Category Archives: Biofilm

Research – Biofilm formation in food industries: A food safety concern

Academia Edu

Foodborne diseases have always been a threat to human health. They are considered an emergent public health concern throughout the world. Many outbreaks have been found to be associated with biofilms. It is well documented that biofilms have become a problem in food industries as it renders its inhabitants resistant to antimicrobial agents and cleaning. In this review, biofilms formation in dairy, fish processing, poultry, meat, and Ready-To-Eat foods industries are discussed, as well as the biofilms forming abilities of various microorganisms and the influence of food contact surface materials on biofilm formation. In addition, the conventional and emergent control strategies used to gain more proximity to efficiently maintain good hygiene throughout food industries is discussed.

Research – Project seeks to grow knowledge of Listeria in dairy sites

Food Safety News

An ongoing project is identifying the bacteria present in dairy processing environments to evaluate the impact on Listeria monocytogenes.

Teagasc in Ireland and the University of Veterinary Medicine Vienna in Austria are collecting samples from dairy processing plants and characterizing the microorganisms, with the aim being to prevent the presence of harmful pathogens.

The LmRNA project is gaining an understanding of Listeria monocytogenes’ response to dairy environment conditions. Mock communities of microorganisms are being created in the laboratory to mimic what is found in dairy environments. The role of other microorganisms is being investigated to determine their impact on Listeria monocytogenes.

A food processing environment is not sterile and the presence of some microorganisms in cheese production can be desired. During dairy processing, milk components may adsorb to surfaces enhancing attachment and biofilm formation.

Research – Interactions Between Infectious Foodborne Viruses and Bacterial Biofilms Formed on Different Food Contact Surfaces


Bacterial biofilms contribute to contamination, spoilage, persistence, and hygiene failure in the food industry, but relatively little is known about the behavior of foodborne viruses evolving in the complex communities that make up biofilm. The aim of this study was to evaluate the association between enteric viruses and biofilms on food contact surfaces. Formed biofilms of mono- and multispecies cultures were prepared on glass, stainless steel, and polystyrene coupons and 105 pfu/ml of murine norovirus, rotavirus, and hepatitis A virus were added and incubated for 15 min, 90 min, and 24 h. The data obtained clearly demonstrate that the presence of biofilms generally influences the adhesion of enteric viruses to different surfaces. Many significant increases in attachment rates were observed, particularly with rotavirus whose rate of viral infectious particles increased 7000 times in the presence of Pseudomonas fluorescens on polystyrene after 24 h of incubation and with hepatitis A virus, which seems to have an affinity for the biofilms formed by lactic acid bacteria. Murine norovirus seems to be the least influenced by the presence of biofilms with few significant increases. However, the different factors surrounding this association are unknown and seem to vary according to the viruses, the environmental conditions, and the composition of the biofilm.

Research – Effect of sub-lethal treatment of carvacrol and thymol on virulence potential and resistance to several bactericidal treatments of Staphylococcus aureusResearch –

Journal of Food Protection

This study examined the changes in biofilm-formation ability, hemolytic/lipase/nuclease/protease activities, and resistance to various bactericidal treatments of Staphylococcus aureus after sublethal treatment with carvacrol and thymol. The minimum inhibitory concentrations (MICs) of carvacrol and thymol for S. aureus were 0.4 and 0.3 mg/ml, respectively, and sublethal concentrations (1/2 and 1/4 MIC) were determined based on these concentrations. Sublethal treatment with carvacrol and thymol did not change the protease and lipase activities but reduced the hemolytic and nuclease activities of S. aureus. After sublethal treatment with carvacrol and thymol, the biofilm-formation ability of S. aureus was decreased, which was found to be due to the decrease in cell surface hydrophobicity. In addition, after sublethal treatment with carvacrol and thymol, the resistance of S. aureus to heating and malic acid treatments increased, whereas resistance to ultraviolet and hypochlorous acid (HOCl) decreased, and resistance to hydrogen peroxide (H2O2) did not change. The results of this study show that sublethal treatment with carvacrol and thymol can effectively suppress some virulence factors of S. aureus and that applying HOCl or ultraviolet radiation would be an effective subsequent treatment to inactivate S. aureus after sublethal treatment.

Research – Influence of Different Stainless-Steel Finishes on Biofilm Formation by Listeria monocytogenes

Journal of Food Protection

Biofilm formation of L. monocytogenes on stainless steel, a widely used abiotic surface in the food processing industry was investigated, focusing on the attachment tendency and behavior of L. monocytogenes 08-5578 on eight different Stainless-steel surfaces: glass bead blasted (rough and fine), deburred (Timesaver), drum deburred, pickled, pickled and drum polished, electrolytic polished and cold rolled (untreated control). The aim was to see if there are finishes with significant lower bacterial attachment. Roughness properties (Ra, Rt, Rz, RSm; determined by interferometry) were also compared with number of adhering cells to detect possible correlations. Cultivation of L. monocytogenes biofilms was carried out using a CDC biofilm reactor (CBR) with 1% TSB set at 20°C for 4, 8, and 24 h. Additionally, a cultivation trial was run with continuous nutrient flow (1% TSB, 6.2 ml/min) for 24 h. Eight hour results showed significant difference ( P < 0.05) in biofilm cell counts in biofilms between the glass bead blasted surfaces (3.23 and 3.26 log CFU/cm 2 for the fine and rough, respectively) and deburred (Timesaver) surface (2.57 log CFU/cm 2 ); between drum deburred and deburred (Timesaver) surface (3.41 vs 2.57 log CFU/cm 2 ); between drum deburred and pickled surface (3.41 vs 2.77 log CFU/cm 2 ). Data gained after 4, 24 h and the additional 24 h continuous flow cultivation showed no significant difference in attachment among surfaces. No correlation between roughness data and attachment was found after all 4 incubation times, suggesting that roughness values, at these ranges, are insufficient in determining surfaces’ affinity to bacteria. This study suggests that roughness values cannot be used to predict the degree of L. monocytogenes attachment to a specific stainless steel surface.

