Table 3.
Antimicrobial susceptibility profile of 95 isolates of A. baumannii, and MIC reductions of the antibiotics in exposure to PAβN
| 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 | – | – | – |
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
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
aMIC of these antibiotics is determined with and without PAβN efflux pump inhibitor
bSince disk diffusion is not accepted for colistin AST, its MIC was assessed according to CLSI