Correlation between E-Test, Disk Diffusion, and Microdilution Methods for Antifungal Susceptibility Testing of Fluconazole and Voriconazole

DOI: 10.1128/AAC.47.5.1647-1651.2003

Article Figures & Data

TABLE 1.

Susceptibilities of 400 Candida spp. to fluconazole and voriconazole as determined by three methods at two incubation times

Species (no. of isolates tested)	Time (h)	Method	Fluconazole^a			Voriconazole^a
Species (no. of isolates tested)	Time (h)	Method	Range	50%	90%	Range^a	50%	90%
C. albicans (205)	24	MD	0.125-128	0.125	0.25	0.031-16	0.031	0.031
		ET	0.125-24	1.5	2	0.008-0.750	0.032	0.047
		DD	45-21	33	29	45-25	34	30
	48	MD	0.125-128	0.25	0.5	0.031-32	0.031	0.06
		ET	0.094->256	1.5	3	0.008-64	0.032	0.064
		DD	47-NZ	33	29	45-15	34	30
C. parapsilosis (66)	24	MD	0.125-64	0.25	1	0.031-2	0.031	0.125
		ET	0.38->256	1.5	6	0.008-2	0.032	0.094
		DD	43-NZ	36	26	45-12	39	31
	48	MD	0.250-128	0.5	4	0.031-4	0.031	0.25
		ET	0.38->256	2	16	0.008-64	0.032	0.25
		DD	44-NZ	36	22	45-NZ	38	25
C. tropicalis (56)	24	MD	0.125-128	0.25	1	0.031-32	0.031	0.125
		ET	0.380->256	1.5	4	0.016-1.5	0.064	0.19
		DD	40-10	33	28	40-12	30	25
	48	MD	0.125-128	1	16	0.031-32	0.125	1
		ET	0.750-512	2	6	0.019-64	0.19	0.75
		DD	38-NZ	28	24	37-NZ	24	18
C. glabrata (39)	24	MD	0.250-64	4	8	0.031-2	0.125	1
		ET	2-512	8	32	0.047-2	0.125	0.38
		DD	38-NZ	27	20	35-12	29	24
	48	MD	0.250-128	8	32	0.031-8	0.5	2
		ET	4-512	24	64	0.094-3	0.38	1
		DD	32-NZ	19	12	32-NZ	20	15
C. krusei (24)	24	MD	0.5-128	16	16	0.031-1	0.125	0.25
		ET	1.5->256	48	96	0.016-105	0.19	0.38
		DD	38-NZ	18	14	42-12	28	23
	48	MD	1-128	32	64	0.031-2	0.5	0.5
		ET	2-512	512	512	0.016-12	0.75	2
		DD	38-NZ	0	0	42-NZ	16	13
Other species (10)	24	MD	0.125-2	0.25	0.5	0.031	0.031	0.031
		ET	0.5-2	0.75	1	0.006-0.023	0.016	0.016
		DD	45-36	40	38	44-38	41	38
	48	MD	0.125-4	0.5	1	0.031-0.125	0.031	0.031
		ET	0.5-4	1	1	0.006-0.023	0.016	0.016
		DD	45-36	42	40	45-38	43	40

↵a The values are MICs (in micrograms per milliliter) for the MD and ET methods and inhibition zone diameter (in millimeters) for the DD method. The value shown is the lowest MIC that was greater than (for the MD and ET methods) or the greatest zone diameter that was less than (for the DD method) 50 or 90% of the observed values, as indicated. NZ, no zone.

TABLE 3.

Comparison of interpretive categories for fluconazole and rates of interpretive agreement^a

Method	Incubation time (h)	Category	Fluconazole MIC50 (μg/ml) at 48 h by MD			Predictive values (%)	No. (%) of discrepant results^b			No. (%) of total agreement
Method	Incubation time (h)	Category	S	S-DD	R	Predictive values (%)	Minor	Major	Very major	No. (%) of total agreement
DD	24	S	337	23	15	96.0^c	30 (7.5)	0 (0.0)	15 (3.8)	355 (88.8)
		I	1	8	4
		R	0	2	10	83.0^d
	48	S	329	5	10	97.1^c	27 (6.7)	4 (1.0)	10 (2.5)	359 (89.8)
		I	5	11	0
		R	4	17	19	47.5^d
ET	24	S	334	14	11	97.0^c	32 (8.0)	1 (0.3)	11 (2.8)	356 (89.0)
		I	3	9	5
		R	1	10	13	54.2^d
	48	S	319	0	9	97.3^c	43 (10.7)	5 (1.3)	9 (2.3)	343 (85.8)
		I	14	5	1
		R	5	28	19	36.5^d

