E-TEST AS SUSCEPTIBILITY TEST AND EPIDEMIOLOGIC TOOL FOR EVALUATION OF NEISSERIA-MENINGITIDIS ISOLATES

The E test (AB Biodisk, Solna, Sweden), a new approach developed to te st antimicrobial susceptibility, was compared with the agar dilution m ethod for seven-drug antibiogram analysis of Neisseria meningitidis is olates. The overall E-test quantitative accuracy (+/- 1 log, dilution) was 93% compared with that of agar dilution testing. The E test was t hen used to perform the susceptibility tests on a 10-year sample of 10 2 N. meningitidis isolates, including 5 from a recent epidemic outbrea k in the University of Iowa (Iowa City) community. The E test proved t o be an efficient methodology for identifying common source clusters o f meningococcal disease having resistance to rifampin or sulfonamides. Moreover, the data demonstrated a recent increase in penicillin MICs (MIC for 90% of strains, 0.094 mug/ml) and an escalation of high-level resistance to trimethoprim-sulfamethoxazole (33%) and rifampin (14%). The E test should be considered a simple and accurate susceptibility method for the emerging need to test meningococci and other pathogenic neisserias. Chocolate Mueller-Hinton agar was observed to provide the best support of growth and E-test MIC results that correlated well wi th results of the reference agar dilution method previously used for n eisserias.