ObjectiveTo study the antibacterial activity of ceftazidime/avibactam against carbapenem-resistant Klebaiella pneumoniae (CRKP) in vitro and detect the resistance genes of CRKP, so as to provide reference for the treatment of patients with CRKP infection.MethodsA total of 120 CRKP strains isolated from clinical specimens from May 2014 to November 2017 were collected. The activitis of 11 antimicrobial agents against those CRKP strains were detected by broth microdilution method, and the genes related to resistance to ceftazidime/avibactam were detected by polymerase chain reaction in the 120 CRKP isolates.ResultsThe resistance rate of the 120 CRKP isolates against ceftazidime/avibactam was 16.67% (20/120), which was significantly lower than that against cefotaxime (100.00%), aztreonam (98.33%), ceftazidime (95.83%), cefoperazone/sulbactam (95.83%), meropenem (95.83%), imipenem (95.00%), levofloxacin(92.50%), amikacin (54.17%), minocycline (39.17%), and tegacycline (23.33%). Among the 20 CRKP strains resistant to ceftazidime/avibactam, there were 12 Klebsiella pneumoniae carbapenemase (KPC)-2-producing strains, 3 KPC-3-producing strains, 1 New Delhi metallo-β-lactamase-1 (NDM-1)-producing strain, and 1 oxacillin β-lactamase-48-producing strain; none of the 20 strains had KPC mutation.ConclusionsCeftazidime/avibactam is an effective agent agianst CRKP, and its resistance rate is significantly lower than that of other commonly used antimicrobial agents, especially other β-lactam antibiotics. In terms of resistance genes, except for one isolate producing NDM-1, no other known gene resistant to ceftazidime/avibactam has been found.
Objective To investigate antimicrobial resistance profiles of carbapenem-resistant Enterobacter spp. (CREn) and the bactericidal effects of aztreonam combined with avibactam. Methods The CREn strains isolated from the West China Hospital of Sichuan University between 2016 and 2021 were identified by gyrB gene amplification and subsequent sequencing. The drug sensitivity results, sample types and distribution of relevant patient departments of these strains were summarized. Colistin-resistant and -intermediate strains were selected to carry out the bactericidal test of colistin and aztreonam combined with avibactam. Results A total of 110 clinical strains of CREn were included. The most common strain was Enterobacter xiangfangensis (91 strains), the highest proportion was in the intensive care unit (27.27%), and the proportion of respiratory tract samples was more than 40%. The antimicrobial sensitivity results showed that CREns were all resistant to carbapenems, the resistance rate to colistin was 23.64%, and the resistance rate to aztreonam combined with avibactam was 0. Among other antimicrobial agents, the antimicrobial resistance rate of amikacin and tigecycline were less than 10%. The time-kill curve showed that for colistin-intermediate strains, colistin could achieve bactericidal effect in a shorter time than aztreonam combined with avibactam. However, whether the strain was resistant to colistin or not, the bactericidal rate of 2 μg/mL aztreonam combined with avibactam in 24 hours could exceed 99%. Conclusion CREn is resistant to most commonly used clinical antibacterial drugs, but remains sensitive to aztreonam combined with avibactam, and aztreonam combined with avibactam has bactericidal effect on it.