Optimizing Voriconazole Susceptibility Testing ofCandida: Effects of Incubation Time, Endpoint Rule, Species of Candida, and Level of Fluconazole Susceptibility

DOI: 10.1128/JCM.37.9.2755-2759.1999

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Fig. 1.
Cross-tabulation of voriconazole and fluconazole MICs. The data are the number of isolates for which the indicated MICs of voriconazole and fluconazole were obtained. MICs were determined as 50% inhibition (Spec-50) spectrophotometrically after 24 h (A) and 48 h (B) of incubation. The lines indicate the MIC at which 90% of the isolates tested were inhibited.

Table 1.

Percents agreement between endpoints for voriconazole and fluconazole^a

Endpoints compared	% Agreement for the following drug at the indicated time
	Voriconazole		Fluconazole
	24 h	48 h	24 h	48 h
BA-1 vs AA-1	90	94	83	95
BA-2 vs AA-2	97	88	94	96
AA-1 vs Spec-50	91	86	92	85
AA-1 vs Spec-80	96	94	95	97
AA-2 vs Spec-50	99	95	99	91
AA-2 vs Spec-80	96	90	97	87

↵a Testing was performed in RPMI 1640–2%, and the paired readings on the 209 isolates were said to be in agreement if they were within 1 dilution of each other. The microtiter plates were visually read before and after agitation. Spectrophotometric readings were made after agitation of the plates. Spec-80 and Spec-50 corresponded to the lowest drug concentrations reducing control growth by 80 and 50%, respectively.

Table 2.

Activities of voriconazole and fluconazole byCandida species

Time and species (no. of isolates)	MIC (μg/ml) of the following drug at the indicated endpoint^a
	Voriconazole				Fluconazole
	Spec-50		Spec-80		Spec-50		Spec-80
	Modal	Range	Modal	Range	Modal	Range	Modal	Range
24 h
C. albicans(125)	0.008	0.008–0.5	0.008	0.008–1	0.125	0.125–32	0.25	0.125–64
C. glabrata(20)	0.0625	0.008–4	0.125	0.031–4	8	0.125–>64	8	0.125–>64
C. krusei(3)	0.008	0.008–0.125	0.008	0.008–0.25	16	8.0–16.0	16	16
C. lipolytica(1)	0.125		0.125		8		16
C. lusitaniae(9)	0.008	0.008	0.008	0.008–0.016	0.5	0.125–1	0.5	0.125–2
C. parapsilosis(25)	0.008	0.008–0.03	0.008	0.008–0.016	0.5	0.125–2	0.5	0.125–2
C. tropicalis(26)	0.008	0.008–0.06	0.008	0.008–>4	0.25	0.125–2	0.25	0.125–>64
48 h
C. albicans(125)	0.008	0.008–1	0.008	0.008–>4	0.25	0.125–64	0.25	0.125–>64
C. glabrata(20)	0.25	0.008–4	0.5	0.063–>4	16	0.125–>64	32	8–>64
C. krusei(3)	0.016	0.016–0.25	0.25	0.25–>4	32	32	64	32–64
C. lipolytica(1)	0.25		0.25		32		32
C. lusitaniae(9)	0.008	0.008–0.03	0.008	0.008–0.06	0.5	0.125–4	0.5	0.25–4
C. parapsilosis(25)	0.008	0.008–0.03	0.0625	0.008–>4	0.5	0.125–4	1	0.25–64
C. tropicalis(26)	0.016	0.008–4	>4	0.016–>4	0.5	0.125–2	0.5	0.125–>64

↵a Activities of voriconazole and fluconazole against 209 isolates in RPMI 1640–2%. The analysis determined two endpoints, Spec-50 and Spec-80, representing 50 and 80% inhibition, respectively, as measured spectrophotometrically. Modal, modal MIC; range, MIC range.