Darton Thomas C, Zhou Liqing, Blohmke Christoph J, Jones Claire, Waddington Claire S, Baker Stephen, Pollard Andrew J
Oxford Vaccine Group, Department of Paediatrics and the NIHR Oxford Biomedical Research Centre, University of Oxford, Oxford, United Kingdom; The Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Viet Nam.
Oxford Vaccine Group, Department of Paediatrics and the NIHR Oxford Biomedical Research Centre, University of Oxford, Oxford, United Kingdom.
J Infect. 2017 Apr;74(4):358-366. doi: 10.1016/j.jinf.2017.01.006. Epub 2017 Jan 24.
Improved diagnostics for typhoid are needed; a typhoid controlled human infection model may accelerate their development and translation. Here, we evaluated a blood culture-PCR assay for detecting infection after controlled human infection with S. Typhi and compared test performance with optimally performed blood cultures.
METHODOLOGY/PRINCIPAL FINDINGS: Culture-PCR amplification of blood samples was performed alongside daily blood culture in 41 participants undergoing typhoid challenge. Study endpoints for typhoid diagnosis (TD) were fever and/or bacteraemia. Overall, 24/41 (59%) participants reached TD, of whom 21/24 (86%) had ≥1 positive blood culture (53/674, 7.9% of all cultures) or 18/24 (75%) had ≥1 positive culture-PCR assay result (57/684, 8.3%). A further five non-bacteraemic participants produced culture-PCR amplicons indicating infection; overall sensitivity/specificity of the assay compared to the study endpoints were 70%/65%. We found no significant difference between blood culture and culture-PCR methods in ability to identify cases (12 mismatching pairs, p = 0.77, binomial test). Clinical and stool culture metadata demonstrated that additional culture-PCR amplification positive individuals likely represented true cases missed by blood culture, suggesting the overall attack rate may be 30/41 (73%) rather than 24/41 (59%). Several participants had positive culture-PCR results soon after ingesting challenge providing new evidence for occurrence of an early primary bacteraemia.
CONCLUSIONS/SIGNIFICANCE: Overall the culture-PCR assay performed well, identifying extra typhoid cases compared with routine blood culture alone. Despite limitations to widespread field-use, the benefits of increased diagnostic yield, reduced blood volume and faster turn-around-time, suggest that this assay could enhance laboratory typhoid diagnostics in research applications and high-incidence settings.
伤寒的诊断方法需要改进；伤寒受控人类感染模型可能会加速其开发和转化。在此，我们评估了一种血培养-聚合酶链反应（PCR）检测方法，用于检测人类感染伤寒杆菌后的感染情况，并将检测性能与最佳血培养结果进行比较。
方法/主要发现：在41名接受伤寒挑战的参与者中，每天进行血培养的同时对血样进行培养-PCR扩增。伤寒诊断（TD）的研究终点为发热和/或菌血症。总体而言，24/41（59%）的参与者达到TD，其中21/24（86%）的血培养结果≥1次为阳性（674次培养中的53次，占所有培养的7.9%），或18/24（75%）的培养-PCR检测结果≥1次为阳性（684次检测中的57次，占8.3%）。另外5名非菌血症参与者产生了表明感染的培养-PCR扩增子；与研究终点相比，该检测方法的总体敏感性/特异性为70%/65%。我们发现血培养和培养-PCR方法在识别病例的能力上没有显著差异（12对不匹配，p = 0.77，二项式检验）。临床和粪便培养元数据表明，培养-PCR扩增阳性的其他个体可能代表血培养遗漏的真正病例，这表明总体发病率可能为30/41（73%），而非24/41（59%）。几名参与者在摄入挑战后不久培养-PCR结果呈阳性，为早期原发性菌血症的发生提供了新证据。
结论/意义：总体而言，培养-PCR检测表现良好，与单独的常规血培养相比，能识别出更多伤寒病例。尽管在广泛的现场应用存在局限性，但诊断率提高、血样量减少和周转时间加快的益处表明，该检测方法可在研究应用和高发病率地区增强实验室伤寒诊断。
