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PRIZE WINNING ESSAY
Year : 2011  |  Volume : 15  |  Issue : 2  |  Page : 111-114  

Biofilms: A microbial home


Department of Periodontics, Modern Dental College and Research Centre, Indore, Madhya Pradesh, India

Date of Submission25-Nov-2009
Date of Acceptance11-Apr-2010
Date of Web Publication30-Aug-2011

Correspondence Address:
Ruchi Banthia
814, Jagriti Nagar, Near Dev Shree Talkies, Indore, Madhya Pradesh - 452 001
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0972-124X.84377

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   Abstract 

Microbial biofilms are mainly implicated in etiopathogenesis of caries and periodontal disease. Owing to its properties, these pose great challenges. Continuous and regular disruption of these biofilms is imperative for prevention and management of oral diseases. This essay provides a detailed insight into properties, mechanisms of etiopathogenesis, detection and removal of these microbial biofilms.

Keywords: Biofilm, microbes, periodontal disease


How to cite this article:
Chandki R, Banthia P, Banthia R. Biofilms: A microbial home. J Indian Soc Periodontol 2011;15:111-4

How to cite this URL:
Chandki R, Banthia P, Banthia R. Biofilms: A microbial home. J Indian Soc Periodontol [serial online] 2011 [cited 2019 Jan 22];15:111-4. Available from: http://www.jisponline.com/text.asp?2011/15/2/111/84377


   Introduction Top


Oral cavity is an open growth system with an uninterrupted introduction and removal of microbes and their nutrients. It offers diverse habitats where-in different species of micro-organisms can prosper. The primary requisite for any group of microbes to flourish in a niche is their ability to adhere to the tooth surfaces and multiply in shielded environments like periodontal pockets and tooth crevices. Such an aggregation of microbes on tooth surfaces has been traditionally referred to as 'plaque' because of its yellowish color, reminiscent of mucosal plaques caused by syphilis.

Dental plaque has been defined as "a specific but highly variable structural entity consisting of micro-organisms and their products embedded in a highly organized intercellular matrix." It represents a true biofilm consisting of a variety of micro-organisms involved in a wide range of physical, metabolic and molecular interactions. The cooperative nature of a microbial community provides advantages to the participating organisms such as a broader habitat range for growth, enhanced resistance to antimicrobial agents and host defenses and enhanced pathogenicity. [1]

Biofilms have been implicated as the chief culprit in the etiopathogenesis of dental caries and periodontal disease. Though uncalcified biofilms can be removed by routine oral hygiene aids or professional dental instruments, they have the potential to calcify into dental calculus making their removal difficult. Hence, these biofilms pose a great challenge to the dental clinician in the control and eradication of biofilm-associated diseases.


   Historical Perspective Top


Biofilms are nothing new. The first description dates back to the 17 th century, when Anton Von Leeuwenhoek - the inventor of the Microscope, saw microbial aggregates (now known to be Biofilms) on scrapings of plaque from his teeth.

The term 'Biofilm' was coined by Bill Costerton in 1978.

In 2002, Donlan and Costerton offered the most salient description of a biofilm. They stated that biofilm is "a microbially derived sessile community characterized by cells that are irreversibly attached to a substratum or interface or to each other, embedded in a matrix of extracellular polymeric substances that they have produced, and exhibit an altered phenotype with respect to growth rate and gene transcription." [2]


   What is a Biofilm? Top


The term Biofilm (Wilderer and Charaklis 1989) describes the relatively indefinable microbial community associated with a tooth surface or any other hard non-shedding material, randomly distributed in a shaped matrix or glycocalyx. [2]

In the lower layers of a biofilm, microbes are bound together in a polysaccharide matrix with other organic and inorganic materials. Above it, is a loose amorphous layer extending into the surrounding medium. The fluid layer bordering the biofilm has stationary and dynamic sub layers.

