Vaccinology Theme, Medical Research Council Unit , Banjul , The Gambia ; Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine , London , United Kingdom.
Vaccinology Theme, Medical Research Council Unit , Banjul , The Gambia.
PeerJ. 2015 Apr 30;3:e903. doi: 10.7717/peerj.903. eCollection 2015.
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.
1 型肺炎链球菌是侵袭性肺炎球菌病的主要病因之一。然而，这种侵袭性血清型在鼻咽无症状携带中很少见，因此需要进行大规模的流行病学研究来评估 1 型感染的动态变化。在冈比亚农村地区进行的一项评估 PCV-7 疫苗接种对鼻咽携带影响的大型聚类随机试验中，我们进行了一项辅助分析，描述了 1 型肺炎链球菌鼻咽携带的流行情况及其更常见基因型的时间变化。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 个月收集鼻咽拭子（NPS）。将接种后时间分为三个时期，以确保样本数量的分布均匀：（1）2006 年 7 月至 2007 年 3 月，（2）2007 年 4 月至 2008 年 3 月，（3）2008 年 4 月至 2009 年 2 月。通过 MLST 对 1 型肺炎链球菌进行了基因分型。从 12319 份 NPS 样本中，有 87 份（0.71%）回收了 1 型肺炎链球菌。在疫苗接种前时期，两个研究组的 1 型血清型流行率均为 0.47%。在接种后时期，完全接种村庄的流行率在第 1 期为 0.08%，第 2 期为 0.165%，而部分接种村庄的流行率在第 3 期为 0.17%，第 2 期为 1.34%。总体而言，获得了四种不同的基因型，其中 ST3081 最为常见（60.71%），其次是 ST618（29.76%）。ST3081 仅在接种后第 2 期和第 3 期发现，而 ST618 在接种后第 3 期已消失。这些主要基因型的分布在两个研究组中相似。ST3081 的出现和 ST618 的同时消失可能表明该地区肺炎链球菌 1 型的分子流行病学发生了变化。这种变化不太可能与缺乏血清型 1 的 PCV-7 的引入有关，因为它在两个研究组中同时观察到。未来的基于人群的流行病学研究将提供进一步的证据，证明肺炎链球菌 1 型流行病学的实质性变化以及可能的机制。
