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Table. 4.

Table. 4.

Fluconazole DDT using two inocula at the first readable time and their categorical agreement with the BMD reference method for 188 isolates of four common Candida species*

Species N of isolates by fluconazole category by the BMD method Inoculum used in DDT* Mean (SD) of the first readable time (hr) % CA N (%) of isolates with discrepancies


FR F-SDD FS Total VME ME Minor
C. albicans 7 0 59 66 Standard 13.0 (2.2) 97.0 2 (3.0) 0 (0.0) 0 (0.0)
Large 11.6 (1.6) 100.0 0 (0.0) 0 (0.0) 0 (0.0)
C. glabrata 33 36 0 69 Standard 11.0 (1.6) 98.6 0 (0.0) 0 (0.0) 1 (1.4)
Large 10.3 (0.8) 98.6 0 (0.0) 0 (0.0) 1 (1.4)
C. parapsilosis 15 0 14 29 Standard 15.4 (2.3) 72.4 3 (10.3) 0 (0.0) 5 (17.2)
Large 12.4 (1.5) 96.6 0 (0.0) 0 (0.0) 1 (3.4)
C. tropicalis 8 0 16 24 Standard 11.0 (1.4) 91.7 1 (4.2) 0 (0.0) 1 (4.2)
Large 10.2 (0.6) 95.8 1 (4.2) 0 (0.0) 0 (0.0)
Total 63 36 125 188 Standard 12.4 (2.5) 93.1 6 (3.2) 0 (0.0) 7 (3.7)
Large 11.1 (1.5) 98.4 1 (0.5) 0 (0.0) 2 (1.1)

*CLSI M27 BMD method was conducted strictly according to CLSI M27-ED4 document (24-hour incubation), but DDT was modified with the use of two cell suspensions (McFarland 0.5, standard inoculum; and 2.5, large inoculum), and inhibition zones were read at 2-hour intervals from 10 hours to 22 hours [15]. P<0.05 between the standard inoculum and large inoculum within a given species.

Abbreviations: BMD, broth microdilution; CA, categorical agreement; DDT, disk diffusion testing; FR, fluconazole resistant; FS, fluconazole susceptible; F-SDD, fluconazole-susceptible dose-dependent; ME, major error; Minor, minor error; SD, standard deviation; VME, very major error.

Ann Lab Med 2021;41:559~567

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