title: Influence of technical factor variations on serum inhibition and bactericidal titers.
abstract: The influence of technical factor variations on serum bactericidal and serum inhibitory titers was studied by using Staphylococcus aureus clinical isolates versus oxacillin-spiked human serum. Parallel tests, both with and without the use of beta-lactamase in count plates to inactivate oxacillin carryover, were performed with a conventional macrodilution approach, a carefully controlled macrodilution procedure, and a standard microdilution method. Careful control of technical factor variations diminished the incidence of low serum bactericidal titers and decreased the dispersion of results, a finding corollary to the known influence of technical factor variations on the measurement of MBCs. The incorporation of beta-lactamase into count plates resulted in a shift of serum bactericidal titers to lower values. The microdilution method appeared to be least influenced by technical variations and, with the addition of beta-lactamase to count plates, provided the best results.
mesh_terms: D006801:Humans; D008826:Microbial Sensitivity Tests; D010068:Oxacillin / Q000097:blood* / Q000494:pharmacology; D013211:Staphylococcus aureus / Q000187:drug effects*; D001618:beta-Lactamases
chemical_list: D001618:beta-Lactamases; D010068:Oxacillin