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Mouse virulent strain of Staphylococcus epidermidis. Relation of antiphagocytic activity to the protection-inducing
Abstract:
Using 10(9) or 10(7) colony-forming units of a strain of Staphylococcus epidermidis (strain 1142) in saline or 5% mucin, respectively, 90 to 100% of mice died within 24 to 48 hr after intraperitoneal challenge infection. These organisms gradually multiplied in the peritoneal cavity when injected intraperitoneally into mice, while the mouse avirulent strain (strain 1124) rapidly decreased and no organisms were found there 20 hr after injection. This strain was capable of inducing resistance against challenge with homologous strains. The resistance appeared as early as the first week and disappeared the 4th week after the immunization. However, no resistance was induced with strain 1124 against challenge with strain 1142. Also, hyperimmune rabbit serum prepared with strain 1142 passively protected against challenge with homologous strain in mice. The protective antibody was absorbed out with homologous organisms but not with strain 1124. Subsequently, a surface substance was obtained from strains 1142 or 1124 by the method of Morse. The 1142 surface substance was capable of inducing a resistance against challenge with the homologous strain but not with the 1124 surface substance. Also, this substance absorbed the protective antibody in hyperimmune rabbit serum prepared with the homologous strain but not with the 1124 surface substance nor with the Smith surface antigen extracted from the Smith strain of Staphylococcus aureus. Conversely, the protective antibody in rabbit anti-Smith strain serum against challenge with the homologous strain was absorbed with the Smith surface antigen but not with the 1142 surface substance. In the agar diffusion test, the 1142 surface substance and the Smith surface antigen produced single precipitin lines only against homologous antisera. Biochemical analysis of the 1142 surface substance showed that the substance contained neither nucleic acids nor proteins but is composed of hexosamine, glycerol, phosphorus, alanine, glycine and phenylalanine.
Insights
A virulent Staphylococcus epidermidis strain (1142) caused lethal infections in mice, while an avirulent strain (1124) induced homologous resistance. A specific surface substance from strain 1142 conferred protection, identifying a potential vaccine target.
Area of Science:
- Microbiology
- Immunology
- Bacteriology
Background:
- Staphylococcus epidermidis is a common bacterium that can cause opportunistic infections.
- Understanding the mechanisms of S. epidermidis virulence and host defense is crucial for developing effective treatments.
Purpose of the Study:
- To investigate the virulence of Staphylococcus epidermidis strain 1142 and its potential for inducing protective immunity.
- To identify the specific bacterial components responsible for virulence and immunogenicity.
Main Methods:
- Mice were infected intraperitoneally with S. epidermidis strains 1142 (virulent) and 1124 (avirulent).
- Resistance was assessed by challenging immunized mice with homologous or heterologous strains.
- Hyperimmune rabbit sera were prepared and tested for passive protection.
- Surface substances were extracted and analyzed biochemically and immunologically.
Main Results:
- Strain 1142 caused high mortality in mice, while strain 1124 was cleared rapidly.
- Immunization with strain 1124 induced resistance only against homologous challenge.
- Passive protection was achieved with rabbit antiserum against strain 1142.
- A surface substance from strain 1142 induced homologous protection and absorbed specific antibodies.
Conclusions:
- A specific surface substance of Staphylococcus epidermidis strain 1142 is responsible for its virulence and elicits a protective immune response.
- This surface substance represents a potential target for vaccine development against S. epidermidis infections.