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Spreading of Serratia marcescens in experimental keratitis and growth suppression by chicken egg white
S Miyagawa1, K Matsumoto, R Kamata
1Department of Ophthalmology, Kumamoto University Medical School, Japan.
Abstract:
We studied the inhibitory effects of chicken egg white ovomacroglobulin, a broad-spectrum protease inhibitor, and a synthetic protease inhibitory peptide, Bz-GFR-O-mercaptoanilide, on the growth of two strains of Serratia marcescens in a synthetic medium. The growth of the virulent protease-producing strain, S. marcescens kums 3958 (kums 3958), was more rapid than that of the strain producing minimal protease, S. marcescens kums NA (kums NA), and kums 3958 was inhibited in a dose-dependent manner by ovomacroglobulin. The synthetic inhibitor also inhibited the growth of kums 3958 weakly. Dose-dependent enhancement of growth of kums NA was observed in the medium treated with the serratial 56 kilo Dalton protease. By immunohistochemical methods using an antibody to the bacteria, the spreading of kums 3958 was also studied in corneal tissue in experimental keratitis of the guinea pig. In vivo, kums 3958 grew locally, and then spread widely by destroying stromal tissue 7-8 hours after intrastromal injection of the organisms (3 x 10(4) colony-forming units). On the other hand, when kums 3958 mixed with ovomacroglobulin was injected into the cornea, the organisms remained locally in the corneal stroma which showed a lower grade of damage. These results indicate that proteases secreted from S. marcescens destroyed corneal stroma, yielding the organisms enough space for further spreading.
Insights
Chicken egg white ovomacroglobulin inhibits virulent Serratia marcescens growth and spread in experimental keratitis. Protease inhibitors show potential for treating bacterial eye infections by limiting bacterial virulence factors.
Area of Science:
- Microbiology
- Ophthalmology
- Biochemistry
Background:
- Serratia marcescens is an opportunistic pathogen causing severe keratitis.
- Bacterial proteases play a key role in tissue destruction and pathogen spread.
- Ovomacroglobulin is a broad-spectrum protease inhibitor found in egg white.
Purpose of the Study:
- To investigate the inhibitory effects of ovomacroglobulin and a synthetic protease inhibitor on Serratia marcescens growth and virulence.
- To evaluate the in vivo efficacy of ovomacroglobulin in a guinea pig model of experimental keratitis.
Main Methods:
- In vitro studies using synthetic media to assess bacterial growth inhibition.
- In vivo experiments involving intrastromal injection of S. marcescens into guinea pig corneas.
- Immunohistochemical analysis to track bacterial spread and tissue damage.
Main Results:
- Ovomacroglobulin dose-dependently inhibited the growth of a virulent protease-producing S. marcescens strain (kums 3958).
- A synthetic inhibitor showed weak inhibition of kums 3958 growth.
- In vivo, ovomacroglobulin limited bacterial spread and reduced corneal tissue damage.
Conclusions:
- Proteases secreted by S. marcescens are crucial for corneal stromal destruction and bacterial dissemination.
- Ovomacroglobulin demonstrates therapeutic potential for controlling S. marcescens keratitis by neutralizing bacterial proteases.
