Gov't Research Support, U. Gov't, Non-P. Furthermore, the treatment of S. Considering the rising number of antibiotic-resistant pathogens, QS inhibitors can be used as a mixture with the remaining sensitive antibiotics to complement their effects. These molecules mainly act by suppressing the QS system, and their practice with antibiotics leads to effective cure at much lower dosages of the drug than necessary, which may result in reduced therapeutic costs. These combinations can be beneficial in the cure of chronic infections, such as chronic urinary tract, cystic fibrosis, or prosthetic infections and biofilms are a barrier to antibiotic diffusion in these chronic diseases.
There is an urgent need for new methods in the cure of biofilm-associated infections. For instance, cyclic di-GMP c-di-GMP is a commonly protected prokaryotic second messenger signal molecule necessary for biofilm development [ 58 ].
New inhibitors of diguanylate cyclase enzymes were identified by using in silico screening, and they tested them successfully in vitro. Inhibitors of flow pumps can also be recommended to complement the effect of antimicrobial agent and needed to be tested in vivo.
The choice of antimicrobial agents also seems to be significant because some of them may act as agonists for biofilm formation and some may disrupt it. The usage and dosages of novel antibiotics should be checked and clinically synthesized antibiotics should be tested at impactful concentrations by considering their distribution in biofilms and the detrimental effects of signaling molecules.
Other compounds act as key enzymes in the biosynthesis of these signaling molecules and play a role in regulating virulence factor production and biofilm formation. A ligand-based strategy will allow the identification of new inhibitors in the future. Better usage of the new active molecules can be supported by understanding mechanisms of antimicrobial agents activity as well as the molecular mechanisms associated with biofilm formation and recalcitrance [ 5 ]. Biofilm infections are highly resistant to antibiotics and physical treatments and it is known that there are many strategies that support biofilm antibiotic resistance and tolerance, such as persistent cells, adaptive responses, and limited antibiotic penetration.
It is also known that the underlying mechanisms of antibiotic tolerance and resistance in biofilms have a genetic basis in many cases. In human diseases, highly organized bacterial cells gradually induce immune responses to form biofilms responsible for chronic infections that lead to tissue damage and permanent pathology.
Therefore, the formation of biofilm is considered a critical concern in health care services. Exploring promising cure methods for biofilm-associated infections is an urgent task.
Few innovative and effective antibiotic strategies have been tried, such as dispersion of biofilms, antibiotic combinations with quorum sensing inhibitors, and a mixture of all these new techniques. Although the mentioned anti-biofilm strategies are important research areas, they are still in infancy and have not undergone clinical research and entered the commercial market.
We hope that new anti-biofilm molecules based on finding universal substances that do not harm cells and synergistic with commonly used antibiotics will be available in the near future. Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution 3.
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Downloaded: Abstract Biofilms can be found on several living and nonliving surfaces, which are formed by a group of microorganisms, complex assembly of proteins, polysaccharides, and DNAs in an extracellular polymeric matrix.
Keywords biofilm antibiotic resistance bacteria antimicrobial agents. Introduction Bacteria can grow in biofilms on a wide variety of surfaces and attach to inert or alive surfaces, including tissues, industrial surfaces, and artificial devices, such as catheters, intrauterine contraceptive devices, and prosthetic medical devices, implants, cardiac valves, dental materials, and contact lenses [ 1 , 2 ].
More Print chapter. How to cite and reference Link to this chapter Copy to clipboard. Available from:. Vats, N. Active detachment of Streptococcus mutans cells adhered to epon-hydroxylapatite surfaces coated with salivary proteins in vitro.
Oral Biol. An interesting and significant report on the regulation of autodispersion of biofilms. Jackson, D. Biofilm formation and dispersion under the influence of the global regulator CsrA of Escherichia coli. Choi, J. Identificationof virulence genes in a pathogenic strain of Pseudomonas aeruginosa by representational difference analysis.
Hubank, M. Nucleic Acids Res. Jander, G. Positive correlation between virulence of Pseudomonas aeruginosa mutants in mice and insects. A well-conducted investigation of the differences in virulence of an important pathogen in different model hosts. Tan, M. Killing of Caenorhabditis elegans by Pseudomonas aeruginosa used to model mammalian bacterial pathogenesis.
Natl Acad. USA 96 , — Pseudomonas aeruginosa killing of Caenorhabditis elegans used to identify P. Brooun, A. A dose-response study of antibiotic resistance in Pseudomonas aeruginosa biofilms. Riddle of biofilm resistance. Latifi, A. A hierarchical quorum-sensing cascade in Pseudomonas aeruginosa links the transcriptional activators LasR and RhlR VsmR to expression of the stationary-phase sigma factor RpoS.