Research – Bacteriocin Production by Escherichia coli during Biofilm Development


Escherichia coli is a highly versatile bacterium ranging from commensal to intestinal pathogen, and is an important foodborne pathogen. E. coli species are able to prosper in multispecies biofilms and secrete bacteriocins that are only toxic to species/strains closely related to the producer strain. In this study, 20 distinct E. coli strains were characterized for several properties that confer competitive advantages against closer microorganisms by assessing the biofilm-forming capacity, the production of antimicrobial molecules, and the production of siderophores. Furthermore, primer sets for E. coli bacteriocins–colicins were designed and genes were amplified, allowing us to observe that colicins were widely distributed among the pathogenic E. coli strains. Their production in the planktonic phase or single-species biofilms was uncommon. Only two E. coli strains out of nine biofilm-forming were able to inhibit the growth of other E. coli strains. There is evidence of larger amounts of colicin being produced in the late stages of E. coli biofilm growth. The decrease in bacterial biomass after 12 h of incubation indicates active type I colicin production, whose release normally requires E. coli cell lysis. Almost all E. coli strains were siderophore-producing, which may be related to the resistance to colicin as these two molecules may use the same transporter system. Moreover, E. coli CECT 504 was able to coexist with Salmonella enterica in dual-species biofilms, but Shigella dysenteriae was selectively excluded, correlating with high expression levels of colicin (E, B, and M) genes observed by real-time PCR. View Full-Text

Research – Control Measurements of Escherichia coli Biofilm: A Review


Escherichia coli (E. coli) is a common pathogen that causes diarrhea in humans and animals. In particular, E. coli can easily form biofilm on the surface of living or non-living carriers, which can lead to the cross-contamination of food. This review mainly summarizes the formation process of E. coli biofilm, the prevalence of biofilm in the food industry, and inhibition methods of E. coli biofilm, including chemical and physical methods, and inhibition by bioactive extracts from plants and animals. This review aims to provide a basis for the prevention and control of E. coli biofilm in the food industry. View Full-Text

Microbial Biofilms at Meat-Processing Plant as Possible Places of Bacteria Survival


Biofilm of antibiotic resistant bacteria

Biofilm contamination in food production threatens food quality and safety, and causes bacterial infections. Study of food biofilms (BF) is of great importance. The taxonomic composition and structural organization of five foods BF taken in different workshops of a meat-processing plant (Moscow, RF) were studied. Samples were taken from the surface of technological equipment and premises. Metagenomic analysis showed both similarities in the presented microorganisms dominating in different samples, and unique families prevailing on certain objects were noted. The bacteria found belonged to 11 phyla (no archaea). The dominant ones were Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria. The greatest diversity was in BFs taken from the cutting table of raw material. Biofilms’ bacteria may be the cause of meat, fish and dairy products spoilage possible representatives include Pseudomonas, Flavobacterium, Arcobacter, Vagococcus, Chryseobacterium, Carnobacterium, etc.). Opportunistic human and animal pathogens (possible representatives include Arcobacter, Corynebacterium, Kocuria, etc.) were also found. Electron-microscopic studies of BF thin sections revealed the following: (1) the diversity of cell morphotypes specific to multispecies BFs; (2) morphological similarity of cells in BFs from different samples, micro-colonial growth; (3) age heterogeneity of cells within the same microcolony (vegetative and autolyzed cells, resting forms); (4) heterogeneity of the polymer matrix chemical nature according to ruthenium red staining.

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



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 – Biofilm Formation of Listeria monocytogenes and Pseudomonas aeruginosa in a Simulated Chicken Processing Environment


This study aims to investigate the mono- and dual-species biofilm formation of Listeria monocytogenes and Pseudomonas aeruginosa incubated in different culture mediums, inoculum ratios, and incubation time. The planktonic cell population and motility were examined to understand the correlation with biofilm formation. The results showed that chicken juice significantly inhibited the biofilm formation of L. monocytogenes (p < 0.05). Pseudomonas aeruginosa was the dominant bacteria in the dual-species biofilm formation in the trypticase soy broth medium. The dynamic changes in biofilm formation were not consistent with the different culture conditions. The growth of planktonic L. monocytogenes and P. aeruginosa in the suspension was inconsistent with their growth in the biofilms. There was no significant correlation between motility and biofilm formation of L. monocytogenes and P. aeruginosa. Moreover, scanning electron microscopy (SEM) results revealed that the biofilm structure of L. monocytogenes was loose. At the same time, P. aeruginosa formed a relatively dense network in mono-species biofilms in an initial adhesion stage (24 h). SEM results also showed that P. aeruginosa was dominant in the dual-species biofilms. Overall, these results could provide a theoretical reference for preventing and controlling the biofilm formation of L. monocytogenes and P. aeruginosa in the food processing environment in the future. View Full-Text

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