Distribution and genetic diversity of suilysin in Streptococcus suis isolated from different diseases of pigs and characterization of the genetic basis of suilysin absence
Distribution and genetic diversity of suilysin in Streptococcus suis isolated from different diseases of pigs and characterization of the genetic basis of suilysin absence
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DOI：
10.1128/iai.69.12.7572-7582.2001
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发表时间：
2001-12-01
影响因子：
3.1
通讯作者：
Whatmore, AM
中科院分区：
文献类型：
--
作者：
King, SJ;Heath, PJ;Whatmore, AM
猪链球菌是一种经济上重要的病原体，可引起猪的多种疾病，包括脑膜炎、败血症、关节炎和肺炎，但其致病机制和毒力因子尚不清楚。在这里，我们报告的分布和遗传多样性的假定毒力因子suilysin，一个成员的巯基活化毒素家族的革兰氏阳性菌。对300余株沙门氏菌进行PCR分析。69.4%的分离株含有猪溶素编码基因sly。然而，从脑膜炎、败血症和关节炎病例中获得的分离株（> 80%）和从无症状扁桃体携带中获得的分离株（> 90%）中sly的比例明显高于与肺炎相关的肺分离株（44%）。除血清型1、14和1/14外，猪溶血素的存在与血清型之间没有强相关性。通过限制性片段长度多态性和序列分析的猪溶素的遗传多样性的分析发现，猪溶素基因，如果存在的话，是高度保守的，最大的1.79%的多样性在核苷酸水平之间看到的SLY等位基因。溶血活性测定和杂交分析没有提供S.猪。反向PCR用于表征Sly侧翼区域，这反过来又允许在缺乏Sly的菌株中首次表征等同区域。Sly阳性（P1/7）和Sly阴性（DHS）菌株的序列比较表明，这两种不同的排列方式都与卤酸脱卤酶样水解酶（S '端）和N-乙酰甘露糖胺-6-磷酸差向异构酶（3'端）具有最高的相似性。然而，sly似乎是完全缺席的替代安排，和一个未知功能的基因位于同等的位置。最后，对多株Sly阳性和Sly阴性菌株的PCR分析表明，这两种不同的基因排列在许多S.猪分离株。
Streptococcus sids is an economically important pathogen of pigs responsible for a variety of diseases including meningitis, septicemia, arthritis, and pneumonia, although little is known about the mechanisms of pathogenesis or virulence factors associated with this organism. Here, we report on the distribution and genetic diversity of the putative virulence factor suilysin, a member of the thiol-activated toxin family of gram-positive bacteria. On the basis of PCR analysis of over 300 isolates of S. suis, the suilysin-encoding gene, sly, was detected in 69.4% of isolates. However, sly was present in a considerably higher proportion of isolates obtained from cases of meningitis, septicemia, and arthritis (> 80%) and isolates obtained from asymptomatic tonsillar carriage (> 90%) than lung isolates associated with pneumonia (44%). With the exception of serotypes 1, 14, and 1/14, there was no strong correlation between the presence of suilysin and serotype. Analysis of the genetic diversity of suilysin by restriction fragment length polymorphism and sequence analysis found that the suilysin gene, where present, is highly conserved with a maximum of 1.79% diversity at the nucleotide level seen between sly alleles. Assays of hemolytic activity and hybridization analysis provided no evidence for a second member of the thiol-activated toxin family in S. suis. Inverse PCR was used to characterize regions flanking sly, which in turn allowed the first characterization of the equivalent region in a strain lacking sly. Sequence comparison of these regions from sly-positive (P1/7) and sly-negative (DHS) strains indicated that two alternative arrangements are both flanked by genes with highest similarity to haloacid dehalogenase-like hydrolases (S' end) and putative N-acetylmannosamine-6-phosphate epimerases (3' end). However, sly appears to be completely absent from the alternative arrangement, and a gene of unknown function is located in the equivalent position. Finally, PCR analysis of multiple sly-positive and -negative strains indicated that these two alternative genetic arrangements are conserved among many S. suis isolates.