Antibacterial mechanism and in vivo efficacy of cladribine against carbapenem-resistant Klebsiella pneumoniae

Abstract Background The proliferation and dissemination of carbapenem-resistant Klebsiella pneumoniae (CRKP) constitutes a critical public health concern, underscoring the urgent need for novel antimicrobial agents. In this study, we identified cladribine, a synthetic purine analogue, as a potential antimicrobial candidate against CRKP. Results Cladribine exhibited an MIC of 64 μg/mL against clinical CRKP isolates. Consistently, growth curve and time-kill assays also demonstrated that cladribine displays measurable inhibitory and bactericidal effects against CRKP, achieving a 4 log 10 CFU reduction. Mechanistically, cladribine increased bacterial membrane permeability and induced oxidative stress, as evidenced by elevated intracellular reactive oxygen species (ROS) and malondialdehyde (MDA) levels, accompanied by the activation of oxidative stress-related genes. Cladribine also impaired bacterial energy metabolism, resulting in reduced succinate dehydrogenase (SDH) and pyruvate kinase (PK) activities and decreased ATP levels. In a mouse lung infection model, treatment with 10 mg/kg and 20 mg/kg cladribine significantly reduced pulmonary bacterial burden by approximately by 2.0 log 10 CFU and 3.0 log 10 CFU, respectively. In addition, cladribine alleviated CRKP-induced lung injury, and suppressed the transcription of pro-inflammatory cytokines, including TNF-α, IL-1β, and IL-6, indicating both antibacterial and anti-inflammatory effects in vivo. Conclusion These findings suggest that cladribine has potential as a therapeutic candidate against CRKP infection and provide preliminary mechanistic insights that may contribute to a better understanding of its antibacterial activity.