Allelic variants of Salmonella fimbrial adhesins

描述（由申请方提供）：肠道沙门氏菌在全球范围内引起大量发病率和死亡率。食源性沙门氏菌病通常是自限性的，健康成人通常不接受治疗。然而，抗微生物治疗通常是必要的，以治疗儿童，老年人和免疫功能低下的患者，以及治疗全身感染，特别是当涉及伤寒血清型。观察到的S. enterica引起了关于经验性抗微生物治疗的有效性的实质性关注。感染和定殖。肠粘附素参与介导与肠上皮细胞的结合 和先天免疫细胞。虽然许多usher-伴侣菌毛类型的基因簇由所有的S。肠球菌血清型中，一些已被证明是宿主限制性的，表明在调节宿主特异性中的潜在作用。作为支持，一些研究已经强调了沙门氏菌菌毛粘附素中的几个氨基酸取代如何显著调节宿主和细胞类型结合特异性。此外，通过介导肠道结合，粘附菌毛延长了局部增殖沙门氏菌的驻留，从而增加了它们在肠道中的密度，这是一种已知有利于抗生素抗性基因水平基因转移（HGT）的环境。因此，我们推测，同源结合的粘附素，以主机特定的肠细胞可能实际上有助于抗生素耐药基因的积累，在持续定植沙门氏菌。对于这个项目，一个新的和成功的预先测试的测序策略将被用来测试我们的假设，即特定的沙门氏菌粘附素及其等位基因变异体决定宿主物种特异性和促进HGT。为此，我们将利用靶向和条形码化的大规模平行测序来表征来自宾夕法尼亚沙门氏菌参考中心的600个记录良好的分离株（来自三种主要沙门氏菌中的每一种的200个独立分离株）的粘附素基因的等位基因变异。在美国流行的肠道血清型）。将评价携带粘附素等位基因变体和特定表型（如宿主种属、疾病体征和抗菌药物耐药性特征）的确定组合的菌株之间的相关性。最后，将在体外和体内研究与特定hos物种或抗生素耐药性具有最显著一致性的粘附素等位基因的因果关系。这些研究的结果将指导未来开发新的粘附竞争剂或抑制剂，以减少沙门氏菌的肠道定植和MDR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.