Multiple-antigen ELISA for melioidosis - a novel approach to the improved serodiagnosis of melioidosis

BMC Infectious Diseases

Table 3 ELISA results for melioidosis confirmed and control sera

Recombinant proteins	Cut-off	Sensitivity (%) (no. positive/total no.*)			Specificity (%) (no. positive/total no. †)
		Culture confirmed	IFAT confirmed	Combined
		(n = 42)	(n = 26)	(n = 68)
TssD-5 (type VI secretion system HCP protein)	0.1094	62 (26/42)	85 (22/26)	71 (48/68)	96 (4/90)
Omp3 (outer membrane protein A)	0.1387	50 (21/42)	73 (19/26)	59 (40/68)	90 (9/90)
smBpF4 (serine protease MprA)	0.1269	38 (16/42)	46 (12/26)	41 (28/68)	89 (10/90)
Omp85 (outer membrane protein)	0.2030	19 (8/42)	19 (5/26)	19 (13/68)	96 (4/90)
Cocktails of 4 recombinant proteins^§	0.1936	64 (27/42)	65 (17/26)	65 (44/68)	99 (1/82**)
Multiple antigens combination (all 4 recombinant proteins^‡)				88.2 (60/68)	96 (4/90)

* melioidosis confirmed sera by ELISA against B. pseudomallei lysate.
† non-melioidosis sera [healthy control (n = 61) and disease control (n = 29)].
** non-melioidosis sera [healthy control (n = 59) and disease control (n = 23)].
^§ Cocktail of 4 recombinant proteins used to coat a single well.
‡ The single antigen ELISA data was re-evaluated and different criteria were used to calculate sensitivity and specificity. The serum tested was determined to be melioidosis positive according to the following criteria: (1) any 2 or more antigens specifically react with serum with the absorbance greater than the cut-off value calculated from the mean absorbance (A_405nm) plus 2 standard deviations of healthy controls or (2) any antigen that specifically reacts with serum when the cut-off value was calculated from the mean absorbance (A_405nm) plus 3 standard deviations of healthy controls.

ISSN: 1471-2334