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Haemophilus test medium interpretive criteria for disk diffusion susceptibility tests with cefdinir, cefetamet, cefmetazole, cefpodoxime, cefdaloxime (RU29246, HR-916 metabolite), and trospectomycin

1992; Elsevier BV; Volume: 15; Issue: 8 Linguagem: Inglês

10.1016/0732-8893(92)90073-3

1879-0070

Ronald N. Jones, Meridith E. Erwin,

Antimicrobial Resistance in Staphylococcus

The disk diffusion zones and the MICs of six newer antimicrobials with significant activity against Haemophilus influenzae were compared using the Haemophilus test medium (HTM) and National Committee for Clinical Laboratory Standards methods. The rank order of potency was cefpodoxime (MIC50, ≤0.03 μg/ml) > cefetamet > cefdinir > cefdaloxime = trospectomycin > cefmetazole (MIC50, 2 μg/ml). Susceptible breakpoint interpretive criteria for HTM tests were established that conformed to prior recommendations for each drug when tested against other species. Absolute agreement between methods ranged from 89% to 100% with ≤1% false-susceptible interpretive errors. The recommended, tentative disk diffusion susceptible interpretive criteria were for 5-μg cefdinir disks ≥20 mm (MIC correlate, ≤1 μg/ml); for 10-μg cefetamet disks ≥18 mm (MIC correlate, ≤4 μg/ml); for 30-μg cefetamet disks ≥21 mm (MIC correlate, ≤4 μg/ml); for 30-μg cefmetazole disks ≥16 mm (MIC correlate, ≤16 μg/ml); for 10-μg cefpodoxime disks ≥21 mm (MIC correlate, ≤2 μg/ml); for 30-μg cefdaloxime disks ≥23 mm (MIC correlate, ≤2 μg/ml) and for 30-μg trospectomycin disks ≥17 mm (MIC correlate, ≤16 μg/ml). β-Lactamase-negative, ampicillin-resistant (BLNAR) H. influenzae isolates consistently had the highest MICs for each cephalosporin tested. These BLNAR strains most influenced the perceived in vitro spectrum of each β-lactam tested and required a recommendation of intermediate and resistant categories for cefdinir, cefetamet, and cefdaloxime.