Department of Infectious Diseases and Microbiology, The University of Hong Kong - Shenzhen Hospital, Shenzhen, Guangdong, China.
Department of Medical Imaging, The University of Hong Kong - Shenzhen Hospital, Shenzhen, Guangdong, China.
PLoS Negl Trop Dis. 2024 Oct 9;18(10):e0012546. doi: 10.1371/journal.pntd.0012546. eCollection 2024 Oct.
Rickettsiosis includes a diversity of culture-negative non-specific systemic infections. Laboratory diagnosis of rickettsiosis is often not easy. In this 12-month study, six patients with a variety of rickettsia infections of the spotted fever group, typhus group and scrub typhus were diagnosed directly or indirectly by metagenomic next-generation sequencing (mNGS). The patient with Japanese spotted fever was rapidly made when mNGS analysis of the patient's blood revealed Rickettsia japonica sequences. For the two patients with Rickettsia felis chest infections, the bacterium was detected in the bronchoalveolar lavage of one case and lung biopsy of the other. Both patients had underlying malignancies, carcinoma of the breast and carcinoma of the lung respectively, and were on chemotherapy with immunosuppressive effect. For the remaining three patients who presented over a period of 13 weeks, all had fever, headache and the typical eschar. They also had increased serum transaminases and responded promptly to doxycycline. However, the Weil-Felix test results of all three patients were negative. Since we considered the three cases typical of rickettsiosis, we submitted their serum samples for mNGS analysis. Results showed that Orientia tsutsugamushi sequences were present in the serum of one case. In view of the positive mNGS results, we repeated the Weil-Felix test for the residual sera of all three patients and it revealed that those of the other two cases showed OX-19 titers of 1:640 and 1:160 respectively, inferring that these two patients probably had rickettsiosis of the typhus group. As for the patient positive for O. tsutsugamushi sequences, we also detected IgM for O. tsutsugamushi in the serum, which double confirmed that it was a case of scrub typhus. mNGS is an important molecular tool and can complement serology for laboratory diagnosis of rickettsiosis.
立克次体病包括多种培养阴性的非特异性全身感染。立克次体病的实验室诊断往往并不容易。在这项为期 12 个月的研究中，通过宏基因组下一代测序（mNGS）直接或间接诊断了 6 例斑点热群、斑疹伤寒群和恙虫病立克次体感染的各种患者。当 mNGS 分析患者血液时发现日本立克次体序列，迅速诊断出日本斑疹热患者。对于两例猫抓病胸部感染的患者，一例的支气管肺泡灌洗液中检测到细菌，另一例的肺活检中检测到细菌。这两例患者均患有恶性肿瘤，分别为乳腺癌和肺癌，且均在接受具有免疫抑制作用的化疗。对于另外 3 例在 13 周期间出现发热、头痛和典型焦痂的患者，所有患者的血清转氨酶均升高，并对强力霉素迅速反应。然而，所有 3 例患者的 Weil-Felix 检测结果均为阴性。由于我们认为这 3 例均为典型的立克次体病，我们提交了他们的血清样本进行 mNGS 分析。结果表明，1 例患者的血清中存在东方体序列。鉴于 mNGS 结果为阳性，我们对所有 3 例患者的剩余血清重新进行了 Weil-Felix 检测，结果显示另外 2 例的 OX-19 滴度分别为 1:640 和 1:160，推断这 2 例患者可能患有斑疹伤寒群立克次体病。对于东方体序列阳性的患者，我们还在血清中检测到了对东方体的 IgM，这进一步证实了这是一例恙虫病。mNGS 是一种重要的分子工具，可以补充血清学用于立克次体病的实验室诊断。
