Histopathological Studies on Rabbits Infected by Bacteria Causing Infectious Keratitis in Human through Eye Inoculation

Abstract

Aim: 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.

Methodology: 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.

Results: 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.

Conclusion: 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.

Fig. 1

Rabbit eye, infected with Pseudomonas aeruginosa at 3^rd day PI, showing loss of the outer epithelial lining of the cornea and neutrophils infiltration in the anterior layer of the stroma. H & E stain × 100.

Fig. 2

Rabbit eye, infected with Pseudomonas aeruginosa at 3^rd day PI, showing loss in normal contour with loss of keratocytes in the edematous stroma. H & E stain × 250.

Fig. 3

Rabbit eye, infected with Pseudomonas aeruginosa at 15^th day PI, showing intensive infiltration of polymorpho-nuclear leukocytes in the corneal stroma. H & E stain × 250.

Fig. 4

Higher magnification of Fig. 3 to show the polymorpho-nuclear leukocytes. H & E stain × 1000.

Fig. 5

Rabbit eye, infected with Pseudomonas aeruginosa at 15^th day PI, showing new vascularisation and loss of Descemet’s membrane. H & E stain × 250.

Fig. 6

Rabbit eye, infected with Staphylococcus aureus at 3^rd day PI, showing corneal epithelial ulceration and intensive infiltration of neutrophils with stromal edema. H & E stain × 100.

Fig. 7

Rabbit eye, infected with Staphylococcus aureus at 7^th day PI, showing superficial loss of corneal epithelium and keratocytes with stromal vascularization, edema and neutrophils infiltrations. H & E stain × 100.

Fig. 8

Rabbit eye, infected with Staphylococcus aureus at 15^th day PI, showing hyperplasia of corneal epithelium with proliferation of keratocytes, newly formed blood vessels and polymorpho-nuclear leukocytic infiltration in the corneal stroma. H & E stain × 250.