In vivo emergence of ceftazidime-avibactam resistance and loss of hypermucoviscosity in carbapenem-resistant Klebsiella pneumoniae during antibiotics treatment

Abstract Background Ceftazidime-avibactam (CZA) is currently one of the few effective antibiotics for carbapenem-resistant Enterobacteriaceae (CRE). We characterized in vivo evolution of carbapenem and CZA resistance and decreased hypermucoviscosity (Hmv) by analyzing two longitudinal carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKp) clinical isolates (FK8578, FK8695) from an ICU patient during antimicrobial treatment. Methods Antibiotic susceptibility testing was performed to investigate the change of antibiotics resistance. String test, quantification of capsule, biofilm inhibition test and Galleria mellonella ( G. mellonella ) infection model were used to investigate the change of Hmv and virulence. Whole genome sequencing (WGS) and comparative genomic analysis were conducted to illustrate the underlying mechanisms. Results Compared with FK8578, minimum inhibitory concentrations (MICs) were increased for CZA while decreased for carbapenems antibacterial drugs in FK8695. Virulence results showed that compared with FK8578, FK8695 was negative in the string test, with decreased capsular production, smaller amounts of biofilm formation and higher survival rate of G. mellonella. The results of WGS showed that mutation of bla KPC−2 to bla KPC−33 was responsible for the change of drug resistance phenotype between FK8578 and FK8695. pLVPK-like virulence plasmid without siderophore synthesis operon was identified in the two strains. The single nucleotide deletion in rmpA gene of FK8695 strain may be responsible for the loss of its Hmv phenotype. Conclusions This is the first report to describe the in vivo emergence of CZA resistance and the loss of Hmv in CR-hvKp strains during CZA treatment and illuminate the mechanism of its resistance and virulence changes. There is an urgent need for CZA resistance monitoring and timely adjustment of anti-infective treatment strategies in clinical settings.