Bacteriophages and phage-delivered CRISPR-Cas system as antibacterial therapy

Gene editing tool-loaded biomimetic cationic vesicles with highly efficient bacterial internalization for in vivo eradication of pathogens

In the post-COVID-19 era, drug-resistant bacterial infections emerge as one of major death causes, where multidrug-resistant Acinetobacter baumannii (MRAB) and drug-resistant Pseudomonas aeruginosa (DRPA) represent primary pathogens. However, the classical antibiotic strategy currently faces the bottleneck of drug resistance. We develop an antimicrobial strategy that applies the selective delivery of CRISPR/Cas9 plasmids to pathogens with biomimetic cationic hybrid vesicles (BCVs), irrelevant to bacterial drug resistance. CRISPR/Cas9 plasmids were constructed, replicating in MRAB or DRPA and expressing ribonucleic proteins, leading to irreparable chromosomal lesions; however, delivering the negatively charged plasmids with extremely large molecular weight to the pathogens at the infection site became a huge challenge. We found that the BCVs integrating the bacterial out membrane vesicles and cationic lipids efficiently delivered the plasmids in vitro/in vivo to the pathogens followed by effective internalization. The BCVs were used by intratracheal or topical hydrogel application against MRAB pulmonary infection or DRPA wound infection, and both of the two pathogens were eradicated from the lung or the wound. CRISPR/Cas9 plasmid-loaded BCVs become a promising medication for drug-resistant bacteria infections.

Pharmacodynamic Evaluation of Phage Therapy in Ameliorating ETEC-Induced Diarrhea in Mice Models

Enterotoxigenic Escherichia coli (ETEC) is a major pathogen causing diarrhea in humans and animals, with increasing antimicrobial resistance posing a growing challenge in recent years. Lytic bacteriophages (phages) offer a targeted and environmentally sustainable approach to combating bacterial infections, particularly in eliminating drug-resistant strains. In this study, ETEC strains were utilized as indicators, and a stable, high-efficiency phage, designated vB_EcoM_JE01 (JE01), was isolated from pig farm manure. The genome of JE01 was a dsDNA molecule, measuring 168.9 kb, and a transmission electron microscope revealed its characteristic T4-like Myoviridae morphology. JE01 effectively lysed multi-drug-resistant ETEC isolates. Stability assays demonstrated that JE01 retained its activity across a temperature range of 20 °C to 50 °C and a pH range of 3-11, showing resilience to ultraviolet radiation and chloroform exposure. Furthermore, JE01 effectively suppressed ETEC adhesion to porcine intestinal epithelial cells (IPEC-J2), mitigating the inflammatory response triggered by ETEC. To investigate the in vivo antibacterial efficacy of phage JE01 preparations, a diarrhea model was established using germ-free mice infected with a drug-resistant ETEC strain. The findings indicated that 12 h post-ETEC inoculation, intragastric administration of phage JE01 significantly reduced mortality, alleviated gastrointestinal lesions, decreased ETEC colonization in the jejunum, and suppressed the expression of the cytokines IL-6 and IL-8. These results demonstrate a therapeutic benefit of JE01 in treating ETEC-induced diarrhea in mice. Additionally, a fluorescent phage incorporating red fluorescent protein (RFP) was engineered, and the pharmacokinetics of phage therapy were preliminarily assessed through intestinal fluorescence imaging in mice. The results showed that the phage localized to ETEC in the jejunum rapidly, within 45 min. Moreover, the pharmacokinetics of the phage were markedly slowed in the presence of its bacterial target in the gut, suggesting sustained bacteriolytic activity in the ETEC-infected intestine. In conclusion, this study establishes a foundation for the development of phage-based therapies against ETEC.

Predicting phage-host interactions via feature augmentation and regional graph convolution

