Table 2.

Susceptibility profile of each DTR-PA clinical isolate and rationales for selecting combination therapy.

ID Cases (Combo)	Susceptibility Profile (MIC in mg/L)	Criteria for Combination Therapy
#1 CID + FOS	AMI ≤ 8; CEP > 8; CTZ 16; CTV > 8; CTT ≤ 1; CIP 1; IMI > 8; MER 32; PIT > 16; FOS 64; CID 1	(1)Ceftolozane-tazobactam supply shortage (2)Ceftazidime-avibactam resistance (3)Potential synergism of combination therapy (4)HAP
#2 CTV + FOS	AMI ≤ 8; CEP > 8; CTZ 16; CTV 8; CTT ≤ 1; CIP 1; IMI > 8; MER 32; PIT > 16; COL 2; FOS 256	(1)Ceftolozane-tazobactam supply shortage (2)Potential synergism of combination therapy according to in vitro evidence (3)VAP
#3 CID + FOS	AMI ≤ 8; CEP > 8; CTZ > 32; CTV > 8; CTT 4; CIP 0.5; IMI > 8; MER 32; PIT > 16; COL 2; FOS 32; CID 2	(1)Ceftolozane-tazobactam supply shortage (2)Ceftazidime-avibactam resistance (3)Potential synergism of combination therapy (4)VAP
#4 CID + FOS	AMI 16; CEP > 8; CTZ > 32; CTV > 8; CTT > 4; CIP > 1; IMI > 8; MER 16; PIT > 16; COL 1; FOS 64; CID 8	(1)Ceftolozane-tazobactam resistance (2)Ceftazidime-avibactam resistance (3)Potential synergism of combination therapy
#5 CID + FOS	AMI 16; CEP > 8; CTZ > 32; CTV > 8; CTT ≤ 1; CIP 1; IMI > 8; MER 32; PIT > 16; COL 1; FOS 32; CID 2	(1)Ceftolozane-tazobactam supply shortage (2)Ceftazidime-avibactam resistance (3)Potential synergism of combination therapy (4)VAP
#6 CTV + FOS	AMI > 16; CEP > 8; CTZ > 32; CTV 8; CTT > 4; CIP > 1; IMI 8; MER 8; PIT > 16; FOS 32	(1)Ceftolozane-tazobactam resistance (2)Potential synergism of combination therapy according to in vitro evidence (3)VAP

AMI: amikacin; CEP; cefepime; CID: cefiderocol; CTZ; ceftazidime; CTV: ceftazidime-avibactam; CTT: ceftolozane-tazobactam; CIP: ciprofloxacin; FOS: fosfomycin; HAP: hospital-acquired pneumonia; IMI: imipenem; MER: meropenem; PIT: piperacillin-tazobactam; VAP: ventilator-acquired pneumonia.