In‐Vitro Activity of Ceftazidime‐Avibactam and Comparator Agents Against Carbapenem‐Resistant Gram‐Negative Isolates at a Tertiary Care Hospital in Lahore, Pakistan: A Cross‐Sectional Study

Carbapenem-resistant Gram-negative bacteria are WHO critical priority pathogens with few treatment options. Ceftazidime-avibactam (CAZ-AVI) inhibits serine carbapenemases (KPC, OXA-48-like) but not metallo-β-lactamases, which are common in South Asia. Local data are scarce; we assessed CAZ-AVI and comparator activity in Pakistan. In this laboratory-based cross-sectional study, consecutive non-duplicate carbapenem-resistant isolates from a tertiary care centre in Lahore (December 2024-May 2025) were tested by MIC and disc diffusion with CLSI interpretation. The primary outcome was CAZ-AVI susceptibility with exact binomial 95% confidence intervals; comparisons used Fisher's exact test, McNemar's test, and multivariable logistic regression. Of 210 isolates, 200 had CAZ-AVI results; susceptibility was 70.5% (141/200; 95% CI 63.7-76.7). It varied by sample source (p = 0.008), from 81.2% in blood cultures to 38.5% (5/13) in other specimens, but not by organism, department, age, or gender. In paired comparisons, CAZ-AVI susceptibility exceeded gentamicin, ciprofloxacin, piperacillin-tazobactam, and trimethoprim-sulfamethoxazole, was similar to amikacin, and was lower than colistin, fosfomycin, and tigecycline. Among 59 resistant isolates, colistin (94.5%), fosfomycin (92.9%), tigecycline (79.5%), and chloramphenicol (76.7%) were most active. Sample source was the only independent predictor (other specimens vs blood culture: adjusted OR 0.18, 95% CI 0.05-0.68; imprecise). CAZ-AVI was active in vitro against 70.5% of carbapenem-resistant Gram-negative isolates. Because nearly one-third were resistant, these findings support surveillance and susceptibility-guided rather than empirical use. Metallo-β-lactamase production is a plausible but unconfirmed explanation. Molecular characterization and evaluation of CAZ-AVI plus aztreonam are needed.