↵a S, susceptible; I, intermediate; R, resistant; S-DD, susceptible-dose dependent; MIC₅₀, MIC at which 50% of isolates are inhibited.
↵b Minor discrepancies, susceptible-dose dependant by one method but susceptible or resistant by the other; Major discrepancies, resistant by the test method but susceptible by the reference test; very major discrepancies, susceptible by the test method but resistant by the reference test.
↵c The value shown is the percentage of the time that a result of susceptible by the agar-based method correlated with a susceptible or susceptible-dose dependent result by the reference MD method.
↵d The value shown is the percentage of the time that a result of resistant by the agar-based method correlated with a result of resistance by the reference MD method.

TABLE 4.

Correlation between results of MD and DD methods for voriconazole after 24 and 48 h of incubation

Time and disk zone diam (mm)	No. of isolates for which the MD MIC (μg/ml) at the indicated times was as follows:
	24 h MD MICs									48 h MD MICs
	0.031	0.062	0.125	0.250	0.5	1.0	2.0	>4.0	Total	0.031	0.062	0.125	0.250	0.5	1.0	2.0	>4.0	Total
24 h
45	3								3	3								3
44	8								8	8								8
43	6								6	6								6
42	11								11	10	1							11
41	8		1					1	10	9					1			10
40	17								17	14	1		1	1				17
39	14		1						15	13	1			1				15
38	24								24	17	3	1	3					24
37	15	1							16	11	3	1					1	16
36	22								22	21							1	22
35	38	1							39	30	6	1		1	1			39
34	37								37	33	2				1		1	37
33	27	3							30	19	3	1	5	1			1	30
32	33	2						1	36	27	3	1	1	1		1	2	36
31	13	2	4	1					20	9	3	1	3	3		1		20
30	17	3	4	2		1			27	12	1	2	2	6	3		1	27
29	6	2	4						12	4	2	1	1	3	1			12
28	7	7	2	2					18	2	3	3	1	5	3		1	18
27	4	1	4	2	1				12		3	2		4	1	2		12
26	1	1	4					1	7		2			2	1		2	7
25	1	2	4	3		1		1	12		1		3	3	2	1	2	12
24			1						1					1				1
23		2	1	1					4		1	1		1		1		4
22		1	1	1					3			1		2				3
21			1	1					1					1				1
20				1					1					1				1
18							1		1							1		1
16				1					1							1		1
12					2	3	1		6						1	4	1	6
Total for 24 h	312	28	31	15	3	5	2	4	400	248	39	16	20	37	15	12	13	400
48 h
45	7								7	7								7
44	10								10	9	1							10
43	14								14	14								14
42	5								5	5								5
41	5								5	5								5
40	11		1					1	13	11			1		1			13
39	10								10	9	1							10
38	15		1						16	13	1	1			1			16
37	12								12	10	1						1	12
36	24								24	22		1			1			24
35	26								26	21	3			2				26
34	39								39	37	1						1	39
33	21								21	18	2						1	21
32	29	2							31	25	5	1						31
31	6								6	5	1							6
30	24								24	20	2			1	1			24
29	8		1						9	4	3		1				1	9
28	10	4							14	4	3	1	2	2			2	14
27	5	1							6	1	2	1		1			1	6
26	4	1							5	2	2				1			5
25	6	1	1	1				1	9	3	1	1	3			1		9
24	2	3	1					2	8	1		1	1	2			3	8
23	5	2							7		2	2	3					7
22	6	3	1						10	1	1	1	1	3	1		2	10
21	3	3							6		4	1				1		6
20	4	3	6						13	1	2	2	1	3	4			13
19			1	1					2					1	1			2
18	1	4	5	1	1	1			13		1	3	3	5		1		13
17		1	1	2					4					3	1			4
16			4	6					10				1	5	2	2		10
15			5			1			6					4	2			6
14			1	2					3					3				3
13			1	2			1		4				1	1		2		4
0			1	1	2	3	1		8					1	1	5	1	8
Total for 48 h	312	28	31	15	3	5	2	4	400	248	39	16	20	37	15	12	13	400