Evidence for re-infection and persistent carriage of Shigella species in adult males reporting domestically acquired infection in England

ObjectivesWe analysed national surveillance typing data of Shigella isolated from adult males with domestically acquired infection (a cohort largely consisting of men who have sex with men (MSM)) to establish whether multiple isolates from the same individual over time represented persistent carriage or re-infection.MethodsWe carried out a retrospective cohort study of adult males diagnosed with Shigella from 2004 to 2018. Median time intervals between multiple isolations of Shigella flexneri and S. sonnei were compared. Analysis of whole genome sequencing data provided strain discrimination at the single nucleotide level and was used to quantify the genetic distance among isolates. Maximum likelihood phylogenies were constructed to determine whether persistent carriage (characterized by multiple isolations of the same strain) or re-infection (characterized by multiple isolations of different strains) was best supported by the phylogenetic analysis. A comparison analysis was carried out using data linked to adult females with domestically acquired shigellosis.ResultsThe number of men reporting multiple isolations of Shigella species was 165/4733 (3.5%) compared with 31/2423 (1.3%) females (p < 0.001). For isolate pairs from men associated with persistent carriage, the isolation time interval range was 6–176 days (median 23.5; IQR 8–70) and single nucleotide polymorphism (SNP) distance range was 0–7 SNPs (median 0.5; IQR 0–2). For those associated with re-infection, the isolation time interval was 34–2636 days (median 732; IQR 191–1258) and the SNP distance was 10–1462 SNPs (median 120; IQR 29–377).DiscussionMultiple Shigella isolations in individuals with domestically acquired infections was more frequently observed in adult males than in adult females. Following the acute phase of infection, carriage can persist for months, and infection can recur within months, even with strains belonging to the same species and the same serotype. A combination of multiple sexual partners, persistent carriage following the acute phase of infection and evidence of recurrent re-infection is likely to contribute to sustained transmission in this population.     

Evaluation of an intragastric challenge model for Shigella dysenteriae 1 in rhesus monkeys (Macaca mulatta) for the pre‐clinical assessment of Shigella vaccine formulations

Shigellosis is a worldwide disease, characterized by abdominal pain, fever, vomiting, and the passage of blood‐ and mucus‐streaked stools. Rhesus monkeys and other primates are the only animals that are naturally susceptible to shigellosis. A suitable animal model is required for the pre‐clinical evaluation of vaccines candidates. In this study, the minimal dose of Shigella dysenteriae1 1617 strain required to produce dysentery in four of five (80% attack rate) monkeys using an escalating dose range for three groups [2 × 10⁸, 2 × 10⁹ and 2 × 10¹⁰ colony forming unit (CFU)] was determined. In addition, the monkeys were re‐infected. The identified optimal challenge dose was 2 × 10⁹ CFU; this dose elicited 60% protection in monkeys when they were re‐challenged with a one log higher dose (2 × 10¹⁰ CFU). The challenge dose, 2 × 10¹⁰ CFU, produced severe dysentery in all monkeys, with one monkey dying within 24 h, elicited 100% protection when re‐challenged with the same dose. All monkeys exhibited immune responses. This study concludes that the rhesus monkey model closely mimics the disease and immune response seen in humans and is a suitable animal model for the pre‐clinical evaluation of Shigella vaccine candidates. Prior infection with the 1617 strain can protect monkeys against subsequent re‐challenges with homologous strains.     

Development of Shigella conjugate vaccines targeting Shigella flexneri 2a and S. flexneri 3a using a simple platform-approach conjugation by squaric acid chemistry

There is a need for vaccines effective against shigella infection in young children in resource-limited areas. Protective immunity against shigella infection targets the O-specific polysaccharide (OSP) component of lipopolysaccharide. Inducing immune responses to polysaccharides in young children can be problematic, but high level and durable responses can be induced by presenting polysaccharides conjugated to carrier proteins. An effective shigella vaccine will need to be multivalent, targeting the most common global species and serotypes such as Shigella flexneri 2a, S. flexneri 3a, S. flexneri 6, and S. sonnei. Here we report the development of shigella conjugate vaccines (SCV) targeting S. flexneri 2a (SCV-Sf2a) and 3a (SCV-Sf3a) using squaric acid chemistry to result in single point sun-burst type display of OSP from carrier protein rTTHc, a 52 kDa recombinant protein fragment of the heavy chain of tetanus toxoid. We confirmed structure and demonstrated that these conjugates were recognized by serotype-specific monoclonal antibodies and convalescent sera of humans recovering from shigellosis in Bangladesh, suggesting correct immunological display of OSP. We vaccinated mice and found induction of serotype-specific OSP and LPS IgG responses, as well as rTTHc-specific IgG responses. Vaccination induced serotype-specific bactericidal antibody responses against S. flexneri, and vaccinated animals were protected against keratoconjunctivitis (Sereny test) and intraperitoneal challenge with virulent S. flexneri 2a and 3a, respectively. Our results support further development of this platform conjugation technology in the development of shigella conjugate vaccines for use in resource-limited settings.     

