Mycobacteriophage SWU1-Functionalized magnetic particles for facile bioluminescent detection of Mycobacterium smegmatis

Fluorescent lateral flow assay strip for Mycobacterium tuberculosis and Mycobacterium smegmatis based on mycobacteriophage tail protein and aptamer

Timely and facile monitoring of Mycobacterium tuberculosis (M. tuberculosis) plays an important role for preventing and controlling tuberculosis infection. Mycobacterium smegmatis (M. smegmatis) has long been employed as a safe surrogate for the investigation of M. tuberculosis. In this work, an aqueous soluble tail protein derived from our previously isolated mycobacteriophage was prepared with a recombinant expression technique and noted as GP89, which shows noticeable binding capacity to Mycobacterium genus. GP89 was sprayed as a capture agent onto a nitrocellulose membrane for forming the test line of a lateral flow assay (LFA) strip. Moreover, an aptamer binding M. tuberculosis and M. smegmatis was labeled with fluorescent microspheres to act as the signal tracer of the LFA method. With the GP89 based LFA, M. tuberculosis and M. smegmatis can be detected with the aid of a handheld UV flashlight or a portable fluorescent strip reader within 10 min. The concentration range for quantitating M. tuberculosis and M. smegmatis are both 1.0 × 102 CFU mL-1 - 1.0 × 106 CFU mL-1, and the detection limits for the two mycobacteria are 2.0 and 24 CFU mL-1 (S/N = 3), respectively. The test strip was applied to detect M. tuberculosis and M. smegmatis in different samples such as physiological salt solution, urine, and saliva. This study offers a promising screening tool for diagnosing M. tuberculosis infection in resource-limited institutes.

Phage LysSA163-CBD mediated specific recognition coupled with ATP bioluminescence for the sensitive detection of viable Staphylococcus aureus in food matrices

BACKGROUND

Staphylococcus aureus is a significant foodborne pathogen, commonly detected in milk and meat products. Conventional detection methods have limited sensitivity and specificity, which are time-consuming and susceptible to background interference from complex samples, and cannot effectively distinguish live and dead bacteria.

RESULTS

Herein, we developed a novel adenosine triphosphate (ATP) bioluminescence method coupled with magnetic separation, which is based on phage-encoded endolysin LysSA163-CBD (CBD 163) for rapid and specific detection of viable Staphylococcus aureus. The expressed protein (CBD 163) was derived from the phage LSA2301 and was successfully expressed in Escherichia coli BL21 following an induction period of 4 h at 37 °C, with a molecular weight approximating 40 kDa. The optimal conditions for CBD-magnetic beads (cMBs) to capture S. aureus cells were determined to be 100 μL/mL cMBs at 25 °C for 30 min. The viable S. aureus cells were disrupted by the Cetyl trimethyl ammonium bromide (CTAB) to release intracellular ATP. Then, the ATP reacted with the firefly luciferase and D-Luciferin-based bioluminescence (BL) reagents solution to generate intensive BL signal. The CBD-magnetic separation-ATP bioluminescence (cMS-BL) assay was able to quickly detect viable S. aureus via ATP bioluminescence in 45 min, with a detection range from 5 × 103 to 5 × 107 CFU/mL and limit of detection (LOD) of 190 CFU/mL. Additionally, the cMS-BL method exhibited high specificity and anti-interference ability, which has been successfully applied to quantify S. aureus cells in crayfish-tail, chicken, and skim milk.

SIGNIFICANCE AND NOVELTY

These results demonstrate the potential of CBD 163 as a versatile and robust biorecognition element for rapid and specific detection of viable S. aureus in food matrices. The proposed phage-derived bacteria-binding proteins-based protocol for BL detection shows various advantages, including high sensitivity, simple operation, and the capability to distinguish live bacteria, providing a strategy for designing high-quality biorecognition element toward foodborne pathogens.

