TABLE 1.

Antibiotic susceptibility of 187 invasive macrolide-resistant S. pneumoniae strains

AntibioticPre-PCV7 (1999-2001) (n = 54)Early-PCV7 (2002-2004) (n = 65)Late-PCV7 (2005-2007) (n = 68)
MIC (μg/ml)%I%RI+RMIC (μg/ml)%I%RI+RPaMIC (μg/ml)%I%RI+RPb
MIC50MIC90RangeMIC50MIC90RangeMIC50MIC90Range
Penicillin
Old CLSI breakpointsc0.52≤0.016-248.227.876.00.52≤0.016-250.723.173.80.790.122≤0.016-244.110.354.40.01
New CLSI breakpointsd
    Meningitis0.52≤0.016-276.076.00.52≤0.016-273.873.80.790.52≤0.016-254.454.40.01
    Nonmeningitis0.52≤0.016-20000.52≤0.016-20000.122≤0.016-2000
Cefotaximee
    Meningitis0.510.01-233.33.737.00.2510.01-127.7027.70.280.1210.01-213.21.514.70.004
    Nonmeningitis0.510.01-23.703.70.2510.01-10000.200.1210.01-21.501.50.09
Erythromycin>256>2564->2560100100>256>2564->2560100100>256>2561->2560100100
Clindamycin>0.5>0.5≤0.25->0.5096.296.2>0.5>0.5≤0.25->0.5087.787.70.09>0.5>0.5≤0.25->0.5088.388.30.11
Tetracycline3264≤0.25-641.988.990.816640.25-1281.575.376.80.058320.25-642.977.980.80.13
Chloramphenicol416≤2-1650.050.0416≤2-1635.435.40.10≤216≤2-3229.429.40.02
Cotrimoxazole>2>2≤0.5->29.353.763.0>2>2≤0.5->21.558.5600.74≤0.5>2≤0.5->22.933.836.7<0.001
  • a P value comparing pre-PCV7 to early-PCV7 periods.

  • b P value comparing pre-PCV7 to late-PCV7 periods.

  • c Old penicillin breakpoints: sensitive ≤ 0.06 μg/ml, intermediate = 0.12 to 1 μg/ml, and resistant ≥ 2 μg/ml.

  • d New penicillin breakpoints: meningeal sensitive ≤ 0.06 μg/ml and resistant ≥ 0.12 μg/ml, and nonmeningeal sensitive ≤ 2 μg/ml; intermediate: 4 μg/ml, resistant ≥ 8 μg/ml.

  • e Cefotaxime breakpoints: meningeal sensitive ≤ 0.5 μg/ml, intermediate = 1 μg/ml, and resistant ≥ 2 μg/ml, nonmeningeal sensitive ≤ 1 μg/ml, intermediate = 2 μg/ml, and resistant ≥ 4 μg/ml.