Use of Recombinant Endolysin to Improve Accuracy of Group B Streptococcus Tests
Use of Recombinant Endolysin to Improve Accuracy of Group B Streptococcus Tests
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DOI：
10.1128/spectrum.00077-21
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发表时间：
2021-08
影响因子：
3.7
通讯作者：
H. Matsui;Jumpei Uchiyama;Masaya Ogata;Tadahiro Nasukawa;Iyo Takemura-Uchiyama;Shin-ichiro Kato;Hironobu Murakami;M. Higashide;H. Hanaki
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作者：
H. Matsui;Jumpei Uchiyama;Masaya Ogata;Tadahiro Nasukawa;Iyo Takemura-Uchiyama;Shin-ichiro Kato;Hironobu Murakami;M. Higashide;H. Hanaki
内溶素是一种源自噬菌体的酶，可降解宿主细菌细胞壁中的肽聚糖；它可以用作选择性消除特定细菌属/种的抗菌剂。 B 族链球菌 (GBS) 通过垂直传播引起新生儿感染；产前 GBS 筛查试验（富集培养后进行细菌鉴定）用于检测孕妇是否存在 GBS。摘要 B 族链球菌 (GBS) 通过垂直传播引起严重的新生儿感染。产前GBS筛查测试在怀孕后期进行，以避免感染风险。在此测试中，先进行富集培养，然后进行 GBS 鉴定。使用选择性培养基进行富集；然而，粪肠球菌是拭子样本中的潜在污染物，可能会干扰 GBS 的生长。这种细菌污染可能导致假阴性结果。内溶素是一种源自噬菌体的酶，可降解细菌细胞壁中的肽聚糖；它是一种有前途的抗菌剂，可选择性消除特定细菌属/种。在这项研究中，我们使用了粪肠球菌特有的重组细胞内溶素EG-LYS；细胞内溶素可能在选择性培养物中富集 GBS。首先，在假阴性模型（GBS 和粪肠球菌共培养，在随后的 GBS 鉴定测试中禁用 GBS 检测）中，0.1 mg/ml EG-LYS 处理改善了 GBS 检测。接下来，我们使用 548 份阴道拭子来测试 EG-LYS 治疗在改善 GBS 检测方面的功效。 EG-LYS 处理 (0.1 mg/ml) 将 GBS 阳性率增加至 17.9%，而对照（磷酸盐缓冲盐水 [PBS] 处理）为 15.7%。此外，在一些样品中，经 EG-LYS 处理后，GBS 菌落数量有所增加。这些结果得到了富集培养物的微生物群分析的支持。总之，EG-LYS 对富集培养物的处理可能会提高产前 GBS 筛查测试的准确性。重要性 内溶素是一种源自噬菌体的酶，可降解宿主细菌细胞壁中的肽聚糖；它可以用作选择性消除特定细菌属/种的抗菌剂。 B 族链球菌 (GBS) 通过垂直传播引起新生儿感染；产前 GBS 筛查试验（富集培养后进行细菌鉴定）用于检测孕妇是否存在 GBS。然而，临床标本中存在粪肠球菌等共生菌，可抑制选择性富集培养中GBS的生长，导致假阴性结果。在这里，我们证明，在富集培养物中应用最初分离的细胞内溶素，可以通过抑制不需要的粪肠球菌生长来提高测试准确性，从而避免假阴性结果，不仅在实验环境中，而且在使用阴道拭子的测试中也是如此。
Endolysin is a bacteriophage-derived enzyme that degrades the peptidoglycan in the cell wall of host bacteria; it could be used as an antimicrobial agent for selectively eliminating specific bacterial genera/species. Group B Streptococcus (GBS) causes neonatal infection via vertical transmission; prenatal GBS screening test, in which enrichment culture is followed by bacterial identification, is used to detect the presence of GBS in pregnant women. ABSTRACT Group B Streptococcus (GBS) causes serious neonatal infection via vertical transmission. The prenatal GBS screening test is performed at the late stage of pregnancy to avoid risks of infection. In this test, enrichment culture is performed, followed by GBS identification. Selective medium is used for the enrichment; however, Enterococcus faecalis, which is a potential contaminant in swab samples, can interfere with the growth of GBS. Such bacterial contamination can lead to false-negative results. Endolysin, a bacteriophage-derived enzyme, degrades peptidoglycan in the bacterial cell wall; it is a promising antimicrobial agent for selectively eliminating specific bacterial genera/species. In this study, we used the recombinant endolysin EG-LYS, which is specific to E. faecalis; the endolysin potentially enriched GBS in the selective culture. First, in the false-negative model (coculture of GBS and E. faecalis, which disabled GBS detection in the subsequent GBS identification test), EG-LYS treatment at 0.1 mg/ml improved GBS detection. Next, we used 548 vaginal swabs to test the efficacy of EG-LYS treatment in improving GBS detection. EG-LYS treatment (0.1 mg/ml) increased the GBS-positive ratio to 17.9%, compared to 15.7% in the control (phosphate-buffered saline [PBS] treatment). In addition, there were an increased number of GBS colonies under EG-LYS treatment in some samples. The results were supported by the microbiota analysis of the enriched cultures. In conclusion, EG-LYS treatment of the enrichment culture potentially improves the accuracy of the prenatal GBS screening test. IMPORTANCE Endolysin is a bacteriophage-derived enzyme that degrades the peptidoglycan in the cell wall of host bacteria; it could be used as an antimicrobial agent for selectively eliminating specific bacterial genera/species. Group B Streptococcus (GBS) causes neonatal infection via vertical transmission; prenatal GBS screening test, in which enrichment culture is followed by bacterial identification, is used to detect the presence of GBS in pregnant women. However, the presence of commensal bacteria such as Enterococcus faecalis in clinical specimens can inhibit GBS growth in the selective enrichment culture, resulting in false-negative result. Here, we demonstrated that the application of originally isolated endolysin in the enrichment culture improved the test accuracy by inhibiting unwanted E. faecalis growth and therefore avoiding false-negative results, not only in experimental settings, but also in tests using vaginal swabs.