Table 1.

Main resistance mechanisms of new antibiotics.

Anti-Pseudomonals in Clinical Use	Main Resistance Mechanisms
Ceftolozane-tazobactam	AmpC structural mutations, β-lactam target modification (PBP) [21,22,47], OprD mutation and efflux pumps upregulation [28], MBL productions [27], OXA-2 and OXA-10 mutations [23,24,25]
Ceftazidime-avibactam	OprD mutation and efflux pumps upregulation [28,47,62,63,64], AmpC structural mutations, β-lactam target modification (PBP) [22,28,47], OXA-2 and OXA-10 mutations [24,25,65], MBL production [61]
Cefiderocol	Mutations in major iron transport pathways, possible AmpC mutations [79] mutations in β-lactamases [78]
Meropenem-vaborbactam	Porin mutations, efflux pump upregulation, MBL and OXA production [108]
Imipenem-cilastatin-relebactam	MBL and GES carbapenemases [85], mutations in MexB or in ParS [98]
Plazomicin	16S rRNA methyltransferases (i.e. Rmt or Arm) [145]