Temporal changes in nasopharyngeal carriage of Streptococcus pneumoniae serotype 1 genotypes in healthy Gambians before and after the 7-valent pneumococcal conjugate vaccine.
Temporal changes in nasopharyngeal carriage of Streptococcus pneumoniae serotype 1 genotypes in healthy Gambians before and after the 7-valent pneumococcal conjugate vaccine.
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作者：
Ebruke C;Roca A;Egere U;Darboe O;Hill PC;Greenwood B;Wren BW;Adegbola RA;Antonio M
肺炎链球菌血清型1是侵袭性肺炎球菌疾病的主要原因之一。然而，这种侵袭性血清型在鼻咽部无症状携带者中很难发现，因此需要进行大规模的流行病学研究来评估血清1型感染的动态。在冈比亚农村进行的一项大型随机分组试验的背景下，以评估PCV-7疫苗接种对鼻咽携带的影响，我们提出了一个辅助分析，描述了鼻咽携带肺炎球菌血清1型的患病率及其更常见的基因型的时间变化。在PCV-7疫苗接种前（2003年12月至2004年5月）和PCV-7疫苗接种后30个月内采集鼻咽拭子（拭子）。疫苗接种后时间分为三个时期，以确保样本数量均匀分布：（1）2006年7月至2007年3月，（2）2007年4月至2008年3月和（3）2008年4月至2009年2月。S.通过MLST对肺炎血清型1进行基因分型。从收集的12，319份样本中回收了87份（0.71%）血清1型。在疫苗接种前阶段，两个研究组中血清1型的患病率均为0.47%。在疫苗接种后阶段，完全接种疫苗的村庄的流行率在阶段1的0.08%和阶段2的0.165%之间，而部分接种疫苗的村庄的流行率在阶段3的0.17%和阶段2的1.34%之间。总体而言，获得了四种不同的基因型，其中ST 3081最普遍（60.71%），其次是ST 618（29.76%）。ST 3081仅在接种后第2和第3阶段发现，而ST 618在接种后第3阶段消失。这些主要基因型的分布在两个研究组中相似。ST 3081的出现和伴随的ST 618的消失可能表明该地区肺炎球菌血清1型的分子流行病学发生了变化。该变化不太可能与PCV-7（缺乏血清1型）的引入相关，因为在两个研究组中同时观察到该变化。未来基于人群的流行病学研究将为肺炎球菌血清1型流行病学的实质性变化及其可能机制提供进一步证据。
Streptococcus pneumoniae serotype 1 is one of the leading causes of invasive pneumococcal disease. However, this invasive serotype is hardly found in nasopharyngeal asymptomatic carriage and therefore large epidemiological studies are needed to assess the dynamics of serotype 1 infection. Within the context of a large cluster randomized trial conducted in rural Gambia to assess the impact of PCV-7 vaccination on nasopharyngeal carriage, we present an ancillary analysis describing the prevalence of nasopharyngeal carriage of pneumococcal serotype 1 and temporal changes of its more frequent genotypes. Nasopharyngeal swabs (NPS) were collected before PCV-7 vaccination (December 2003–May 2004) and up to 30 months after PCV-7 vaccination. The post-vaccination time was divided in three periods to ensure an equal distribution of the number of samples: (1) July 2006–March 2007, (2) April 2007–March 2008 and (3) April 2008–Feb 2009. S. pneumoniae serotype 1 were genotyped by MLST. Serotype 1 was recovered from 87 (0.71%) of 12,319 NPS samples collected. In the pre-vaccination period, prevalence of serotype 1 was 0.47% in both study arms. In the post-vaccination periods, prevalence in the fully vaccinated villages ranged between 0.08% in period 1 and 0.165% in period 2, while prevalence in partly vaccinated villages was between 0.17% in period 3 and 1.34% in period 2. Overall, four different genotypes were obtained, with ST3081 the most prevalent (60.71%), followed by ST618 (29.76%). ST3081 was found only in post-vaccination period 2 and 3, while ST618 had disappeared in post-vaccination period 3. Distribution of these major genotypes was similar in both study arms. Emergence of ST3081 and concomitant disappearance of ST618 may suggest a change in the molecular epidemiology of pneumococcal serotype 1 in this region. This change is not likely to be associated with the introduction of PCV-7 which lacks serotype 1, as it was observed simultaneously in both study arms. Future population-based epidemiological studies will provide further evidence of substantive changes in the pneumococcal serotype 1 epidemiology and the likely mechanisms.
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