In vitro Antibacterial Effect of Reduning Combined with Polymyxin on Carbapenem Resistant Klebsiella pneumoniae

Objective: This study aimed to investigate the status of carbapenem-resistant strains of Klebsiella pneumoniae isolated from the Department of Microbiology, Zhejiang Tongde Hospital between September 2023 and February 2024, and to examine the in vitro antibacterial effect of Reduning combined with polymyxin on carbapenem-resistant Klebsiella pneumoniae (CRKP), which may provide evidence on the application of Reduning in the clinical anti-infective therapy.

Methods: A total of 50 different isolates of CRKP were collected, and the minimum inhibitory concentrations (MIC) of polymyxin, Reduning and polymyxin plus Reduning were measured with microbroth dilution method. Then, the fractional inhibition concentration index (FICI) was calculated.

Results: A total of 50 strains of CRKP were isolated, sputum and clean urine were the most common source of CRKP, and intensive care unit was the most common source department. More than 90% of CRKP strains were resistant to cefepime, ceftazidime, piperacillin/tazobactam, and cefoperazone/sulbactam. The rate of resistance to levofloxacin was high, but that to tobramycin, tigecycline, and compound sulfamethoxazole was low. In addition, MIC of Reduning plus polymyxin for CRKP was lower than that of Reduning or polymyxin alone. Among 50 strains of CRKP, FICI ≤0.5 was noted in 7 strains, 0.5 < FICI ≤ 1.0 in 43 strains, and none had FICI >1.0. The results showed Reduning combined with polymyxin B exerted additive effect on CRKP and conferred synergistic effect on several strains of CRKP.

Conclusion: Reduning has antibacterial effect on CRKP in vitro, and the addition of Reduning can reduce the dose of polymyxin in the treatment of CRKP.