Detection of Methicillin-Resistant Staphylococcus aureus Using a Specific Anti-PBP2a Chicken IgY Antibody

A Wireless, CRISPR-Polymer Dot Electrochemical Sensor for the Diagnosis of Bacterial Pneumonia and Multi-Drug Resistance

Rapid and accurate diagnosis is crucial for managing the global health threat posed by multidrug-resistant bacterial infections; however, current methods have limitations in either being time-consuming, labor-intensive, or requiring instruments with high costs. Addressing these challenges, we introduce a wireless electrochemical sensor integrating the CRISPR/Cas system with electroconductive polymer dot (PD) nanoparticles to rapidly detect bacterial pathogens from human sputum. To enhance the electroconductive properties, we synthesized copper-ion-immobilized PD (PD-Cu), followed by conjugation of the deactivated Cas9 protein (dCas9) onto PD-Cu-coated Si electrodes to generate the dCas9-PD-Cu sensor. The dCas9-PD-Cu sensor integrated with isothermal amplification can specifically detect target nucleic acids of multidrug-resistant bacteria, such as the antibiotic resistance genes kpc-2 and mecA. The dCas9-PD-Cu sensor exhibits high sensitivity, allowing for the detection of ∼54 femtograms of target nucleic acids, based on measuring the changes in resistivity of the Si electrodes through target capture by dCas9. Furthermore, a wireless sensing platform of the dCas9-PD-Cu sensor was established using a Bluetooth module and a microcontroller unit for detection using a smartphone. We demonstrate the feasibility of the platform in diagnosing multidrug-resistant bacterial pneumonia in patients' sputum samples, achieving 92% accuracy. The current study presents a versatile biosensor platform that can overcome the limitations of conventional diagnostics in the clinic.

IgYs: on her majesty's secret service

There has been an increasing interest in using Immunoglobulin Y (IgY) antibodies as an alternative to "classical" antimicrobials. Unlike traditional antibiotics, they can be utilized on a continual basis without leading to the development of resistance. The veterinary IgY antibody market is growing because of the demand for minimal antibiotic use in animal production. IgY antibodies are not as strong as antibiotics for treating infections, but they work well as preventative agents and are natural, nontoxic, and easy to produce. They can be administered orally and are well tolerated, even by young animals. Unlike antibiotics, oral IgY supplements support the microbiome that plays a vital role in maintaining overall health, including immune system function. IgY formulations can be delivered as egg yolk powder and do not require extensive purification. Lipids in IgY supplements improve antibody stability in the digestive tract. Given this, using IgY antibodies as an alternative to antimicrobials has garnered interest. In this review, we will examine their antibacterial potential.

The Revolution of Lateral Flow Assay in the Field of AMR Detection

The global spread of antimicrobial resistant (AMR) bacteria represents a considerable public health concern, yet their detection and identification of their resistance mechanisms remain challenging. Optimal diagnostic tests should provide rapid results at low cost to enable implementation in any microbiology laboratory. Lateral flow assays (LFA) meet these requirements and have become essential tools to combat AMR. This review presents the versatility of LFA developed for the AMR detection field, with particular attention to those directly triggering β-lactamases, their performances, and specific limitations. It considers how LFA can be modified by detecting not only the enzyme, but also its β-lactamase activity for a broader clinical sensitivity. Moreover, although LFA allow a short time-to-result, they are generally only implemented after fastidious and time-consuming techniques. We present a sample processing device that shortens and simplifies the handling of clinical samples before the use of LFA. Finally, the capacity of LFA to detect amplified genetic determinants of AMR by isothermal PCR will be discussed. LFA are inexpensive, rapid, and efficient tools that are easy to implement in the routine workflow of laboratories as new first-line tests against AMR with bacterial colonies, and in the near future directly with biological media.

