A Multiwell-Plate Caenorhabditis elegans Assay for Assessing the Therapeutic Potential of Bacteriophages against Clinical Pathogens

Tracking Chlamydia - Host interactions and antichlamydial activity in Caenorhabditis elegans

The fading efficacy of antibiotics is a growing global health concern due to its life-threatening consequences and increased healthcare costs. Non-genetic mechanisms of antimicrobial resistance, such as those employed by Chlamydia pneumoniae and Chlamydia trachomatis, complicate treatment as these bacteria can enter a non-replicative, persistent state under stress, evading antibiotics and linking to inflammatory conditions. Understanding chlamydial persistence at the molecular level is challenging, and new models for studying Chlamydia-host interactions in vivo are urgently needed. Caenorhabditis elegans offers an alternative given its immune system and numerous orthologues of human genes. This study established C. elegans as an in vivo model for chlamydial infection. Both Chlamydia species reduced the worm's lifespan, their DNA being detectable at three- and six-days post-infection. Azithromycin at its MIC (25 nM) failed to prevent the infection-induced lifespan reduction, indicating a persister phenotype. In contrast, the methanolic extract of Schisandra chinensis berries showed anti-chlamydial activity both in vitro (in THP-1 macrophages) and in vivo, significantly extending the lifespan of infected C. elegans and reducing the bacterial load. Moreover, S. chinensis increased the transcriptional activity of SKN-1 in the worms, but was unable to impact the bacterial load or lifespan in a sek-1 defective C. elegans strain. In summary, this study validated C. elegans as a chlamydial infection model and showcased S. chinensis berries' in vivo anti-chlamydial potential, possibly through SEK/SKN-1 signaling modulation.

Molecular characterization and environmental impact of newly isolated lytic phage SLAM_phiST1N3 in the Cornellvirus genus for biocontrol of a multidrug-resistant Salmonella Typhimurium in the swine industry chain

Salmonella Typhimurium is a highly lethal pathogenic bacterium in weaned piglets, causing significant treatment costs and economic losses in the swine industry. Additionally, due to its ability to induce zoonotic diseases, resulting in harm to humans through the transmission of the pathogen from pork, it presents a serious public health issue. Bacteriophages (phages), viruses that infect specific bacterial strains, have been proposed as an alternative to antibiotics for controlling pathogenic bacteria. In this study, we isolated SLAM_phiST1N3, a phage infecting a multidrug-resistant (MDR) S. Typhimurium wild-type strain isolated from diseased pigs. First, comparative genomics and phylogenetic analysis revealed that SLAM_phiST1N3 belongs to the Cornellvirus genus. Moreover, utilizing a novel classification approach introduced in this study, SLAM_phiST1N3 was classified at the species level. Host range experiments demonstrated that SLAM_phiST1N3 did not infect other pathogenic bacteria or probiotics derived from pigs or other livestock. While complete eradication of Salmonella was not achievable in the liquid inhibition assay, surprisingly, we succeeded in largely eliminating Salmonella in the FIMM analysis, a gut simulation system using weaned piglet feces. Furthermore, using the C. elegans model, we showcased the potential of SLAM_phiST1N3 to prevent S. Typhimurium infection in living organisms. In addition, it was confirmed that bacterial control could be achieved when phage was applied to Salmonella-contaminated pork. pH and temperature stability experiments demonstrated that SLAM_phiST1N3 can endure swine industry processes and digestive conditions. In conclusion, SLAM_phiST1N3 demonstrates potential environmental impact as a substance for Salmonella prevention across various aspects of the swine industry chain.

Animal models of Klebsiella pneumoniae mucosal infections

Klebsiella pneumoniae is among the most relevant pathogens worldwide, causing high morbidity and mortality, which is worsened by the increasing rates of antibiotic resistance. It is a constituent of the host microbiota of different mucosa, that can invade and cause infections in many different sites. The development of new treatments and prophylaxis against this pathogen rely on animal models to identify potential targets and evaluate the efficacy and possible side effects of therapeutic agents or vaccines. However, the validity of data generated is highly dependable on choosing models that can adequately reproduce the hallmarks of human diseases. The present review summarizes the current knowledge on animal models used to investigate K. pneumoniae infections, with a focus on mucosal sites. The advantages and limitations of each model are discussed and compared; the applications, extrapolations to human subjects and future modifications that can improve the current techniques are also presented. While mice are the most widely used species in K. pneumoniae animal studies, they present limitations such as the natural resistance to the pathogen and difficulties in reproducing the main steps of human mucosal infections. Other models, such as Drosophila melanogaster (fruit fly), Caenorhabditis elegans, Galleria mellonella and Danio rerio (zebrafish), contribute to understanding specific aspects of the infection process, such as bacterial lethality and colonization and innate immune system response, however, they but do not present the immunological complexity of mammals. In conclusion, the choice of the animal model of K. pneumoniae infection will depend mainly on the questions being addressed by the study, while a better understanding of the interplay between bacterial virulence factors and animal host responses will provide a deeper comprehension of the disease process and aid in the development of effective preventive/therapeutic strategies.

