Department of Bioscience and Bioengineering, Indian Institute of Technology Jodhpurgrid.462385.e, Jodhpur, Rajasthan, India.
Department of Microbiology, All India Institute of Medical Sciences Jodhpurgrid.463267.2, Jodhpur, Rajasthan, India.
Microbiol Spectr. 2022 Jun 29;10(3):e0039322. doi: 10.1128/spectrum.00393-22. Epub 2022 Jun 1.
Klebsiella pneumoniae can be broadly classified into classical strains that cause drug-resistant, hospital-associated infections and hypervirulent strains that cause invasive, community-acquired, drug-susceptible infections. Hypermucoviscosity in Klebsiella pneumoniae has been associated with immune evasion and hypervirulence. A string-test-positive, hypermucoviscous strain of Klebsiella pneumoniae, P34, was isolated from the cystic lesion of a patient who reported to a tertiary care hospital in Jodhpur, Rajasthan, India. Given the antibiotic-susceptible and hypermucoviscous nature of the isolate, it was suspected to belong to the hypervirulent lineage of Klebsiella pneumoniae. However, P34 did not overproduce capsular polysaccharides and also remained susceptible to the antimicrobial effects of human serum when tested alongside strains that were non-hypermucoviscous. Sequencing of the genome of P34 revealed the absence of any large virulence plasmids or integrative conjugative elements that usually carry hypermucoviscosity- and hypervirulence-associated genes. P34 also lacked key virulence determinants such as aerobactin, yersiniabactin, and salmochelin biosynthesis clusters. In addition, P34 lacked homologs for genes associated with enhanced capsule synthesis and hypermucoviscosity, such as , , , and (egulator of ucoid henotype). These observations suggest that P34 may harbor novel genetic determinants of hypermucoviscosity independent of the indirectly acting and the recently described . Hypermucoviscosity is a characteristic of hypervirulent Klebsiella pneumoniae strains, which are capable of causing invasive disease in community settings. This study reports phenotyping and genomic analysis of an unusual clinical isolate of Klebsiella pneumoniae, P34, which exhibits hypermucoviscosity and yet does not harbor (egulator of ucoid henotype) genes, which are known determinants of hypermucoviscosity ( and ). Similar clinical isolates belonging to the K. pneumoniae complex that are hypermucoviscous but do not harbor the loci have been reported from India and abroad, indicating the prevalence of unknown determinants contributing to hypermucoviscosity. Therefore, strains like P34 will serve as model systems to mechanistically study potentially novel determinants of hypermucoviscosity in the K. pneumoniae complex.
肺炎克雷伯菌可大致分为引起耐药性、医院相关感染的经典菌株和引起侵袭性、社区获得性、药物敏感感染的高毒力菌株。肺炎克雷伯菌的高黏液性与免疫逃避和高毒力有关。从印度拉贾斯坦邦焦特布尔的一家三级保健医院的囊性病变患者中分离出一株呈.string-试验阳性、高黏液性的肺炎克雷伯菌 P34 菌株。鉴于该分离株具有抗生素敏感性和高黏液性，怀疑其属于肺炎克雷伯菌的高毒力谱系。然而，P34 并没有过度产生荚膜多糖，并且当与非高黏液性菌株一起测试时，它仍然对人血清的抗菌作用敏感。P34 基因组的测序显示，它没有携带通常携带高黏液性和高毒力相关基因的大型毒力质粒或整合性 conjugative 元件。P34 还缺乏关键的毒力决定因素，如 aerobactin、yersiniabactin 和 salmochelin 生物合成簇。此外，P34 缺乏与增强荚膜合成和高黏液性相关的基因的同源物，如 、 、 和 （ucoid 表型调节剂）。这些观察结果表明，P34 可能含有独立于间接作用的 和最近描述的 的高黏液性的新型遗传决定因素。高黏液性是高毒力肺炎克雷伯菌菌株的特征，这些菌株能够在社区环境中引起侵袭性疾病。本研究报告了一种不寻常的肺炎克雷伯菌临床分离株 P34 的表型和基因组分析，该分离株表现出高黏液性，但不携带 （ucoid 表型调节剂）基因，这些基因是高黏液性的已知决定因素（和）。来自印度和国外的报道表明，属于肺炎克雷伯菌复合体的类似临床分离株具有高黏液性，但不携带 基因座，表明存在未知决定因素导致高黏液性。因此，像 P34 这样的菌株将作为模型系统，用于从机制上研究肺炎克雷伯菌复合体中高黏液性的潜在新型决定因素。
