TABLE 1.
Susceptibilities of 181 isolates of S. pneumoniae stratified by penicillin susceptibility
| Antimicrobial agent and penicillin susceptibility (n)a | Breakpoint (μg/ml)b | MIC (μg/ml)c
|
No. (%) of isolates not susceptible to indicated antimicrobial agentb | ||
|---|---|---|---|---|---|
| Range | 50% | 90% | |||
| Penicillin | >0.06 | ||||
| S (56) | 0.023–0.064 | 0.032 | 0.064 | 0 (0) | |
| I (27) | 0.094–1 | 0.19 | 1 | 27 (100) | |
| R (98) | 1.5–6 | 2 | 4 | 98 (100) | |
| Total (181) | 0.023–6 | 1.5 | 3 | 125 (69.1) | |
| Cefuroxime | >0.5 | ||||
| S | 0.023–0.19 | 0.023 | 0.064 | 0 (0) | |
| I | 0.064–3 | 0.38 | 4 | 12 (44.4) | |
| R | 2–16 | 4 | 6 | 98 (100) | |
| Total | 0.023–16 | 3 | 4 | 110 (60.8)d | |
| Cefpodoxime | NA | ||||
| S | 0.023–0.94 | 0.032 | 0.064 | NA | |
| I | 0.05–2 | 0.38 | 2 | NA | |
| R | 1–8 | 3 | 4 | NA | |
| Total | 0.023–8 | 2 | 3 | NA | |
| Ceftibuten | NA | ||||
| S | 2–48 | 4 | 12 | NA | |
| I | 6–>256 | 96 | >256 | NA | |
| R | >256 | >256 | >256 | NA | |
| Total | 2–>256 | >256 | >256 | NA | |
| Ceftriaxone | >0.5 | ||||
| S | 0.012–0.19 | 0.023 | 0.032 | 0 (0) | |
| I | 0.032–0.5 | 0.19 | 0.5 | 0 (0) | |
| R | 0.25–3 | 0.75 | 1 | 80 (81.6) | |
| Total | 0.012–3 | 0.5 | 1 | 80 (44.2)d | |
| Cefepime | >0.5 | ||||
| S | 0.023–0.94 | 0.047 | 0.094 | 1 (1.8) | |
| I | 0.094–1.5 | 0.5 | 1.5 | 12 (44.4) | |
| R | 0.75–3 | 1.5 | 2 | 98 (100)d | |
| Total | 0.023–3 | 1.5 | 2 | 111 (61.3) | |
| Meropenem | >0.25 | ||||
| S | 0.012–0.12 | 0.012 | 0.02 | 0 (0) | |
| I | 0.023–0.38 | 0.064 | 0.38 | 5 (18.5) | |
| R | 0.094–0.75 | 0.5 | 0.75 | 95 (96.9) | |
| Total | 0.012–0.75 | 0.38 | 0.5 | 100 (55.2)d | |
| Erythromycin | >0.25; >0.5 | ||||
| S | 0.032–>256 | 0.13 | >256 | 22 (39.3); 22 (39.3) | |
| I | 0.13–>256 | >256 | >256 | 23 (85.2); 23 (85.2) | |
| R | 0.13–>256 | 4 | >256 | 97 (98.9); 97 (98.9) | |
| Total | 0.032–>256 | 4 | >256 | 142 (78.5); 142 (78.5)d | |
| Azithromycin | >0.5; >4 | ||||
| S | 0.094–>256 | 1.5 | >256 | 45 (80.3); 22 (39.3) | |
| I | 0.75–>256 | >256 | >256 | 27 (100); 23 (85.2) | |
| R | 1–>256 | 24 | >256 | 98 (100); 91 (92.9) | |
| Total | 0.094–>256 | 24 | >256 | 170 (93.9); 136 (75.1)d | |
| Clindamycin | >0.25 | ||||
| S | 0.023–>256 | 0.19 | >256 | 12 (21.4) | |
| I | 0.094–>256 | >256 | >256 | 17 (62.9) | |
| R | 0.064–>256 | 0.19 | >256 | 16 (16.3) | |
| Total | 0.023–>256 | 0.19 | >256 | 45 (24.7) | |
| Ciprofloxacin | NA | ||||
| S | 0.38–8 | 1 | 2 | NA | |
| I | 0.5–>32 | 1 | 4 | NA | |
| R | 0.38–>32 | 1 | 12 | NA | |
| Total | 0.38–>32 | 1 | 6 | NA | |
| Levofloxacin | >2 | ||||
| S | 0.5–1.5 | 0.75 | 1 | 0 (0) | |
| I | 0.5–24 | 0.75 | 1.5 | 1 (3.7) | |
| R | 0.38–>32 | 1 | 3 | 9 (9.2) | |
| Total | 0.38–>32 | 1 | 1.5 | 10 (5.5)d | |
| Trovafloxacin | >1 | ||||
| S | 0.094–0.38 | 0.19 | 0.25 | 0 (0) | |
| I | 0.094–0.38 | 0.19 | 0.25 | 0 (0) | |
| R | 0.064–>32 | 0.19 | 0.5 | 4 (4) | |
| Total | 0.064–>32 | 0.19 | 0.38 | 4 (2.2) | |
| Vancomycin | >1 | ||||
| S | 0.38–1 | 0.5 | 0.75 | 0 (0) | |
| I | 0.38–0.75 | 0.75 | 0.75 | 0 (0) | |
| R | 0.25–1 | 0.5 | 0.75 | 0 (0) | |
| Total | 0.25–1 | 0.5 | 0.75 | 0 (0) | |
a
S, susceptible; I, intermediate; R, resistant.
b
Breakpoints are given in accordance with NCCLS standard M100-S (10) or guidelines from the manufacturer of the E-test. The breakpoints and interpretations according to the recommendations of the manufacturer of the E-test are underlined. Both intermediate and resistant strains were included as nonsusceptible.
c
50% and 90%, MICs required to inhibit 50 and 90% of the isolates, respectively.
d
Penicillin-susceptible versus penicillin-nonsusceptible strains. P < 0.05 by chi-square or Fisher exact test.