Phage-Based Biosensing for Rapid and Specific Detection of Staphylococcus aureus

Staphylococcus aureus (S. aureus) is a major foodborne pathogen. Rapid and specific detection is crucial for controlling staphylococcal food poisoning. This study reported a Staphylococcus phage named LSA2302 showing great potential for applications in the rapid detection of S. aureus. Its biological characteristics were identified, including growth properties and stability under different pH and temperature conditions. The genomic analysis revealed that the phage has no genes associated with pathogenicity or drug resistance. Then, the phage-functionalized magnetic beads (pMB), serving as a biological recognition element, were integrated with ATP bioluminescence assays to establish a biosensing method for S. aureus detection. The pMB enrichment brought high specificity and a tenfold increase in analytical sensitivity during detection. The whole detection process could be completed within 30 min, with a broad linear range of 1 × 104 to 1 × 108 CFU/mL and a limit of detection (LOD) of 2.43 × 103 CFU/mL. After a 2 h pre-cultivation, this method is capable of detecting bacteria as low as 1 CFU/mL. The recoveries of S. aureus in spiked skim milk and chicken samples were 81.07% to 99.17% and 86.98% to 104.62%, respectively. Our results indicated that phage-based biosensing can contribute to the detection of target pathogens in foods.

Phages for the treatment of Mycobacterium species

Highly drug-resistant strains are not uncommon among the Mycobacterium genus, with patients requiring lengthy antibiotic treatment regimens with multiple drugs and harmful side effects. This alarming increase in antibiotic resistance globally has renewed the interest in mycobacteriophage therapy for both Mycobacterium tuberculosis complex and non-tuberculosis mycobacteria. With the increasing number of genetically well-characterized mycobacteriophages and robust engineering tools to convert temperate phages to obligate lytic phages, the phage cache against extensive drug-resistant mycobacteria is constantly expanding. Synergistic effects between phages and TB drugs are also a promising avenue to research, with mycobacteriophages having several additional advantages compared to traditional antibiotics due to their different modes of action. These advantages include less side effects, a narrow host spectrum, biofilm penetration, self-replication at the site of infection and the potential to be manufactured on a large scale. In addition, mycobacteriophage enzymes, not yet in clinical use, warrant further studies with their additional benefits for rupturing host bacteria thereby limiting resistance development as well as showing promise in vitro to act synergistically with TB drugs. Before mycobacteriophage therapy can be envisioned as part of routine care, several obstacles must be overcome to translate in vitro work into clinical practice. Strategies to target intracellular bacteria and selecting phage cocktails to limit cross-resistance remain important avenues to explore. However, insight into pathophysiological host-phage interactions on a molecular level and innovative solutions to transcend mycobacteriophage therapy impediments, offer sufficient encouragement to explore phage therapy. Recently, the first successful clinical studies were performed using a mycobacteriophage-constructed cocktail to treat non-tuberculosis mycobacteria, providing substantial insight into lessons learned and potential pitfalls to avoid in order to ensure favorable outcomes. However, due to mycobacterium strain variation, mycobacteriophage therapy remains personalized, only being utilized in compassionate care cases until there is further regulatory approval. Therefore, identifying the determinants that influence clinical outcomes that can expand the repertoire of mycobacteriophages for therapeutic benefit, remains key for their future application.

Recent advances in airborne pathogen detection using optical and electrochemical biosensors

