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Role of coagulase-negative staphylococci and micrococci in ocular disease
Abstract:
Forty-nine strains of coagulase-negative staphylococci and 26 strains of micrococci isolated from human eyes were classified by the Baird-Parker system of 1966. The staphylococci belonged to subgroups II, III, IV, and V with one strain each in subgroups III and IV. However, when biotyped by Baird-Parker's system of 1974, less than 50% (23/49) of strains were typable and they belonged to biotypes 1 and 2. With our proposed modified classification all strains could be classified into biotypes 1, 2, and 3. All the 26 strains of micrococci belonged to subgroup VII. Staphylococci isolated from diverse sources produced, qualitatively and quantitatively, different corneal pathology in rabbits when compared to those isolated from healthy conjunctiva. This bore no relation to the present system of subtyping based on biochemical reactions. Micrococci were incapable of producing experimental corneal lesions in the rabbit.
Insights
A modified classification system effectively categorized ocular staphylococci and micrococci strains. This new method improved upon the limitations of the Baird-Parker system for identifying these bacteria from eye infections.
Area of Science:
- Microbiology
- Ophthalmology
Background:
- Coagulase-negative staphylococci and micrococci are common inhabitants of the human eye.
- Current classification systems, like the Baird-Parker method, have limitations in accurately typing these ocular bacteria.
Purpose of the Study:
- To evaluate the efficacy of the Baird-Parker classification system for ocular staphylococci and micrococci.
- To propose and validate a modified classification system for improved bacterial identification.
Main Methods:
- Classification of 49 coagulase-negative staphylococci and 26 micrococci strains from human eyes using the Baird-Parker system (1966 and 1974).
- Development and application of a modified classification system.
- Assessment of corneal pathology in rabbits induced by different staphylococcal isolates.
Main Results:
- The 1974 Baird-Parker system could only type less than 50% of staphylococcal strains (biotypes 1 and 2).
- The proposed modified classification successfully categorized all staphylococcal strains into biotypes 1, 2, and 3.
- Micrococci strains (26) were consistently classified into subgroup VII.
- Staphylococci from diverse sources induced varying corneal pathology in rabbits, unrelated to current subtyping.
- Micrococci did not cause experimental corneal lesions.
Conclusions:
- The modified classification system offers superior accuracy for typing ocular staphylococci compared to the existing Baird-Parker method.
- Bacterial source and strain variation influence the severity of experimentally induced corneal pathology.
- Micrococci appear to be non-pathogenic in the context of experimental rabbit corneal lesions.