In Vitro Activity of Ceftazidime/Avibactam Against Multidrug-Resistant Gram-Negative Bacilli in Niger

The rise of multidrug-resistant Gram-negative bacilli (MDR-GNB) necessitates the evaluation of new antibiotics such as ceftazidime-avibactam (CZA). Data on its efficacy in Niger is scarce. This study assessed the in vitro activity of CZA against clinical MDR-GNB isolates.

This prospective cross-sectional study was carried out on 306 non-duplicate MDR-GNB isolates from a National Reference Laboratory from December 2023 to November 2024. Antimicrobial susceptibility testing was performed, and CZA resistance rates were determined. Statistical analysis identified factors associated with resistance.

Overall, 23.4% of MDR isolates were resistant to CZA. However, resistance varied dramatically by phenotype: 7.6% in ESBL-producing Enterobacterales (ESBL-E), 33.3% in carbapenem-resistant Pseudomonas aeruginosa (CRPA), 61.7% in carbapenem-resistant Enterobacterales (CRE), and 100% in carbapenem-resistant Acinetobacter baumannii (CRAB). Multivariate analysis confirmed that carbapenem resistance was the strongest predictor of CZA resistance (OR=19.00, 95% CI: 9.96-38.27, p<0.001).

CZA demonstrates potent activity against ESBL-E in Niger, supporting its role as a carbapenem-sparing agent. However, the high resistance rates in CRE and CRAB preclude its empirical use for suspected infections with these pathogens. These findings underscore the critical need for routine CZA susceptibility testing and enhanced stewardship to preserve its utility.