Table 1.

Susceptibilities of 181 isolates of S. pneumoniae stratified by penicillin susceptibility

Antimicrobial agent and penicillin susceptibility (n)aBreakpoint (μg/ml)bMIC (μg/ml)cNo. (%) of isolates not susceptible to indicated antimicrobial agentb
Range50%90%
Penicillin>0.06
 S (56)0.023–0.0640.0320.0640 (0)
 I (27)0.094–10.19127 (100)
 R (98)1.5–62498 (100)
  Total (181)0.023–61.53125 (69.1)
Cefuroxime>0.5
 S0.023–0.190.0230.0640 (0)
 I0.064–30.38412 (44.4)
 R2–164698 (100)
  Total0.023–1634110 (60.8)d
CefpodoximeNA
 S0.023–0.940.0320.064NA
 I0.05–20.382NA
 R1–834NA
  Total0.023–823NA
CeftibutenNA
 S2–48412NA
 I6–>25696>256NA
 R>256>256>256NA
  Total2–>256>256>256NA
Ceftriaxone>0.5
 S0.012–0.190.0230.0320 (0)
 I0.032–0.50.190.50 (0)
 R0.25–30.75180 (81.6)
  Total0.012–30.5180 (44.2)d
Cefepime>0.5
 S0.023–0.940.0470.0941 (1.8)
 I0.094–1.50.51.512 (44.4)
 R0.75–31.5298 (100)d
  Total0.023–31.52111 (61.3)
Meropenem>0.25
 S0.012–0.120.0120.020 (0)
 I0.023–0.380.0640.385 (18.5)
 R0.094–0.750.50.7595 (96.9)
  Total0.012–0.750.380.5100 (55.2)d
Erythromycin>0.25;>0.5
 S0.032–>2560.13>25622 (39.3); 22 (39.3)
 I0.13–>256>256>25623 (85.2); 23 (85.2)
 R0.13–>2564>25697 (98.9); 97 (98.9)
  Total0.032–>2564>256142 (78.5); 142 (78.5) d
Azithromycin>0.5; >4
 S0.094–>2561.5>25645 (80.3); 22 (39.3)
 I0.75–>256>256>25627 (100); 23 (85.2)
 R1–>25624>25698 (100); 91 (92.9)
  Total0.094–>25624>256170 (93.9); 136 (75.1) d
Clindamycin>0.25
 S0.023–>2560.19>25612 (21.4)
 I0.094–>256>256>25617 (62.9)
 R0.064–>2560.19>25616 (16.3)
  Total0.023–>2560.19>25645 (24.7)
CiprofloxacinNA
 S0.38–812NA
 I0.5–>3214NA
 R0.38–>32112NA
  Total0.38–>3216NA
Levofloxacin>2
 S0.5–1.50.7510 (0)
 I0.5–240.751.51 (3.7)
 R0.38–>32139 (9.2)
  Total0.38–>3211.510 (5.5)d
Trovafloxacin>1
 S0.094–0.380.190.250 (0)
 I0.094–0.380.190.250 (0)
 R0.064–>320.190.54 (4)
  Total0.064–>320.190.384 (2.2)
Vancomycin>1
 S0.38–10.50.750 (0)
 I0.38–0.750.750.750 (0)
 R0.25–10.50.750 (0)
  Total0.25–10.50.750 (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.