Evaluation of monoclonal antibody based immunochromatographic strip test for direct detection of Vibrio cholerae O1 contamination in seafood samples

Generation and Characterization of Monoclonal Antibodies to the Ogawa Lipopolysaccharide of Vibrio cholerae O1 from Phage-Displayed Human Synthetic Fab Library

Vibrio cholerae, cause of the life-threatening diarrheal disease cholera, can be divided into different serogroups based on the structure of its lipopolysaccharide (LPS), which consists of lipid-A, corepolysaccharide and O-antigen polysaccharide (O-PS). The O1 serogroup, the predominant cause of cholera, includes two major serotypes, Inaba and Ogawa. These serotypes are differentiated by the presence of a single 2-O-methyl group in the upstream terminal perosamine of the Ogawa O-PS, which is absent in the Inaba O-PS. To ensure the consistent quality and efficacy of the current cholera vaccines, accurate measurement and characterization of each of these two serotypes is highly important. In this study, we efficiently screened a phage-displayed human synthetic Fab library by bio-panning against Ogawa LPS and finally selected three unique mAbs (D9, E11, and F7) that specifically react with Ogawa LPS. The mAbs bound to Vibrio cholerae vaccine in a dose-dependent fashion. Sequence and structure analyses of antibody paratopes suggest that IgG D9 might have the same fine specificity as that of the murine mAbs, which were shown to bind to the upstream terminal perosamine of Ogawa O-PS, whereas IgGs F7 and E11 showed some different characteristics in the paratopes. To our knowledge, this study is the first to demonstrate the generation of Ogawa-specific mAbs using phage display technology. The mAbs will be useful for identification and quantification of Ogawa LPS in multivalent V. cholerae vaccines.

Electrochemical Immuno- and Aptamer-Based Assays for Bacteria: Pros and Cons over Traditional Detection Schemes

Microbiological safety of the human environment and health needs advanced monitoring tools both for the specific detection of bacteria in complex biological matrices, often in the presence of excessive amounts of other bacterial species, and for bacteria quantification at a single cell level. Here, we discuss the existing electrochemical approaches for bacterial analysis that are based on the biospecific recognition of whole bacterial cells. Perspectives of such assays applications as emergency-use biosensors for quick analysis of trace levels of bacteria by minimally trained personnel are argued.

Development of a rapid immunochromatographic strip test for the detection of Vibrio parahaemolyticus toxin B that cause acute hepatopancreatic necrosis disease

Here, two monoclonal antibodies (MAbs) specific to different epitopes on ToxB, a toxin produced by Vibrio parahaemolyticus that causes acute hepatopancreatic necrosis disease (VP_AHPND ), were employed to develop a rapid strip test. One MAb was conjugated to colloidal gold to bind to ToxB at the application pad, and another MAb was used to capture colloidal gold MAb-protein complexes at the test line (T) on the nitrocellulose strip. To validate test performance, a downstream control line (C) of goat anti-mouse immunoglobulin G antibody was used to capture the free colloidal gold conjugate MAb. The sample in the application buffer could be applied directly to the application well, and the test result was obtained within 15 min. The sensitivity of the kit is approximately 6.25 µg/ml of toxin, which was equivalent to the toxin produced by approximately 10⁷  cfu/ml of bacteria. This kit is convenient and easy to use since it can be used to identify VP_AHPND directly using a single colony of bacteria grown on agar culture plates. Because of its high specificity and simplicity, as well as not being reliant on sophisticated equipment or specialized skills, this strip test could be used by farmers for surveillance for ToxB-producing bacteria.

Simultaneous Lateral Flow Immunoassay for Multi-Class Chemical Contaminants in Maize and Peanut with One-Stop Sample Preparation

Multi-class chemical contaminants, such as pesticides and mycotoxins, are recognized as the major risk factors in agro products. It is thus necessary to develop rapid and simple sensing methods to fulfill the on-site monitoring of multi-class chemical contaminants with different physicochemical properties. Herein, a lateral flow immunoassay via time-resolved fluorescence was developed for the rapid, on-site, simultaneous, and quantitative sensing aflatoxin B₁ (AFB₁), zearalenone (ZEA), and chlorothalonil (CTN) in maize and peanut. The sample preparation was optimized to a single step, combining the grinding and extraction. Under optimal conditions, the sensing method lowered the limits of detection (LOD) to 0.16, 0.52, and 1.21 µg/kg in maize and 0.18, 0.57, and 1.47 µg/kg in peanut with an analytical range of 0.48⁻20, 1.56⁻200, and 3.63⁻300 µg/kg for AFB₁, ZEA and CTN, respectively. The protocol could be completed within 15 min, including sample preparation and lateral flow immunoassay. The recovery range was 83.24⁻110.80%. An excellent correlation was observed between this approach and high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) for mycotoxins and gas chromatography-tandem mass spectrometry (GC-MS/MS) for pesticide in maize and peanut. This work could be applied in on-site multi-class sensing for food safety.

Ultrasensitive Biosensor for the Detection of Vibrio cholerae DNA with Polystyrene-co-acrylic Acid Composite Nanospheres

An ultrasensitive electrochemical biosensor for the determination of pathogenic Vibrio cholerae (V. cholerae) DNA was developed based on polystyrene-co-acrylic acid (PSA) latex nanospheres-gold nanoparticles composite (PSA-AuNPs) DNA carrier matrix. Differential pulse voltammetry (DPV) using an electroactive anthraquninone oligonucleotide label was used for measuring the biosensor response. Loading of gold nanoparticles (AuNPs) on the DNA-latex particle electrode has significantly amplified the faradaic current of DNA hybridisation. Together with the use of a reported probe, the biosensor has demonstrated high sensitivity. The DNA biosensor yielded a reproducible and wide linear response range to target DNA from 1.0 × 10-21 to 1.0 × 10-8 M (relative standard deviation, RSD = 4.5%, n = 5) with a limit of detection (LOD) of 1.0 × 10-21 M (R 2 = 0.99). The biosensor obtained satisfactory recovery values between 91 and 109% (n = 3) for the detection of V. cholerae DNA in spiked samples and could be reused for six consecutive DNA assays with a repeatability RSD value of 5% (n = 5). The electrochemical biosensor response was stable and maintainable at 95% of its original response up to 58 days of storage period.

Novel strategies to enhance lateral flow immunoassay sensitivity for detecting foodborne pathogens

Food contaminated by foodborne pathogens causes diseases, affects individuals, and even kills those affected individuals. As such, rapid and sensitive detection methods should be developed to screen pathogens in food. One current detection method is lateral flow immunoassay, an efficient technique because of several advantages, including rapidity, simplicity, stability, portability, and sensitivity. This review presents the format and principle of lateral flow immunoassay strip and the development of conventional lateral flow immunoassay for detecting foodborne pathogens. Furthermore, novel strategies that can be applied to enhance the sensitivity of lateral flow immunoassay to detect foodborne pathogens are presented; these strategies include innovating new label application, designing new formats of lateral flow immunoassay, combining with other methods, and developing signal amplification systems. With these advancements, detection sensitivity and detection time can be greatly improved.