Abstract
Turbid broth (0.5 ml) from blood culture bottles was inoculated into 0.5 ml of brain heart infusion broth, incubated for 3 to 6 h, diluted 1:500 in distilled water, and then inoculated directly into microtiter broth dilution susceptibility trays to test for minimal inhibitory concentrations. The results were compared to the standard tests performed 24 h later on colonies from subculture plates. The minimal inhibitory concentrations measured by these two methods were compared in 1,875 organism-antibiotic tests. The two minimal inhibitory concentrations were identical in 86.0% and within one twofold dilution in 98.0% of the tests. An organism was judged to be susceptible by one method and resistant by the other in 13 tests (0.7%). These 13 discrepancies were distributed among several organism-antibiotic combinations; no more than two were seen for any one combination. Highly accurate susceptibility testing can be achieved by using direct inoculation of turbid blood culture broths.
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Selected References
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