Efflux pumps expression and its association with porin down-regulation and β-lactamase production among Pseudomonas aeruginosa causing bloodstream infections in Brazil

Table 2 Association of resistance mechanisms identified among the P. aeruginosa isolates (n = 59) and the modal MICs for tested antimicrobials observed in each association.

Isolates and determinant of antimicrobial resistance (No. of isolates with OprD -)		Modal MIC^a(μg/ml)
		MER	IPM	ATM	CAZ	FEP	AMK	GEN	CIP
PAO1 reference strain	-	0.25	1	4	0.5	0.25	2	4	0.25-
No mechanisms of resistance identified	7 (0)	4	2	4-8^b	4	2	8	4	16
XY+, MBL	7 (6)	>32	>32	8	256	>32	>256	>256	>32
XY+	7 (5)	16	8/16^b	32	8/256^b	>32	256	2/>256^b	0.5/>32^b
ABM+, XY+	5 (2)	0.25/8^b	0.25/2^b	16	8	4	256	2- >256^c	32
ABM+, XY+, MBL	4 (3)	>32	>32	8	256	>32	>256	>256	>32
ABM+	3 (2)	0.5-16^b	1	16	2-8^c	4	4-32^c	1-8^c	0.25-8^c
XY+, GES-1	3 (2)	8- >32^c	8- >32^c	8	128	>32	>256	256	16
ABM+, XY+, AmpC+	2 (2)	16/>32^b	>32	8/32^b	32/64^b	16/32^b	4/64^b	1/8^b	2/4^b
ABM+, GES-5	1 (1)	>32	32	8	32	>32	128	128	32
ABM+, CTX-M2	1 (1)	4	1	>32	2	>32	128	256	16
XY+, AmpC+, MBL	2 (2)	32/>32^b	>32	16/>32^b	128/>256^b	>32	>256	>256	>32
MBL	2 (2)	>32	>32	8	256	>32	>256	>256	32
AmpC+	3 (2)	1-8	2-16^c	4-32^c	16-256^c	16	4	2	0.5-32^c
OprD-	12 (12)	≤0.25	1-2	8	2	2	8	2	0.25

MER, meropenem; IPM, imipenem; ATM, aztreonam; CAZ, ceftazidime; FEP, cefepime; AMK, amikacin; GEN, gentamicin; CIP, ciprofloxacin.
The abbreviations XY+, ABM+, and AmpC+ designate MexXY, MexAB-OprM, and AmpC overexpression, respectively.
MBL, metallo-β-lactamase producer
OprD-, reduced expression of OprD porin.
^a, Modal MIC is defined as the antimicrobial MICs that were more frequently observed at each association of resistance mechanisms.
^b, two modal MICs observed;
^c MIC range when no modal MIC was observed.

ISSN: 1471-2180