Alexander S, Ison C
Sexually Transmitted Bacteria Reference Laboratory, Health Protection Agency, Centre for Infections, 61 Colindale Ave, London NW9 5HT, UK.
Sex Transm Infect. 2008 Feb;84(1):29-31. doi: 10.1136/sti.2007.026880. Epub 2007 Sep 12.
A new variant C trachomatis (nvCT) strain has been recently isolated in Sweden, which has a 377 bp deletion in a portion of the plasmid that is the target area for some C trachomatis nucleic acid amplification tests (NAATs). Consequently, these platforms generate false negative results when presented with this strain.
To determine if nvCT is present in England and Wales.
Specimens which had been determined to be C trachomatis positive using an unaffected platform were tested for the presence of the deletion using an in-house nested PCR assay which generated a 253 bp fragment in new variant strains and a 630 bp fragment in wild-type strains. The specimens tested could be divided into two main groups: (a) 933 specimens sourced from patients attending both genitourinary medicine services and the National Chlamydia Screening Programme were forwarded from eight key laboratories within England and Wales; (b) 179 specimens were sourced from men who have sex with men and forwarded from 30 clinics throughout the UK.
A total of 1112 specimens were screened for the presence of the 377 bp deletion. An in-house PCR method showed that 1066 were wild-type strains. Forty-six strains failed to generate an amplicon and were therefore untypable. This is consistent with differences in the analytical sensitivity of different NAATs and probably reflective of low C trachomatis DNA load. No nvCT strains were identified.
Currently, there is no evidence that nvCT is present in England and Wales. However, screening and prevalence studies are continuing and UK clinicians and microbiologists should remain vigilant for suspicious, negative results.
瑞典最近分离出一种新型沙眼衣原体（nvCT）菌株，其质粒的一部分存在377 bp的缺失，而该区域是一些沙眼衣原体核酸扩增检测（NAATs）的靶标区域。因此，当检测到这种菌株时，这些检测平台会产生假阴性结果。
确定英格兰和威尔士是否存在nvCT。
使用未受影响的平台确定为沙眼衣原体阳性的标本，通过内部巢式PCR检测缺失情况，该检测在新型菌株中产生253 bp片段，在野生型菌株中产生630 bp片段。检测的标本可分为两个主要组：（a）来自英格兰和威尔士八个主要实验室的933份标本，这些标本来自就诊于泌尿生殖医学服务机构和国家衣原体筛查计划的患者；（b）179份标本来自男男性行为者，由英国各地的30家诊所提供。
共筛查了1112份标本是否存在377 bp的缺失。内部PCR方法显示，1066份为野生型菌株。46株未能产生扩增子，因此无法分型。这与不同NAATs的分析灵敏度差异一致，可能反映了沙眼衣原体DNA载量较低。未鉴定出nvCT菌株。
目前，没有证据表明英格兰和威尔士存在nvCT。然而，筛查和患病率研究仍在继续，英国临床医生和微生物学家应对可疑的阴性结果保持警惕。
