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. 2010 Aug 12;10:217. doi: 10.1186/1471-2180-10-217

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 4-8b 4 2 8 4 16

XY+, MBL 7 (6) >32 >32 8 256 >32 >256 >256 >32

XY+ 7 (5) 16 8/16b 32 8/256b >32 256 2/>256b 0.5/>32b

ABM+, XY+ 5 (2) 0.25/8b 0.25/2b 16 8 4 256 2- >256c 32

ABM+, XY+, MBL 4 (3) >32 >32 8 256 >32 >256 >256 >32

ABM+ 3 (2) 0.5-16b 1 16 2-8c 4 4-32c 1-8c 0.25-8c

XY+, GES-1 3 (2) 8- >32c 8- >32c 8 128 >32 >256 256 16

ABM+, XY+, AmpC+ 2 (2) 16/>32b >32 8/32b 32/64b 16/32b 4/64b 1/8b 2/4b

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/>32b >32 16/>32b 128/>256b >32 >256 >256 >32

MBL 2 (2) >32 >32 8 256 >32 >256 >256 32

AmpC+ 3 (2) 1-8 2-16c 4-32c 16-256c 16 4 2 0.5-32c

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.