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Polymyxin susceptibility in staphylococci differentiating coagulase-positive and coagulase-negative strains
Abstract:
47 staphylococcal reference strains representing 13 species were tested for polymyxin sensitivity using tablet and disc diffusion methods. Corresponding MIC and IC50 values were determined with a plate dilution assay. Coagulase-positive strains were found to be more resistant towards polymyxin, and could thereby be separated from coagulase-negative strains. Furthermore, 100 recently isolated staphylococci from clinical specimens were tested, and again the coagulase-positive strains could be identified by their smaller tablet inhibition zones. We conclude that the polymyxin test is an aid in the fast differentiation of staphylococci in laboratories performing primary sensitivity tests.
Insights
Polymyxin sensitivity testing effectively differentiates coagulase-positive staphylococci from coagulase-negative strains. This rapid method aids in identifying staphylococcal species in clinical laboratories.
Area of Science:
- Microbiology
- Clinical Diagnostics
- Antimicrobial Susceptibility Testing
Background:
- Staphylococcal infections pose a significant clinical challenge.
- Accurate and rapid identification of staphylococcal species is crucial for effective treatment.
- Distinguishing between coagulase-positive and coagulase-negative staphylococci is diagnostically important.
Purpose of the Study:
- To evaluate the utility of polymyxin sensitivity testing for differentiating staphylococcal species.
- To determine if polymyxin resistance correlates with coagulase-positive staphylococci.
- To assess the feasibility of using polymyxin tests in routine laboratory settings.
Main Methods:
- Testing 47 staphylococcal reference strains from 13 species for polymyxin sensitivity.
- Employing tablet and disc diffusion methods for sensitivity assessment.
- Determining Minimum Inhibitory Concentration (MIC) and IC50 values via plate dilution assays.
- Analyzing polymyxin inhibition zones in 100 clinical isolates.
Main Results:
- Coagulase-positive staphylococcal strains exhibited higher resistance to polymyxin compared to coagulase-negative strains.
- Smaller tablet inhibition zones were observed in coagulase-positive staphylococci.
- Polymyxin sensitivity testing demonstrated a clear distinction between coagulase-positive and coagulase-negative staphylococci.
Conclusions:
- Polymyxin sensitivity testing serves as a valuable tool for the rapid differentiation of staphylococci.
- This method can assist laboratories in primary sensitivity testing for improved staphylococcal identification.
- The findings support the integration of polymyxin testing into routine diagnostic workflows for staphylococcal species.