Fuqua, W. Quorum sensing in bacteria: the LuxR-LuxI family of cell density-responsive transcriptional regulators. May, T. Alginate synthesis by Pseudomonas aeruginosa : a key pathogenic factor in chronic pulmonary infections of cystic fibrosis patients.
Singh, P. Quorum-sensing signals indicate that cystic fibrosis lungs are infected with bacterial biofilms. Download references. You can also search for this author in PubMed Google Scholar. A microscopy technique which uses scanning laser light to excite fluorescent dyes within a thick sample, such as a biofilm. The image is collected in two dimensions and several images can be combined in an image stack to produce a cross sectional image through a sample or to create a three-dimensional rendering of the sample.
CLSM is particularly useful for imaging the positioning of biological structures within a three dimensional space.
Infection of the gingival crevice periodontal pocket of the oral cavity with a variety of microorganisms, causing inflammation of the periodontal tissue and bone loss. Caused by members of the genus Capnocytophaga , Porphyromonas , Rothia and others.
A molecular pump integrated into the cell envelop of certain bacteria which is able to transport antibiotics into and out of the cell. Latin for nest, but in this context a place or point in a host where a pathogen can develop and breed. A complex of blood serum proteins of the immune system that interact sequentially with antibody—antigen complexes.
A network of long-chain polymers produced by microorganisms of a biofilm which supports the structure of the biofilm. Upon exhaustion of nutrients, members of the group of fruiting myxobacteria swarmer cells migrate together and undergo differentiation into stalk cells, forming a vertical structure rising above a surface.
A structure of the fruiting myxobacteria at the end of a stalk composed of differentiated cells which are converted to myxospores resting bodies. A mobile segment of DNA that has the ability to integrate into a chromosome. Transposons usually carry genes that are used in transposition as well as other genes, often selectable markers, such as for antibiotic resistance. The disaggregation of a biofilm or biofilm microcolony as a result of physiological activity of the resident microorganisms.
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Skip to main content Thank you for visiting nature. Key Points Biofilm bacteria have been demonstrated to be significant contributors to human disease, yet our understanding of the nature of biofilm infections and their effective treatment remains underdeveloped. Access through your institution. Buy or subscribe. Rent or Buy article Get time limited or full article access on ReadCube.
Figure 1: Five stages of biofilm development. Figure 2: Biofilm resistance to anibiotic addition. Figure 3: Antibiotic penetration. Figure 4: Metabolic activity in a biofilm mirocolony. References 1 Lawrence, J. Google Scholar 14 Luppens, S. Google Scholar 23 Yu, F. Google Scholar 28 Olson, M. Google Scholar 31 Moran, F. Google Scholar 41 Campanac, C. Google Scholar 52 Morisaki, H.
Google Scholar 64 Santos, R. Google Scholar 65 Davies, D. The interaction between these and other factors determines its fate [ 46 ]. As shown in Figures 1 and 2 , structural and physiological change takes place after cells have been attached to conditioned surfaces. Structural polymeric substances produced are acting as a barrier [ 31 ] and prevent the entrance of antibiotics and sanitizer agents. Bacterial cell growth within biofilm is very slow and produces persistent cells that can survive hostile conditions such as exposure to antibiotics and other biocides [ 6 , 33 ] Figure 2.
Microbial cells within a biofilm are very close to each other so that they can communicate through chemicals that enable them to coordinate and respond to any ecological, environmental, and host related cues [ 49 ].
According to Oliveira et al. For this cooperative activity, there must be cell-to-cell communication. This cell-to-cell communication mechanism within the microbial community is known as quorum sensing in which microorganisms use signaling such as acyl homoserine lactone AHL in Gram-negative bacteria, the autoinducing peptide AIP in Gram-positive bacteria, and the autoinducer-2 AI-2 in both Gram-negative and -positive bacteria for a different purpose [ 36 , 51 ].
Quorum sensing QS system is a mechanism by which bacteria regulate the gene expression profile according to the size of the microbial population, causing the formation of different forms of biofilm [ 7 ]. As a general quorum sensing is a process by which bacteria produce and detect signal molecules and thereby coordinate their behavior in a cell-density-dependent manner [ 36 ].
