Starr Kimberly F, Porsch Eric A, Seed Patrick C, Heiss Christian, Naran Radnaa, Forsberg L Scott, Amit Uri, Yagupsky Pablo, Azadi Parastoo, St Geme Joseph W
Department of Pediatrics and Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC.
Department of Pediatrics, The Children's Hospital of Philadelphia, Philadelphia, PA.
PLoS Pathog. 2016 Oct 19;12(10):e1005944. doi: 10.1371/journal.ppat.1005944. eCollection 2016 Oct.
Kingella kingae is an encapsulated gram-negative organism that is a common cause of osteoarticular infections in young children. In earlier work, we identified a glycosyltransferase gene called csaA that is necessary for synthesis of the [3)-β-GalpNAc-(1→5)-β-Kdop-(2→] polysaccharide capsule (type a) in K. kingae strain 269-492. In the current study, we analyzed a large collection of invasive and carrier isolates from Israel and found that csaA was present in only 47% of the isolates. Further examination of this collection using primers based on the sequence that flanks csaA revealed three additional gene clusters (designated the csb, csc, and csd loci), all encoding predicted glycosyltransferases. The csb locus contains the csbA, csbB, and csbC genes and is associated with a capsule that is a polymer of [6)-α-GlcpNAc-(1→5)-β-(8-OAc)Kdop-(2→] (type b). The csc locus contains the cscA, cscB, and cscC genes and is associated with a capsule that is a polymer of [3)-β-Ribf-(1→2)-β-Ribf-(1→2)-β-Ribf-(1→4)-β-Kdop-(2→] (type c). The csd locus contains the csdA, csdB, and csdC genes and is associated with a capsule that is a polymer of [P-(O→3)[β-Galp-(1→4)]-β-GlcpNAc-(1→3)-α-GlcpNAc-1-] (type d). Introduction of the csa, csb, csc, and csd loci into strain KK01Δcsa, a strain 269-492 derivative that lacks the native csaA gene, was sufficient to produce the type a capsule, type b capsule, type c capsule, and type d capsule, respectively, indicating that these loci are solely responsible for determining capsule type in K. kingae. Further analysis demonstrated that 96% of the invasive isolates express either the type a or type b capsule and that a disproportionate percentage of carrier isolates express the type c or type d capsule. These results establish that there are at least four structurally distinct K. kingae capsule types and suggest that capsule type plays an important role in promoting K. kingae invasive disease.
金氏金杆菌是一种有荚膜的革兰氏阴性菌，是幼儿骨关节炎感染的常见病因。在早期研究中，我们鉴定出一个名为csaA的糖基转移酶基因，它是金氏金杆菌269 - 492菌株合成[3)-β-GalpNAc-(1→5)-β-Kdop-(2→]多糖荚膜（a型）所必需的。在本研究中，我们分析了来自以色列的大量侵袭性分离株和携带菌分离株，发现只有47%的分离株含有csaA。使用基于csaA侧翼序列的引物对该菌株库进行进一步检测，发现了另外三个基因簇（命名为csb、csc和csd位点），所有这些基因簇都编码预测的糖基转移酶。csb位点包含csbA、csbB和csbC基因，与一种由[6)-α-GlcpNAc-(1→5)-β-(8-OAc)Kdop-(2→]组成的聚合物荚膜（b型）相关。csc位点包含cscA、cscB和cscC基因，与一种由[3)-β-Ribf-(1→2)-β-Ribf-(1→2)-β-Ribf-(1→4)-β-Kdop-(2→]组成的聚合物荚膜（c型）相关。csd位点包含csdA、csdB和csdC基因，与一种由[P-(O→3)[β-Galp-(1→4)]-β-GlcpNAc-(1→3)-α-GlcpNAc-1-]组成的聚合物荚膜（d型）相关。将csa、csb、csc和csd位点分别导入KK01Δcsa菌株（269 - 492菌株的衍生物，缺乏天然的csaA基因），足以分别产生a型荚膜、b型荚膜、c型荚膜和d型荚膜，这表明这些位点是金氏金杆菌中决定荚膜类型的唯一因素。进一步分析表明，96%的侵袭性分离株表达a型或b型荚膜，而携带菌分离株中表达c型或d型荚膜的比例过高。这些结果表明，金氏金杆菌至少有四种结构不同的荚膜类型，并提示荚膜类型在促进金氏金杆菌侵袭性疾病中起重要作用。
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