Simple and economical method for identification and speciation of Staphylococcus epidermidis and other coagulase
Suresh Sah1, Priyanka Bordoloi1, D Vijaya2
1Department of Biotechnology, School of Life Sciences, Pondicherry University, Pondicherry, India.
Abstract:
Coagulase-negative staphylococci (CoNS) have been increasingly recognized as a clinically important group of species that can cause several opportunistic nosocomial infections. There are at least 47 known species of Staphylococci and to differentiate all these species >40 biochemical tests need to be performed. The present study was able to refine the CoNS identification process by using only five tests to identify S. epidermidis from the rest and used six other tests to identify eleven other clinically significant CoNS species. A total of 242 CoNS isolates were collected from tertiary care hospitals and included in the study. The five-biochemical test scheme devised based on mathematical probability derived from a computer algorithm included fermentation of mannitol, maltose, mannose, trehalose and novobiocin susceptibility to differentiate S. epidermidis from other CoNS species. The remaining CoNS isolates other than S. epidermidis were further characterized with the help of six additional tests, which identified another eleven species. Species-specific PCR and 16SrDNA sequencing were used to confirm and validate the identification scheme. Species-specific PCR and 16SrDNA sequencing showed 100% agreement with non-divergent phenotypic test results, indicating that the five selected assays are highly specific for identifying S. epidermidis. In conclusion, this study used only 11 tests to identify most of the clinically significant CoNS that can reduce cost and time. This scheme is easy to perform in any laboratory with basic resources, the results of this study were validated using more accurate molecular methods such as PCR and 16S rDNA typing to confirm the utility of the proposed scheme.
Insights
This study simplifies coagulase-negative staphylococci (CoNS) identification using only 11 biochemical tests. This efficient method accurately distinguishes clinically significant CoNS species, including Staphylococcus epidermidis, saving time and resources in clinical laboratories.
Area of Science:
- Clinical microbiology
- Bacterial identification
- Nosocomial infections
Background:
- Coagulase-negative staphylococci (CoNS) are opportunistic pathogens causing hospital-acquired infections.
- Traditional identification requires over 40 biochemical tests, making it time-consuming and resource-intensive.
- Accurate and rapid identification of CoNS is crucial for effective patient management.
Purpose of the Study:
- To develop and validate a simplified biochemical testing scheme for identifying clinically significant CoNS species.
- To reduce the number of tests required for CoNS identification, specifically differentiating Staphylococcus epidermidis.
- To provide a cost-effective and time-efficient diagnostic tool for clinical laboratories.
Main Methods:
- A panel of 242 CoNS isolates from tertiary care hospitals was analyzed.
- A five-test scheme (mannitol, maltose, mannose, trehalose fermentation, and novobiocin susceptibility) was devised to identify S. epidermidis.
- An additional six tests were used to identify eleven other clinically significant CoNS species.
- Species-specific PCR and 16S rDNA sequencing were employed for validation.
Main Results:
- The five-test scheme accurately differentiated S. epidermidis from other CoNS species.
- The comprehensive 11-test scheme identified eleven additional clinically significant CoNS species.
- Molecular methods (PCR and 16S rDNA sequencing) confirmed 100% agreement with the phenotypic identification scheme.
- The proposed scheme demonstrated high specificity for S. epidermidis identification.
Conclusions:
- A simplified 11-test scheme effectively identifies major clinically significant CoNS species.
- This approach significantly reduces the cost and time associated with CoNS identification.
- The validated scheme is practical for laboratories with basic resources, enhancing diagnostic capabilities for nosocomial infections.
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