Open AccessComparison of Direct and Standardized Antimicrobial Susceptibility Testing of Positive Blood Cultures
Author(s) -
James E. Johnson,
John A. Washington
Publication year - 1976
Publication title -
antimicrobial agents and chemotherapy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.07
H-Index - 259
eISSN - 1070-6283
pISSN - 0066-4804
DOI - 10.1128/aac.10.2.211
Subject(s) - staphylococcus epidermidis , penicillin , ampicillin , microbiology and biotechnology , antibiotics , agar dilution , blood culture , biology , gram positive cocci , klebsiella , minimum inhibitory concentration , staphylococcus , medicine , staphylococcus aureus , bacteria , escherichia coli , biochemistry , gene , genetics
In an effort to determine the feasibility and accuracy of performing direct susceptibility tests from positive blood cultures, minimal inhibitory concentrations (MICs), determined by the agar dilution method, of direct and standardized tests with seven antibiotics were compared. Results were analyzed as to the number of very major (change in MIC from susceptible in preliminary direct testing to resistant in final standardized testing), major (change in MIC from resistant to susceptible), and minor (change in MIC without change in interpretation) discrepancies. The results for gram-positive cocci and for gram-negative bacilli were 5, 6, and 82 of 162 strains tested and 3, 12, and 79 of 90 strains tested, respectively. Of the total number of susceptibility tests compared, major and very major discrepancies occurred in only 1 and 2.4% of instances with gram-positive and -negative isolates, respectively. The majority of discrepancies were noted withStaphylococcus epidermidis (four very major, five major),Klebsiella (two very major, four major), andAlcaligenes (five major). The antibiotics most often exhibiting discrepancies were penicillin, ampicillin, and cephalothin. The results indicate that preliminary susceptibility testing directly from positive blood culture bottles is generally both feasible and accurate.