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A single emm gene-specific oligonucleotide probe does not recognise all members of the Streptococcus pyogenes M type
T J Penney1, D R Martin, L C Williams
1ESR Communicable Disease Centre, Porirua, New Zealand.
Abstract:
Serological typing of the streptococcal M protein has recently been challenged by a number of unique molecular methodologies based on oligonucleotide recognition of allelic variations within the M protein (emm) gene. In these methods, stringent hybridization of an oligonucleotide probe to a polymerase chain reaction amplified emm gene is used as confirmation of specific M type identity. A sample of 17 isolates from 7 previously defined distinct genotypes were tested using a single M1 oligonucleotide probe. Isolates from only three of the genotypes hybridized with the probe. The results demonstrate that a single emm-specific oligonucleotide probe can not identify all members of M type 1, as defined by conventional serotyping using polyclonal antisera.
Insights
Molecular methods for typing streptococcal M protein face challenges. A single M1 oligonucleotide probe could not identify all M type 1 strains, highlighting limitations in current molecular typing techniques.
Area of Science:
- Microbiology
- Molecular Biology
- Immunology
Background:
- Serological typing of streptococcal M protein is a standard method.
- Molecular methods using emm gene variations are emerging for M protein typing.
- Oligonucleotide probes are used for specific M type identification via hybridization.
Purpose of the Study:
- To evaluate the efficacy of a single M1 oligonucleotide probe for identifying M type 1 Streptococcus strains.
- To compare molecular typing results with conventional serotyping using polyclonal antisera.
Main Methods:
- Polymerase chain reaction (PCR) amplification of the emm gene.
- Hybridization of a single M1-specific oligonucleotide probe to amplified emm gene sequences.
- Testing of 17 Streptococcus isolates from 7 distinct genotypes.
Main Results:
- Only isolates from three of the seven tested genotypes hybridized with the M1 oligonucleotide probe.
- The M1 probe failed to identify all M type 1 strains as defined by serological methods.
- Significant allelic variation within the emm gene impacts probe specificity.
Conclusions:
- A single emm-specific oligonucleotide probe is insufficient for comprehensive identification of all M type 1 strains.
- Current molecular typing methods require refinement to account for emm gene allelic diversity.
- Conventional serotyping remains a valuable tool for M protein identification, complementing molecular approaches.