Epidemiological features of hypermucoviscous Klebsiella pneumoniae infection in a coastal city of China: clinical and molecular perspectives.

PURPOSE: The present study aimed to investigate the overall clinical and molecular characteristics of hypermucoviscous Klebsiella pneumoniae (hmKP) infection in Yantai, China.

METHODS

A retrospective study was conducted in Yantai Yuhuangding Hospital from October 2024 to December 2024. As the inclusion criterion, all clinical isolates of K. pneumoniae were analyzed by a string test, in which an inoculation loop was used to generate sticky strings of >5 mm length from a K. pneumoniae colony. The isolates showing a positive test result were designated as hmKP. The clinical characteristics of patients with hmKP infection were retrospectively reviewed. Antibiotic susceptibility tests were performed for all hmKP isolates, and whole-genome sequencing studies were conducted for these isolates to determine their epidemiological characteristics.

RESULTS

A total of 88 unique hmKP isolates were collected from 485 strains of K. pneumoniae, accounting for 18.1%. Patients with hmKP infection were distributed across different age groups, clinical departments, and specimen types. Whole-genome sequencing revealed the predominance of K1/ST23 and K2/ST65 clones in the hmKP group. Virulence determinants such as rmpA, rmpA2, iuc, iro, peg-344, and clb were commonly present in the hmKP isolates. All hmKP isolates carried multiple resistance genes; however, the antibiotic resistance phenotype did not fully match with the resistance genes. Additionally, two hypervirulent carbapenem-resistant Klebsiella pneumoniae(HCKP) strains were detected in this study.

CONCLUSION

HmKP infection is prevalent in Yantai, China, with dominant K1/ST23 and K2/ST65 clones carrying prevalent virulence genes. Vigilance is required to prevent the spread of HCKP in clinical practice.