Chanter N, Collin N, Holmes N, Binns M, Mumford J
Animal Health Trust, Newmarket, Suffolk, UK.
Epidemiol Infect. 1997 Apr;118(2):125-35. doi: 10.1017/s0950268896007285.
The 16S-23S RNA gene intergenic spacers of isolates of Streptococcus equi (n = 5), S. zooepidemicus (n = 5), S. equisimilis (n = 3) and S. dysgalactiae (n = 2) were sequenced and compared. There were distinct regions within the spacer, arranged in the order 1-9 for all S. equi and one S. zooepidemicus isolate and 1,2 and 4-9 for the remaining isolates. Region 4 was identical to the tRNA(ala) gene found in the 16S-23S intergenic spacers of other streptococci. Regions 1, 5, 6 and 7 had distinct variations, each conserved in different isolates. However, amongst the intergenic spacers there were different combinations of variant regions, suggesting a role for DNA recombination in their evolution. The intergenic spacer of all isolates of S. equi and one S. zooepidemicus isolate were almost identical. Primers derived from the variant sequences of regions 1 and 5 to 6 were used to group all S. zooepidemicus (n = 17) and S. equi (n = 5) into 1 of 8 types by polymerase chain reaction; three S. zooepidemicus isolates typed the same as S. equi. S. equi and S. zooepidemicus were clearly distinguishable from S. equisimilis and S. dysgalactiae which had shorter regions 5 and 6 and no region 7. Most homology for the group C sequences was found in previously published sequences for the 16S-23S intergenic spacers of S. anginosis, S. constellatus, S. intermedius, S. salivarius and S. agalactiae. A 75-90 nucleotide length shared with S. anginosus and S. intermedius in opposite orientations in the two main variants of region 6 supported the role for DNA recombination in the evolution of the spacer. The 16S-23S intergenic spacers indicate that S. zooepidemicus was the archetypal species for S. equi and that both are genetically more distant from S. equisimilis and S. dysgalactiae. The intergenic spacer can be used to identify specifically the group C streptococci and as an epidemiological marker for S. zooepidemicus.
对马链球菌（n = 5）、兽疫链球菌（n = 5）、类马链球菌（n = 3）和停乳链球菌（n = 2）分离株的16S - 23S RNA基因间隔区进行测序并比较。间隔区内存在不同区域，所有马链球菌和一株兽疫链球菌分离株的区域排列顺序为1 - 9，其余分离株的区域排列顺序为1、2和4 - 9。区域4与其他链球菌16S - 23S间隔区中发现的tRNA(ala)基因相同。区域1、5、6和7存在明显变异，每个变异在不同分离株中保守。然而，在间隔区之间存在变异区域的不同组合，表明DNA重组在其进化中起作用。所有马链球菌分离株和一株兽疫链球菌分离株的间隔区几乎相同。根据区域1和5至6的变异序列设计的引物，通过聚合酶链反应将所有兽疫链球菌（n = 17）和马链球菌（n = 5）分为8种类型中的1种；三株兽疫链球菌分离株的分型与马链球菌相同。马链球菌和兽疫链球菌与类马链球菌和停乳链球菌明显不同，后两者的区域5和6较短且无区域7。在先前发表的咽峡炎链球菌、星座链球菌、中间链球菌、唾液链球菌和无乳链球菌16S - 23S间隔区序列中，发现该组C序列的同源性最高。在区域6的两个主要变体中，与咽峡炎链球菌和中间链球菌以相反方向共享的75 - 90个核苷酸长度支持了DNA重组在间隔区进化中的作用。16S - 23S间隔区表明，兽疫链球菌是马链球菌的原型物种，两者在遗传上与类马链球菌和停乳链球菌的距离更远。间隔区可用于特异性鉴定C组链球菌，并作为兽疫链球菌的流行病学标志物。
