Bacteriophage Tail Proteins as a Tool for Bacterial Pathogen Recognition-A Literature Review

Phage probe on RAFT polymer surface for rapid enumeration of E. coli K12

This study presents a simple, fast, and sensitive label-free sensing assay for the precise enumeration of modeled pathogenic Escherichia coli K12 (E. coli K12) bacteria for the first time. The method employs the covalent binding bacteriophage technique on the surface of a reversible addition-fragmentation chain transfer (RAFT) polymer film. The Nyquist plots obtained from electrochemical impedance spectroscopy (EIS) identified the charge transfer resistance Rct was calculated from a suitable electrochemical circuit model through an evaluation of the relevant parameter after the immobilization of the bacteriophage and the binding of specific E. coli K12. The impedimetric biosensor reveals specific and reproducible detection with sensitivity in the linear working range of 104.2-107.0 CFU/mL, a limit of detection (LOD) of 101.3 CFU/mL, and a short response time of 15 min. The SERS response validates the surface roughness and interaction of the SERS-tag with E. coli K12-modified electrodes. Furthermore, the covalently immobilized active phage selectivity was proved against various non-targeting bacterial strains in the presence of targeted E.coli K12 with a result of 94 % specificity and 98 % sensitivity. Therefore, the developed phage-based electrode surface can be used as a disposable, label-free impedimetric biosensor for rapid and real-time monitoring of serum samples.

Characterization of two virulent Salmonella phages and transient application in egg, meat and lettuce safety

Salmonella, a prominent foodborne pathogen, has posed enduring challenges to the advancement of food safety and global public health. The escalating concern over antibiotic misuse, resulting in the excessive presence of drug residues in animal-derived food products, necessitates urgent exploration of alternative strategies for Salmonella control. Bacteriophages emerge as promising green biocontrol agents against pathogenic bacteria. This study delineates the identification of two novel virulent Salmonella phages, namely phage vB_SalS_ABTNLsp11241 (referred to as sp11241) and phage 8-19 (referred to as 8-19). Both phages exhibited efficient infectivity against Salmonella enterica serotype Enteritidis (SE). Furthermore, this study evaluated the effectiveness of two phages to control SE in three different foods (whole chicken eggs, raw chicken meat, and lettuce) at different MOIs (1, 100, and 10000) at 4°C. It's worth noting that sp11241 and 8-19 achieved complete elimination of SE on eggs after 3 h and 6 h at MOI = 100, and after 2 h and 5 h at MOI = 10000, respectively. After 12 h of treatment with sp11241, a maximum reduction of 3.17 log10 CFU/mL in SE was achieved on raw chicken meat, and a maximum reduction of 3.00 log10 CFU/mL was achieved on lettuce. Phage 8-19 has the same effect on lettuce as sp11241, but is slightly less effective than sp11241 on chicken meat (a maximum 2.69 log10 CFU/mL reduction). In conclusion, sp11241 and 8-19 exhibit considerable potential for controlling Salmonella contamination in food at a low temperature and represent viable candidates as green antibacterial agents for food applications.

Electrochemical biosensors for pathogenic microorganisms detection based on recognition elements

The worldwide spread of pathogenic microorganisms poses a significant risk to human health. Electrochemical biosensors have emerged as dependable analytical tools for the point-of-care detection of pathogens and can effectively compensate for the limitations of conventional techniques. Real-time analysis, high throughput, portability, and rapidity make them pioneering tools for on-site detection of pathogens. Herein, this work comprehensively reviews the recent advances in electrochemical biosensors for pathogen detection, focusing on those based on the classification of recognition elements, and summarizes their principles, current challenges, and prospects. This review was conducted by a systematic search of PubMed and Web of Science databases to obtain relevant literature and construct a basic framework. A total of 171 publications were included after online screening and data extraction to obtain information of the research advances in electrochemical biosensors for pathogen detection. According to the findings, the research of electrochemical biosensors in pathogen detection has been increasing yearly in the past 3 years, which has a broad development prospect, but most of the biosensors have performance or economic limitations and are still in the primary stage. Therefore, significant research and funding are required to fuel the rapid development of electrochemical biosensors. The overview comprehensively evaluates the recent advances in different types of electrochemical biosensors utilized in pathogen detection, with a view to providing insights into future research directions in biosensors.