Immunofluorescence Targeting PBP2a Protein: A New Potential Methicillin Resistance Screening Test

The indiscriminate use of first-line drugs contributed to the spread of resistant bacteria, a major concern for both human and veterinary medicine. Methicillin resistance is acquired through the mecA gene, which encodes for the PBP2a protein and lends the resistance to β-lactams. Verifying the correspondence between gene harboring and protein expression and accelerating methicillin resistance diagnosis is critical to improve the management of antimicrobial administration and to reduce the spread of drug resistances. We tested the applicability of immunofluorescence targeting PBP2a protein to identify a new potential methicillin resistance screening test, ancillary to conventional culture methods. We collected 26 clinical Staphylococcus pseudintermedius (SP) isolates: 25 from canine pyoderma and 1 from dermatitis in a dog owner. SP is one of the most important etiological agents in canine pyoderma and can harbor the mecA gene. We performed PCR for mecA gene detection, broth microdilution (BMD) for phenotypic methicillin resistance, and immunofluorescence targeting PBP2a protein. Compared to the PCR as the gold standard, immunofluorescence showed an apparent prevalence of 34.6% vs. a true prevalence of 53.8%, with 100% specificity, 64.3% sensitivity, and 80.8% diagnostic accuracy. PBP2a expression showed isolate-dependent variability: in some isolates, most of the bacterial cells showed an intense and clearly membranous pattern, while in others only a few of them could be detected. Performing the assay in duplicate improved the diagnostic accuracy. Since the mecA gene is shared among the members of the Staphylococcus genus, the test can be applied to identify methicillin resistance independently from the staphylococcal species, both in human and animal samples. Being a rapid and easy method and providing the unique possibility to study the expression of PBP2a by directly visualizing the morphology, it could represent a new interesting tool for both research and diagnostics. To accelerate methicillin resistance diagnosis, it would be worth further testing of its performance on cytological samples.

Immunoglobulin Y for Potential Diagnostic and Therapeutic Applications in Infectious Diseases

Antiviral, antibacterial, and antiparasitic drugs and vaccines are essential to maintaining the health of humans and animals. Yet, their production can be slow and expensive, and efficacy lost once pathogens mount resistance. Chicken immunoglobulin Y (IgY) is a highly conserved homolog of human immunoglobulin G (IgG) that has shown benefits and a favorable safety profile, primarily in animal models of human infectious diseases. IgY is fast-acting, easy to produce, and low cost. IgY antibodies can readily be generated in large quantities with minimal environmental harm or infrastructure investment by using egg-laying hens. We summarize a variety of IgY uses, focusing on their potential for the detection, prevention, and treatment of human and animal infections.

Simultaneous electrochemical determination of nuc and mecA genes for identification of methicillin-resistant Staphylococcus aureus using N-doped porous carbon and DNA-modified MOF

The detection of Staphylococcus aureus specific gene in combination with the mecA gene is vitally important for accurate identification of methicillin-resistant Staphylococcus aureus (MRSA). A homogeneous electrochemical DNA sensor was fabricated for simultaneous detection of mecA and nuc gene in MRSA. Metal-organic framework (type UiO-66-NH₂) was applied as nanocarrier. Two electroactive dyes, methylene blue (MB) and epirubicin (EP), were encapsulated in UiO-66-NH₂, respectively, and were locked by the hybrid double-stranded DNA. Based on the target-response electroactive dye release strategy, once target DNA exists, it completely hybridizes with displacement DNA (D_EP and D_MB). So D_EP and D_MB is displaced from the MOF surface, causing the release of electroactive dyes. Co-Zn bimetallic zeolitic imidazolate framework-derived N-doped porous carbon serves for electrode modification to improve electrocatalytic performance and sensitivity. The differential pulse voltammetry peak currents of MB and EP were accurately detected at - 0.14 V and - 0.53 V versus the Ag/AgCl reference electrode, respectively. Under the optimal conditions, the detection limits of mecA gene and nuc gene were 3.7 fM and 1.6 fM, respectively. Combining the effective application of MOFs and the homogeneous detection strategy, the sensor exhibited satisfactory performance for MRSA identification in real samples. The recovery was 92.6-103%, and the relative standard deviation was less than 5%. Besides, MRSA and SA can also be distinguished. This sensor has great potential in practical applications.

