Biomedical subjects
Publications and source records attributed to J R Zeitinger.
Twelve lots of commercially prepared Mueller-Hinton agar from four medium manufacturers were evaluated for performance with recommended quality control organisms, medium pH, agar depth and uniformity, and characteristics of the zones of inhibition. Only 2 of 12 lots were acceptable for disk diffusion susceptibility tests. Significant problems were observed with the preparation and pouring of the agar media.
We retested 2,181 bacteria-antibiotic combinations with the Kirby-Bauer disc-diffusion technique and found interpretive changes with 120 (5.5%). Most changes (101 of 120) were single steps (i.e. from R to I, I to R or S, or S to I). Of the 19 remaining, 10 of them were from R to S and nine from S to R. These changes were significantly more frequent for combinations with zone diameters clustered near interpretive breakpoints (within 2mm) than for other combinations, and there was a linear relationship between decreased reproducibility and increased clustering near interpretive breakpoints. Based on an analysis of all susceptibility testing results performed in 1978, combinations most commonly clustered near interpretive breakpoints included: Ampicillin with Klebsiella pneumoniae; erythromycin with enterococci; chloramphenicol with Serratia marcescens; gentamicin with Pseudomonas aeruginosa and enterocci; and tetracycline with Enterobacter spp., Escherichia coli, and K. pneumoniae.