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Category Archives: Biofilm
Biofilms are large aggregates of various species of bacteria or other microorganisms tightly attached to surfaces through an intricate extracellular matrix. These complex microbial communities present quite the challenge in the food processing industry, as conditions such as raw meats and diverse food product content in contact with workers, drains, machinery, and ventilation systems, make for prime circumstances for contamination. Adding to the challenge is the highly resistant nature of these biofilm growths and the need to keep in mind that any antimicrobials utilized in these situations risk health implications with human consumption of the products that are being processed in these locations. For that reason, the ideal means of sanitizing areas of foodborne biofilms would be natural means. Herein, we review a series of innovative natural methods of targeting foodborne biofilms, including bacteriocins, bacteriophages, fungi, phytochemicals, plant extracts, essential oils, gaseous and aqueous control, photocatalysis, enzymatic treatments, and ultrasound mechanisms.
Research – Exploring the Diversity of Biofilm Formation by the Food Spoiler Brochothrix thermosphacta
Brochothrix thermosphacta is considered as a major spoiler of meat and seafood products. This study explores the biofilm formation ability and the biofilm structural diversity of 30 multi-origin B. thermosphacta strains using a set of complementary biofilm assays (biofilm ring test, crystal violet staining, and confocal laser scanning microscopy). Two major groups corresponding to low and high biofilm producers were identified. High biofilm producers presented flat architectures characterized by high surface coverage, high cell biovolume, and high surface area.
Biofilms, complex communities of bacteria, abound around us: on the surface of cheese where they give off flavors and aromas, in streams where they form the slimy substance on rocks, on our teeth where they form plaque.
Living in a biofilm provides numerous advantages to bacteria: things like resource sharing, shelter from predators, and increased resistance to toxic compounds such as antibiotics.
But having the option to leave the biofilm when environmental conditions deteriorate can be a plus for bacteria, too, allowing them to relocate to a more hospitable environment.
”For the bacterium Caulobacter crescentus, the biofilm becomes a kind of prison in perpetuity: once cells are attached to a surface through a strong adhesive at one end of the cell, they cannot leave the biofilm,” said Yves Brun, a professor in the Department of Microbiology, Infectious Diseases and Immunology at Université de Montréal.
”However, when these attached cells divide, their unattached ‘daughter’ cells have a choice of joining the biofilm or swimming away.”
Research -Application of a novel phage ZPAH7 for controlling multidrug-resistant Aeromonas hydrophila on lettuce and reducing biofilms
Aeromonas hydrophila is an important pathogenic bacterium that causes foodborne illness worldwide. In this study, virulent phages from the sediment of a fish farm were propagated and isolated on a multidrug-resistant strain of A. hydrophila, ZYAH75. One phage, designated as ZPAH7, featured a unique turbid halo around a clear plaque on the bacterial lawn (indicative of potential depolymerase activity), and was selected for further analysis. ZPAH7 was classified as podophage by morphological and genomic methods. Further comparisons of genome nucleotide similarity, ratios of homologous proteins and phylogenetic relatedness among the terminase large subunit and major capsid proteins of similar phage deposited in GENBANK, led us to propose a new genus, ZPAH7virus, in the Autographivirinae subfamily of Podoviridae. ZPAH7 had an adsorption rate of 79% in 5 min, an eclipse period of 15 min, a latent period of 25 min, and a burst size of 148 ± 9 PFU/cell. Antimicrobial application experiments showed that ZPAH7 lead to significantly reduction on A. hydrophila on lettuce. Additionally, ZPAH7 was able to inhibit biofilm formation, as well as degrade and kill bacteria in established biofilms. Furthermore, lytic activity of ZPAH7 remained stable across a wide range of temperatures and pH measurements. These results suggest ZPAH7 could be used as a potential biological control agent against A. hydrophila on food and/or biofilms on food contact surfaces.
Research – Bacterial Attachment and Biofilm Formation on Antimicrobial Sealants and Stainless Steel Surfaces
Biofilms are highly resistant to external forces, especially chemicals. Hence, alternative control strategies, like antimicrobial substances, are forced. Antimicrobial surfaces can inhibit and reduce microbial adhesion to surfaces, preventing biofilm formation. Thus, this research aimed to investigate the bacterial attachment and biofilm formation on different sealants and stainless steel (SS) surfaces with or without antimicrobials on two Gram-positive biofilm forming bacterial strains. Antimicrobial surfaces were either incorporated or coated with anti-microbial, -fungal or/and bactericidal agents. Attachment (after 3 h) and early-stage biofilm formation (after 48 h) of Staphylococcus capitis (S. capitis) and Microbacterium lacticum (M. lacticum) onto different surfaces were assessed using the plate count method. In general, bacterial adhesion on sealants was lower compared to adhesion on SS, for surfaces with and without antimicrobials. Antimicrobial coatings on SS surfaces played a role in reducing early-stage biofilm formation for S. capitis, however, no effects were observed for M. lacticum. S. capitis adhesion and biofilm formation were reduced by 8% and 25%, respectively, on SS coated with an antimicrobial substance (SS_4_M), compared to the same surface without the antimicrobial coating (SS_4_control). Incorporation of both antifungicidal and bactericidal agents (S_5_FB) significantly reduced (p ≤ 0.05) early-stage biofilm formation of M. lacticum, compared to the other sealants incoportating either solely antifungal agents (S_2_F) or no active compound (S_control). Furthermore, the thickness of the coating layer correlated weakly with the antimicrobial effect. Hence, equipment manufacturers and food producers should carefully select antimicrobial surfaces as their effects on bacterial adhesion and early-stage biofilm formation depend on the active agent and bacterial species.
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.
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 –
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
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.