Assessing the quality of the Alexander Project.

Controlled, standardized methods and quality control strains should be used in order to ensure that susceptibility data is valid and reproducible. Small differences in the methods used can lead to important variations in the results obtained. Comparisons between related agents and between studies, using statistical analysis, also indicate whether susceptibility data are consistent with known antimicrobial-organism relationships. The Alexander Project has demonstrated a consistently high level of quality, allowing the comparison of susceptibility data from over 27,500 organisms isolated from patients with lower respiratory tract infection.