In addition to communication, these close contacts microbial communities enable them to exchange genetic material, and even the frequency of gene transfer is high when compared to their free form [ 52 ]. Therefore, horizontal microbial gene transfer and biofilm formation are interrelated [ 53 ]. For biofilm formation, microorganisms should transit from their free form into a sessile form which requires stepwise physiological and structural changes [ 47 , 54 ].
Thus, these stepwise and dynamical process comprises a initial or reversible attachment on the conditioned surface, b irreversible attachment c , microcolony or early development of biofilm structure, d maturation of biofilm which forms mushroom or tower-like structure, and e dispersion or detachment in which cells slough off from the matrix and return to their original free form [ 47 , 55 ] Figure 1.
Therefore, the aim of this review article is to provide an overview of the role of bacterial biofilm in antibiotic resistance and food contamination. Bacterial surface attachment represents a turning point from planktonic life to the biofilm mode [ 56 ]. Reversible attachment involves an interaction of planktonic microorganisms with a conditioned surface [ 57 — 59 ].
But the interaction is very weak which involves van der Waals, electrostatic forces and hydrophobic interactions. It has been reported that the attachment will be best on surfaces that are rough, hydrophobic, and coated with different organic substances [ 44 ].
Bacterial structures such as the fimbriae, pili and flagella give strength to the interaction between bacteria and the surface of attachment [ 60 ]. Generally, cell appendages involved in the reversible attachment and bacteria at this stage commit to the biofilm lifestyle or leave the surface and return to the planktonic lifestyle [ 56 ].
After microorganisms are attached on preconditioned and permissive surfaces, then the cell starts an irreversible adhesion and accumulates as multilayered cell clusters [ 61 ]. As recent studies revealed biofilm formation is commenced with a layer of polymeric substances EPS in which microbial cells are swarming on the surface with subsequent growth of the biofilm [ 62 ]. During this step, a number of physiological and structural changes have occurred, such as nonmotility of the attached cells [ 58 ].
Microbial cells embedded within the extracellular matrix undergo coordinated community growth that leads to the formation of microcolonies. According to Dunne, microcolony formation results from simultaneous aggregation and growth of microorganisms and is accompanied by the production of EPS [ 57 ].
Microcolonies which are basic units of biofilm are compartmentalized by channels with different distinct microenvironments [ 29 ] Figure 1. After these sequential events, microcolonies are produced. If conditions are suitable for sufficient growth and differentiation, a biofilm may develop into spatially well-arranged, three-dimensional mature biofilm structures [ 61 ] such as mushroom or tower-like structures interspersed with fluid filled channels in which nutrients, oxygen, and essential substances can be diffused and circulate in each microenvironment [ 51 ] Figure 1 and 2.
The development of biofilm is a cooperative group behavior mediated by density-dependent chemical signals released by bacterial populations embedded in a self-produced extracellular matrix [ 63 ].
This signaling mechanism is known as quorum sensing which is used to communicate and orchestrate group behaviors, including virulence factor secretion and biofilm formation [ 64 , 65 ]. Quorum sensing activates the maturation and disassembly of the biofilm in a coordinate manner [ 63 ]. Generally, cell-to-cell signaling plays a tremendous role in cell attachment and detachment from biofilm [ 66 ].
Biofilm formation is a cyclical process in which bacterial cells are detached from the mature biofilm and enter into their previous mode of life, i. As shown in Figure 1 , detached bacterial cells will seek new surfaces to attach and start up a new round of biofilm formation. From a food contamination point of view, this step is important to disseminate microorganisms into food products.
Biofilm cells can be detached from actively growing cells or from the deprived environment, communication, or removal of aggregates. It has been reported that nutrient limitation forces microorganisms to seek new environments [ 29 , 46 ]. The emergence and spread of antimicrobial resistance among bacteria are the most important health problems worldwide [ 67 — 69 ].
Antibiotic resistance is one of the consequences of the bacterial biofilm communities which contribute to chronic infections [ 67 ]. Biofilm-forming Klebsiella pneumoniae is an important multidrug-resistant MDR pathogen affecting humans and a major source for hospital infections associated with high morbidity and mortality due to limited treatment options [ 70 ]. It has been reported that biofilm formation is a means for a bacterium to resist hostile environmental influences such as antibiotics and antimicrobial agents [ 70 — 73 ].
As Verderosa et al. This is because the formation of biofilms and subsequent encasement of bacterial cells in a complex matrix can enhance resistance to antimicrobials and sterilizing agents making these organisms difficult to eradicate and control [ 75 — 77 ]. The extracellular polymeric substances EPS matrix protects bacteria from antibiotics, avoiding drug penetration at bactericidal concentrations [ 38 ] Figures 1 and 2.
