High ceftazidime hydrolysis activity and porin OmpK35 deficiency contribute to the decreased susceptibility to ceftazidime/avibactam in KPC-producing Klebsiella pneumoniae.
To investigate mechanisms for the decreased susceptibility to ceftazidime/avibactam in KPC-producing Klebsiella pneumoniae (KPC-KP).



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.



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.



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.
Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China.|Key Laboratory of Clinical Pharmacology of Antibiotics, National Health and Family Planning Commission of People's Republic of China, Shanghai, China.
Zhen
Z
Shen
Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China.|Key Laboratory of Clinical Pharmacology of Antibiotics, National Health and Family Planning Commission of People's Republic of China, Shanghai, China.
Baixing
B
Ding
Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China.|Key Laboratory of Clinical Pharmacology of Antibiotics, National Health and Family Planning Commission of People's Republic of China, Shanghai, China.
Meiping
M
Ye
Department of Infectious Diseases, Shanghai Jiaotong University Affiliated Sixth Hospital, Shanghai, China.
Peng
P
Wang
Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China.|Key Laboratory of Clinical Pharmacology of Antibiotics, National Health and Family Planning Commission of People's Republic of China, Shanghai, China.
Yingmin
Y
Bi
Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China.|Key Laboratory of Clinical Pharmacology of Antibiotics, National Health and Family Planning Commission of People's Republic of China, Shanghai, China.
Shi
S
Wu
Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China.|Key Laboratory of Clinical Pharmacology of Antibiotics, National Health and Family Planning Commission of People's Republic of China, Shanghai, China.
Xiaogang
X
Xu
Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China.|Key Laboratory of Clinical Pharmacology of Antibiotics, National Health and Family Planning Commission of People's Republic of China, Shanghai, China.
Qinglan
Q
Guo
Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China.|Key Laboratory of Clinical Pharmacology of Antibiotics, National Health and Family Planning Commission of People's Republic of China, Shanghai, China.
Minggui
M
Wang
D053961:Azabicyclo Compounds / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002442:Ceftazidime / Q000378:metabolism* / Q000494:pharmacology; D004338:Drug Combinations; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D006868:Hydrolysis; D007710:Klebsiella Infections / Q000382:microbiology; D007711:Klebsiella pneumoniae / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D018272:Porins / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D065093:beta-Lactamase Inhibitors / Q000494:pharmacology*; D001618:beta-Lactamases / Q000096:biosynthesis / Q000235:genetics
D053961:Azabicyclo Compounds; D001426:Bacterial Proteins; D004338:Drug Combinations; C119261:OmpK35 porin, Klebsiella pneumoniae; C092233:OmpK36 protein, Klebsiella pneumoniae; D018272:Porins; C000595613:avibactam, ceftazidime drug combination; D065093:beta-Lactamase Inhibitors; C543519:avibactam; D002442:Ceftazidime; D001618:beta-Lactamases; C547585:beta-lactamase KPC-2, Klebsiella pneumoniae