Overcoming resistance barriers: Using the salvage therapy of Ceftazidime-Avibactam and Aztreonam for difficult-to-treat gram-negative infections at a tertiary care hospital in Karachi-A retrospective cohort pilot

Background & Objective: Rise of carbapenem resistance poses a major global health challenge, particularly in Pakistan where treatment options for Gram-negative carbapenem-resistant Enterobacteriaceae (CRE), are extremely limited. Last-resort agents such as colistin, tigecycline, and fosfomycin are constrained by toxicity and emerging resistance. Aztreonam, active against metallo-β-lactamase–producing organisms, is often unavailable or unaffordable. At Indus Hospital and Health Network (IHHN), Ceftazidime-Avibactam (CAZ-AVI) combined with Aztreonam (ATM) was used as salvage therapy between September 2023 and September 2024. The study aimed to evaluate outcomes of using CAZ-AVI with Aztreonam in patients with CRE. Methodology: This retrospective cohort study was conducted at IHHN from September 2023 to September 2024. Patients with carbapenem-resistant infections treated with CAZ-AVI + ATM were included, excluding CRAB. Due to limited availability of ATM in Pakistan, only 21 patients received this regimen, enabling it as pilot study. Clinical and microbiological data were extracted from HMIS and analyzed using SPSS. Results: Among 21 treated patients, the regimen yielded an in-hospital survival rate of 85.7% and clinical improvement in 83% of survivors, with minimal adverse effects. These findings suggest meaningful clinical benefit in patients with limited therapeutic options. Conclusion: CAZ-AVI plus ATM appears to be an effective salvage therapy for carbapenem-resistant Gram-negative infections in resource-limited settings. The study also underscores a need for reliable aztreonam availability in tertiary care hospitals. Significant findings yielded from this limited data set calls for larger prospective comparative studies to further validate these results.