The team found that about a dozen bacterial genera dominated the eye’s conjunctiva, a third of which could not be classified. On the corneal surface, the researchers found a slightly different community. Again, about a dozen genera dominated. And everywhere they’ve looked, the researchers have found more than just bacteria. “We haven’t published on this yet, but I have been surprised by how often we find phage or viruses on the normal ocular surface,” Van Gelder told The Scientist in an e-mail.
“People can have a huge variation in microflora and still have healthy eyes, making our job difficult, but really amazing,” Shestopalov said.
The researchers also found that during keratitis infections—infections of the cornea—only about half as many bacterial varieties were present, most prominently Pseudomonas strains. The changes typically occurred well before a diagnosis of an eye infection, suggesting the ocular microbiome could inform future diagnostics, Shestopalov noted. His team is refining the algorithm for predicting infection based on the dynamics of these changes in bacterial composition.
One factor that may be expected to impact the composition of ocular microbiota is the use of contact lenses. Contact lens wear is one of the biggest factors leading to corneal infection. Common bacterial infections that can cause irritation and redness affect an estimated 7 percent to 25 percent of contact lens–wearers, and much rarer keratitis infections can even cause blindness. Researchers believe contact lenses make it easier for pathogens to colonize the surface of the eye by giving the bacteria something to adhere to. Sequencing biofilms from used contact lenses, Shestopalov’s team found evidence of microbial communities that were different from the ocular microbiomes of people who don’t use contacts. On the lenses themselves, the researchers have found much less diversity—many of the bacterial genera that dominate the conjunctiva and cornea were depleted. In their place, Staphylococcus dominated.
To tackle the potential-infection problem, Mark Willcox, a medical microbiologist at the University of New South Wales in Australia, has developed antimicrobial contact lenses. Together with colleagues Debarun Dutta and Jerome Ozkan of the Brien Holden Vision Institute in Sydney, Willcox bonded the naturally occurring antimicrobial peptide melimine to the surface of normal contact lenses. The researchers reported on preclinical studies on rabbits, and in April, on the first phase of human trials, which included 17 volunteers. They found that the antimicrobial lenses appeared as safe as regular lenses and maintained their antimicrobial activity against two major pathogens, P. aeruginosa and S. aureus. The researchers next plan to test the lenses in a larger sample of about 100 to 200 people, but it will be some time before antimicrobial lenses are available on the market.
The lenses are not likely to harm normal, commensal bacteria on the eye. “As the peptide is bound to the surface of the lens we believe it will only affect the growth of those microbes that attempt to bind to the lens surface and not those cultured from the surface of the eye,” Willcox told The Scientist in an e-mail. “But large-scale clinical trials are needed to prove this hypothesis.”
Whether the bacteria identified living on the surface of the eye are permanent residents or transient colonizers remains to be seen. The work of deconstructing the ocular microbiome is just getting started, but preliminary results have suggested it is distinct from the rest of the bacterial community that inhabits our bodies. “It stands apart,” Shestopalov said. “There’s statistical evidence of its difference from any other human microbiome.”
The team found that about a dozen bacterial genera dominated the eye’s conjunctiva, a third of which could not be classified. On the corneal surface, the researchers found a slightly different community. Again, about a dozen genera dominated. And everywhere they’ve looked, the researchers have found more than just bacteria. “We haven’t published on this yet, but I have been surprised by how often we find phage or viruses on the normal ocular surface,” Van Gelder told The Scientist in an e-mail.
“People can have a huge variation in microflora and still have healthy eyes, making our job difficult, but really amazing,” Shestopalov said.
The researchers also found that during keratitis infections—infections of the cornea—only about half as many bacterial varieties were present, most prominently Pseudomonas strains. The changes typically occurred well before a diagnosis of an eye infection, suggesting the ocular microbiome could inform future diagnostics, Shestopalov noted. His team is refining the algorithm for predicting infection based on the dynamics of these changes in bacterial composition.
One factor that may be expected to impact the composition of ocular microbiota is the use of contact lenses. Contact lens wear is one of the biggest factors leading to corneal infection. Common bacterial infections that can cause irritation and redness affect an estimated 7 percent to 25 percent of contact lens–wearers, and much rarer keratitis infections can even cause blindness. Researchers believe contact lenses make it easier for pathogens to colonize the surface of the eye by giving the bacteria something to adhere to. Sequencing biofilms from used contact lenses, Shestopalov’s team found evidence of microbial communities that were different from the ocular microbiomes of people who don’t use contacts. On the lenses themselves, the researchers have found much less diversity—many of the bacterial genera that dominate the conjunctiva and cornea were depleted. In their place, Staphylococcus dominated.
To tackle the potential-infection problem, Mark Willcox, a medical microbiologist at the University of New South Wales in Australia, has developed antimicrobial contact lenses. Together with colleagues Debarun Dutta and Jerome Ozkan of the Brien Holden Vision Institute in Sydney, Willcox bonded the naturally occurring antimicrobial peptide melimine to the surface of normal contact lenses. The researchers reported on preclinical studies on rabbits, and in April, on the first phase of human trials, which included 17 volunteers. They found that the antimicrobial lenses appeared as safe as regular lenses and maintained their antimicrobial activity against two major pathogens, P. aeruginosa and S. aureus. The researchers next plan to test the lenses in a larger sample of about 100 to 200 people, but it will be some time before antimicrobial lenses are available on the market.
The lenses are not likely to harm normal, commensal bacteria on the eye. “As the peptide is bound to the surface of the lens we believe it will only affect the growth of those microbes that attempt to bind to the lens surface and not those cultured from the surface of the eye,” Willcox told The Scientist in an e-mail. “But large-scale clinical trials are needed to prove this hypothesis.”
Whether the bacteria identified living on the surface of the eye are permanent residents or transient colonizers remains to be seen. The work of deconstructing the ocular microbiome is just getting started, but preliminary results have suggested it is distinct from the rest of the bacterial community that inhabits our bodies. “It stands apart,” Shestopalov said. “There’s statistical evidence of its difference from any other human microbiome.”
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