Aztreonam: correlation between disk diffusion and agar plate dilutions susceptibility tests.

Regression lines and error rate-bounded analyses were performed for correlating inhibitory zone diameters with the 30-μg aztreonam disk and aztreonam minimal inhibitory concentration for gram-negative aerobic clinical isolates. A correlation coefficient of-0.81 was found for the regression line. Preliminary proposed criteria to distinguish susceptible isolates from resistant ones are: susceptible > 22mm (MIC 32 μg/ml). Using these criteria, the rates for false-susceptible and false-resistant isolates were zero.