Performance characteristics and costs of serological tests for brucellosis in a pastoralist community of northern Tanzania

The control of brucellosis across sub-Saharan Africa is hampered by the lack of standardized testing and the use of tests with poor performance. This study evaluated the performance and costs of serological assays for human brucellosis in a pastoralist community in northern Tanzania. Serum collected from 218 febrile hospital patients was used to evaluate the performance of seven index tests, selected based on international recommendation or current use. We evaluated the Rose Bengal test (RBT) using two protocols, four commercial agglutination tests and a competitive enzyme-linked immunosorbent assay (cELISA). The sensitivity, specificity, positive predictive value, negative predictive value, Youden’s index, diagnostic accuracy, and per-sample cost of each index test were estimated. The diagnostic accuracy estimates ranged from 95.9 to 97.7% for the RBT, 55.0 to 72.0% for the commercial plate tests, and 89.4% for the cELISA. The per-sample cost range was $0.69–$0.79 for the RBT, $1.03–$1.14 for the commercial plate tests, and $2.51 for the cELISA. The widely used commercial plate tests performed poorly and cost more than the RBT. These findings provide evidence for the public health value of discontinuing the use of commercial agglutination tests for human brucellosis in Tanzania

Time-Resolved Fluorescent Resonance Energy Transfer Assay for Simple and Rapid Detection of Anti-Brucella Antibodies in Ruminant Serum Samples▿

Brucellosis is a globally significant zoonosis, the control of which is difficult and resource intensive. Serological tests form a vital part of a multifactorial approach to control and are often performed in large numbers. The aim of the present study was to develop a new assay to improve the efficiency, ease, and effectiveness of serological testing. An existing competitive enzyme-linked immunosorbent assay (cELISA) was adapted to a completely homogeneous time-resolved fluorescent resonance energy transfer (TR-FRET) assay. This was achieved by labeling an anti-Brucella monoclonal antibody with a long-lifetime donor fluorophore and Brucella smooth lipopolysaccharide with a compatible acceptor and optimizing the reading conditions. The assay was performed in a 96-well plate with a single 30-min incubation period and no separation (wash) steps and was concluded by a single plate-reading step. The performance of the assay was evaluated with a panel of serum samples from infected (n = 73) and uninfected (n = 480) sources and compared to the performance of the parent cELISA, an indirect ELISA (iELISA), and fluorescence polarization assay (FPA). The performance of the TR-FRET assay matched the performance of the iELISA, which had 100% diagnostic sensitivity and specificity, and surpassed the performance of the cELISA and the FPA. The results also demonstrated that the TR-FRET technique is effective with poor-quality serum samples from the field. To the knowledge of the authors, this is the first homogeneous TR-FRET assay to detect antibodies raised against an infectious disease. The technique appears to be sufficiently adaptable to meet the needs of many other similar testing requirements to identify infectious diseases

Evaluation of Competitive ELISA for Detection of Antibodies to Brucella Infection in Domestic Animals

Aim To evaluate competitive enzyme-linked immunosorbent assay (cELISA) for its suitability as an additional serological test for the diagnosis of animal brucellosis. Methods cELISA, which was developed at the Veterinary Laboratories Agency, has been evaluated for its accuracy and suitability as an additional serological test for the diagnosis of animal brucellosis. Samples from naturally and experimentally infected animals and those from Brucella-free flocks and herds were tested. Results Data obtained since 1991 were analyzed from routine surveillance, animals experimentally infected with Brucella, and stored sera to validate cELISA for the detection of antibodies to Brucella in cows, small ruminants, and pigs. The sensitivity of the test ranged from 92.31% to 100%, in comparison with 77.14% to 100% for the complement fixation test (CFT). Specificities for cELISA, indirect enzymelinked immunosorbent assay, and CFT were greater than 90%. Conclusion cELISA can be used on a variety of animal species, and an added advantage is its suitability for use on poor-quality samples such as those affected by hemolysis

If You're Not Confused, You're Not Paying Attention: Ochrobactrum Is Not Brucella

Bacteria of the genus Brucella are facultative intracellular parasites that cause brucellosis, a severe animal and human disease. Recently, a group of taxonomists merged the brucellae with the primarily free-living, phylogenetically related Ochrobactrum spp. in the genus Brucella. This change, founded only on global genomic analysis and the fortuitous isolation of some opportunistic Ochrobactrum spp. from medically compromised patients, has been automatically included in culture collections and databases. We argue that clinical and environmental microbiologists should not accept this nomenclature, and we advise against its use because (i) it was presented without in-depth phylogenetic analyses and did not consider alternative taxonomic solutions; (ii) it was launched without the input of experts in brucellosis or Ochrobactrum; (iii) it applies a non-consensus genus concept that disregards taxonomically relevant differences in structure, physiology, population structure, core-pangenome assemblies, genome structure, genomic traits, clinical features, treatment, prevention, diagnosis, genus description rules, and, above all, pathogenicity; and (iv) placing these two bacterial groups in the same genus creates risks for veterinarians, medical doctors, clinical laboratories, health authorities, and legislators who deal with brucellosis, a disease that is particularly relevant in low- and middle-income countries. Based on all this information, we urge microbiologists, bacterial collections, genomic databases, journals, and public health boards to keep the Brucella and Ochrobactrum genera separate to avoid further bewilderment and harm.Las bacterias del género Brucella son parásitos intracelulares facultativos causantes de la brucelosis, una grave enfermedad animal y humana. Recientemente, un grupo de taxónomos fusionó las brucelas con las Ochrobactrum spp., principalmente de vida libre y filogenéticamente emparentadas, en el género Brucella. Este cambio, fundado únicamente en análisis genómicos globales y en el aislamiento fortuito de algunas Ochrobactrum spp. oportunistas de pacientes médicamente comprometidos, se ha incluido automáticamente en colecciones de cultivos y bases de datos. Sostenemos que los microbiólogos clínicos y ambientales no deberían aceptar esta nomenclatura, y desaconsejamos su uso porque (i) se presentó sin análisis filogenéticos en profundidad y no consideró soluciones taxonómicas alternativas; (ii) se lanzó sin la aportación de expertos en brucelosis u Ochrobactrum; (iii) aplica un concepto de género no consensuado que ignora las diferencias taxonómicamente relevantes en estructura, fisiología, estructura poblacional, ensamblajes del núcleo-pangenoma, estructura genómica, rasgos genómicos, características clínicas, tratamiento, prevención, diagnóstico, reglas de descripción del género y, sobre todo, patogenicidad; y (iv) colocar estos dos grupos bacterianos en el mismo género crea riesgos para veterinarios, médicos, laboratorios clínicos, autoridades sanitarias y legisladores que se ocupan de la brucelosis, una enfermedad especialmente relevante en países de renta baja y media. Basándonos en toda esta información, instamos a los microbiólogos, las colecciones bacterianas, las bases de datos genómicos, las revistas y los consejos de salud pública a mantener separados los géneros Brucella y Ochrobactrum para evitar más desconcierto y perjuicios.Universidad Nacional, Costa RicaEscuela de Medicina Veterinari