Allelic variants of Salmonella fimbrial adhesins

描述(申请人提供)：肠道沙门氏菌在世界范围内导致大量的发病率和死亡率。食源性沙门氏菌病通常是自我限制的，通常在健康的成年人中不会得到治疗。然而，对于儿童、老年人和免疫功能低下的患者以及系统性感染的治疗，尤其是涉及伤寒血清型的情况下，抗菌治疗往往是必要的。观察到的肠球菌多重耐药(MDR)菌株的流行增加引起了人们对经验性抗菌治疗的有效性的极大关注。肠链球菌的感染和定植涉及菌毛粘附素的参与，该粘附素介导与肠上皮细胞的结合 和先天免疫细胞。虽然许多引座型-伴随型菌毛的基因簇由所有肠杆菌血清型携带，但一些已被证明是宿主限制的，这表明在宿主特异性调节中可能起到作用。作为支持，几项研究强调了沙门氏菌菌毛粘附素中的几个氨基酸替换如何显著调节宿主和细胞类型的结合特异性。此外，通过介导肠道结合，粘附性菌毛延长了局部增殖的沙门氏菌的停留时间，从而增加了它们在肠道中的密度，这种环境有利于抗生素耐药性基因的水平基因转移(HGT)。因此，我们假设粘附素与宿主特异性肠道细胞的同源结合实际上可能有助于持续定植沙门氏菌的抗生素耐药性基因的积累。对于这个项目，一种新的和成功的预先测试的测序策略将被用来检验我们的假设，即特定的沙门氏菌粘附素及其等位基因变异决定宿主物种特异性并促进HGT。为此，我们将利用目标和条形码大规模并行测序来表征来自宾夕法尼亚州沙门氏菌参考中心的600个有良好记录的分离物(来自美国流行的三个主要肠杆菌血清型各200个独立分离物)的粘附素基因的等位基因变异。将评估携带粘附素等位基因变异定义组合的菌株与特定表型之间的相关性，如寄主物种、疾病征兆和抗菌素耐药性图谱。最后，将在体外和体内研究特定宿主物种或抗生素耐药性中具有最显著一致性的粘附素等位基因的因果关系。这些研究结果将指导未来开发新的黏附竞争对手或抑制剂，以减少沙门氏菌的肠道定植和多药耐药沙门氏菌的扩张。

DESCRIPTION (provided by applicant): Salmonella enterica causes substantial morbidity and mortality worldwide. Foodborne salmonellosis is typically self-limiting and can generally be left untreated in healthy adults. However, antimicrobial therapy is often necessary to treat children, the elderly, and immunocompromised patients, as well as for the treatment of systemic infections, particularly when typhoidal serovars are involved. The observed increase in the prevalence of multiple drug resistant (MDR) strains of S. enterica raises substantial concerns regarding the efficacy of empiric antimicrobial therapy. Infection and colonization by S. enterica involves the participation of fimbrial adhesins that mediate binding to intestinal epithelial cells and innate immune cells. While gene clusters for many usher-chaperone types of fimbriae are carried by all S. enterica serovars, some have been shown to be host restricted, suggesting a potential role in regulation of host specificity. In support, several studies have highlighted how even a few amino acid substitutions in a Salmonella fimbrial adhesin significantly modulate host- and cell-type binding specificity. In addition, by mediating intestinal binding, adhesive fimbriae prolong the residence of locally proliferating Salmonella, thereby increasing their density in the intestines, an environment known to favor horizontal gene transfer (HGT) of antibiotic resistance genes. Thus, we hypothesize that cognate binding of adhesins to host-specific intestinal cells may actually contribute to the accumulation of antibiotic resistance genes in persistently colonizing Salmonella. For this project, a novel and successfully pretested sequencing strategy will be used to test our hypothesis that specific Salmonella adhesins and their allelic variants determine host species specificity and facilitate HGT. For this, we will utilize targeted and barcoded massive parallel sequencing to characterize allelic variation of adhesin genes from 600 well documented isolates from the Pennsylvania Salmonella Reference Center (200 independent isolates from each of the three major S. enterica serovars prevalent in the US). Correlations will be evaluated between strains that carry defined combinations of adhesin allelic variants and specific phenotypes such as host species, disease signs and antimicrobial resistance profiles. Finally, adhesin alleles with the most significant congruence for specific hos species or for antibiotic resistance will be studied in vitro and in vivo for cause effect relationships. The result of these investigations will guide future development of novel adhesion competitors or inhibitors to reduce both intestinal colonization by Salmonella and the expansion of MDR Salmonella.