Emergence of Ceftazidime–Avibactam Resistance and Decreased Virulence in Carbapenem-Resistant ST11 Klebsiella pneumoniae During Antibiotics Treatment

Mengxin Xu,1 Changrui Qian,2 Huaiyu Jia,1 Luozhu Feng,3 Shiyi Shi,1 Ying Zhang,3 Lingbo Wang,1 Jianming Cao,3 Tieli Zhou,1 Cui Zhou1 1Department of Clinical Laboratory, the First Affiliated Hospital of Wenzhou Medical University, Key Laboratory of Clinical Laboratory Diagnosis and Translational Research of Zhejiang Province, Wenzhou, People’s Republic of China; 2School of Basic Medical Sciences, Wenzhou Medical University, Wenzhou, People’s Republic of China; 3Department of Medical Laboratory Science, School of Laboratory Medicine and Life Science, Wenzhou Medical University, Wenzhou, People’s Republic of ChinaCorrespondence: Tieli Zhou; Cui Zhou, Department of Clinical Laboratory, the First Affiliated Hospital of Wenzhou Medical University; Key Laboratory of Clinical Laboratory Diagnosis and Translational Research of Zhejiang Province, Wenzhou, 325035, People’s Republic of China, Tel +86 0577 8668 9885, Email wyztli@163.com; ZHOUCUI0826@163.comIntroduction: Carbapenem-resistant Klebsiella pneumoniae (CRKP) poses a serious threat to human public health. Ceftazidime–avibactam (CZA) is currently one of the few effective antibiotics for carbapenem-resistant Enterobacteriaceae (CRE).Methods and Results: Here, we analyzed two longitudinal Klebsiella pneumoniae clinical isolates (FK8578, FK8695) that were isolated from an ICU patient during antimicrobial treatment. Broth microdilution method, whole-genome sequencing (WGS) and comparative genomic analysis were used to elucidate the dynamics and mechanisms of antibiotic resistance. String test, quantification of capsule, biofilm inhibition test and Galleria mellonella (G. mellonella) infection model were used to explore the changes in virulence of the two clinical isolates. During antibiotic treatment, CRKP FK8578 underwent a series of drug resistance and virulence changes, including CZA resistance, carbapenem susceptibility and virulence attenuation. The results of WGS showed that mutation of blaKPC-2 to blaKPC-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. On the other hand, the loss of hypermucoviscosity phenotype in the FK8695 strain may be related to a single nucleotide deletion of the rmpA gene, which would further lead to a decrease in virulence. 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.Conclusion: This is the first report of CZA resistance and decreased virulence in ST11 CRKP strains during antimicrobial treatment. It is urgent to monitor CZA resistance and timely adjust anti-infective treatment strategies.Keywords: ceftazidime–avibactam, carbapenem-resistantKlebsiella pneumoniae, whole-genome sequencing, hypermucoviscosity, pLVPK-like plasmid, virulence attenuation