Introduction: Tigecycline is one of the last resorts for carbapenem-resistant K. pneumoniae  (CRKP) infections. Indeed, tigecycline-non-susceptible K. pneumoniae  (TNSKP) strains are increasingly treated with the use of tigecycline. In this study, we attempted to better understand their epidemiological trends and characteristics. K. pneumoniae  were collected from 2017 to 2020 at the First Affiliated Hospital of Nanchang University.
Methods: Thirty-four TNSKP strains were selected during the study period, all of which were analyzed using antimicrobial susceptibility testing, multilocus sequence typing (MLST), and pulsed-field gel electrophoresis (PFGE). PCR and DNA sequencing were performed for the detection of β-lactamase genes and carbapenemase genes, and the mutation analysis of tet (A ), tet (X ), tet (L ), tet (M ), rpsJ , ramR , and oqxR , which are related to tigecycline resistance. Virulence gene and capsular genotype testing were conducted to identify whether the TNSKP strains were hypervirulent Klebsiella pneumoniae .
Results: An epidemiology analysis showed that Klebsiella pneumoniae  carbapenemase-2 (KPC-2 ) was the predominant carbapenemase in tigecycline non-susceptible carbapenem-resistant K. pneumoniae  (TNSCRKP) (96.7%), and the dominant clone type was ST11-K14K64 (82.4%). Among them, 55.9% (19/34) of strains were from each department of ICU, particularly EICU and neurosurgery ICU. In order to further understand the molecular mechanisms of the TNSKP, a polymerase chain reaction of the resistant determinants was carried out. The results detected many tigecycline-resistant genes, such as tet (A ) (97.1%), tet (X ) (17.6%), rpsJ  (97.1%), and ramR  (8.8%).
Conclusion: As the results of this study reveal, we should take effective measures to control the increase in TNSKP.
Keywords: carbapenem-resistant, tigecycline-non-susceptible, Klebsiella pneumoniae