Classification of Biofilms

*On basis of its location [3]

  1. Supragingival - Present coronal to the gingival margin
  2. Subgingival - Present apical to the gingival margin


*On basis of pathogenicity

  1. Cariogenic - Generally acidogenic and gram-positive
  2. Periopathogenic - Mostly basophilic and gram-negative



   Formation of a Biofilm Top


Formation of a biofilm is a complex process that follows several distinct phases, beginning with adsorption on to the tooth surface of a conditioning film derived from bacterial and host molecules, which forms immediately following tooth eruption or tooth cleaning. This adsorption is followed by passive transport of bacteria mediated by weak long-range forces of attraction. Covalent and hydrogen bonds create strong, short-range forces that result in irreversible attachment.

The primary colonizers form a biofilm by autoaggregation (attraction between same species) and coaggregation (attraction between different species). Coaggregation [4] results in a functional organization of plaque bacteria and formation of different morphologic structures such as Corncobs and Rosettes. The microenvironment now changes from aerobic/capnophilic to facultative anaerobic. The attached bacteria multiply and secrete an extracellular matrix, which results in a mature mixed-population biofilm.

After one day, the term Biofilm is fully deserved because organization takes place within it. Transmission occurs from other sites, leading to incorporation of new members into the biofilm and the formation of a climax community. The thickness of the plaque increases slowly with time, increasing to 20 to 30 ΅m after three days.

Four stages of dental plaque biofilm growth (as shown in [Figure 1])
Figure 1: Showing growth of biofilm

Click here to view


Stage I - Attachment (lag - not inert, but metabolically reduced)

Stage II - Growth (log - exponential growth)

Stage III - Maturity (stationary)

Stage IV - Dispersal (death)


   Microbiology of Biofilms Top


Plaque biofilm consists of different complexes of periodontal microorganisms which are based on the frequency with which microorganisms are recovered together. These complexes have been depicted in [Figure 2].
Figure 2: Showing microbiology of biofilms

Click here to view



   Properties of Biofilms Top


Biofilms are ubiquitous; they form on virtually all surfaces immersed in natural aqueous environments. A biofilm confers certain properties to bacteria that are not seen in the planktonic state, a fact that justifies recognition of dental plaque as a biofilm.

A major advantage is the protection that biofilm provides to the colonizing species from competing micro-organisms, environmental factors such as host defense mechanisms and potentially toxic substances like lethal chemicals or antibiotics. Biofilms also facilitate processing and uptake of nutrients, cross feeding and removal of potentially harmful metabolic products through the voids or water channels between the micro-colonies, acting as a primitive circulatory system. [1] They also create an appropriate physicochemical environment such as a properly reduced oxidation reduction potential.

An important characteristic seen in Biofilm-associated bacteria is Quorum sensing, or cell density mediated gene expression. [5] This involves the regulation of expression of specific genes through the accumulation of signaling compounds that mediate intercellular communication. Quorum sensing may give biofilms their distinct properties. Eg.- Expression of genes for antibiotic resistance at high cell densities may provide protection. It also has the potential to influence community structure by encouraging the growth of species beneficial to the biofilm and discouraging the growth of competitors.

Another important characteristic of biofilm associated bacteria is the gene transfer [6] through which bacteria communicates with each other. In S. mutans, quorum sensing is mediated by competence stimulating peptide, wherein genes are responsible for multiple functions - biofilm formation, competence and acid tolerance.

Biofilm related Regulation of gene expression has been shown in certain bacteria. eg. Exposure of S. gordonii to saliva results in induction of genes that mediate host surface binding and coaggregation with P. gingivalis and Actinomyces. Similarly, genes encoding glucan and fructan synthesis are differentially regulated in Biofilm-associated S. mutans.


