Infectious Diseases Unit, Hospital Universitari Mútua de Terrassa, Barcelona, Spain; Universitat Internacional de Catalunya, Barcelona, Spain; Universitat de Barcelona, Barcelona, Spain.
Infectious Diseases Unit, Hospital Universitari Mútua de Terrassa, Barcelona, Spain.
Clin Microbiol Infect. 2022 Jan;28(1):138.e1-138.e7. doi: 10.1016/j.cmi.2021.05.049. Epub 2021 Jun 8.
The aim of the study was to assess the performance of real-time PCR targeting the lytA gene (rtPCR-lytA) in plasma, urine and nasopharyngeal (NP) samples for the diagnosis of pneumococcal community-acquired pneumonia (P-CAP).
Prospective observational study including all consecutive adults with CAP from November 2015 to May 2017. P-CAP was defined if pneumococcus was identified using conventional methods (CM) and/or a positive rtPCR-lytA was detected in blood, urine or NP samples (NP cut-off ≥8000 copies/mL). Diagnostic performance of each test was calculated.
A total of 133 individuals with CAP were included. Of these, P-CAP was diagnosed in 62 (46.6%). The proportion of P-CAP diagnosed by rtPCR-lytA methods was significantly higher than that diagnosed by CM (87.1% versus 59.7%, p 0.005). The rtPCR-lytA identified Streptococcus pneumoniae in 25 patients (40.3% of all individuals with P-CAP) whose diagnosis would have been missed by CM. NP-rtPCR-lytA allowed diagnosis of 62.3% of P-CAP. A nasopharyngeal colonization density ≥2351 copies/mL predicted P-CAP diagnosis (area under the curve = 0.82, sensitivity 83.3%, specificity 80.9%). There was a positive correlation between increasing bacterial load in blood and CURB-65 score (Spearman correlation coefficient r = 0.4, p 0.001), pneumonia severity index (r = 0.3, p 0.02) and time to clinical stability (r = 0.33, p 0.01). Median bacterial load in blood was higher in P-CAP patients with bacteraemia (0.65 × 10 versus 0 × 10 copies/mL, p 0.002), intensive care unit admission (0.68 × 10 versus 0 × 10 copies/mL, p 0.04) or mechanical ventilation (7.45 × 10 versus 0 × 10 copies/mL, p 0.04).
The use of rtPCR-lytA methods significantly increased the diagnosis of P-CAP compared with CM. Nasopharyngeal swabs rtPCR-lytA detection, with an accurate cut-off value, was the most promising among molecular methods for the diagnosis of P-CAP.
本研究旨在评估针对 lytA 基因（rtPCR-lytA）的实时 PCR 在血浆、尿液和鼻咽（NP）样本中用于诊断社区获得性肺炎（CAP）的性能。
这是一项包括 2015 年 11 月至 2017 年 5 月期间所有连续成人 CAP 患者的前瞻性观察性研究。如果使用传统方法（CM）鉴定出肺炎链球菌和/或血液、尿液或 NP 样本中检测到阳性 rtPCR-lytA（NP 截止值≥8000 拷贝/mL），则诊断为 CAP。计算每种检测方法的诊断性能。
共纳入 133 例 CAP 患者，其中 62 例（46.6%）诊断为 CAP。通过 rtPCR-lytA 方法诊断的 CAP 比例明显高于通过 CM 诊断的比例（87.1%对 59.7%，p<0.005）。rtPCR-lytA 在 25 例患者（所有 CAP 患者的 40.3%）中鉴定出肺炎链球菌，而 CM 可能会漏诊这些患者。NP-rtPCR-lytA 可诊断 62.3%的 CAP。鼻咽定植密度≥2351 拷贝/mL 可预测 CAP 诊断（曲线下面积=0.82，敏感性 83.3%，特异性 80.9%）。血液中细菌负荷增加与 CURB-65 评分（Spearman 相关系数 r=0.4，p<0.001）、肺炎严重指数（r=0.3，p=0.02）和临床稳定时间（r=0.33，p=0.01）呈正相关。菌血症（0.65×10 对 0×10 拷贝/mL，p<0.002）、入住重症监护病房（0.68×10 对 0×10 拷贝/mL，p=0.04）或机械通气（7.45×10 对 0×10 拷贝/mL，p=0.04）患者的血液中细菌负荷中位数较高。
与 CM 相比，使用 rtPCR-lytA 方法可显著提高 CAP 的诊断率。NP 拭子 rtPCR-lytA 检测，具有准确的截止值，是诊断 CAP 最有前途的分子方法之一。
