Mycoplasma, Corneal Ulcers, and Cats
Mycoplasma are single cell organisms similar to bacteria, and are the smallest free-living, self-replicating organisms known. Unlike bacteria that have a rigid cell wall, Mycoplasma have thin, flexible membranes, which contain its cytoplasma. This lack of a cell wall allows Mycoplasma to resist many of the antibiotics that are useful against most bacteria. Mycoplasma are difficult to detect in human and animal specimens and difficult to culture in the laboratory.
Mycoplasma felis is one of over 150 different species of Mycoplasma that have been identified. M. felis has been associated with upper respiratory infection and conjunctivitis in cats. However, its importance as the primary agent of the infection has been questioned. In one study, it was difficult to reproduce the infection without prior immunosuppression, i.e. corticosteroids. It has also been considered as an opportunistic organism, secondary to feline herpes virus.
I have had several cases with deep stromal ulceration (atypical for feline herpes keratitis) from which Mycoplasma felis was cultured and positively identified. I believe that while it may not be the primary infectious agent, Mycoplasma represented the most serious threat to the eye. Without antibiotic therapy, specific to Mycoplasma felis, the globe could have been lost to vision.
For more information and illustrations, please refer to:
"Clinical Use of rRNA Gene Sequencing to Identify
Mycoplasma felis and Mycoplasma gateae
Associated with Feline Ulcerative Keratitis"
Larry D. Gray, Ph.D.
Kerry L. Ketring, D.V.M.
Yi-Wei Tang, M.D., Ph.D.
The following cases are typical in appearance of Mycoplasma corneal ulcerations.
1.5 year old Domestic Shorthair
This is the right eye showing moderate conjunctival hyperemia, a thickened hyperemic prolapsed nictitating membrane, and moderate corneal vascularization. The significant finding is the stromal ulcer (arrows) which had necrotic margins and deep infiltrates.
4 year old Domestic Shorthair
The right eye has severe hyperemia of the conjunctiva, increased lacrimation, and severe vascularization of the cornea. The deep axial corneal ulcer(arrow) with necrosis was the site of the culture.