Evaluation of two rapid immunochromatographic tests for diagnosis of brucellosis infection in cattle

Brucellosis is a serious infectious disease that causes significant economic losses in the livestock industry. Its early diagnosis allows an adequate disease control in cattle. DAVIH Laboratories designed a lateral flow immunochromatographic assay using protein A-colloidal gold as a detector reagent (LFIA-PA). The objective of this work was to compare the performance of this assay using protein G-colloidal gold (LFIA-PG) with its performance using protein A-colloidal gold as the detector reagent. The assays were carried out with 20 μL of serum and 130 μL of running buffer. Interpretation of bands was by visual inspection with the naked eye at 15- 20 minutes after sample application. The tests were evaluated with 449 samples of bovine serum (111 positive and 338 negative). The diagnostic sensitivity and specificity, the positive and negative predictive values, and the efficacy of both assays were calculated, and their concordance was estimated by calculating the kappa (k) index. The estimated values of the parameters for LFIA-PG and LFPIA-PA were 100% and 95.2% of diagnostic sensitivity, 96.2% and 97.3% of diagnostic specificity, 89.5% and 92.3% for the positive predictive value, 100% and 98.5% for the negative predictive value, and 97.1% and 96.89% of efficacy, respectively. The concordance between both tests was very good (k = 0.95). It was shown the possibilities of developing a system with LFIA-PG capable of detecting antibodies against Brucella spp. The performance of the test makes possible its use as a screening method in the diagnosis of brucellosis.

Evaluation of up-converting phosphor technology-based lateral flow strips for rapid detection of Bacillus anthracis Spore, Brucella spp., and Yersinia pestis

Bacillus anthracis, Brucella spp., and Yersinia pestis are zoonotic pathogens and biowarfare- or bioterrorism-associated agents that must be detected rapidly on-site from various samples (e.g., viscera and powders). An up-converting phosphor technology-based lateral flow (UPT-LF) strip was developed as a point-of-care testing (POCT) to satisfy the requirements of first-level emergency response. We developed UPT-LF POCT to quantitatively detect the three pathogens within 15 min. Sample and operation-error tolerances of the assay were comprehensively evaluated. The sensitivity of UPT-LF assay to bacterial detection reached 10(4) cfu · mL(-1) (100 cfu/test), with a linear quantitative range of 4 to 6 orders of magnitude. Results revealed that the UPT-LF assay exhibited a high specificity with the absence of false-positive results even at 10(9) cfu · mL(-1) of non-specific bacterial contamination. The assay could tolerate samples with a wide pH range (2 to 12), high ion strengths (≥ 4 mol · L(-1) of NaCl), high viscosities (≤ 25 mg · mL(-1) of PEG20000 or ≥ 20% of glycerol), and high concentrations of bio-macromolecule (≤ 200 mg · mL(-1) of bovine serum albumin or ≥ 80 mg · mL(-1) of casein). The influence of various types of powders and viscera (fresh and decomposed) on the performance of UPT-LF assay was determined. The operational error of liquid measurement exhibited few effects on sensitivity and specificity. The developed UPT-LF POCT assay is applicable under field conditions with excellent tolerance to sample complexity and operational error.

Rapid immunofiltration assay as a field diagnostic tool for ovine brucellosis

This work describes the development of two rapid immunofiltration assays, enzymatic (ERIFA) and non-enzymatic (NERIFA), for the rapid detection of ovine anti-Brucella antibodies. Brucella abortus lipopolysaccharide and total bacterial extract were dotted separately as diagnostic antigens on a nitrocellulose filter-membrane of the individual assay unit along with a third dot of purified sheep IgG as an internal control. The assay's diagnostic performance was evaluated in comparison with a modified rose bengal test (mRBT) and an indirect enzyme-linked immunosorbent assay (ELISA) through usage of 590 serum samples from healthy, vaccinated, or infected sheep. The ERIFA and indirect ELISA were found to be significantly more sensitive than NERIFA, while mRBT was determined to be statistically equivalent to NERIFA. A perfect agreement (κ = 0.984) and a statistical equivalence to indirect ELISA suggest that the bi-antigenic ERIFA can be used as an "individual rapid ELISA" for screening ovine anti-Brucella antibody both in the field and in limited laboratory conditions.