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Molecular typing of selected Enterococcus faecalis isolates: pilot study using multilocus sequence typing and
Sreedhar R Nallapareddy1, Ruay-Wang Duh, Kavindra V Singh
1Division of Infectious Diseases, Department of Internal Medicine, University of Texas Medical School, Houston, Texas 77030, USA.
Journal of Clinical Microbiology
|March 7, 2002
Summary
Multilocus sequence typing (MLST) effectively differentiates Enterococcus faecalis subspecies, matching the performance of pulsed-field gel electrophoresis (PFGE). This sequence-based method aids in identifying outbreak isolates and understanding bacterial relationships.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Accurate subspecies differentiation of Enterococcus faecalis is crucial for epidemiological studies and outbreak investigations.
- Pulsed-field gel electrophoresis (PFGE) is a well-established but labor-intensive method for bacterial typing.
- Novel molecular typing techniques are needed for efficient and precise bacterial isolate characterization.
Purpose of the Study:
- To compare the efficacy of multilocus sequence typing (MLST) with PFGE for subspecies differentiation of Enterococcus faecalis.
- To evaluate MLST's utility in identifying outbreak-related isolates and understanding clonal relationships.
- To assess the discriminatory power of MLST using specific antigen-encoding and housekeeping genes.
Main Methods:
- Sequencing of intragenic regions from four Enterococcus faecalis genes: ace, efaA, salA (antigen-encoding), and pyrC (housekeeping).
- Analysis of 22 genetically diverse Enterococcus faecalis isolates, including outbreak strains.
- Comparison of sequence types (STs) generated by MLST with pulsed-field gel electrophoresis (PFGE) types.
Main Results:
- MLST identified 13 distinct sequence types (STs) among the 22 isolates, with high sequence identity (98.3–100%).
- Allelic profiles from the ace and salA genes alone were sufficient to distinguish all 13 STs.
- MLST results corresponded closely to PFGE types, with 13 STs matching 12 PFGE types, confirming its discriminatory power and ability to resolve closely related strains.
Conclusions:
- MLST is a valuable, sequence-based method for subspecies differentiation of Enterococcus faecalis, comparable to PFGE.
- MLST effectively identifies outbreak isolates and confirms clonal relationships within Enterococcus faecalis populations.
- This pilot study supports MLST as a reliable tool for microbial typing and epidemiological surveillance.