Prevalence of Carbapenem-Resistant Hypervirulent and Hypervirulent Carbapenem-Resistant in China Determined Mouse Lethality Tests.

Objective: To investigate the epidemiology of carbapenem-resistant hypervirulent (CR-HvKP) and hypervirulent carbapenem-resistant (Hv-CRKP).

Methods: Totally 436 strains were collected from 7 hospitals in mainland China between 2017.01 and 2018.02. Sequence types, serotypes, antimicrobial-resistance and virulence genes were analyzed. Additionally, string test, capsule stain, Periodic Acid Schiff stain, fitness analysis, quantitative real-time PCR and mouse lethality test were also performed. Molecular combinations were used to screen putative (+)-HvKP and Hv-(+)-KP, followed by the confirmation of mouse lethality test.

Results: Diverse detection rates were found for the virulence genes, ranging from (0.0%) to (100.0%). According to the molecular criteria, 127, 186, 9 and 26 strains were putatively denoted as HvKP, (+)-KP, (+)-HvKP and Hv-(+)-KP. Mouse lethality test confirmed 2 (+)-HvKP strains (JS184 and TZ20) and no Hv-(+)-KP. JS184 showed K2 serotype, thin capsule, positive exopolysaccharid and string test. TZ20 presented K20 serotype, thin capsule, negative exopolysaccharide and string test. Compared with the positive control NTUH-K2044, equal expression and growth curves were confirmed for JS184 and TZ20.

Conclusions: Molecular determination of CR-HvKP and Hv-CRKP brings remarkable bias compared with mouse lethality test. The exact prevalence of CR-HvKP is less than 1.0%, which of Hv-CRKP is much lower.