Bacteria within a biofilm are several orders of magnitude more resistant to antibiotics, compared with planktonic bacteria [ 78 ]. For instance, biofilms can tolerate antimicrobial agents at concentrations of 10— times that needed to inactivate genetically equivalent planktonic bacteria [ 79 ].
As shown in Figures 1 and 2 , the nature of biofilm structure and other physiological changes such as slow growth rate assists them to be resistant to antimicrobial agents [ 66 , 80 ] Figures 1 and 2. These mechanisms are critical for antibiotic resistance and survival of biofilm bacteria [ 73 , 82 ]. The antibiotic resistance used by bacteria in biofilm is distinct and different from natural or innate resistance mechanisms [ 48 ] Figure 2.
As similar findings revealed bacteria within biofilm develop different molecular strategies to protect their cells from hostile conditions such as the interaction of biofilm matrix with antibiotics that can retard or lower their activities, slow growth rates in which antibiotics will not be effective, genetic related resistance, and producing persistent cells which are tolerant to different antibiotics [ 38 ] Figure 2.
In biofilm-forming bacteria, there is a high rate of mutation that enables them to develop resistant mechanisms, and this, in turn, gives an opportunity for their genes to produce enzymes that inactivate the antibiotics or expel the antibiotics using efflux pumps [ 34 , 83 ].
Bacteria within biofilm produce persister cells that are metabolically inert and it is one of their mechanisms to escape from antibiotics and even they have the ability to survive in high concentration of antibiotics [ 84 ] Figure 2.
Biofilm plays a critical role in the spread of antibiotic resistance. Within the high dense bacterial population, efficient horizontal transfer of resistance and virulence genes takes place [ 85 ]. The number of microorganisms within the matrix is too dense so that there is close contact between different microorganisms which enable them to exchange resistant genes and finally, the whole community may acquire that resistant gene [ 68 ] Figures 1 and 2.
Therefore, genetic diversification of microorganisms in biofilm is largely responsible for shaping antibiotic resistance [ 7 ]. As studies have suggested that biofilm is important for the transfer of conjugative plasmids due to the high proximity of cells within this multicellular structure [ 86 ]. The resistance of biofilm to antibiotics depends on different factors such as physical, physiological, and gene-related factors [ 34 ]. Thus, this multifactorial nature of biofilm development and drug tolerance imposes great challenges for the use of conventional antimicrobials [ 37 ].
To sum up, bacterial biofilm is a key player in the development of antimicrobial resistance [ 38 ]. Food contamination by pathogenic microorganisms has been a critical public health problem and a cause of huge economic losses worldwide [ 4 ]. Microbial biofilm contains both food spoiler and disease-causing bacteria and results in postprocessing contamination which lowers the quality and shelf life of products and could be a means for disease transmission [ 87 — 89 ].
Among many pathogens, Staphylococcu s aureus and Pseudomonas aeruginosa are capable of constructing the biofilm on materials and equipment [ 91 ]. Friedlander et al. Biofilm production by bacteria such as Listeria monocytogenes is supposed to be one of the ways that confer its increased resistance and persistence in the food chain [ 93 ].
The formation of biofilms on biotic and abiotic surfaces is a potential hazard, contributing to the constant circulation of pathogens in the conditions of food production and contamination of foods [ 94 ]. Pathogenic bacteria penetrate food production areas and may remain there in the form of a biofilm covering the surfaces of machines and equipment [ 95 ].
Therefore, biofilm formation by pathogenic bacteria leads to severe contamination problems in food, food processing, and other areas that directly affect human health and life [ 10 , 96 ]. In a hygienic point of view, the attachment of pathogenic microorganisms to food-contact surfaces can lead to potential sanitation problems since it is persistent for long periods in hostile conditions and reservoir for contamination [ 16 , 23 , 96 , 97 ].
In a research conducted on Cronobacter sakazakii , it has been reported that this bacterium is able to adhere to different surfaces such as silicon, latex, polycarbonate, stainless steel, glass, and polyvinyl chloride PVC.
Biofilm formation on stainless steel surfaces of food processing plants, leading to foodborne illness outbreaks, is enabled by the attachment and confinement of pathogens within microscale cavities of surface roughness grooves, scratches [ 98 ].
The attachment of microorganisms on the food preparation surface could enable microorganisms to form biofilm and become a source of contamination [ 87 ]. In addition to being the source of contamination, biofilms also reduce the efficiency of production and materials used in food processing [ 99 ].