Modern Tools for Rapid Diagnostics of Antimicrobial Resistance

Fast, robust, and affordable antimicrobial susceptibility testing (AST) is required, as roughly 50% of antibiotic treatments are started with wrong antibiotics and without a proper diagnosis of the pathogen. Validated growth-based AST according to EUCAST or CLSI (European Committee on Antimicrobial Susceptibility Testing, Clinical Laboratory Standards Institute) recommendations is currently suggested to guide the antimicrobial therapy. Any new AST should be validated against these standard methods. Many rapid diagnostic techniques can already provide pathogen identification. Some of them can additionally detect the presence of resistance genes or resistance proteins, but usually isolated pure cultures are needed for AST. We discuss the value of the technologies applying nucleic acid amplification, whole genome sequencing, and hybridization as well as immunodiagnostic and mass spectrometry-based methods and biosensor-based AST. Additionally, we evaluate the potential of integrated systems applying microfluidics to integrate cultivation, lysis, purification, and signal reading steps. We discuss technologies and commercial products with potential for Point-of-Care Testing (POCT) and their capability to analyze polymicrobial samples without pre-purification steps. The purpose of this critical review is to present the needs and drivers for AST development, to show the benefits and limitations of AST methods, to introduce promising new POCT-compatible technologies, and to discuss AST technologies that are likely to thrive in the future.

Egg yolk antibodies (IgY) and their applications in human and veterinary health: A review

Egg yolk constitutes a relevant alternative source of antibodies. It presents some advantages over mammalian serum immunoglobulins regarding productivity, animal welfare and specificity. The main immunoglobulin present in avian blood (IgY) is transmitted to their offspring and accumulates in egg yolks, which enables the non-invasive harvesting of high amounts of antibodies. Moreover, due to structural differences and phylogenetic distance, IgY is more suitable for diagnostic purposes than mammalian antibodies, since it does not react with certain components of the human immune system and displays greater avidity for mammalian conserved proteins. IgY has been extensively used in health researches, as both therapeutic and diagnostic tool. This article aims to review its applications in both human and veterinary health.

Development of an IgY-based lateral flow immunoassay for detection of fumonisin B in maize

Fumonisin is one of the most prevalent mycotoxins in maize, causing substantial economic losses and potential health risks in human and animals. In the present study, in-house polyclonal IgY antibody against fumonisin group B (FB) was applied for the development of a competitive lateral flow immunoassay detecting these mycotoxins in maize grains with the limit of detection of 4000 µg/kg, which corresponds to the maximum residue limit adopted by The International Codex Alimentarius Commission. To this end, factors affecting the test performance including nitrocellulose membrane type, dilution factor of maize homogenates in running buffer, amount of detection conjugate, and incubation time between detection conjugate and samples were optimized. Under the optimal condition (UniSart ^®CN140 nitrocellulose membrane, FB ₁-BSA immobilized at 1 µg/cm, 1:10 dilution factor, 436 ng of gold nanoparticle conjugate, 30 minutes of incubation), the developed test could detect both FB ₁ and FB ₂ in maize with limit of detection of 4000 µg/kg, and showed no cross-reactivity to deoxynivalenol, ochratoxin A, aflatoxin B1 and zearalenone. When applied to detect FB ₁ and FB ₂ in naturally contaminated maize samples, results obtained from the developed assay were in good agreement with those from the high-performance liquid chromatography method. This lateral flow immunoassay is particularly suitable for screening of fumonisins in maize because of its simplicity and cost-effectiveness.

