High ceftazidime hydrolysis activity and porin OmpK35 deficiency contribute to the decreased susceptibility to ceftazidime/avibactam in KPC-producing Klebsiella pneumoniae

  • J Antimicrob Chemother. 2017 Jul 1;72(7):1930-1936. doi: 10.1093/jac/dkx066.
Zhen Shen  1  2 ,  Baixing Ding  1  2 ,  Meiping Ye  1  2 ,  Peng Wang  3 ,  Yingmin Bi  1  2 ,  Shi Wu  1  2 ,  Xiaogang Xu  1  2 ,  Qinglan Guo  1  2 ,  Minggui Wang  1  2
Affiliations
  • 1. Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China.
  • 2. Key Laboratory of Clinical Pharmacology of Antibiotics, National Health and Family Planning Commission of People's Republic of China, Shanghai, China.
  • 3. Department of Infectious Diseases, Shanghai Jiaotong University Affiliated Sixth Hospital, Shanghai, China.
PMID: 28333323 DOI: 10.1093/jac/dkx066
Abstract

Objectives: To investigate mechanisms for the decreased susceptibility to ceftazidime/avibactam in KPC-producing Klebsiella pneumoniae (KPC-KP).

Methods: A total of 24 isolates, 8 each with ceftazidime/avibactam MICs of 4-8, 1-2 and ≤0.5 mg/L, were randomly selected from 214 clinical isolates of KPC-KP, and the β-lactamase hydrolysis activity and porin expression profiles were determined. Plasmid profile and relative expression and copy number of the bla KPC gene were also analysed.

Results: Ceftazidime/avibactam MIC 50 and MIC 90 were 2 and 4 mg/L, respectively, for the 214 KPC-KP isolates. The hydrolysis activities of nitrocefin and ceftazidime in both of the ceftazidime/avibactam MIC 4-8 and 1-2 mg/L groups were significantly higher than those of the MIC ≤0.5 mg/L group, while the hydrolysis activities were 4-4.6-fold higher in the MIC 4-8 mg/L group than in the Other two groups when 4 mg/L avibactam was added. The relative expression and copy number of the bla KPC gene in the MIC 4-8 mg/L group were 4.2-4.8-fold higher than in the Other two groups. Meanwhile, SDS-PAGE showed that all isolates in the two groups with MIC ≥1 mg/L lacked OmpK35, which had either an early frameshift with a premature stop codon ( n = 15, ST11) or overexpression of the negative regulation genes, micF and ompR ( n = 1, ST15), whereas OmpK35 and OmpK36 could both be observed in all isolates with MIC ≤0.5 mg/L.

Conclusions: Decreased ceftazidime/avibactam susceptibility in KPC-KP clinical isolates is caused by high ceftazidime hydrolysis activity and OmpK35 porin deficiency and the majority of isolates belong to ST11.

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