting effect. Based on results selenoesters could be promising compounds to overcome bacterial MDR. Full article
(This article belongs to the Special Issue Bacterial Biofilms and Its Eradication in Food Industry)
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Open AccessArticle
Ascorbic Acid Changes Growth of Food-Borne Pathogens in the Early Stage of Biofilm Formation
Microorganisms 2020, 8(4), 553; https://doi.org/10.3390/microorganisms8040553 - 11 Apr 2020
Cited by 1 | Viewed by 843
Abstract
Since bacterial biofilm may contribute to the secondary contamination of food during the manufacturing/processing stage there is a need for new methods allowing its effective eradication. Application of food additives such as vitamin C already used in food industry as antioxidant food industry [...] Read more.
Since bacterial biofilm may contribute to the secondary contamination of food during the manufacturing/processing stage there is a need for new methods allowing its effective eradication. Application of food additives such as vitamin C already used in food industry as antioxidant food industry antioxidants may be a promising solution. The aim of this research was evaluation of the impact of vitamin C (ascorbic acid), in a range of concentrations 2.50 µg mL−1–25.0 mg mL−1, on biofilms of Staphylococcus aureus, Escherichia coli, and Listeria monocytogenes strains isolated from food. The efficacy of ascorbic acid was assessed based on the reduction of optical density (λ = 595 nm). The greatest elimination of the biofilm was achieved at the concentration of vitamin C of 25.0 mg mL−1. The effect of the vitamin C on biofilm, however, was strain dependent. The concentration of 25.0 mg mL−1 reduced 93.4%, 74.9%, and 40.5% of E. coli, L. monocytogenes, and S. aureus number, respectively. For E. coli and S. aureus lower concentrations were ineffective. In turn, for L. monocytogenes the biofilm inhibition was observed even at the concentration of 0.25 mg mL−1. The addition of vitamin C may be helpful in the elimination of bacterial biofilms. Nonetheless, some concentrations can induce growth of the pathogens, posing risk for the consumers’ health. Full article
(This article belongs to the Special Issue Bacterial Biofilms and Its Eradication in Food Industry)
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Open AccessArticle
Quantitative and Compositional Study of Monospecies Biofilms of Spoilage Microorganisms in the Meat Industry and Their Interaction in the Development of Multispecies Biofilms
Microorganisms 2019, 7(12), 655; https://doi.org/10.3390/microorganisms7120655 - 05 Dec 2019
Cited by 5 | Viewed by 806
Abstract
Food spoilage is a serious problem in the food industry, since it leads to significant economic losses. One of its main causes is the cross-contamination of food products from industrial surfaces. Three spoilage bacterial species which are highly present in meat and the [...] Read more.
Food spoilage is a serious problem in the food industry, since it leads to significant economic losses. One of its main causes is the cross-contamination of food products from industrial surfaces. Three spoilage bacterial species which are highly present in meat and the gastrointestinal tract of chickens were selected: Pseudomonas fragi, Leuconostoc gasicomitatum, and Lactobacillus reuteri. The dual aim was to determine their ability to form monospecies biofilms and to examine how they interact when they coexist together. To do so, mature monospecies biofilms were produced statically for seven days at a temperature of 30 °C. L. gasicomitatum was also used to investigate the behavior of P. fragi and L. reuteri in the formation of multispecies biofilms. The structure and composition of the monospecies biofilms were evaluated by direct epifluorescence microscopy, and the multispecies biofilms were evaluated by plate counting. Both L. gasicomitatum and L. reuteri were able to form biofilms, with counts of approximately 7 Log CFU/cm2 and a defined structure. However, P. fragi obtained counts to the order of 4 Log CFU/cm2, which is significantly different from the previous species (P < 0.05), and it had no network of cell conglomerates. The content of the L. gasicomitatum and L. reuteri biofilm matrices were 70–80% protein, unlike P. fragi, which presented a higher polysaccharide content (P < 0.05). In the multispecies biofilms, the presence of P. fragi did not affect the growth of L. gasicomitatum, which remained at between 5.76 to 6.1 Log CFU/cm2. However, L. reuteri was able to displace L. gasicomitatum growth after 24 h of coexisting in a mixed biofilm, presenting differences in counts of approximately 2 Log CFU/cm2. The study of the biofilms constructed by food industry resident microbiota can help to understand the ecological relations that exist between species, characterize them, and propose strategies to eliminate them. The name of genes and species should be written in italic. Full article
(This article belongs to the Special Issue Bacterial Biofilms and Its Eradication in Food Industry)
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Open AccessArticle
Risk Comparison of the Diarrheal and Emetic Type of Bacillus cereus in Tofu
Microorganisms 2019, 7(11), 536; https://doi.org/10.3390/microorganisms7110536 - 07 Nov 2019
Cited by 2 | Viewed by 736
Abstract
We investigated the ability of biofilm formation, survival, and behavior of diarrheal and emetic Bacillus cereus vegetative cells and spores in tofu. Both diarrheal and emetic B. cereus did not proliferate at a temperature below 9 °C in tofu. However, the emetic B. [...] Read more.
