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背景:目前世界正在开展很多结核病流行病学研究。对IS6110杂交带少于6条的菌株应用一个二级标志物指纹分析增强了菌株的追踪,但它对人群结论的影响尚未很好地研究。 目的:对低拷贝结核分支杆菌菌株应用多态性富含GC重复序列(PGRS)进行二级基因分型。探讨其对以人群为研究背景的流行病学研究结论的影响。 设计:对1991—1996年旧金山结核病例,通过单用IS6110及联合采用PGRS/IS6110定义菌株成簇,以便1)估计近期的传播;2)评价细菌群体参数在理论上对这些估计的影响;3)评价近期传播的危险因素。 结果:对低拷贝菌株(所有菌株的20.3％)进行二级分型,使近期传播的估算值由29.1％下降到25.3％(P=0.03)。补充基因分型造成不同估算值的最主要的影响参数是低拷贝菌株的比例和成簇的数量。对于上述两种分析方法而言。导致近期传播的危险因素是一样的。 结论:结核分支杆菌二级基因分型的统计和推论似乎取决于人群中低拷贝菌株的比例。该比例低时,或没有多少二级特型匹配时,补充基因分型在人群水平研究中的作用可能就很小。
Background: There are many tuberculosis epidemiological studies in the world. The use of a secondary marker fingerprinting to enhance strain tracking of strains with less than 6 IS6110 crosses enhanced the strain’s tracing but its impact on population conclusions has not been well studied. Objective: To classify low-copy Mycobacterium tuberculosis strains using polymorphism-rich GC repeats (PGRS) for secondary genotyping. To explore its impact on population-based epidemiological studies. Design: San Francisco tuberculosis cases 1991-1996, strains grouped by IS6110 alone and in combination with PGRS / IS6110 to cluster 1) to estimate recent transmission; 2) to assess the theoretical impact of bacterial population parameters on these estimates; 3 ) To evaluate the recent spread of risk factors. RESULTS: Secondary classification of low-copy strains (20.3% of all strains) resulted in a reduction in the estimated spread from 29.1% to 25.3% (P = 0.03). The most important influence parameters for different estimates resulting from supplemental genotyping are the proportion of low-copy strains and the number of clusters. For both methods of analysis above. The risk factors leading to the recent spread are the same. Conclusions: The statistics and inferences about secondary genotyping of M. tuberculosis seem to depend on the proportion of low-copy strains in the population. When this ratio is low, or when there are not many secondary trait matches, the role of complementary genotyping in population-level studies may be small.