Development of an IgY-based lateral flow immunoassay for detection of fumonisin B in maize

Fumonisin is one of the most prevalent mycotoxins in maize, causing substantial economic losses and potential health risks in human and animals. In the present study, in-house polyclonal IgY antibody against fumonisin group B (FB) was applied for the development of a competitive lateral flow immunoassay detecting these mycotoxins in maize grains with the limit of detection of 4000 µg/kg, which corresponds to the maximum residue limit adopted by The International Codex Alimentarius Commission. To this end, factors affecting the test performance including nitrocellulose membrane type, dilution factor of maize homogenates in running buffer, amount of detection conjugate, and incubation time between detection conjugate and samples were optimized. Under the optimal condition (UniSart ®CN140 nitrocellulose membrane, FB 1-BSA immobilized at 1 µg/cm, 1:10 dilution factor, 436 ng of gold nanoparticle conjugate, 30 minutes of incubation), the developed test could detect both FB 1 and FB 2 in maize with limit of detection of 4000 µg/kg, and showed no cross-reactivity to deoxynivalenol, ochratoxin A, aflatoxin B1 and zearalenone. When applied to detect FB 1 and FB 2 in naturally contaminated maize samples, results obtained from the developed assay were in good agreement with those from the high-performance liquid chromatography method. This lateral flow immunoassay is particularly suitable for screening of fumonisins in maize because of its simplicity and cost-effectiveness.

Genetic diversity of 21 experimental chicken lines with diverse origins and genetic backgrounds

The genetic characteristics and diversity of 21 experimental chicken lines registered with the National BioResource Project of Japan were examined using mitochondrial D-loop sequences and 54 microsatellite DNA markers. A total of 12 haplotypes were detected in the 500-bp mitochondrial DNA sequences of the hypervariable segment I for 349 individuals of 21 lines. The 12 haplotypes belonged to three (A, D, and E) haplogroups, out of the eight (A‒H) common haplogroups in domestic chickens and red junglefowls. The haplogroups A and D were widely represented in indigenous chickens in the Asian and Pacific regions, and the haplogroup E was the most prevalent in domestic chickens. Genetic clustering by discriminant analysis of principal components with microsatellite markers divided 681 individuals of 21 lines into three groups that consisted of Fayoumi-, European-, and Asian- derived lines. In each of the cladograms constructed with Nei's genetic distances based on allele frequencies and the membership coefficients provided by STRUCTURE and with the genetic distance based on the proportion of shared alleles, the genetic relationships coincided well with the breeding histories of the lines. Microsatellite markers showed remarkably lower genetic heterozygosities (less than 0.1 observed heterozygosity) for eight lines (GSP, GSN/1, YL, PNP, BM-C, WL-G, BL-E, and #413), which have been maintained as closed colonies for more than 40 years (except for #413), indicating their usefulness as experimental chicken lines in laboratory animal science research.

Aptamer-based fluorometric assay for direct identification of methicillin-resistant Staphylococcus aureus from clinical samples

Accurate and rapid identification of methicillin-resistant Staphylococcus aureus (MRSA) is of important clinical significance. In this study, a novel aptamer-based fluorometric assay was developed for detection of MRSA in clinical samples by coupling with immunomagnetic separation. The S. aureus cells in clinical specimens were enriched by magnetic separation. Following lysis by staphylococcal lysin, the PBP2a proteins were released from S. aureus cells and detected by the aptamer-based fluorometric assay. Without lengthy period of bacteria cultivation in the traditional susceptibility testing, this test has an overall testing time of only 2 h with the detection limit of 2.63 × 10³ and 1.38 × 10³ CFU/mL in PBS and spiked nasal swab, respectively. Since it is simple, rapid and sensitive, this method could be used for the detection of MRSA in various clinical samples.

Identification and characterization of two novel superantigens among Staphylococcus aureus complex

Staphylococcal enterotoxins (SEs), also known as superantigens, play a very important role in infections and food poisoning caused by Staphylococcus aureus. Recently, S. argenteus and S. schweitzeri were recognized as novel species closely related to S. aureus. In this study of these three species, it was found that two putative SE genes were located upstream of some vSaβ pathogenicity islands and the deduced amino acid sequences showed < 65.3% identity with those of known SEs. The related proteins, designated staphylococcal enterotoxin-like toxin 26 (SEl26) and 27 (SEl27), were identified and characterized among the three species. The mRNAs encoding SEl26 and SEl27 were expressed during all the growth phases. Recombinant SEl26 and SEl27 exhibited superantigenic activity in human peripheral blood mononuclear cells and mouse splenocytes by examining cell proliferation and cytokine production. Interestingly, these two genes were present universally in S. argenteus sequence type 2250 with clinical importance. Meanwhile, SEl27 variants from different species showed differential sensitivity to human peripheral blood mononuclear cells, which corresponded to the primary bacterial species hosts. It was demonstrated from these results that SEl26 and SEl27 were characterized to be two novel SE toxins and some SEs evolved along with the bacteria when the organisms adapted the hosts' immune systems.

