Affiliation:
1. Instituto de Estudios de la Inmunidad Humoral, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina
Abstract
ABSTRACT
Agrobacterium
,
Sinorhizobium
, and
Ochrobactrum
are genera closely related to
Brucella
but, in contrast to the latter, are not pathogenic for humans and animals. We studied by an indirect enzyme-linked immunosorbent assay (ELISA) the reactivities of brucellosis sera against cytosolic (CYT) and membrane (MA) antigens from these nonpathogenic bacteria, and we evaluated the potential usefulness of these cross-reactions for the diagnosis of brucellosis in humans, sheep, cows, and dogs. Canine infection by
Brucella canis
was detected with high specificity by CYT antigen-based ELISAs (96% for
Agrobacterium
, 96% for
Sinorhizobium
, and 91% for
Ochrobactrum
), while sensitivity was variable (58% for
Agrobacterium
, 88% for
Sinorhizobium
, and 84% for
Ochrobactrum
). In addition, it was possible to diagnose canine disease shortly after exposure to the pathogen (15 days). Similar results for canine brucellosis were obtained with MA antigens. In contrast, normal sera from humans, sheep, and cattle reacted strongly with all the antigens (CYT and MA antigens from the three bacteria), producing high cutoff values and, consequently, low sensitivities. While for some host species the reactivity patterns of normal sera by Western blotting were similar to those produced with sera from infected individuals, the reactivity pattern of bovine sera against
Sinorhizobium meliloti
antigens exhibited some differential bands for the two groups of sera. These results show that crude fractions from nonpathogenic alpha-proteobacteria can be used to diagnose canine brucellosis but may need to be further separated into simpler fractions to have diagnostic usefulness in ovine, bovine, or human infection. By reducing the biosafety requirements, the use of antigens derived from these nonpathogenic bacteria would simplify the production of diagnostic kits for brucellosis, especially in settings where biosafety level-3 facilities are scarce or absent.
Publisher
American Society for Microbiology
Subject
Microbiology (medical),Clinical Biochemistry,Immunology,Immunology and Allergy
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