Martín Ana, Herranz Marta, Lirola Miguel Martínez, Fernández Rosa Fernández, Bouza Emilio, García de Viedma Darío
Servicio de Microbiología Clínica y Enfermedades Infecciosas, Hospital Gregorio Marañón, Universidad Complutense, Madrid, CIBER-Enfermedades Respiratorias CIBERES, Spain.
BMC Microbiol. 2008 Feb 14;8:30. doi: 10.1186/1471-2180-8-30.
The phenomenon of misdiagnosing tuberculosis (TB) by laboratory cross-contamination when culturing Mycobacterium tuberculosis (MTB) has been widely reported and it has an obvious clinical, therapeutic and social impact. The final confirmation of a cross-contamination event requires the molecular identification of the same MTB strain cultured from both the potential source of the contamination and from the false-positive candidate. The molecular tool usually applied in this context is IS6110-RFLP which takes a long time to provide an answer, usually longer than is acceptable for microbiologists and clinicians to make decisions. Our purpose in this study is to evaluate a novel PCR-based method, MIRU-VNTR as an alternative to assure a rapid and optimized analysis of cross-contamination alerts.
MIRU-VNTR was prospectively compared with IS6110-RFLP for clarifying 19 alerts of false positivity from other laboratories. MIRU-VNTR highly correlated with IS6110-RFLP, reduced the response time by 27 days and clarified six alerts unresolved by RFLP. Additionally, MIRU-VNTR revealed complex situations such as contamination events involving polyclonal isolates and a false-positive case due to the simultaneous cross-contamination from two independent sources.
Unlike standard RFLP-based genotyping, MIRU-VNTR i) could help reduce the impact of a false positive diagnosis of TB, ii) increased the number of events that could be solved and iii) revealed the complexity of some cross-contamination events that could not be dissected by IS6110-RFLP.
在培养结核分枝杆菌（MTB）时，因实验室交叉污染导致误诊结核病（TB）的现象已被广泛报道，且具有明显的临床、治疗和社会影响。交叉污染事件的最终确认需要对来自潜在污染源和假阳性样本中培养出的相同MTB菌株进行分子鉴定。在此情况下通常应用的分子工具是IS6110-RFLP，但其得出结果所需时间较长，通常超出微生物学家和临床医生做出决策所能接受的时间。本研究的目的是评估一种基于PCR的新方法——间隔寡核苷酸重复序列可变数目串联重复分析（MIRU-VNTR），作为确保对交叉污染警报进行快速且优化分析的替代方法。
前瞻性地比较了MIRU-VNTR与IS6110-RFLP，以澄清来自其他实验室的19例假阳性警报。MIRU-VNTR与IS6110-RFLP高度相关，将响应时间缩短了27天，并澄清了6个RFLP未能解决的警报。此外，MIRU-VNTR还揭示了复杂情况，如涉及多克隆分离株的污染事件以及由两个独立来源同时交叉污染导致的假阳性病例。
与基于标准RFLP的基因分型不同，MIRU-VNTR：i）有助于减少结核病假阳性诊断的影响；ii）增加了可解决事件的数量；iii）揭示了一些IS6110-RFLP无法剖析的交叉污染事件的复杂性。
