Sub-Department of Molecular Genetics, Biomedical Department, Public Health Institute, Santiago, Chile.
Pan American Health Organization/ World Health Organization, Washington, D.C., United States of America.
PLoS One. 2018 Mar 8;13(3):e0193572. doi: 10.1371/journal.pone.0193572. eCollection 2018.
Neisseria meningitidis is a human exclusive pathogen that can lead to invasive meningococcal disease or may be carried in the upper respiratory tract without symptoms. The relationship between carriage and disease remains poorly understood but it is widely accepted that decreasing carriage by immunization should lead to a reduction of invasive cases. Latin America has experienced an increased incidence of serogroup W invasive cases of Neisseria meningitidis in the last decade. Specifically in Chile, despite low total incidence of invasive cases, serogroup W has become predominant since 2011 and has been associated with elevated mortality. Expecting to gain insight into the epidemiology of this disease, this study has used molecular typing schemes to compare Neisseria meningitidis isolates causing invasive disease with those isolates collected from adolescent carriers during the same period in Chile. A lower carriage of the serogroup W clonal complex ST-11/ET37 than expected was found; whereas, the same clonal complex accounted for 66% of total invasive meningococcal disease cases in the country that year. A high diversity of PorA variable regions and fHbp peptides was also ascertained in the carrier isolates compared to the invasive ones. According to the results shown here, the elevated number of serogroup W invasive cases in our country cannot be explained by a rise of carriage of pathogenic isolates. Overall, this study supports the idea that some strains, as W:cc11 found in Chile, possess an enhanced virulence to invade the host. Notwithstanding hypervirulence, this strain has not caused an epidemic in Chile. Finally, as genetic transfer occurs often, close surveillance of Neisseria meningitidis strains causing disease, and particularly hypervirulent W:cc11, should be kept as a priority in our country, in order to prepare the best response to face genetic changes that could lead to enhanced fitness of this pathogen.
脑膜炎奈瑟菌是一种人类专有的病原体，可导致侵袭性脑膜炎球菌病，也可能在上呼吸道无症状携带。携带和疾病之间的关系仍知之甚少，但人们普遍认为，通过免疫接种减少携带量应导致侵袭性病例减少。在过去十年中，拉丁美洲经历了侵袭性脑膜炎奈瑟菌 W 群血清型病例的发病率增加。特别是在智利，尽管侵袭性病例的总发病率较低，但自 2011 年以来，W 群已成为主要血清型，并且与死亡率升高有关。预计深入了解这种疾病的流行病学，本研究使用分子分型方案比较了引起侵袭性疾病的脑膜炎奈瑟菌分离株与同期从青少年携带者中分离的分离株。发现携带 W 群克隆复合物 ST-11/ET37 的比例低于预期；而同年该国总侵袭性脑膜炎球菌病病例中，同一克隆复合物占 66%。与侵袭性分离株相比，携带者分离株中的 PorA 可变区和 fHbp 肽也具有更高的多样性。根据这里显示的结果，我国侵袭性 W 群病例数量的增加不能用携带致病性分离株的增加来解释。总体而言，这项研究支持了这样一种观点，即某些菌株，如在智利发现的 W：cc11，具有增强的侵袭宿主的毒力。尽管具有高毒力，但该菌株在智利尚未引起流行。最后，由于遗传转移经常发生，应密切监测引起疾病的脑膜炎奈瑟菌菌株，特别是高毒力的 W：cc11，并将其作为我国的优先事项，以便为应对可能导致该病原体适应性增强的遗传变化做好准备。