We investigated the ability of biofilm formation, survival, and behavior of diarrheal and emetic Bacillus cereus vegetative cells and spores in tofu. Both diarrheal and emetic B. cereus did not proliferate at a temperature below 9 °C in tofu. However, the emetic B. cereus grew faster than diarrheal B. cereus at 11 °C and had better survival ability at low temperatures. Both diarrheal and emetic B. cereus were able to form a biofilm on stainless steel. These biofilm cells were transferred to tofu in live state. The transferred biofilm cells could not grow at a temperature below 9 °C but grew over 11 °C, like planktonic cells. B. cereus contamination in tofu at a high concentration (>6 logs CFU/g) was not entirely killed by heating at 80, 85, or 90 °C for 2 h. Spores and emetic B. cereus had higher resistance to heat than vegetative cells and diarrheal B. cereus, respectively. Full article
(This article belongs to the Special Issue Bacterial Biofilms and Its Eradication in Food Industry)
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Open AccessArticle
Disinfectant Susceptibility of Biofilm Formed by Listeria monocytogenes under Selected Environmental Conditions
Microorganisms 2019, 7(9), 280; https://doi.org/10.3390/microorganisms7090280 - 21 Aug 2019
Cited by 6 | Viewed by 1196
Abstract
Listeria monocytogenes is a one of the most important food-borne pathogens. Its ability to form biofilm contributes to increased resistance to disinfectants and inefficient disinfection, posing a serious threat for the food industry, and in the end the consumer. The aim of this [...] Read more.
Listeria monocytogenes is a one of the most important food-borne pathogens. Its ability to form biofilm contributes to increased resistance to disinfectants and inefficient disinfection, posing a serious threat for the food industry, and in the end the consumer. The aim of this study was the comparison of the biofilm formation ability of L. monocytogenes strains on stainless steel, under different environmental conditions (temperature, pH, NaCl concentration, nutrients availability), and the assessment of biofilm susceptibility to disinfectants. The bactericidal activity of four disinfectants in two concentrations (100% and 50% of working solution) against biofilm was conducted on four clinical strains, four strains isolated from food and one reference strain ATCC 19111. It was found that biofilm susceptibility to disinfectants was influenced by environmental conditions. Biofilm susceptibility correlated with the decrease of temperature, pH, nutrients availability and salinity of the environment. The least sensitive to disinfectants was biofilm produced at pH = 4 (the bacterial number ranged from 0.25 log CFU × cm−2 to 1.72 log CFU × cm−2) whereas the most sensitive was biofilm produced at pH = 9 (5.16 log CFU × cm−2 to 7.84 log CFU × cm−2). Quatosept was the most effective disinfectant, regardless of the conditions. In conclusion, biofilm susceptibility to disinfectants is strain-dependent and is affected by environmental conditions. Full article
(This article belongs to the Special Issue Bacterial Biofilms and Its Eradication in Food Industry)
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