Biofilms embedded in the protective extracellular polymeric substances EPS are difficult to remove in food production facilities [ ]. Therefore, there must be appropriate methods to prevent, reduce, control, and eradicate biofilm formation on food and processing surfaces.
Biofilm has a detrimental impact on antibiotic resistance and food contamination [ 61 ]. Biofilm-forming pathogenic microorganisms are a major public health problem that is tolerant or recalcitrant to sanitizer [ 12 , 23 ]. Prevention of the formation of biofilms in the industry is a crucial step in fulfilling the requirement of a safe and high-quality product. However, practically preventing or eradicating biofilm formation on food and the food processing environment once and for all is difficult [ ].
These principles are critical in inspecting early failures in food processing and production so that immediate action will be taken without product, economy, and time wastage.
Most biofilm remediation approaches involve antibiofilm agents that target early stages of biofilm formation or biofilm dispersal agents which disrupt the biofilm cell community [ 74 ]. For instance, the utilization of acidic electrolyzed water is aimed at disrupting microbial matrix and selected as a promising sanitizing agent in the food sector [ ].
Small molecules such as antivirulence compounds, antibiofilm compounds, aryl rhodanines, chelators, N-acetylcysteine, and others can act as antibiofilm to inhibit biofilm formation [ 71 ]. Using biocontrol strategies such as bacteriocins and enzymes is considered important for the maintenance of biofilm-free systems for the quality and safety of foods [ 13 , — ]. Similarly, different methods have been suggested and used to prevent and control biofilm formation such as surface modifications, cell-signal inhibition, chemical treatments, nonthermal plasma treatments, and the use of biosurfactants [ 13 , ].
For example, Brackman and Coenye [ 36 ] suggested quorum sensing inhibitors as promising antibiofilm agents. The other methods employed in preventing or reducing biofilm formation are disinfection. The apparatus used in the industries should be properly cleaned and disinfected, which would avoid any growth of microorganisms [ 23 ]. However, the disinfection of food-contact surfaces and environments is difficult because of sanitizer and disinfectant resistance of biofilm associated bacteria.
Therefore, to overcome this problem, appropriate usage and selection of detergents and disinfectants coupled with physical methods can be suitably applied for controlling biofilm formation on food-contact surfaces [ ]. There are also alternative approaches such as essential oil and bacteriophage tested as an option for the disinfection of microbial-contaminated food-contact surfaces [ 21 , , ]. A similar recommendation was also forwarded by Sadekuzzaman et al.
As an example, antimicrobial peptides are effective and used to inhibit biofilm formation by the following mechanisms: a dismantling the membrane that embeds bacterial cells, b inhibition of their communication networks or signaling systems [ ], c disrupting the polymeric matrix, d blocking the alarmone system to prevent a bacterial response, and f downregulating of genes critical for biofilm formation [ ].
Similar findings showed that both natural compounds and synthetic analogues were used and were effective in preventing biofilm formation by quorum-quenching [ 76 , ]. Foods can be contaminated by different microorganisms and become a vehicle for foodborne pathogens and intoxication. Food contamination has been attributed to biofilms which are microbial communities living together that can be attached to biotic and abiotic surfaces.
Once they attached irreversibly on these surfaces, they develop mature structures that act as a barrier against sanitizer and other agents. Consequently, they will be a source of postcontamination on later stages and resistant to harsh environmental conditions such as sanitizer.
The surface in which foods can be processed must be cleaned and disinfected frequently using appropriate and effective sanitizers that can disrupt microbial cells and their attachment on food surfaces and environments. The nature of the surface in which foods can be processed is also paramount for biofilm formation.
Therefore, it is better to design appropriate materials using technology which will reduce microbial attachment and conducive for cleaning. In addition to applying sanitizers and other agents, it is better also to understand their genes which are involved in encoding microbial cell surfaces that are important for attachment.
The other critical issue in microbial biofilm formation is molecular cross talk or communication with their relatives by releasing signaling molecules that can alarm others for survival in hostile environments. Thus, appropriate methods should be developed to block their communication systems. Biofilm-forming microorganisms present a serious problem in the medical sector. Biofilm-forming bacteria are encased in a matrix that enables them to exclude antibiotics and host immune response.
In addition to having structural barriers, biofilm-forming bacteria can undergo physiological changes such as slow growth rate and producing persistent cells. In these occasions, antibiotics cannot inhibit, kill, or eradicate these slow-growing and persistent cells which are found inside the biofilm matrix.
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