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Table 3 Antimicrobial susceptibility profile of 95 isolates of A. baumannii, and MIC reductions of the antibiotics in exposure to PAβN

From: Characteristics and diversity of mutations in regulatory genes of resistance-nodulation-cell division efflux pumps in association with drug-resistant clinical isolates of Acinetobacter baumannii

Antimicrobial agents Disk diffusion Without PAβN/with PAβN (25 µg/ml)
S no. (%) I no. (%) R no (%) MIC range (µg/ml) MIC50 (µg/ml) MIC90 (µg/ml) S no. (%) I no. (%) R no. (%)
Imipenema 2 (2) 6 (6) 87 (92) 0.38–32/0.38–32 32/32 32/32 1 (1)/1 (1) 0/0 94 (99)/94 (99)
Meropenem 1 (1) 0 94 (99)
Doripenem 0 1 (1) 94 (99)
Cefotaxime 0 1 (1) 94 (99)
Ceftazidime 1 (1) 0 94 (99)
Cefepimea 1 (1) 7 (7) 87 (92) 3–256/3–256 256/96 256/256 1 (1)/1 (1) 0/0 94 (99)/94 (99)
Ampicillin-Sulbactam 12 (13) 22 (23) 61 (64)
Ticarcillin-clavulanic 1 (1) 0 94 (99)
Piperacillin-Tazobactam 0 0 95 (100)
Gentamicina 5 (5) 16 (17) 74 (78) 0.75–256/0.38–256 96/32 256/256 4 (4)/4 (4) 6 (6)/14 (15) 85 (90)/77 (81)
Amikacin 11 (12) 7 (7) 77 (81)
Tobramycin 46 (48) 2 (2) 47 (50)
Tetracycline 6 (6) 22 (23) 67 (71)
Minocycline 76 (80) 12 (13) 7 (7)
Tigecyclinea 0.016–16/0.016–12 4/2 12/6 25 (26)/58 (61) 31 (33)/20 (21) 39 (41)/17 (18)
Cotrimoxazole 1 (1) 0 94 (99)
Levofloxacina 1 (1) 0 94 (99) 0.064–32/0.064–32 32/12 32/32 2 (2)/2 (2) 13 (14)/13 (14) 80 (84)/80 (84)
Ciprofloxacin 1 (1) 1 (1) 93 (98)
Gatifloxacin 2 (2) 0 93 (98)
Colistinb 0.047–1.0 0.75 1.0
  1. Disks concentration: imipenem, 10 µg; meropenem, 10 µg; doripenem, 10 µg; cefotaxime, 30 µg; ceftazidime, 30 µg; cefepime, 30 µg; ampicillin-sulbactam, 10/10 µg; ticarcillin-clavulanic, 75/10 µg; piperacillin-tazobactam, 100/10 µg; gentamicin, 10 µg; amikacin, 30 µg; tobramycin, 10 µg; tetracycline, 30 µg; minocycline, 30 µg; trimethoprim/sulfamethoxazole, 1.25/23.75 µg; levofloxacin, 5 µg; ciprofloxacin, 5 µg; Gatifloxacin, 5 µg
  2. PAβN, phenylalanine-arginine beta-naphthylamide; MIC, minimum inhibitory concentration; MIC50 and MIC90, MIC for 50% and 90% of the isolates, respectively. Changes in MIC and AST pattern after addition of PAβN, are shown in bold
  3. aMIC of these antibiotics is determined with and without PAβN efflux pump inhibitor
  4. bSince disk diffusion is not accepted for colistin AST, its MIC was assessed according to CLSI