Validation of a simple universal IELISA for the diagnosis of human brucellosis

Abstract

The definitive diagnosis of brucellosis requires isolation of the agent, although negative isolation does not rule out the infection. In contrast, serological testing is more sensitive and, therefore, preferred in clinical practice. The majority of reported cases around the world were caused by Brucella melitensis, B. abortus, B. suis and B. canis. The first three species contain O-polysaccharide (OPS) on the cell surface, but B. canis contains no measurable OPS on the rough lipopolysaccharide (R-LPS). A universal indirect enzyme immunoassay for the detection of serum antibody to smooth and rough Brucella spp. in both normal (u-IELISA®) and rapid forms (R-u-IELISA®) has been developed, and, therefore, the potential use of this method was assessed in comparison to cELISA, conventional tests, IELISA and RSAT on a total of 478 sera. The 77 sera from blood donors with no clinical or epidemiological evidence of brucellosis and negative serological tests showed a specificity of 100 % for both u-IELISA® and R-u-IELISA®, with a cut-off value of %P 24 and %P 18, respectively. Sera from 49 culture-positive cases (16 B. suis, 15 B. abortus, 12 B. melitensis and 6 B. canis) yielded a sensitivity of 98 % for u-IELISA® and 95.9 % for R-u-IELISA®. In general, u-IELISA® showed good correlation with cELISA and IELISA for the detection of antibodies to smooth and rough Brucella strains, as well as for monitoring patients during treatment, but R-u-IELISA® seems to need additional optimisation. u-IELISA® is simple to perform and could be a suitable test for field laboratories and hospitals lacking skilled personnel.