Persistent Bacteremia from Pseudomonas aeruginosa with In Vitro Resistance to the Novel Antibiotics Ceftolozane-Tazobactam and Ceftazidime-Avibactam

Table 2

Antimicrobial susceptibility of Pseudomonas aeruginosa isolated from the blood.

Antimicrobial	Day 1		Day 5		Day 10		Day 15
	MIC	Int	MIC	Int	MIC	Int	MIC	Int
Piperacillin-tazobactam	32	S	≥128	R	≥128	R	≥128	R
Cefepime	8	S	32	R	≥64	R	≥64	R
Aztreonam	16	I	16	I	≥64	R	≥64	R
Meropenem	4	S	4	S	≥16	R	≥16	R
Amikacin	16	S	16	S	16	S	16	S
Gentamicin	8	I	8	I	≥16	R	≥16	R
Tobramycin	≤1	S	≤1	S	≤1	S	≤1	S
Ciprofloxacin	≥4	R	≤4	R	≥4	R	≥4	R
Tigecycline	≥8	R	≤8	R	≥8	R	≥8	R

Int, interpretation; MIC, minimum inhibitory concentration; R, resistant; S, susceptible; and I, intermediate.
Antimicrobial susceptibility testing of P. aeruginosa against ceftolozane-tazobactam (C/T) and ceftazidime-avibactam (CZA) by -test was performed for the Pseudomonas isolate from Day 10. -test showed 0 mm zone of inhibition for CZA (resistant) and 16 mm for C/T (resistant). Cefepime was used as a surrogate for ceftazidime susceptibility.