Table 3.
Mechanism of beta-lactam resistance detected by phenotypic methods and effect of fosfomycin on different beta-lactam resistant isolates
| Mechanism of beta-lactamsresistance detected phenotypically | Isolates with visible growth at different concentration of fosfomycin and (%) resistance of isolates to fosfomycin | ||||||
|---|---|---|---|---|---|---|---|
| MIC of fosfomycin [µgm/mL] | 16 | 32 | 64 | 128 | 256 | 512 | 1026 |
| ESBL producers N=319 |
|||||||
|
Escherichia coli* N=216 |
0 | 0 | 0 | 0 | 0 | 0 | 0 |
|
K.pneumoniae# N=49 |
14 (30) | 14 (30) | 14 (30) | 14 (30) | 10 (20) | 6 (12.2) | 2 (4) |
|
Pseudomonas sppα N=32 |
16 (50) | 16 (50) | 16 (50) | 16 (50) | 16 (50) | 12 (38.4) | 3 (9) |
|
Enterobacter sppδ N=22 |
15 (68) | 10 (45) | 10(45) | 9 (40) | 9 (40) | 5 (22.7) | 1 (4) |
| MBL producers N=138 |
|||||||
|
Escherichia coli* N=44 |
0 | 0 | 0 | 0 | 0 | 0 | 0 |
|
K.pneumoniae# N=38 |
19 (50) | 19 (50) | 19 (50) | 19 (50) | 19 (50) | 18 (47.3) | 4 (10) |
|
Pseudomonas sppα N=32 |
16 (50) | 16 (50) | 16 (50) | 16 (50) | 16 (50) | 12 (37.5) | 3 (9) |
|
Enterobacter sppδ N=20 |
9 (45) | 9 (45) | 9 (45) | 9 (45) | 8 (40) | 8 (40) | 2 (10) |
| AmpC BL Producers N=158 |
|||||||
|
Escherichia coli* N=64 |
0 | 0 | 0 | 0 | 0 | 0 | 0 |
|
K.pneumoniae# N=38 |
16 (42) | 16 (42) | 16 (42) | 15 (39) | 10 (26) | 10 (26) | 3 (8) |
|
Pseudomonas sppα N=32 |
16 (50) | 16 (50) | 16 (50) | 16 (50) | 16 (50) | 12 (37.5) | 3 (9) |
|
Enterobacter sppδ N=20 |
8 (40) | 8 (40) | 8 (40) | 8 (40) | 6 (30) | 4 (20) | 1 (5) |
Notes: *For Escherichia coli the MIC of fosfomycin according to CLSI (S 64 µgm/mL, I=128 µgm/mL. R 256 µgm/mL).The MIC 50 and MIC 90 of fosfomycin in Escherichia coli was 1 µgm/mL and 2 µgm/mL respectively. #For Klebsiella pneumoniae the MIC of fosfomycin according to EUCAST interpretative criteria (S≤32, R>32). The MIC50 and MIC 90 of fosfomycin in Klebsiella pneumoniae was 32 µgm/mL and 1026 µgm/mL respectively. αFor Pseudomonas aeruginosa the MIC of fosfomycin according to EUCAST interpretative criteria (S≤32, R>32). The MIC50 and MIC 90 of fosfomycin in Pseudomonas aeruginosa was 32 µgm/mL and 1026 µgm/mL respectively. δFor Enterobacter spp the MIC of fosfomycin according to EUCAST interpretative criteria (S≤32, R>32). The MIC50 and MIC 90 of fosfomycin in Enterobacter spp was 32 µgm/mL and 1026 µgm/mL respectively.