Efficacy of cefiderocol in combination with xeruborbactam versus taniborbactam against cefiderocol-resistant NDM-producing Pseudomonas aeruginosa.

We evaluated the in vitro activity of cefiderocol in combination with either taniborbactam or xeruborbactam against cefiderocol-resistant, blaNDM-positive Pseudomonas aeruginosa clinical isolates from Vietnam and Nigeria. Taniborbactam restored cefiderocol susceptibility in most isolates (20/21, 95.2%), while xeruborbactam had no effect. Resistance was reversed by dipicolinic acid, which confirmed New-Delhi Metallo-β-Lactamase (NDM-mediated) resistance. One isolate that was unresponsive to taniborbactam carried multiple copies of blaNDM-1. These findings highlight the species-specific limitations of xeruborbactam in P. aeruginosa.