On the challenges of detecting whole Staphylococcus aureus cells with biosensors

Due to the increasing number of nosocomial infections and multidrug-resistant bacterial strains, Staphylococcus aureus is now a major worldwide concern. Rapid detection and characterization of this bacterium has become an important issue for biomedical applications. Biosensors are increasingly appearing as low-cost, easy-to-operate and fast alternatives for rapid detection. In this review, we will introduce the main characteristics of S. aureus and will focus on the interest of biosensors for a faster detection of whole S. aureus cells. In particular, we will review the most promising strategies in the choice of ligand for the design of selective and efficient biosensors. Their specific characteristics as well as their advantages and/or disadvantages will also be commented.

Prevalence of Methicillin-Resistant Staphylococcus aureus and Other Staphylococcus Species in Raw Meat Samples Intended for Human Consumption in Benin City, Nigeria: Implications for Public Health

The present study was designed to characterize methicillin-resistant staphylococci from raw meat. A total of 126 meat samples were obtained from open markets between February and April, 2015. Antimicrobial susceptibility testing was carried out using the disc diffusion method. Molecular profiling was conducted using 16S rRNA, mecA, nuc, and PVL gene signatures were detected by polymerase chain reaction assay. Fifty isolates of methicillin-resistant Staphylococcus spp. were detected in 26 (52%) pork, 14 (28%) beef and 10 (20%) chicken samples. The staphylococcal isolates were identified through partial 16S ribosomal ribonucleic acid (16S rRNA) nucleotide sequencing, and BLAST analysis of the gene sequence revealed 98%–100% staphylococcal similarity. All isolates from beef and chicken samples amplified the mecA gene, while 100% of the MRSA isolates amplified the PVL gene. The multidrug resistance profile (resistant to ≥1 antimicrobial agent in ≥3 classes of antimicrobial agents) of the staphylococcal isolates showed that 7 isolates were resistant to methicillin, penicillin, clindamycin, chloramphenicol, trimethoprim-sulfamethoxazole, kanamycin, amoxicillin, cloxacillin, erythromycin, vancomycin, and gentamycin. There was a significant regression effect from the multidrug-resistant profile on the number of isolates (p < 0.05) suggesting a consequence of the dissemination of resistant strains within bacterial populations. The findings of the present study indicate that raw meats in the Benin metropolis were possibly contaminated with pathogenic and multi-drug resistant staphylococci strains and therefore could constitute a risk to public health communities.

Method for generation of peptide-specific IgY antibodies directed to Staphylococcus aureus extracellular fibrinogen binding protein epitope

The IgY antibodies offer an attractive alternative to mammalian IgGs in research, diagnosis and medicine. The isolation of immunoglobulin Y from the egg yolks is efficient and economical, causing minimal suffering to animals. Here we present the methodology for the production of IgY antibodies specific to Staphylococcus aureus fibrinogen binding protein (Efb) and its peptidyl epitope (spanning residues 127-140). The Efb is an extracellular, adhesion protein which binds both human fibrinogen and complement C3 protein thus contributing to the high infectious potential of this pathogen. The selected epitope of Efb protein is responsible for the interaction with C3. The immunochemical characterization of both anti-Efb and epitope-specific IgY antibodies revealed their similar avidity, titer, and reactivity profile, although some differences in the hen's immune response to administered antigens is discussed.

