Study Proves a Resident Ocular Microbiome
“Bugs in your eyes may be a good thing.”
New research is showing that immune responses that protect the eye from infection are due to microbes living on the surface of the eye. Research conducted at the National Eye Institute (NEI), part of the National Institutes of Health, indicates the existence of a resident ocular microbiome that trains the developing immune system to fend off pathogens.
Until recently, it was thought that the surface the eye was sterile due to the existence of an enzyme called lysozyme that eliminates bacteria, antimicrobial peptides, and other components that rid the eye of microbes that may land from the air (or from our fingers) onto the surface of the eye. Recently, researchers were able to culture bacteria from the mouse conjunctiva, finding several species of Staphylococci, which are often found on the skin, and Corynebacterium mastitidis (C. mast). It wasn’t clear if the microbes had just arrived on the eye and were about to be eliminated, or if they lived on the eye for prolonged periods of time. To figure out how the microbes were affecting the immune response in the eye of mice, researchers set up two groups. One control, which had normal C. mast, and the other using an antibiotic to fend off C. mast and other ocular bacteria, and giving both groups a fungus called Candida albicans. The variable group was unable to fend off the fungal infection and ended up having full-blown ocular infection. The control mice however, were able to fend off the fungus. Researchers also noticed that mice from the NIH animal facility had C. mast on their eyes, but mice from Jackson Laboratory and other commercial vendors did not, which allowed them to investigate and determine if C. mast was actually resident microbe or a transient microb that lands on the eye from the environment. They also determined that the microbes could not be transmitted by cagemates, even after eight weeks of co-housing.
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Photo credit: Rachel Caspi and Anthony St. Leger
NIH, National Eye Institute (NEI). “Eye microbiome trains immune cells to fend off pathogens in mice.” ScienceDaily. ScienceDaily, 11 July 2017. <www.sciencedaily.com/releases/2017/07/170711125700.htm>.