The world is currently facing an adverse condition due to the pandemic of airborne pathogen SARS-CoV-2. Prevention is better than cure; thus, the rapid detection of airborne pathogens is necessary because it can reduce outbreaks and save many lives. Considering the immense role of diverse detection techniques for airborne pathogens, proper summarization of these techniques would be beneficial for humans. Hence, this review explores and summarizes emerging techniques, such as optical and electrochemical biosensors used for detecting airborne bacteria (Bacillus anthracis, Mycobacterium tuberculosis, Staphylococcus aureus, and Streptococcus pneumoniae) and viruses (Influenza A, Avian influenza, Norovirus, and SARS-CoV-2). Significantly, the first section briefly focuses on various diagnostic modalities applied toward airborne pathogen detection. Next, the fabricated optical biosensors using various transducer materials involved in colorimetric and fluorescence strategies for infectious pathogen detection are extensively discussed. The third section is well documented based on electrochemical biosensors for airborne pathogen detection by differential pulse voltammetry, cyclic voltammetry, square-wave voltammetry, amperometry, and impedance spectroscopy. The unique pros and cons of these modalities and their future perspectives are addressed in the fourth and fifth sections. Overall, this review inspected 171 research articles published in the last decade and persuaded the importance of optical and electrochemical biosensors for airborne pathogen detection.

A Review on Mycobacteriophages: From Classification to Applications

Mycobacterial infections are a group of life-threatening conditions triggered by fast- or slow-growing mycobacteria. Some mycobacteria, such as Mycobacterium tuberculosis, promote the deaths of millions of lives throughout the world annually. The control of mycobacterial infections is influenced by the challenges faced in the diagnosis of these bacteria and the capability of these pathogens to develop resistance against common antibiotics. Detection of mycobacterial infections is always demanding due to the intracellular nature of these pathogens that, along with the lipid-enriched structure of the cell wall, complicates the access to the internal contents of mycobacterial cells. Moreover, recent studies depicted that more than 20% of M. tuberculosis (Mtb) infections are multi-drug resistant (MDR), and only 50% of positive MDR-Mtb cases are responsive to standard treatments. Similarly, the susceptibility of nontuberculosis mycobacteria (NTM) to first-line tuberculosis antibiotics has also declined in recent years. Exploiting mycobacteriophages as viruses that infect mycobacteria has significantly accelerated the diagnosis and treatment of mycobacterial infections. This is because mycobacteriophages, regardless of their cycle type (temperate/lytic), can tackle barriers in the mycobacterial cell wall and make the infected bacteria replicate phage DNA along with their DNA. Although the infectivity of the majority of discovered mycobacteriophages has been evaluated in non-pathogenic M. smegmatis, more research is still ongoing to find mycobacteriophages specific to pathogenic mycobacteria, such as phage DS6A, which has been shown to be able to infect members of the M. tuberculosis complex. Accordingly, this review aimed to introduce some potential mycobacteriophages in the research, specifically those that are infective to the three troublesome mycobacteria, M. tuberculosis, M. avium subsp. paratuberculosis (MAP), and M. abscessus, highlighting their theranostic applications in medicine.

Lateral flow assay of methicillin-resistant Staphylococcus aureus using bacteriophage cellular wall-binding domain as recognition agent

As one of the most common and noticeable superbugs, methicillin-resistant Staphylococcus aureus (MRSA) has long been a major threat to public health. To meet the demand for effective diagnosis of MRSA-induced infection, it is urgent to establish rapid assay method for this type of pathogen. In this study, an aqueous soluble cellular wall-binding domain (CWBD) protein from bacteriophage P108 was obtained with a recombinant expression technique. It can act as a wide-spectrum binding agent for all MRSA strains and exclude the interference from methicillin-susceptible strains of Staphylococcus aureus and other species of bacteria. To establish a lateral flow assay (LFA) method for MRSA, CWBD-coupled time-resolved fluorescent microspheres (FMs) were used as signal probes for tracing MRSA, and a nitrocellulose membrane immobilized with porcine IgG was used to capture MRSA. With the LFA based on sandwich format, MRSA can be assayed within 10 min with a broad linear range of 6.6 × 10²-6.6 × 10⁷ CFU/mL. Its application potential has been demonstrated by assaying different types of bacteria-contaminated real samples. The results suggest that the LFA strip using recombinant CWBD as the recognition agent provides a rapid, portable, cost-effective approach for point-of-care testing of MRSA.