A brain heart infusion broth and agar biphasic bottle was compared with a vented broth brain heart infusion bottle for the recovery of fungi from blood. A total of 40 fungi, all yeasts, were recovered from 5,000 blood cultures. The biphasic bottle slightly increased the overall recovery of six species of yeasts. In addition, yeasts were first detected more often in the biphasic bottle (73%) than in the vented broth bottle (38%). A routine early (6- to 24-h) or late (5-day) subculture of macroscopically negative cultures may not be required for yeast isolation when a biphasic medium is used. Of the yeasts initially detected in the biphasic medium, 83% were seen to be growing on the agar slant. Only four were detected from a 24-h subculture, a Candida glabrata of questionable clinical significance, was recovered after our routine blood culture period of 7 days; however, other fungi, not recovered in this study, require extended incubation periods.

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.