In epidemic regions of the world, brucellosis is a reemerging zoonosis with minimal mortality but is a serious public hygiene problem. Currently, there are various methods for brucellosis diagnosis, however few of them are available to be used to diagnose, especially for serious cross-reaction with other bacteria. To overcome this disadvantage, we explored a novel multi-epitope recombinant protein as human brucellosis diagnostic antigen. We established an indirect enzyme-linked immunosorbent assay (ELISA) based on this recombinant protein. 248 sera obtained from three different groups including patients with brucellosis (146 samples), non-brucellosis patients (82 samples), and healthy individuals (20 samples) were tested by indirect ELISA. To evaluate the assay, a receiver-operating characteristic (ROC) analysis and immunoblotting were carried out using these characterized serum samples. For this test, the area under the ROC curve was 0.9409 (95 % confidence interval, 0.9108 to 0.9709), and a sensitivity of 88.89 % and a specificity of 85.54 % was given with a cutoff value of 0.3865 from this ROC analysis. The Western blot results indicate that it is feasible to differentiate human brucellosis and non-brucellosis with the newly established method based on this recombinant protein. Our results obtained high diagnostic accuracy of the ELISA assay which encourage the use of this novel recombinant protein as diagnostic antigen to implement serological diagnosis of brucellosis.

Fluorescence-based assays are efficient tools for the detection of Listeria monocytogenes (L. monocytogenes). However, they are always restricted by the phenomenon of aggregation-caused quenching (ACQ). The emergence of aggregation-induced emission (AIE) materials perfectly overcomes this shortcoming. Through harnessing the AIE characteristic with magnetic enrichment, we propose an approach to achieve a promising detection method that combines an aptamer and antibody-based dual recognition units. Aptamer-coupled magnetic beads were used for the specific capture of L. monocytogenes. IgG-TPE-OH@BSA NPs were facilely synthesized through encapsulating 1-(4-hydroxyphenyl)-1,2,2-triphenylethene (TPE-OH) in bovine serum albumin (BSA) microspheres, and possessed a bright fluorescence signal due to the aggregation of TPE-OH in BSA NPs. Rabbit immunoglobulin G (IgG) antibodies were labelled on the surface. In the detection system, the fluorescence intensity of the IgG-TPE-OH@BSA NPs in the supernatant was monitored to avoid the signal interference resulting from the deposit after magnetic separation. Using our strategy, the range of detection for L. monocytogenes is 10–10⁶ cfu mL⁻¹, and the detection limit is as low as 10 cfu mL⁻¹ with a good selectivity. Upon analysis of spiked samples, the recoveries ranged from 95.37% to 101.90% without any pre-enrichment.

Brucella spp. are facultative intracellular bacteria that cause zoonotic disease of brucellosis worldwide. Traditional methods for detection of Brucella spp. take 48–72 h that does not meet the need of rapid detection. Herein, a new rapid detection method of Brucella was developed based on polyclonal antibody-conjugating quantum dots and antibody-modified magnetic beads. First, polyclonal antibodies IgG and IgY were prepared and then the antibody conjugated with quantum dots (QDs) and immunomagnetic beads (IMB), respectively, which were activated by N-(3-dimethylaminopropyl)-N’-ethylcar-bodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) to form probes. We used the IMB probe to separate the Brucella and labeled by the QD probe, and then detected the fluorescence intensity with a fluorescence spectrometer. The detection method takes 105 min with a limit of detection of 103 CFU/mL and ranges from 10 to 105 CFU/mL (R 2 = 0.9983), and it can be well used in real samples.