Role of coagulase-negative staphylococci and micrococci in ocular disease

Prof Lalit Prakash Agarwal (1922-2004)-The Planner of the First-Ever National Blindness Control Program of the World

Prof Lalit Prakash Agarwal drafted the National Programme for Prevention of Visual Impairment and Control of Blindness (now called National Programme for Control of Blindness) in India in 1976, first of its kind in the world. With his vision well ahead of his time, he brought the concept of super-specialty in Indian ophthalmology. He founded Dr. Rajendra Prasad Centre for Ophthalmic Sciences, the apex governmental ophthalmological center of India. His contributions to modern Indian Ophthalmology were so profound that we may not be mistaken by calling him “the father of modern Indian Ophthalmology.”

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

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.

Acute bacterial infections of the eye: their aetiology and treatment

The aerobic microbial flora of 823 eyes with acute bacterial conjunctivitis, corneal ulceration, dacryocystitis, discharging sockets, blepharitis, and postoperative infections has been investigated. Staphylococci, Streptococcus pneumoniae, and nonfermenting Gram-negative bacilli including Pseudomonas aeruginosa were the main pathogens. Fermenting coliforms were also infrequently isolated. The least overall resistance of 30.9% was to chloramphenicol, but no one antibiotic was effective against all pathogens. Cloxacillin is the best drug for staphylococcal and polymyxin B for pseudomonas infections.

Toxigenic strains of Staphylococcus epidermidis and their experimental corneal pathogenicity in rabbits

Thirty strains of Staphylococcus epidermidis, ten each from normal conjunctival sacs, corneal ulcer cases and from those who developed postoperative endophthalmitis, were examined for their dermonecrotic and haemolytic activities. Dermonecrosis was studied on rabbit skin whereas haemolysis was determined against sheep, guinea pig, rabbit and human erythrocytes. None of the cell free filtrates from strains derived from normal sacs showed any evidence of toxin production. Four strains from corneal ulcer cases and five from postoperative infections produced + to + + + dermonecrosis whereas haemolytic activity was exhibited by one strain in the former and by two in the latter. Only those strains that were highly dermonecrotoxic were haemolytic. Experimental corneal lesions in the rabbit were mild by strains from normal sacs. Those showing highest dermonecrotoxic reaction, irrespective of their source, produced identical and most severe corneal pathology when compared to those producing minimal necrosis.

Pseudomonas aeruginosa: isolation from ocular tissues. Aeruginocin typing and its relationship to corneal pathogenicity in rabbits

Fifty strains of Pseudomonas aeruginosa isolated from human eyes were aeruginocin typed by the method of Shriniwas (1974) using ten indicator strains. These belonged to types A1 (3), B (2), F1 (1) and 14 (1). Fifteen (30%) were nontypable and 28 (56.0%) were unclassifiable presenting twenty inhibition patterns. The strains showed a wide range of antibiotic sensitivities. The highest number of insensitive strains were those obtained from corneal ulcers. Experimental keratitis produced by strains of pseudomonas was either mild, moderate or severe and was unrelated to their source. Mild keratitis was produced by types UC 7-, UC 79- and 14 isolated from pre-operative, corneal ulcer and post-operative patients. Lesions of moderate severity were produced by types 189+ & A1 whereas the severest pathology was produced by UC 23478-, B and UC 810- types. The fact that strain 23478- always produced severest pathology irrespective of whether originated from group I, II, or IV strongly suggests relationship of pathogenicity with aeruginocin type.