Department of Hospital Infection Control, Narayana Health City, Bengaluru, India.
Department of Microbiology, Narayana Health City, Bengaluru, India.
Indian J Med Res. 2017 Jul;146(Supplement):S15-S22. doi: 10.4103/ijmr.IJMR_1201_16.
BACKGROUND & OBJECTIVES: Outbreaks of infection due to Salmonella enterica servovar Typhi (S. Typhi) are a great threat to public health. A rapid molecular typing method to characterize strains implicated in an outbreak is critical in implementing appropriate control measures. This study was done to demonstrate the power of a PCR-based method to provide rapid insights into the genetic relatedness amongst the Salmonella isolates implicated in a suspected typhoid fever outbreak.
Forty two S. Typhi isolates originating from three geographically distinct areas, with one area suspected to have a single-source outbreak were included in the study. The genetic fingerprint of all isolates was generated using enterobacterial repetitive intergenic consensus sequence based-PCR (ERIC-PCR). The antimicrobial susceptibility profiles were also evaluated.
ERIC-PCR was found to be rapid and reproducible with a discriminatory index of 0.766. The dendrogram constructed based on ERIC-PCR fingerprinting revealed the existence of 12 distinct genotypes. The location suspected to have an outbreak displayed two genotypes amongst the 24 isolates. The other two locations (18 isolates) displayed genetic heterogeneity. The clonality of the outbreak isolates from the time-matched control isolates was established. The observed antimicrobial susceptibility profiles did not have any discriminatory power to subtype the isolates compared to the genetic fingerprints.
INTERPRETATION & CONCLUSIONS: Our study demonstrated the discriminatory power and value of ERIC-PCR in the typing of S. Typhi isolates and providing valuable epidemiological insights.
肠沙门氏菌血清型 Typhi（S. Typhi）引起的感染爆发对公共卫生构成了巨大威胁。快速的分子分型方法对于鉴定爆发中涉及的菌株至关重要，这有助于实施适当的控制措施。本研究旨在展示基于 PCR 的方法在提供有关疑似伤寒爆发中沙门氏菌分离株遗传相关性的快速见解方面的强大功能。
本研究纳入了来自三个地理位置不同的地区的 42 株 S. Typhi 分离株，其中一个地区疑似发生单一来源的爆发。使用肠杆菌重复基因间一致序列聚合酶链反应（ERIC-PCR）生成所有分离株的遗传指纹图谱。还评估了抗菌药物敏感性谱。
ERIC-PCR 快速且可重复， discriminatory index 为 0.766。基于 ERIC-PCR 指纹图谱构建的聚类树状图显示存在 12 种不同的基因型。疑似爆发的地区在 24 株分离株中显示出两种基因型。其他两个地区（18 株分离株）显示出遗传异质性。从时间匹配的对照分离株中确定了爆发分离株的克隆性。与遗传指纹图谱相比，观察到的抗菌药物敏感性谱没有任何区分能力来对分离株进行亚型分类。
我们的研究表明，ERIC-PCR 在 S. Typhi 分离株的分型方面具有区分能力和价值，并提供了有价值的流行病学见解。
