Table 3.
Minimum inhibitory concentration (MIC; ppm) and minimum bactericidal concentration (MBC; ppm) for nine antibiotics of clinical interest on eight strains of Listeria monocytogenes.
| Strain | Antibiotic | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| AMP | KF | FOX | E | C | CN | TE | VA | FOS | |
| ATCC 19111 | 7 (10) |
150 (150) |
170 (180) |
0.05 (4) |
20 (70) |
45 (50) |
15 (30) |
80 (90) |
350 (350) |
| ATCC 19112 | 11 (11) |
140 (140) |
160 (170) |
0.10 (5) |
4 (10) |
45 (45) |
14 (18) |
45 (50) |
160 (160) |
| ATCC 19114 | 9 (9) |
80 (90) |
140 (180) |
0.05 (5) |
20 (70) |
20 (20) |
8 (11) |
20 (20) |
230 (290) |
| ATCC 19117 | 1 (5) |
8 (20) |
150 (200) |
0.20 (5) |
20 (55) |
4 (15) |
2 (10) |
2 (3) |
430 (450) |
| ATCC 13932 | 9 (9) |
70 (70) |
160 (160) |
0.20 (5) |
35 (60) |
20 (20) |
11 (11) |
20 (20) |
250 (260) |
| STCC 936 | 5 (6) |
8 (9) |
20 (70) |
0.20 (5) |
5 (30) |
3 (5) |
2 (3) |
20 (20) |
170 (180) |
| STCC 937 | 15 (15) |
150 (150) |
170 (200) |
0.20 (5) |
50 (70) |
50 (50) |
15 (30) |
35 (40) |
240 (280) |
| STCC 938 | 13 (20) |
150 (160) |
150 (150) |
0.20 (5) |
5 (9) |
100 (100) |
15 (30) |
50 (60) |
220 (230) |
| CUT-OFF POINTS S ≤ - R > |
1–1 | 0.12–0.50 * | 4–8 | 1–1 | 8–8 | 1–1 | 1–2 | 2–2 | 32–32 |
AMP—ampicillin; KF—cephalothin; FOX—cefoxitin; E—erythromycin; C—chloramphenicol; CN—gentamicin; TE—tetracycline; VA—vancomycin; FOS—fosfomycin. LM—Listeria monocytogenes. ATCC—American Type Culture Collection; STCC—Spanish Type Culture Collection. Values not in brackets correspond to minimum inhibitory concentrations (MICs), and those in brackets to minimum bactericidal concentrations (MBC). The cut-off points for MIC used to classify strains as susceptible (MIC ≤ lower cut-off), of reduced susceptibility (MIC > lower cut-off and ≤ upper cut-off), and resistant (MIC > upper cut-off) are indicated. The criteria for AMP and E were specifically for L. monocytogenes [35]. Those used for C, TE, and FOS were initially intended for Staphylococcus spp. [35], those used for CN and VA were intended for S. aureus [35] and those used for KF and FOX were also intended for S. aureus [36]. *—quality control range. Green shading shows susceptible strains, yellow shading shows strains with reduced susceptibility, and red shading indicates strains that are resistant, in accordance with the criteria applied.