Keller Lance E, Robinson D Ashley, McDaniel Larry S
Department of Microbiology and Immunology, University of Mississippi Medical Center, Jackson, Mississippi, USA.
Department of Microbiology and Immunology, University of Mississippi Medical Center, Jackson, Mississippi, USA
mBio. 2016 Mar 22;7(2):e01792. doi: 10.1128/mBio.01792-15.
While significant protection from pneumococcal disease has been achieved by the use of polysaccharide and polysaccharide-protein conjugate vaccines, capsule-independent protection has been limited by serotype replacement along with disease caused by nonencapsulatedStreptococcus pneumoniae(NESp). NESp strains compose approximately 3% to 19% of asymptomatic carriage isolates and harbor multiple antibiotic resistance genes. Surface proteins unique to NESp enhance colonization and virulence despite the lack of a capsule even though the capsule has been thought to be required for pneumococcal pathogenesis. Genes for pneumococcal surface proteins replace the capsular polysaccharide (cps) locus in some NESp isolates, and these proteins aid in pneumococcal colonization and otitis media (OM). NESp strains have been isolated from patients with invasive and noninvasive pneumococcal disease, but noninvasive diseases, specifically, conjunctivitis (85%) and OM (8%), are of higher prevalence. Conjunctival strains are commonly of the so-called classical NESp lineages defined by multilocus sequence types (STs) ST344 and ST448, while sporadic NESp lineages such as ST1106 are more commonly isolated from patients with other diseases. Interestingly, sporadic lineages have significantly higher rates of recombination than classical lineages. Higher rates of recombination can lead to increased acquisition of antibiotic resistance and virulence factors, increasing the risk of disease and hindering treatment. NESp strains are a significant proportion of the pneumococcal population, can cause disease, and may be increasing in prevalence in the population due to effects on the pneumococcal niche caused by pneumococcal vaccines. Current vaccines are ineffective against NESp, and further research is necessary to develop vaccines effective against both encapsulated and nonencapsulated pneumococci.
虽然使用多糖和多糖 - 蛋白结合疫苗已实现对肺炎球菌疾病的显著保护,但非荚膜依赖性保护受到血清型替换以及由非包膜肺炎链球菌(NESp)引起的疾病的限制。NESp菌株约占无症状携带者分离株的3%至19%,并携带多种抗生素抗性基因。尽管缺乏荚膜,但NESp特有的表面蛋白可增强定植和毒力,尽管人们一直认为荚膜是肺炎球菌发病机制所必需的。在一些NESp分离株中,肺炎球菌表面蛋白的基因取代了荚膜多糖(cps)基因座,这些蛋白有助于肺炎球菌定植和中耳炎(OM)。NESp菌株已从侵袭性和非侵袭性肺炎球菌疾病患者中分离出来,但非侵袭性疾病,特别是结膜炎(85%)和中耳炎(8%)的患病率更高。结膜菌株通常属于由多位点序列类型(STs)ST344和ST448定义的所谓经典NESp谱系,而散发性NESp谱系如ST1106更常见于患有其他疾病的患者中分离出来。有趣的是,散发性谱系的重组率明显高于经典谱系。更高的重组率可导致抗生素抗性和毒力因子的获得增加,增加疾病风险并阻碍治疗。NESp菌株在肺炎球菌群体中占很大比例,可引起疾病,并且由于肺炎球菌疫苗对肺炎球菌生态位的影响,其在人群中的患病率可能正在增加。目前的疫苗对NESp无效,因此有必要进一步研究开发对包膜和非包膜肺炎球菌均有效的疫苗。