TABLE 1.
Comparison of E-test- and agar dilution-determined MICs of penicillin and ceftriaxone for the 79 S. pneumoniae clinical isolates
| Antimicrobial agent | No. of isolates for which E-test MICs differed from agar dilution MICs by indicated no. of log2 dilutionsa
|
% Agreementb | % Interpretive errorc
|
||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| −2 | −1.5 | −1 | −0.5 | 0 | +0.5 | +1 | +1.5 | +2 | Very major | Major | Minor | ||
| Penicillin | 2 | 11 | 11 | 21 | 28 | 6 | 97.5 | 0 | 0 | 2.5 | |||
| Ceftriaxone | 1 | 1 | 7 | 13 | 23 | 20 | 11 | 3 | 93.7 | 0 | 0 | 1.0 | |
a
A difference of 0 indicates that the MICs were identical; −1 and +1 indicate a ±1 log2 dilution difference, etc.
b
Percentage of isolates for which MICs of the indicated agent differed by the two methods within ±1 log2 dilution.
c
Very major error, number of false-susceptible results/number of resistant isolates × 100; major error, number of false-resistant results/number of susceptible isolates × 100; minor error, number of susceptible-to-intermediate, intermediate-to-susceptible, resistant-to-intermediate, or intermediate-to-resistant results/total number of isolates tested × 100.