Department of Obstetrics and Gynecology, University Hospitals of Geneva, Geneva, Switzerland.
Gynecol Obstet Invest. 2010;70(4):250-5. doi: 10.1159/000314014. Epub 2010 Oct 16.
Group B Streptococcus (GBS) and Escherichiacoli(E. coli) are the leading causes of early-onset neonatal disease (EOD). Intrapartum antibiotic prophylaxis of GBS-colonized women decreases vertical transmission and EOD due to GBS. Nevertheless, no intervention has been developed to reduce the risk of EOD related to E. coli. Timely and accurate identification of colonized mothers is necessary to implement preventive strategies against neonatal sepsis. To screen for colonization during labor, we developed a real-time PCR assay for the simultaneous detection of GBS and neonatal invasive strains of E. coli.
Specific DNA targets for GBS are publicly available. For neonatal invasive E. coli, we analyzed candidate DNA targets by DNA hybridization on microarrays of invasive strains isolated from neonatal E. coli sepsis or meningitis (K1 and not K1 'invasive' serotypes). Specificity of DNA probes was tested against a panel of bacteria and by simulating clinical conditions (spiking vaginal samples from pregnant women). Then, the characteristics of the selected probes were evaluated in a pilot study including 200 women in labor.
Prevalence of rectovaginal GBS and of vaginal and cervical E. coliserotype K1 colonization were 16.0, 3.5 and 3.5% by culture and 27, 10 and 8.5% by PCR, respectively. The prevalence of other invasive E. coli in the vagina and in the cervix, detected by PCR, was around 10%. Compared to the culture, considered as the gold standard, the sensitivities of the PCRs for the GBS and E. coli K1 were 97 and 71%, respectively. Specificities were 86 and 92%, respectively. Specificity is difficult to interpret, as a false-positive PCR result may in fact be a false-negative result of the culture. The turnaround time needed for PCR analysis was 2.5 h, compared to a minimum of 48 h for the culture.
Our rapid PCR is reliable in detecting GBS in women in labor. Optimization of the PCR for invasive E. coli is needed before its implementation in clinical practice. More efforts to fight against main causes of neonatal sepsis need to be undertaken to prevent this terrible medical complication.
B 群链球菌（GBS）和大肠杆菌（E. coli）是导致早发性新生儿疾病（EOD）的主要原因。对 GBS 定植的产妇进行产时抗生素预防可降低 GBS 垂直传播和 EOD 的风险。然而，尚未开发出干预措施来降低与大肠杆菌相关的 EOD 风险。及时准确地识别定植的产妇是实施新生儿败血症预防策略的必要条件。为了在分娩时筛查定植，我们开发了一种实时 PCR 检测方法，用于同时检测 GBS 和新生儿侵袭性大肠杆菌。
GBS 的特定 DNA 靶标是公开的。对于新生儿侵袭性大肠杆菌，我们通过对分离自新生儿大肠杆菌败血症或脑膜炎的侵袭性菌株的微阵列进行 DNA 杂交来分析候选 DNA 靶标（K1 而非 K1'侵袭性'血清型）。DNA 探针的特异性通过针对一组细菌进行测试和模拟临床条件（从孕妇阴道样本中添加）来测试。然后，在包括 200 名分娩妇女的试点研究中评估所选探针的特征。
通过培养法，直肠阴道 GBS 和阴道及宫颈 E. coli K1 定植的流行率分别为 16.0%、3.5%和 3.5%，PCR 检测结果分别为 27.0%、10.0%和 8.5%。通过 PCR 检测，阴道和宫颈中其他侵袭性大肠杆菌的流行率约为 10%。与作为金标准的培养相比，GBS 和 E. coli K1 的 PCR 检测的敏感性分别为 97%和 71%。特异性分别为 86%和 92%。特异性较难解释，因为 PCR 结果的假阳性可能实际上是培养的假阴性结果。PCR 分析所需的周转时间为 2.5 小时，而培养法的最短时间至少为 48 小时。
我们的快速 PCR 可可靠地检测分娩妇女中的 GBS。需要进一步优化 PCR 检测侵袭性大肠杆菌的方法，然后再将其应用于临床实践。需要更加努力地应对新生儿败血症的主要原因，以预防这种可怕的医疗并发症。
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