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Corneal rings with gram-negative bacteria
Abstract:
Corneal rings have been described with corneal ulcerations caused by Gram-negative bacteria. Corneal rings were produced by intracorneal injections of viable Pseudomonas aeruginosa as well as heat-inactivated suspensions of Gram-negative bacteria (P aeruginosa and Escherichia coli) but not Gram-positive bacteria (Staphylococcus aureus) or Freund's adjuvant. It is suggested that endotoxin is the factor responsible for their production since purified endotoxin produced corneal rings after intracorneal injection. Histopathological examination of the areas corresponding to the corneal rings disclosed that the rings represented accumulations of polymorphonuclear leukocytes. Direct immunofluorescent studies of the corneal rings revealed staining for properdin and C3 complement but not for immunoglobulins. The present report suggests that endotoxin has the ability to stimulate the alternate pathway of complement through properdin activation with the production of chemotactic fragments that attract polymorphonuclear leukocytes into the cornea.
Insights
Corneal rings, often seen with Gram-negative bacterial infections, are caused by endotoxins stimulating the complement system. This process attracts white blood cells, forming these characteristic rings in the cornea.
Area of Science:
- Ophthalmology
- Microbiology
- Immunology
Background:
- Corneal rings are observed in cases of corneal ulceration linked to Gram-negative bacterial infections.
- The precise mechanism of corneal ring formation, particularly the role of bacterial components, requires elucidation.
Purpose of the Study:
- To investigate the causative agent and mechanism behind the formation of corneal rings.
- To determine if bacterial endotoxins are responsible for inducing corneal rings.
Main Methods:
- Intracorneal injections of viable and inactivated Gram-negative bacteria (Pseudomonas aeruginosa, Escherichia coli), Gram-positive bacteria (Staphylococcus aureus), and purified endotoxin.
- Histopathological examination of corneal tissues.
- Direct immunofluorescence studies for complement components and immunoglobulins.
Main Results:
- Corneal rings were induced by viable and heat-inactivated Gram-negative bacteria, as well as purified endotoxin, but not by Gram-positive bacteria or Freund's adjuvant.
- Histopathology revealed corneal rings as accumulations of polymorphonuclear leukocytes.
- Immunofluorescence showed the presence of properdin and C3 complement, but not immunoglobulins, within the corneal rings.
Conclusions:
- Bacterial endotoxin is implicated as the primary factor responsible for the production of corneal rings.
- Endotoxin likely stimulates the alternate complement pathway via properdin activation.
- This activation generates chemotactic fragments that recruit polymorphonuclear leukocytes, leading to the observed corneal ring structures.