Separation and colorimetric detection of Escherichia coli by phage tail fiber protein combined with nano-magnetic beads

A colorimetric detection method for Escherichia coli (E. coli) in water was established based on a T7 phage tail fiber protein-magnetic separation. Firstly, the tail fiber protein (TFP) was expressed and purified to specifically recognize E. coli, which was verified by using fusion protein GFP-tagged TFP (GFP-TFP) and fluorescence microscopy. Then TFP conjugated with magnetic beads were applied to capture and separate E. coli. The TFP was covalently immobilized on the surface of magnetic beads and captured E. coli as verified by scanning electron microscopy (SEM). Finally, polymyxin B was used to lyse E. coli in solution and the released intracellular β-galactosidase (β-gal) could hydrolyze the colorimetric substrate chlorophenol red-β-D-galactopyranoside (CPRG), causing color change from yellow to purple. The high capture efficiencies of E. coli ranged from 88.70% to 95.65% and E. coli could be detected at a concentration of 10² CFU/mL by naked eyes. The specificity of the chromogenic substrate was evaluated using five different pathogen strains as competitors and tests with four kinds of real water samples showed recoveries of 86.00% to 92.25%. The colorimetric changes determined by visual inspection can be developed as an efficient platform for point-of-care detection of E. coli in resource-limited regions.

Phages for treatment of Staphylococcus aureus infection

Combating multi-drug resistant bacterial infections should be a universal urgency. The gram- positive Staphylococcus aureus (S. aureus) bacteria are generally harmless; healthy people frequently have them on their skin and nose. These bacteria, for the most part, produce no difficulties or only minor skin diseases. Antibiotics and cleansing of the affected region are usually the treatments of choice. S. aureus can become virulent causing serious infections that may lead to pustules to sepsis or death. Normally, it is thought that antibiotics may solve problems concerning bacterial infection; but unfortunately, Staphylococci have evolved mechanisms to resist drugs. Methicillin-Resistant Staphylococcus aureus (MRSA); both in hospitals and in the community, infections are evolving into dangerous pathogens. Health care practitioners may need to use antibiotics with more adverse effects to treat antibiotic-resistant S. aureus infections. Amid existing efforts to resolve this problem, phage therapy proposes a hopeful alternate to face Staphylococcal infections. When the majority of antibiotics have failed to treat infections caused by multidrug-resistant bacteria, such as methicillin- and vancomycin-resistant S. aureus, phage therapy may be an option. Here, we appraise the potential efficacy, current knowledge on bacteriophages for S. aureus, experimental research and information on their clinical application, and limitations of phage therapy for S. aureus infections.

Development of a Novel Phagomagnetic-Assisted Isothermal DNA Amplification System for Endpoint Electrochemical Detection of Listeria monocytogenes

The hitherto implemented Listeria monocytogenes detection techniques are cumbersome or require expensive non-portable instrumentation, hindering their transposition into on-time surveillance systems. The current work proposes a novel integrated system resorting to loop-mediated isothermal amplification (LAMP), assisted by a bacteriophage P100-magnetic platform, coupled to an endpoint electrochemical technique, towards L. monocytogenes expeditious detection. Molybdophosphate-based optimization of the bacterial phagomagnetic separation protocol allowed the determination of the optimal parameters for its execution (pH 7, 25 °C, 32 µg of magnetic particles; 60.6% of specific capture efficiency). The novel LAMP method targeting prfA was highly specific, accomplishing 100% inclusivity (for 61 L. monocytogenes strains) and 100% exclusivity (towards 42 non-target Gram-positive and Gram-negative bacteria). As a proof-of-concept, the developed scheme was successfully validated in pasteurized milk spiked with L. monocytogenes. The phagomagnetic-based approach succeeded in the selective bacterial capture and ensuing lysis, triggering Listeria DNA leakage, which was efficiently LAMP amplified. Methylene blue-based electrochemical detection of LAMP amplicons was accomplished in 20 min with remarkable analytical sensitivity (1 CFU mL^-1). Hence, the combined system presented an outstanding performance and robustness, providing a 2.5 h-swift, portable, cost-efficient detection scheme for decentralized on-field application.