一起痢疾暴发菌株脉冲场凝胶电泳分型研究

目的：探讨一起痢疾暴发中所分离菌株间的内在联系及变异,探明暴发原因。方法：用限制性内切酶NotI对2007年江苏省一起痢疾暴发中的15株福氏4c型志贺菌和3株地方散发株进行PFGE分型,用非加权配对算术平均法（UPGMA）进行聚类分析,相似性系数采用Dice系数。结果：15株暴发株呈9种带型,2种优势带型占46．7％,带型问差异主要在336．5～310．1bp呈现1～3条不等条带,相似性系数92％～100％;食品加工人员菌株带型与主要带型CNJZXN11．01仅存在1条之差,相似性系数97％;3株散发株呈现3种带型,与暴发株相似性系数82％～87％。结论：暴发分离株之间遗传关系紧密,可认为该起暴发由同一克隆群菌株引起;食品加工点的病原携带者是该起暴发的可疑传染源。     

磷霉素钠在志贺氏菌痢疾治疗中的协同作用

志贺氏菌属的耐药现象日趋严重,为进一步提高志贺氏菌痢疾的疗效,合理交替选用抗菌药物,我们对110例志贺氏菌痢疾患者随机分为3组.分别给予磷霉素钠+丁胺卡那霉素、磷霉素钠+氟哌酸或单用氟哌酸治疗,并进行疗效比较.     

Purification and characterization of an immunogenic outer membrane protein of Shigella flexneri 2a

In the present study we purified 34 kDa major outer membrane protein (MOMP) of Shigella flexneri 2a for the first time, which was cross-reactive and antigenically conserved among Shigella spp. and the epitope was surface exposed on the intact bacterium. The purified antigen was found to be glycosylated, which aids in binding to macrophages and up-regulated the production of nitric oxide, granulocyte-colony stimulating factor and IL-12p70, indicating that the MOMP is immunogenic and has the ability to commence protective immune responses against intracellular pathogens, thereby it may be considered as a potential vaccine candidate.     

2003—2006年包头市感染性腹泻细菌病原学监测结果

目的了解并掌握包头市腹泻病的发生、流行特征、变化趋势及细菌性病原分布特点，为制定预防措施和临床治疗提供参考依据。方法2003—2006年对包头市腹泻病哨点监测医院中就诊的急性腹泻病患者，用肛拭子采集粪便标本进行增菌后，分别接种4种培养基（碱性蛋白胨水、SS、EMB、中国蓝平板）作霍乱弧菌、沙门菌、志贺菌以及致泻性大肠埃希菌的检验。结果从1028份粪便样本中，检出各种病原菌82株，检出率7．98％，其中志贺菌占86．58％，其余为沙门菌和大肠埃希菌。结论2003—2006年该市检出的阳性菌群中未发现霍乱弧菌，主要以志贺菌为主，初步揭示了包头市细菌性腹泻病原谱。     

2003-2007年西安市感染性腹泻监测点细菌病原学监测结果

目的了解并掌握西安市腹泻病的发生、流行特征、变化趋势及细菌性病原分布特点，为制定预防措施和临床治疗提供参考依据。方法2003-2007年对西安市腹泻病哨点监测医院中就诊的急性腹泻病患者，用肛拭子采集粪便标本进行增菌后，分别接种4种培养基（碱性蛋白胨水、SS、EMB、中国蓝平板）作霍乱弧菌、沙门菌、志贺菌以及致泻性大肠埃希菌的检验。结果从1310份粪便样本中，检出各种病原菌90株，检出率6．87％。其中志贺菌占85．56％，还有沙门菌、大肠埃希菌和副溶血弧菌。结论2003-2007年检出的阳性菌群中主要以志贺菌为主，初步揭示了西安市细菌性腹泻病原谱。