Analysis of multidrug resistant group B streptococci with reduced penicillin susceptibility forming small, less hemolytic colonies.
Analysis of multidrug resistant group B streptococci with reduced penicillin susceptibility forming small, less hemolytic colonies.
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DOI：
10.1371/journal.pone.0183453
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发表时间：
2017
期刊：
影响因子：
3.7
通讯作者：
Arakawa Y
中科院分区：
文献类型：
--
作者：
Banno H;Kimura K;Tanaka Y;Sekizuka T;Kuroda M;Jin W;Wachino JI;Yamada K;Shibayama K;Arakawa Y
B族链球菌（GBS;无乳链球菌（Streptococcus agalactiae）是新生儿侵袭性疾病的主要原因，也是老年人的重要病原体。到目前为止，几乎所有青霉素敏感性降低的GBS（PRGBS）都显示出β-溶血活性，并在羊血琼脂上生长。然而，我们先前已经报道了三种携带CylK缺失的PRGBS临床分离株，其形成较小的溶血性菌落。在这项研究中，我们研究了这些临床分离株中小的、溶血性较小的菌落形成的原因。对同基因菌株进行测序以鉴定与小菌落大小相关的突变。我们在硫胺素焦磷酸激酶（tpk）基因中发现了276_277insG核酸插入，导致TPK第103位氨基酸提前终止，作为导致小菌落形成的候选突变。在tpk基因上插入276_277insG的重组菌株Δtpk表现出小菌落形成。重组菌株ΔcylK（其在cylK中具有G379 T置换）显示溶血活性降低。两种重组菌株的表型分别通过完整TPK或CylK的表达来补充。此外，使用Rapid ID 32 API和VITEK MS鉴定菌株为GBS，对临床分离株和重组菌株进行了评价。VITEK MS（而非Rapid ID 32 API）能够准确鉴定菌株为GBS。总之，我们确定tpk和cylK突变分别导致小菌落和溶血活性降低，并详细描述了临床分离株的特征。
Group B streptococci (GBS; Streptococcus agalactiae) are the leading cause of neonatal invasive diseases and are also important pathogens for elderly adults. Until now, nearly all GBS with reduced penicillin susceptibility (PRGBS) have shown β-hemolytic activity and grow on sheep blood agar. However, we have previously reported three PRGBS clinical isolates harboring a CylK deletion that form small less hemolytic colonies. In this study, we examined the causes of small, less hemolytic colony formation in these clinical isolates. Isogenic strains were sequenced to identify the mutation related to a small colony size. We identified a 276_277insG nucleic acid insertion in the thiamin pyrophosphokinase (tpk) gene, resulting in premature termination at amino acid 103 in TPK, as a candidate mutation responsible for small colony formation. The recombinant strain Δtpk, which harbored the 276_277insG insertion in the tpk gene, showed small colony formation. The recombinant strain ΔcylK, which harbored the G379T substitution in cylK, showed a reduction in hemolytic activity. The phenotypes of both recombinant strains were complemented by the expression of intact TPK or CylK, respectively. Moreover, the use of Rapid ID 32 API and VITEK MS to identify strains as GBS was evaluated clinical isolates and recombinant strains. VITEK MS, but not Rapid ID 32 API, was able to accurately identify the strains as GBS. In conclusion, we determined that mutations in tpk and cylK caused small colonies and reduced hemolytic activity, respectively, and characterized the clinical isolates in detail.
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影响因子：
4.4
作者：
Miyamoto M;Motooka D;Gotoh K;Imai T;Yoshitake K;Goto N;Iida T;Yasunaga T;Horii T;Arakawa K;Kasahara M;Nakamura S
通讯作者：
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作者：
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作者：
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通讯作者：
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影响因子：
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作者：
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通讯作者：
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影响因子：
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作者：
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通讯作者：
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