Characterization and genome analysis of a novel phage Kayfunavirus TM1

Escherichia coli is a common conditional pathogen, for which antibiotic therapy is considered an effective treatment. The imprudent use of antibiotics has led to the increase of multiple-antibiotic-resistant E. coli species. With the incidence of antibiotic resistance reaching a crisis point, it is imperative to find alternative treatments for multidrug-resistant infections. Using phage for pathogen control is a promising treatment option to combat bacterial resistance. In this study, a novel virulent Podoviridae phage Kayfunavirus TM1 infecting Escherichia coli was isolated from pig farm sewage in Guangxi, China. The one-step growth curve with the optimal multiplicity of infection of 0.01 revealed a latent period of 10 min and a burst size of 50 plaque-forming units per cell. The stability test reveals that it is stable from 4 to 60 °C and pH from 3 to 11. The double-stranded DNA genome of phage Kayfunavirus TM1 is composed of 39,948 base pairs with a GC content of 50.03%.

Deciphering Bacteriophage T5 Host Recognition Mechanism and Infection Trigger

Bacteriophages, viruses infecting bacteria, recognize their host with high specificity, binding to either saccharide motifs or proteins of the cell wall of their host. In the majority of bacteriophages, this host recognition is performed by receptor binding proteins (RBPs) located at the extremity of a tail. Interaction between the RBPs and the host is the trigger for bacteriophage infection, but the molecular details of the mechanisms are unknown for most bacteriophages. Here, we present the electron cryomicroscopy (cryo-EM) structure of bacteriophage T5 RBPpb5 in complex with its Escherichia coli receptor, the iron ferrichrome transporter FhuA. Monomeric RBPpb5 is located at the extremity of T5's long flexible tail, and its irreversible binding to FhuA commits T5 to infection. Analysis of the structure of RBPpb5 within the complex, comparison with its AlphaFold2-predicted structure, and its fit into a previously determined map of the T5 tail tip in complex with FhuA allow us to propose a mechanism of transmission of the RBPpb5 receptor binding to the straight fiber, initiating the cascade of events that commits T5 to DNA ejection. IMPORTANCE Tailed bacteriophages specifically recognize their bacterial host by interaction of their receptor binding protein(s) (RBPs) with saccharides and/or proteins located at the surface of their prey. This crucial interaction commits the virus to infection, but the molecular details of this mechanism are unknown for the majority of bacteriophages. We determined the structure of bacteriophage T5 RBPpb5 in complex with its E. coli receptor, FhuA, by cryo-EM. This first structure of an RBP bound to its protein receptor allowed us to propose a mechanism of transmission of host recognition to the rest of the phage, ultimately opening the capsid and perforating the cell wall and, thus, allowing safe channeling of the DNA into the host cytoplasm.

Acinetobacter Baumannii Phages: Past, Present and Future

Acinetobacter baumannii (A. baumannii) is one of the most common clinical pathogens and a typical multi-drug resistant (MDR) bacterium. With the increase of drug-resistant A. baumannii infections, it is urgent to find some new treatment strategies, such as phage therapy. In this paper, we described the different drug resistances of A. baumannii and some basic properties of A. baumannii phages, analyzed the interaction between phages and their hosts, and focused on A. baumannii phage therapies. Finally, we discussed the chance and challenge of phage therapy. This paper aims to provide a more comprehensive understanding of A. baumannii phages and theoretical support for the clinical application of A. baumannii phages.