Synergistic activity of ceftazidime/avibactam combined with aztreonam against MBL-producing exoY+/exoT+/exoU+/exoS- extensively drug-resistant Pseudomonas aeruginosa

The underlying resistance mechanisms of XDR-PA isolates involve the overexpression of efflux pump <i>mexA</i> and the existence of MBL. In addition, ST1971 was the predominant ST type in our study, with carrying both NDM-1 and <i>exoY+/exoT+/exoU+/exoS-</i>. Furthermore, combined antimicrobial susceptibility testing suggested that CZA and ATM combination has potential against MBL-producing <i>exoY+/exoT+/exoU+/exoS-</i> XDR-PA. These findings may provide clues for the prevention, control and treatment strategies of XDR-PA infections.