   Mechanism of Increased Antibiotic Resistance in Biofilms Top


Organisms in a Biofilm are 1000-1500 times more resistant to antibiotics than in their planktonic state. The mechanisms [2] of this increased resistance differ from species to species, antibiotic to antibiotic and for biofilms growing in different habitats. This antibiotic resistance in bacteria is thought to be affected by their nutritional status, growth rate, temperature, pH and prior exposure to sub-effective concentrations of antimicrobial agents. Another important mechanism appears to be the slower rate of growth of bacterial species in a biofilm, which makes them less susceptible to bactericidal antibiotics. Biofilm matrix can resist diffusion of antibiotics. Eg. strongly charged or chemically highly reactive agents can fail to reach the deeper zones of the biofilm as it acts as an ion exchanger in removing such molecules from solution.

'Super-resistant' bacteria have been identified within a biofilm, which have multidrug-resistance pumps that can extrude antimicrobial agents from the cell. Since these pumps place the antibiotics outside the outer membrane, the process offers protection against antibiotics that target cell wall synthesis. Above mentioned observations are critical to the use of antimicrobials in the treatment of Biofilm-associated infections. [7]


   Biofilms and Infectious Diseases Top


Biofilms have been found to be involved in a wide variety of microbial infections (by one estimate 80% of all infections). These include dental caries, periodontal disease, otitis media, musculoskeletal infections, necrotizing fascitis, biliary tract infection, osteomyelitis, bacterial prostatitis, native valve endocarditis, meloidosis, cystic fibrosis pneumonia and peri-implantitis. Salient features of these infections are persistence and chronicity. [2]


   Management Protocol Top


Detection and assessment of biofilms: Biofilms can only be revealed by staining with dyes - either basic fuschin or erythrosine. These are called disclosing agents. [7] Two tone dyes contain FDC Red no.3 and FDC Green no.3, which stain immature and mature plaque respectively. Laser confocal microscopy is the latest method for plaque detection.

Criteria utilized in the assessment of Dental Biofilm: (Ribeiro et al. 1999):

0 No visible biofilm

1 Thin biofilm only on anterior teeth

2 Easily removed thin biofilm distributed on anterior and posterior teeth

3 Firmly adhered thick biofilm only on anterior or posterior teeth

4 Firmly adhered thick biofilm on anterior teeth and thin biofilm on posterior teeth, or firmly adhered thick biofilm on posterior teeth and thin biofilm on anterior teeth

5 Firmly adhered thick biofilm on anterior and posterior teeth

Treatment of periodontal biofilms

As with other branches of dentistry, there is no 'cook book' approach that works for every site in every patient. Individual considerations must be taken care of, while treatment planning. No matter what, biofilm control is fundamental to the maintenance of oral health and to the prevention of dental caries, gingivitis and periodontitis.

Possible strategies to control oral biofilms

  • Inhibition of bacterial colonization
  • Inhibition of bacterial growth and metabolism
  • Disruption of established plaque
  • Modification of plaque biochemistry
  • Alteration of plaque ecology


Clinical approaches

  • Mechanical plaque control [8]
    • Tooth brushes
    • Manual
    • Electrical
    • Interdental cleaning aids
    • Dental floss
    • Wooden tips
    • Perio-aid
    • Interdental brushes
    • Rubber tip
    • Oral irrigation devices
  • Chemical plaque control [9]
    • Enzymes
      • Mucinase
      • Dehydrated pancrease
      • Lactoperoxidase hypothiocyanate
    • Antibiotics
      • Penicillin
      • Vancomycin
      • Erythromycin
    • Phenols
      • Thymol
      • Delmopinol
    • Quarternary ammonium compounds
      • Benzalkonium chloride
      • Cetylpyridinium chloride
    • Bisbiguanides
      • Chlorhexidine
      • Alexidine
    • Bispyridines
      • Octenidine
    • Metallic salts
      • Zinc
      • Tin
      • Copper
    • Herbal extracts
      • Sanguinarine
    • Amino alchohols
      • Octapenol
      • Decapenol
    • Other surfactants
      • Sodium lauryl sulphate
    • Professional oral prophylaxis
      • Calculus-associated Biofilm can effectively be removed by Scaling and Root planing and Tissue-associated Biofilms by Gingival Curettage.