Development and identification of fully human scFv-Fcs against Staphylococcus aureus

BACKGROUND

Staphylococcus aureus, a gram-positive pathogen, causes many human infections. Methicillin-resistant S. aureus (MRSA) is the most common drug-resistance bacteria. Nearly all MRSA bacteria are resistant to several drugs. Specific antibodies are the main components of the host's humoral immunity, and play a significant role in the process of the host's resistance to bacterial infection.

RESULTS

A single-chain variable fragment (scFv) library was constructed using mRNA from the peripheral blood mononuclear cells of S. aureus infected volunteers. After the scFv library DNA was transformed into Escherichia coli TG1, ~1.7 × 10(7) independent clones with full-length scFv inserts. The scFv library was screened by phage display for three rounds using S. aureus as an antigen. The single clones were chosen at random and the scFvs were expressed for enzyme-linked immunosorbent assay (ELISA) assessment. Approximately 50 % of the clones were positive with good binding activity to S. aureus. To improve the stability of scFvs, scFv-fragment crystallizable regions (-Fcs) were constructed and expressed in E. coli DH5α. The expressed scFv-Fcs were purified and identified by western blot. These antibodies were further characterized and analyzed for bioactivity. The results showed that the expression level and folding of scFv-Fcs induced at 25 °C without isopropyl β-D-1-thiogalactopyranoside (IPTG) were higher than that induced at 32 °C with 1.0 mmol/L IPTG. scFv-Fcs had good bioactivity and could specifically bind with S. aureus.

CONCLUSION

scFv-Fcs against S. aureus were successfully constructed and are good candidates for the development of future adjunctive therapy for severe S. aureus infections.

Evaluation of Shiga toxin 2e-specific chicken egg yolk immunoglobulin: production and neutralization activity

Chicken egg yolk immunoglobulin (IgY) against Shiga toxin 2e (Stx2e), a major cause of swine edema disease, was prepared to evaluate its possible clinical applications. The titer of Stx2e-specific IgY in egg yolk derived from three chickens that had been immunized with an Stx2e toxoid increased 2 weeks after primary immunization and remained high until 90 days after this immunization. Anti-Stx2e IgY was found to neutralize the toxicity of Stx2e by reacting with its A and B subunits, indicating that IgY is a cost-effective agent to develop for prophylactic foods or diagnosis kits for edema disease.

Bacteriophage-based latex agglutination test for rapid identification of Staphylococcus aureus

Rapid diagnosis is essential for the management of Staphylococcus aureus infections. A host recognition protein from S. aureus bacteriophage phiSLT was recombinantly produced and used to coat streptavidin latex beads to develop a latex agglutination test (LAT). The diagnostic accuracy of this bacteriophage-based test was compared with that of a conventional LAT, Pastorex Staph-Plus, by investigating a clinical collection of 86 S. aureus isolates and 128 coagulase-negative staphylococci (CoNS) from deep tissue infections. All of the clinical S. aureus isolates were correctly identified by the bacteriophage-based test. While most of the CoNS were correctly identified as non-S. aureus isolates, 7.9% of the CoNS caused agglutination. Thus, the sensitivity of the bacteriophage-based LAT for identification of S. aureus among clinical isolates was 100%, its specificity was 92.1%, its positive predictive value (PPV) was 89.6%, and its negative predictive value (NPV) was 100%. The sensitivity, specificity, PPV, and NPV of the Pastorex LAT for the identification of S. aureus were 100%, 99.2%, 98.9%, and 100%, respectively. Among the additionally tested 35 S. aureus and 91 non-S. aureus staphylococcal reference and type strains, 1 isolate was false negative by each system; 13 and 8 isolates were false positive by the bacteriophage-based and Pastorex LATs, respectively. The ability of the phiSLT protein to detect S. aureus was dependent on the presence of wall teichoic acid (WTA) and corresponded to the production of ribitol phosphate WTA, which is found in most S. aureus clones but only a small minority of CoNS. Bacteriophage-based LAT identification is a promising strategy for rapid pathogen identification. Finding more specific bacteriophage proteins would increase the specificity of this novel diagnostic approach.