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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.

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

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