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Toxigenic strains of Staphylococcus epidermidis and their experimental corneal pathogenicity in rabbits
Abstract:
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.
Insights
Staphylococcus epidermidis strains from infected eyes, not normal ones, produced toxins causing dermonecrosis and hemolysis. High toxin levels correlated with severe corneal damage in experimental models.
Area of Science:
- Ophthalmology
- Microbiology
- Infectious Diseases
Background:
- Staphylococcus epidermidis is a common cause of ocular infections, including keratitis and endophthalmitis.
- The pathogenic mechanisms of Staphylococcus epidermidis, particularly toxin production, are not fully understood.
Purpose of the Study:
- To investigate the dermonecrotic and haemolytic activities of Staphylococcus epidermidis strains isolated from different ocular sources.
- To correlate toxin production with the severity of experimental corneal lesions.
Main Methods:
- Thirty Staphylococcus epidermidis strains were isolated from normal conjunctival sacs, corneal ulcers, and postoperative endophthalmitis.
- Dermonecrosis was assessed on rabbit skin, and haemolytic activity was tested against various erythrocytes.
- Experimental corneal lesions were induced in rabbits using selected strains.
Main Results:
- Strains from normal conjunctival sacs did not produce detectable toxins.
- Strains from corneal ulcers and postoperative endophthalmitis exhibited varying degrees of dermonecrosis and haemolysis.
- A strong correlation was observed between high dermonecrotoxic activity and haemolytic activity.
- Strains with the highest dermonecrotoxic potential induced the most severe corneal pathology in experimental models, regardless of their origin.
Conclusions:
- Dermonecrotic and haemolytic toxins produced by Staphylococcus epidermidis are associated with ocular infections.
- The severity of corneal pathology is directly related to the dermonecrotoxic potential of the infecting strain.
- These findings highlight the role of specific toxins in Staphylococcus epidermidis-induced ocular disease.