   The Future Top


Biofilms have become a hot topic in environmental and infectious disease microbiology as well in the popular press. In recent years, dental researchers have begun to view plaque as a biofilm. This shifting view on plaque has important implications for future efforts in its prevention and treatment.


   Conclusion Top


It is universally acknowledged that oral diseases are multifactorial, with each factor exerting its own influence thereby propelling the host towards diseased state. Even then, dental plaque is recognized as the single most important etiological factor. Dental health professionals have been waging a constant battle against biofilms.

Biofilms are difficult to locate, remove and penetrate and have an uncanny adaptive ability or to create their own environment. The need of the hour is to supplement the conventional treatment strategies like Scaling, Root planing and Surgery with Chemical Plaque Control Agents, Antimicrobials (e.g. chemically Modified Tetracyclines and Low Dose Tetracyclines), irrigational devices and Local Drug Delivery (LDD) systems to fight the menace of biofilms. Above all, the role of the dental office and the patient himself in maintaining adequate plaque control cannot be overemphasized. Conventional mechanical plaque control methods like efficient tooth brushing and interdental cleaning aids are still the easiest, cheapest and the most convenient weapons against oral biofilms. The role of a dentist extends much beyond the removal of biofilms but encompasses educating and motivating the patient to do so. This would go a long way in creating and maintaining a disease-free oral environment.

 
   References Top

1.Lang NP, Mombelli A, Attstrom R. Oral Biofilms and Calculus In Lindhe J, Lang NP, Karring T. Clinical Periodontology and Implant Dentistry. 5th ed. Oxford: Blackswell- Munksgaard; 2008. p. 183-267.  Back to cited text no. 1
    
2.Socransky SS, Haffajee AD. Dental biofilms: difficult therapeutic targets. Periodontol 2000 2008;28:12-55.  Back to cited text no. 2
    
3.Ximénez-Fyvie LA, Haffajee AD, Socransky SS. Comparison of microbiota of supra- and subgingival plaque in subjects in health and periodontitis. J Clin Periodontol 2000;27:648-57.  Back to cited text no. 3
    
4.Quirynen M, Teughels W, Haake SK, Newman MG. Microbiology of Periodontal Diseases In Newman MG, Takei HH, Klokkevold PR, Carranza FA. Carranza's Clinical Periodontology. 10th ed. St. Louis, Missouri: Elsevier (Saunders); 2006. p. 134-69.  Back to cited text no. 4
    
5.Processor JI. Quorum Sensing in biofilms. Dental Plaque revisitedIn: Newman HN, Wilson M, editors. Cardiff: Bioline; 1999. p. 79-88.  Back to cited text no. 5
    
6.Tatakis DN, Kumar PS. Etiology and pathogenesis of periodontal diseases in periodontology: present status and future concepts. Dent Clin North Am 2005;49:493-7.  Back to cited text no. 6
    
7.Peterson FC, Scheie AA. Chemical Plaque Control: A Comparison of Oral Health Care Products In Busscher HJ, Evans LV. Oral Biofilms and Plaque Control. India: Harwood Academic Publishers; 1998. p. 277-94.  Back to cited text no. 7
    
8.Petersilka GJ, Ehmke B, Flemmig TF. Antimicrobial effects of mechanical debridement. Periodontol 2000 2008;28:56-71.  Back to cited text no. 8
    
9.Quirynen M, Teughels W, De Soete M, van Steenberghe D. Topical antiseptics and antibiotics in the initial therapy of chronic adult periodontitis: microbiological aspects. Periodontol 2000 2008;28:72-90.  Back to cited text no. 9
    


    Figures

  [Figure 1], [Figure 2]



 

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  In this article
    Abstract
   Introduction
    Historical Persp...
   What is a Biofilm?
    Formation of a B...
    Microbiology of ...
    Properties of Bi...
    Mechanism of Inc...
    Biofilms and Inf...
   Management Protocol
   The Future
   Conclusion
    References
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