Comparative in vitro Activity and Clinical Outcomes of Eravacycline, Tigecycline, and Omadacycline Against Carbapenem-Resistant Acinetobacter baumannii and Klebsiella pneumoniae

Diandian Chen,1,* He Lan,1,* Wenshuo Yang,1,* Dequan Tian,1 Yunyi Liu,1 Leyang Ju,1 Qiao Song,1 Rong Min,1 Yan Wang,1 Ying Li,1 Peichang Wang,1,2 Jingrong Cao1,2 1Department of Clinical Laboratory, Xuanwu Hospital Capital Medical University, National Gerontic Disease Clinical Research Center, Beijing, 100053, People’s Republic of China; 2Department of Clinical Laboratory, Xiong’an Xuanwu Hospital, Xiong’an New Area, Hebei Province, 070001, People’s Republic of China*These authors contributed equally to this workCorrespondence: Jingrong Cao, Department of Clinical Laboratory, Xuanwu Hospital Capital Medical University, National Gerontic Disease Clinical Research Center, No. 45 Changchun Street, Xicheng District, Beijing, 100053, People’s Republic of China, Email [email protected] Peichang Wang, Department of Clinical Laboratory, Xuanwu Hospital Capital Medical University, National Gerontic Disease Clinical Research Center, No. 45 Changchun Street, Xicheng District, Beijing, 100053, People’s Republic of China, Email [email protected]: Carbapenem-resistant Acinetobacter baumannii (CRAB) and Klebsiella pneumoniae (CRKP) pose a serious public health threat, underscoring the urgent need for novel therapeutic options. This study compared the in vitro antimicrobial activity and associated clinical outcomes of three tetracycline-class antibiotics—eravacycline (ERV), tigecycline (TGC), and omadacycline (OMC)—against regional carbapenem-resistant isolates.Patients and Methods: A total of 106 CRKP and 117 CRAB non-duplicate clinical isolates were collected from Xuanwu Hospital (Beijing) between December 2024 and June 2025. Minimum inhibitory concentrations (MICs) were determined using broth microdilution (CLSI M07 guidelines). Time-kill assays (0– 48 h) were used to evaluate bactericidal activity, and clinical outcomes were analyzed in patients treated with TGC or ERV.Results: ERV demonstrated superior in vitro activity: its MIC90 against CRKP (0.5 μg/mL) was 4-fold lower than TGC (2 μg/mL) and 8-fold lower than OMC (4 μg/mL). For CRAB, ERV’s MIC90 (0.25 μg/mL) was 4-fold lower than TGC (1 μg/mL). ERV maintained sustained bactericidal activity (≥ 3-log10 CFU/mL reduction) for 24– 36 h against CRAB— 2.3-fold longer than TGC and 3.1-fold longer than OMC. ERV-treated patients (n = 20) showed a 5% mortality rate (6.7% for CRAB and 0% for CRKP), compared with 18.9% (CRAB) and 16.7% (CRKP) in TGC-treated patients.Conclusion: Current evidence indicates that ERV exhibits strong in vitro bactericidal activity and demonstrates more favorable clinical efficacy comparable to that of TGC against CRKP and CRAB infections, as observed in our retrospective clinical cohort.Plain Language Summary: Faced with the increasing threat of CRAB and CRKP, this study evaluated effectiveness of three tetracycline-class antibiotics against these resistant bacteria. ERV showed superior in vitro potency than TGC and OMC, with lower concentrations needed to inhibit bacterial growth. ERV also killed CRAB more effectively and for a longer duration than the other two antibiotics. In clinical settings, patients treated with ERV had a 5% mortality rate, compared with 18.9% for CRAB patients treated with TGC. Although limited by a small number of patients, the results suggest that ERV could be a promising treatment option for CRAB and CRKP infections, warranting further multi-center validation.Keywords: carbapenem-resistant Acinetobacter baumannii, carbapenem-resistant Klebsiella pneumoniae, broth microdilution, time-kill assays, tetracycline-class antibiotics