Abstract

Whooping cough still occupies a leading position in the group of controlled infectious diseases, despite worldwide mass vaccination. In recent decades, there has been a significant increase in the incidence of whooping cough and the spread of atypical forms among adolescents and adults. It has been proposed that the formation of an anthropogenic source of infection evolves due to Bordetella pertussis bacteria with reduced or completely lost virulence that are capable of long-term persistence in the human body and restoration of infectivity under certain conditions. The persistence mechanisms of the causative agent of whooping cough have not yet been studied completely. We hypothesize that one of the mechanisms may be a change of the bvgAS operon, which regulates the expression of all virulence genes of B. pertussis bacteria because of the integration of IS-elements. Mobile IS-elements are known to have the ability to both embed into the host genome sites and be cut out of them with the restoration of impaired functions. The purpose of this study was to evaluate the duration of persistence and to analyze the population composition of B. pertussis bacteria in children with whooping cough and contact persons in family foci. In this study, 80 children with confirmed diagnosis of pertussis and 116 people from 59 family foci of pertussis in contact with those children were examined. Patients were included in the study after they signed an informed consent. To detect B. pertussis DNA in nasopharyngeal swabs and to register IS-element integrations, the PCR-RT-IS test-system developed at the Gamaleya Research Institute was used along with nested PCR and sequencing. It has been shown to be possible to detect the causative agent of whooping cough in patients at different stages of the disease and in family members who have been in contact with patients for a long period. It has been found that, in the period of convalescence from whooping cough, the formation of insertional avirulent mutants of B. pertussis in the upper respiratory tract, which are capable of long-term persistence in the human body, is observed in 25% of patients. The appearance of avirulent mutants has been registered at a lower frequency (15%) in contact persons from family foci. The long-term detection of the causative agent of whooping cough and the registration of B. pertussis bvg-mutants containing the integration of IS-elements in bacterial carriers confirm the hypothesis that bacterial transition to persistence because of the insertional inactivation of bvgAS operon is possible. Identifying persistent B. pertussis bacteria and studying the mechanisms of their formation is important for creating new vaccination strategies and improvement of pertussis vaccines.

中文翻译：

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百日咳患者及接触者中百日咳博德特氏菌的种群构成及持续时间

摘要

尽管世界范围内进行了大规模疫苗接种，但百日咳仍然在受控传染病中占据主导地位。近几十年来，百日咳的发病率显着增加，并且非典型形式在青少年和成人中传播。有人提出，人为感染源的形成是由于毒力降低或完全丧失的百日咳博德特氏菌进化而来，这些细菌能够在人体内长期存留并在一定条件下恢复感染性。百日咳病原体的持续机制尚未得到完全研究。我们假设其中一种机制可能是bvgAS的变化操纵子，由于 IS 元件的整合而调节百日咳博德特氏菌所有毒力基因的表达。众所周知，移动 IS 元件能够嵌入宿主基因组位点，并通过恢复受损功能而将其从宿主基因组位点中切除。本研究的目的是评估百日咳儿童和家庭疫区接触者中百日咳杆菌的持续时间并分析其种群组成。本研究对80名确诊为百日咳的儿童以及与这些儿童接触过的59个百日咳家庭疫源地的116人进行了检查。患者签署知情同意书后被纳入研究。检测百日咳博德特氏菌为了检测鼻咽拭子中的 DNA 并记录 IS 元件整合，使用了 Gamaleya 研究所开发的 PCR-RT-IS 测试系统以及巢式 PCR 和测序。事实证明，可以在不同疾病阶段的患者以及与患者长期接触的家庭成员中检测出百日咳的病原体。研究发现，在百日咳恢复期，百日咳博德特氏菌插入性无毒突变体的形成在 25% 的患者中观察到了上呼吸道的细菌，这种细菌能够在人体内长期持续存在。在来自家庭疫源地的接触者中，无毒突变体的出现频率较低（15%）。对百日咳病原体的长期检测以及在细菌载体中整合了 IS 元件的百日咳博德特氏菌bvg 突变体的登记证实了这样的假设：由于bvg AS 操纵子的插入失活，细菌转变为持久性是可能的。鉴定持久性百日咳杆菌并研究其形成机制对于制定新的疫苗接种策略和改进百日咳疫苗非常重要。