Abstract
This study aimed to investigate the pathogenic effect of bacteria causing infectious keratitis among patients through experimental study conducted on rabbits' eyes with the aid of histopathology as eye infection is a common disease in developing countries that may complicate to loss of vision. 100 swab samples were collected from human infected eyes, at Qassim region during 2012, for the isolation of Pseudomonas aeruginosa and Staphylococcus aureus. The isolated pathogenic bacteria were tested to various antibiotics using some selected antibiotics discs through agar-well diffusion method. Then, experimental study conducted on 27 rabbits. The rabbits were divided randomly into three equal groups, each containing 9 rabbits. Rabbits of group (1) served as control group (Negative Control) and their eyes were inoculated with the buffer only. Rabbits of group (2) were inoculated through eyes with the isolated Pseudomonas aeruginosa. Rabbits of group (3) were inoculated through eyes with the isolated Staphylococcus aureus. Out of 100 collected swab samples from human infected eyes, Pseudomonas aeruginosa and Staphylococcus aureus were isolated with a total percentage of 25.21% and 15.65%; respectively and used in this study. Both bacterial isolates were sensitive to Gentamicin and Cefuroxime. Clinically, experimentally infected rabbits by Pseudomonas aeruginosa, revealed varying degree corneal abrasions, corneal abscess and dense corneal opacity. Histopathologically, at 3(rd) day post-infection (PI), the cornea revealed polymorpho-nuclear cells infiltration with loss of the outer epithelial lining. At 7(th) day PI, neutrophils were seen in the stroma. At 15(th) day PI, proliferation of fibroblasts and new vascularisation were seen in the stroma. Clinically, rabbits experimentally infected with Staphylococcus aureus, revealed corneal ulcers and focal abscesses. Histopathologically, at 3(rd) and 7(th) day PI, the cornea revealed edema and infiltration of leukocytes. At 15(th) day PI, hyperplasia of corneal epithelium and proliferation of keratocytes were evident. The liver and kidneys of experimented rabbits revealed no remarkable histopathological alterations along the period of experiment. Pseudomonas aeruginosa and Staphylococcus aureus are common eye infection in human, both induced severe lesions in the eyes of rabbits that could interfere with vision, therefore, strict measures to control these infections in human is recommended.
Highlights
The cornea in domestic animals including rabbits is composed of five histological layers: anterior epithelium, subepithelial basement membrane, substantia propria or stroma, posterior limiting membrane (Descemet’s membrane), and posterior epithelium. [1, 2, 3, 4] The epithelium is completely avascular and is nourished by lacrimal secretion, as well as by aqueous humor of the anterior chamber
Out of 100 collected swab samples from human infected eyes, Pseudomonas aeruginosa and Staphylococcus aureus were isolated with a total percentage of 25.21% and 15.65%; respectively and used in this study
Pseudomonas aeruginosa and Staphylococcus aureus are common eye infection in human, both induced severe lesions in the eyes of rabbits that could interfere with vision, strict measures to control these infections in human is recommended
Summary
The cornea in domestic animals including rabbits is composed of five histological layers: anterior epithelium, subepithelial basement membrane, substantia propria or stroma, posterior limiting membrane (Descemet’s membrane), and posterior epithelium (corneal endothelium). [1, 2, 3, 4] The epithelium is completely avascular and is nourished by lacrimal secretion, as well as by aqueous humor of the anterior chamber. Pseudomonas aeruginosa is usually the most common bacterial pathogen isolated from cases of corneal keratitis. [25] Infection can occur following relative minor injury or compromise to the corneal surface and progresses rapidly, with the potential to involve the entire cornea within 2 days. More severe eye involvement can ensue, leading to perforation of the cornea, infection and inflammation in the anterior chamber of the eye, and potentially endophthalmitis. Staphylococcus aureus is the leading cause of bacterial keratitis in adults, including those who have sustained penetrating corneal injuries or are compromised by immunodeficiency. This study aimed to isolate bacterial infection (Pseudomonas aeruginosa and Staphylococcus aureus) in infectious keratitis with investigating the mechanism of action/pathogenesis of these ocular pathogenic bacteria on rabbits through experimental infection with the aid of histopathological examinations Staphylococcus aureus is the leading cause of bacterial keratitis in adults, including those who have sustained penetrating corneal injuries or are compromised by immunodeficiency. [26, 27] Tissue damage during bacterial keratitis results from the action of bacterial products on ocular tissues and from the host inflammatory response to the infection. [28, 29] Staphylococcus keratitis can result in irreversible corneal scarring, resulting in a loss of visual acuity.
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