How bacteria load creates a biofilm

March 21, 2016

First acquired during birth from the mother and rapidly thereafter from the surrounding environment, bacteria colonize our conjunctiva and lacrimal systems. It is estimated that more than 200 species of bacteria commonly inhabit the human conjunctival mucosa.

First acquired during birth from the mother and rapidly thereafter from the surrounding environment, bacteria colonize our conjunctiva and lacrimal systems. It is estimated that more than 200 species of bacteria commonly inhabit the human conjunctival mucosa.1 The ocular surface is chock full of nutrients to sustain resident bacteria; in fact, in a balanced and intact ocular surface system, commensal bacterial species may protect the ocular surface from pathogenic infection.2 Of course, microscopic life abounds at the lid margin and surrounding lids and eyelashes.

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Biofilm and the eye

Bacterial life is versatile. Independent, mobile, free-floating microorganisms are referred to as in their “planktonic” form. Interestingly, however, the life cycle of most bacteria is in sessile aggregates: microbes most often construct and live in a complex, film-like meshwork known as a biofilm.

Costerton et al defined biofilm as a structural community of bacterial cells enclosed in a self-produced polymeric matrix that can adhere to inert (abiotic) or living (biotic) surfaces.3 The bacterial-constructed biofilm environment provides physical protection to bacteria and, because of their close proximity to each other, allows them to communicate through a process called quorum sensing.4 Via a class of signaling chemicals (homoserine lactones), bacterial genes are regulated, which often leads to an increase in their virulence and propensity to cause infection.5

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With the constant physical disruption of blinking, tear exchange, tear antimicrobial agents, enzymes, and mucins, bacteria generally face a robust ocular surface defense system that prevents generating a biofilm. However, when abiotic surfaces such as contact lenses, ocular prostheses, corneal sutures, and punctal plugs are introduced, biofilm formation becomes a greater concern. Biofilms can also form on biotic surfaces such as the lid margin, particularly in circumstances that favor aggregation. In fact, a recent study demonstrated that microorganisms that remained at the end of cataract surgery-even after standard and customary lid/lash and ocular surface disinfection-had the capacity to produce biofilms and had high antibiotic resistance.6

Next: The importance of lid hygiene

 

The importance of lid hygiene

Considering the above, it is intuitive that appropriate lid hygiene practices are in order to stem the tide of bacterial load on the eyelid/margin and eyelashes, aiding the natural ocular surface defense mechanisms. Professor Benitez-Del Castillo suggests that “eyelid hygiene should be incorporated into a broader concept of eyelid health in which eyelid cleansing is part of a more complete program of care that includes screening and risk assessment, patient education, and coaching.”7 I concur.

I recommend-and most patients prefer-commercially prepared lid hygiene products. Most of these are available as foaming cleansers or pre-moistened wipes. New to the lid/eyelash cleanser product inventory is iLast Clean gel and iLast Care cream pairing from Paragon Bioteck formulated with sodium hyaluronate.  The water-binding properties of high-molecular weight sodium hyaluronate hydrates the eyelid skin. Skin hydration is important for the flexibility and function of the skin: reduced hydration leads to skin characterized by reduced elasticity, roughness and scaliness.8

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NovaBay Pharmaceutical’s Avenova, a bottled, liquid solution containing Neutrox (pure hypochlorous acid) and OCuSOFT’s HypoChlor containing hypochlorous acid have antimicrobial and anti-inflammatory activity. Hypochlorous acid is naturally produced by host white blood cells to defend against pathogenic microorganisms. OCuSOFT has also expanded its lid product line with OCuSOFT Lid Scrub Plus Platinum that contains phytosphingosine (PSG-2), a water-binding agent that mimics the natural lipid layer of the outer epidermis. Of course, in-office removal of eyelid/lash debris and de-bulking microbial load and biofilms can be achieved with Rysurg LLC’s instrument BlephEx that mechanically debrides treated surfaces.

There is much to learn about biofilm ecology and how it relates to bacterial virulence. In the meantime, it would seem prudent to clear away bacteria of concern before pathology sets in.

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References

1. Dong Q, Brulc JM, Iovieno, et al. Diversity of bacteria at healthy human conjunctiva. Invest Ophthalmol Vis Sci. 2011 Jul;52(8):5408-13.

2. Miller D, Iovieno A . The role of microbial flora on the ocular surface. Curr Opin Allergy Clin Immunol. 2009 Oct;9(5):466-70.

3. CostertonJW, Philip S, Greenberg EP. Bacterial biofilms: a common cause of persistent infections. Science. 1999 May 21;284(5418):1318-22.

4. De Kievit TR, Iglewski BH. Bacterial quorum sensing in pathogenic relationships. Infect Immun. 2000 Sep;68(9):4839-49.

5. Bjarsholt T. The role of bacterial biofilms in chronic infections. APMIS Suppl. 2013 May;(136):1-51.

6. Kıvanç SA, Kıvanç M, Bayramlar H. Microbiology of corneal wounds after cataract surgery: biofilm formation and antibiotic resistance patterns. J Wound Care. 2016 Jan 2;25(1):12, 14-9.

7. Benitez-Del Castillo JM. How to promote and preserve eyelid health. Clin Ophthalmol. 2012;6:1689-98.

8. Campos PM, deMelo MO, deCamargo FB. Effects of Polysacchride-based formulations on human skin. Polysacchrides. 2014 Sep;1-18.