In vitro and in vivo evaluation of the biofilm-degrading Pseudomonas phage Motto, as a candidate for phage therapy

Infections caused by Pseudomonas aeruginosa are becoming increasingly difficult to treat due to the emergence of strains that have acquired multidrug resistance. Therefore, phage therapy has gained attention as an alternative to the treatment of pseudomonal infections. Phages are not only bactericidal but occasionally show activity against biofilm as well. In this study, we describe the Pseudomonas phage Motto, a T1-like phage that can clear P. aeruginosa infections in an animal model and also exhibits biofilm-degrading properties. The phage has a substantial anti-biofilm activity against strong biofilm-producing isolates (n = 10), with at least a twofold reduction within 24 h. To demonstrate the safety of using phage Motto, cytotoxicity studies were conducted with human cell lines (HEK 293 and RAW 264.7 macrophages). Using a previously established in vivo model, we demonstrated the efficacy of Motto in Caenorhabditis elegans, with a 90% survival rate when treated with the phage at a multiplicity of infection of 10.

The applications of animal models in phage therapy: An update

The rapid increase in antibiotic resistance presents a dire situation necessitating the need for alternative therapeutic agents. Among the current alternative therapies, phage therapy (PT) is promising. This review extensively summarizes preclinical PT approaches in various in-vivo models. PT has been evaluated in several recent clinical trials. However, there are still several unanswered concerns due to a lack of appropriate regulation and pharmacokinetic data regarding the application of phages in human therapeutic procedures. In this review, we also presented the current state of PT and considered how animal models can be used to adapt these therapies for humans. The development of realistic solutions to circumvent these constraints is critical for advancing this technology.

Therapeutic evaluation of the Acinetobacter baumannii phage Phab24 for clinical use

Phages have shown to be effective in treating bacterial infections. However, when evaluating the therapeutic potential of novel phage isolates which have the ability to infect and kill a pathogen, it is important to include parameters such as stability (crucial for storage and delivery), infection dynamics in vitro and in vivo (for efficacy and dosing), and an in-depth genome analysis (to exclude the presence of virulence or lysogeny genes), among others. In this study, we characterized bacteriophage Phab24, which infects a colistin-resistant strain of the notorious nosocomial pathogen Acinetobacter baumannii. Our study is crucial for the use of Phab24 in therapy, while also advancing our understanding of phage predation.

Flagellotropic Bacteriophages: Opportunities and Challenges for Antimicrobial Applications

Bacteriophages (phages) are the most abundant biological entities in the biosphere. As viruses that solely infect bacteria, phages have myriad healthcare and agricultural applications including phage therapy and antibacterial treatments in the foodservice industry. Phage therapy has been explored since the turn of the twentieth century but was no longer prioritized following the invention of antibiotics. As we approach a post-antibiotic society, phage therapy research has experienced a significant resurgence for the use of phages against antibiotic-resistant bacteria, a growing concern in modern medicine. Phages are extraordinarily diverse, as are their host receptor targets. Flagellotropic (flagellum-dependent) phages begin their infection cycle by attaching to the flagellum of their motile host, although the later stages of the infection process of most of these phages remain elusive. Flagella are helical appendages required for swimming and swarming motility and are also of great importance for virulence in many pathogenic bacteria of clinical relevance. Not only is bacterial motility itself frequently important for virulence, as it allows pathogenic bacteria to move toward their host and find nutrients more effectively, but flagella can also serve additional functions including mediating bacterial adhesion to surfaces. Flagella are also a potent antigen recognized by the human immune system. Phages utilizing the flagellum for infections are of particular interest due to the unique evolutionary tradeoff they force upon their hosts: by downregulating or abolishing motility to escape infection by a flagellotropic phage, a pathogenic bacterium would also likely attenuate its virulence. This factor may lead to flagellotropic phages becoming especially potent antibacterial agents. This review outlines past, present, and future research of flagellotropic phages, including their molecular mechanisms of infection and potential future applications.

The Role of Antimicrobial Peptides as Antimicrobial and Antibiofilm Agents in Tackling the Silent Pandemic of Antimicrobial Resistance

Just over a million people died globally in 2019 due to antibiotic resistance caused by ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species). The World Health Organization (WHO) also lists antibiotic-resistant Campylobacter and Helicobacter as bacteria that pose the greatest threat to human health. As it is becoming increasingly difficult to discover new antibiotics, new alternatives are needed to solve the crisis of antimicrobial resistance (AMR). Bacteria commonly found in complex communities enclosed within self-produced matrices called biofilms are difficult to eradicate and develop increased stress and antimicrobial tolerance. This review summarises the role of antimicrobial peptides (AMPs) in combating the silent pandemic of AMR and their application in clinical medicine, focusing on both the advantages and disadvantages of AMPs as antibiofilm agents. It is known that many AMPs display broad-spectrum antimicrobial activities, but in a variety of organisms AMPs are not stable (short half-life) or have some toxic side effects. Hence, it is also important to develop new AMP analogues for their potential use as drug candidates. The use of one health approach along with developing novel therapies using phages and breakthroughs in novel antimicrobial peptide synthesis can help us in tackling the problem of AMR.