Characterization of the Lancefield group C streptococcus 16S-23S RNA gene intergenic spacer and its potential for identification and sub-specific typing.

This research focuses on understanding the intergenic spacers among various streptococcus species and exploiting these variations for species identification and typing.

Identification of Streptococcus species through Intergenic spacers

An array of Streptococcus isolates were studied in this research, including S. equi, S. zooepidemicus, S. equisimilis, and S. dysgalactiae. Their 16S-23S RNA gene intergenic spacers, the non-coding regions between genes that might have regulatory functions, were sequenced.

• The researchers observed distinct regions within the spacer in a specific order in all S. equi and one S. zooepidemicus isolate. For other isolates, slightly different orders were noticed.
• They identified a region, region 4, which was identical to the tRNA(ala) gene found in the intergenic spacers of other streptococci species. This suggests a common ancestry or similar evolutionary pressures across these species.
• They noted distinct variations, conserved among different isolates, in regions 1, 5, 6, and 7 of the intergenic spacer.
• These variations suggest a role for DNA recombination events in the evolution of these spacers.

Primers and Polymerase Chain Reaction in Streptococcus differentiation

Primers, short pieces of DNA that are necessary for DNA replication, were derived from the distinct variant sequences of the aforementioned regions.

• These primers were successively used to categorize various isolates of S. zooepidemicus and S. equi into one of eight types via polymerase chain reaction (PCR), a common technique for amplifying specific DNA segments.
• Interestingly, three S. zooepidemicus isolates were of the same type as S. equi.
• S. equi and S. zooepidemicus were discernible from S. equisimilis and S. dysgalactiae, which displayed shorter regions 5 and 6 and lacked region 7. This provides a genetic method to distinguish these groups of bacteria.

Intergenic Spacer as a Marker for Streptococcus Identification

The research concludes that the 16S-23S intergenic spacer can be used to identify group C streptococci.

• Most homology for the group C sequences was found in previously published sequences for other Streptococcus species such as S. anginosis, S. constellatus, S. intermedius, S. salivarius, and S. agalactiae.
• The researchers propose S. zooepidemicus as the archetype species for S. equi, based on their similarities and differ substantially from S. equisimilis and S. dysgalactiae.
• The results suggest the potential for these intergenic spacer regions to be used as an epidemiological marker for S. zooepidemicus in addition to distinguishing group C streptococci.