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Pseudocoagulase activity of staphylococci
Abstract:
A total of 245 strains of staphylococci isolated from various pathological specimens derived from cases of human infections was tested for staphylocoagulase activity. Test systems employing normal citrated rabbit plasma and the same substrate supplemented with inhibitors of thrombin and proteolytic enzymes (but not influencing the staphylocoagulase activity) were used for testing suspensions of bacteria and cell-free culture supernatants. A total of 237 strains clotted normal rabbit plasma; however, addition of Trasylol and heparin resulted in positive results in 222 strains, whereas plasma supplemented with Trasylol and hirudin was coagulated definitely by only 173 strains. It is postulated that proteolytic enzymes of staphylococci interfere with staphylocoagulase-induced clotting and may simulate coagulase-positive activity of staphylococci. To avoid such false results, a test system for detection of staphylocoagulase should include proteolytic enzyme inhibitors. Possible mechanisms of these findings are discussed.
Insights
Staphylocoagulase activity in human infection strains was assessed. Proteolytic enzymes in staphylococci can interfere with accurate staphylocoagulase testing, necessitating enzyme inhibitors for reliable results.
Area of Science:
- Microbiology
- Clinical Diagnostics
Background:
- Staphylocoagulase is a key virulence factor in Staphylococcus species.
- Accurate detection of staphylocoagulase is crucial for identifying pathogenic strains.
Purpose of the Study:
- To evaluate staphylocoagulase activity in clinical isolates.
- To investigate the interference of bacterial proteolytic enzymes in staphylocoagulase assays.
Main Methods:
- Tested 245 staphylococci strains from human infections for coagulase activity.
- Utilized rabbit plasma with and without thrombin/proteolytic enzyme inhibitors (Trasylol, heparin, hirudin).
- Assessed both bacterial suspensions and cell-free supernatants.
Main Results:
- 237 strains clotted normal plasma.
- Inhibitor addition affected results: 222 with heparin, 173 with hirudin.
- Proteolytic enzymes likely interfere with staphylocoagulase-induced clotting.
Conclusions:
- Proteolytic enzymes in staphylococci can lead to false-positive coagulase tests.
- Incorporating proteolytic enzyme inhibitors enhances the accuracy of staphylocoagulase detection.
- Refined diagnostic methods are needed to avoid misidentification of staphylococcal strains.