Tentative minimum inhibitory concentration and zone diameter breakpoints for moxifloxacin using BSAC criteria

Abstract

Tentative MIC and zone diameter breakpoints were determined for moxifloxacin using BSAC criteria. An MIC breakpoint of ≤ 1 mg/L, denoting sensitivity, is suggested for Enterobacteriaceae, staphylococci, haemophili, moraxellae, pneumococci and enterococci. For pseudomonads high and low breakpoints of 4 mg/L and 1 mg/L are suggested to allow for an intermediate category of sensitivity. A 1 μg moxifloxacin disc content is suggested for testing all of the organisms previously mentioned, except pseudomonads, for which a 5 μg disc is needed to discriminate between the intermediate and sensitive populations. Corresponding zone diameter breakpoints for a 1 μg disc are ≥ 20 mm for Enterobacteriaceae and staphylococci, 18 mm for the respiratory pathogens (Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis) and 15 mm for enterococci. For Pseudomonas aeruginosa with a 5 μg disc, three bands are suggested for interpretation, that of ≥ 25 mm (sensitive), 18-24 mm (intermediate) and ≤ 17 mm (resistant).