In vitro research of combination therapy for multidrug-resistant Klebsiella pneumoniae bloodstream infections

Objective Multidrug-resistant Klebsiella pneumoniae (MDR KP) bloodstream infections are a serious problem. The objective of this study was to investigate the effects of appropriate combination therapies on MDR KP bloodstream infections. Methods MDR KP strains isolated from clinical samples were assessed for antibiotic susceptibility using the broth microdilution method. Twenty consecutive MDR KP clinical isolates from patients with bloodstream infections were examined in this study. The experiments were conducted at the Bacterial Laboratory of Tongde Hospital from March to August 2021. Antibiotic combination tests were performed using the minimum inhibitory concentration (MIC) test, and the sum of the fractional inhibitory concentration was used to assess synergy. Results Following treatment with a combination of two antibiotic agents, the MIC50 and MIC90 values decreased compared with that before treatment. MIC50 decreased by at least 50%, with one value reduced to 6.25% of the pretreatment value. None of the antibiotic combinations were antagonistic. Combination of polymyxin B with rifampicin or tigecycline had a synergistic effect on 70% and 65% of the strains, respectively. Conclusions In vitro combination therapies with two active drug agents (polymyxin B plus rifampicin or tigecycline) had a better effect on MDR KP infections compared with that in other regimens.