Objective To assess the loop-mediated isothermal amplification (LAMP) to detect cell-free DNA from Streptococcus pneumoniae in urine samples from children with pneumococcal pneumonia.

Methods LAMP reactions using four primers (backward inner primer, forward inner primer, B3, and F3) targeting conserved regions of the S. pneumoniae ply gene and DNA from the recombinant plasmid pTrc99A-ply were optimized for temperature (65°C) and MgSO₄ concentration (8 mM) conditions. Urine samples from 71 patients with symptoms of pneumonia and from 17 healthy children were tested side by side using the isothermal methodology LAMP and the commercial urinary antigen test, BinaxNOW S. pneumoniae assay. Percentages of sensitivity, specificity, positive predictive value (PPV), negative predictive value, and positive (LR) were calculated to compare both tests.

Results The specificity of the LAMP reaction was confirmed against several species of bacteria and yeast that can cause pneumonia or urine infections. The suitability of the LAMP assay was evaluated in urine samples from 71 patients and 17 healthy children. All patients (100%) with confirmed pneumococcal pneumonia were positive for the LAMP assay. Among patients with possible/probable pneumonia, 74.1% were identified as positive using the LAMP test. Notably, a higher specificity (95.4%), PPV (94.1%) and positive LR (21.7) were found compared with the urinary antigen test.

Conclusion The presence of S. pneumoniae cell-free DNA in urine samples of pediatric patients can be used as a specific diagnostic biomarker for community-acquired pneumonia by using the LAMP methodology.

目的 评估环介导的等温扩增（LAMP）技术检测肺炎球菌性肺炎患儿尿液样本中肺炎链球菌的无细胞DNA 。

方法 使用针对肺炎链球菌ply基因保守区域的四种引物（向后内部引物，向前内部引物，B3和F3）进行LAMP反应，并针对温度（65°C）和MgSO4优化重组质粒pTrc99A- ply的DNA _4个浓度（8 mM）条件。使用等温方法LAMP和商业尿液抗原测试BinaxNOW肺炎链球菌测定，对71例有肺炎症状的患者和17例健康儿童的尿液样品进行了并行测试。计算敏感性，特异性，阳性预测值（PPV），阴性预测值和阳性（LR）的百分比以比较两种测试。

结果 证实了LAMP反应对几种细菌和酵母的特异性，这些细菌和酵母可能引起肺炎或尿液感染。在来自71名患者和17名健康儿童的尿液样本中评估了LAMP分析的适用性。所有确诊为肺炎球菌性肺炎的患者（100％）LAMP测定均为阳性。在LAMP试验中，在可能/可能的肺炎患者中，有74.1％被鉴定为阳性。值得注意的是，与尿液抗原检测相比，发现特异性更高（95.4％），PPV（94.1％）和LR阳性（21.7）。

结论小儿肺炎链球菌无细胞DNA 的存在可以通过LAMP方法作为社区获得性肺炎的诊断生物标志物。