Identifying phage-host interactions (PHIs) is a crucial step in developing phage therapy, which is the promising solution to addressing the issue of antibiotic resistance in superbugs. However, the lifestyle of phages, which strongly depends on their host for life activities, limits their cultivability, making the study of predicting PHIs time-consuming and labor-intensive for traditional wet lab experiments. Although many deep learning (DL) approaches have been applied to PHIs prediction, most DL methods are predominantly based on sequence information, failing to comprehensively model the intricate relationships within PHIs. Moreover, most existing approaches are limited for sub-optimal performance, due to the potential risk of overfitting induced by the highly data sparsity in the task of PHIs prediction. In this study, we propose a novel approach called MI-RGC, which introduces mutual information for feature augmentation and employs regional graph convolution to learn meaningful representations. Specifically, MI-RGC treats the presence status of phages in environmental samples as random variables, and derives the mutual information between these random variables as the dependency relationships among phages. Consequently, a mutual information-based heterogeneous network is construted as feature augmentation for sequence information of phages, which is utilized for building a sequence information-based heterogeneous network. By considering the different contributions of neighboring nodes at varying distances, a regional graph convolutional model is designed, in which the neighboring nodes are segmented into different regions and a regional-level attention mechanism is employed to derive node embeddings. Finally, the embeddings learned from these two networks are aggregated through an attention mechanism, on which the prediction of PHIs is condcuted accordingly. Experimental results on three benchmark datasets demonstrate that MI-RGC derives superior performance over other methods on the task of PHIs prediction.

Delivery of functional Cas:DNA nucleoprotein complexes into recipient bacteria through a type IV secretion system

CRISPR-associated (Cas) endonucleases and their derivatives are widespread tools for the targeted genetic modification of both prokaryotic and eukaryotic genomes. A critical step of all CRISPR-Cas technologies is the delivery of the Cas endonuclease to the target cell. Here, we investigate the possibility of using bacterial conjugation to translocate Cas proteins into recipient bacteria. Conjugative relaxases are translocated through a type IV secretion system into the recipient cell, covalently attached to the transferred DNA strand. We fused relaxase R388-TrwC with the endonuclease Cas12a and confirmed that it can be transported through a T4SS. The fusion protein maintained its activity upon translocation by conjugation into the recipient cell, as evidenced by the induction of the SOS signal resulting from DNA breaks produced by the endonuclease in the recipient cell, and the detection of mutations at the target position. We further show how a template DNA provided on the transferred DNA can be used to introduce specific mutations. The guide RNA can also be encoded by the transferred DNA, enabling its production in the recipient cells where it can form a complex with the Cas nuclease transferred as a protein. This self-contained setup enables to target wild-type bacterial cells. Finally, we extended this strategy to the delivery of relaxases fused to base editors. Using TrwC and MobA relaxases as drivers, we achieved precise editing of transconjugants. Thus, conjugation provides a delivery system for Cas-derived editing tools, bypassing the need to deliver and express a cas gene in the target cells.

Bacteriophage as a potential biotherapeutics to combat present-day crisis of multi-drug resistant pathogens

The rise of Multi-Drug Resistant (MDR) bacterial pathogens to most, if not all, currently available antibacterial agents has become a global threat. As a consequence of the antibiotic resistance epidemic, phage therapy has emerged as a potential alternative to conventional antibiotics. Despite the high therapeutic advantages of phage therapy, they have not yet been successfully used in the clinic due to various limitations of narrow host specificity compared to antibiotics, poor adhesion on biofilm surface, and susceptibility to both human and bacterial defences. This review focuses on the antibacterial effect of bacteriophage and their recent clinical trials with a special emphasis on the underlying mechanism of lytic phage action with the help of endolysin and holin. Furthermore, recent clinical trials of natural and modified endolysins and some marketed products have also been emphasized with future prospective.

Bacteriophage-resistant carbapenem-resistant Klebsiella pneumoniae shows reduced antibiotic resistance and virulence

Phage therapy has shown great promise in the treatment of bacterial infections. However, the effectiveness of phage therapy is compromised by the inevitable emergence of phage-resistant strains. In this study, a phage-resistant carbapenem-resistant Klebsiella pneumoniae strain SWKP1711R, derived from parental carbapenem-resistant K. pneumoniae strain SWKP1711 was identified. The mechanism of bacteriophage resistance in SWKP1711R was investigated and the molecular determinants causing altered growth characteristics, antibiotic resistance, and virulence of SWKP1711R were tested. Compared to SWKP1711, SWKP1711R showed slower growth, smaller colonies, filamentous cells visible under the microscope, reduced production of capsular polysaccharide (CPS) and lipopolysaccharide, and reduced resistance to various antibiotics accompanied by reduced virulence. Adsorption experiments showed that phage vB_kpnM_17-11 lost the ability to adsorb onto SWKP1711R, and the adsorption receptor was identified to be bacterial surface polysaccharides. Genetic variation analysis revealed that, compared to the parental strain, SWKP1711R had only one thymine deletion at position 78 of the open reading frame of the lpcA gene, resulting in a frameshift mutation that caused alteration of the bacterial surface polysaccharide and inhibition of phage adsorption, ultimately leading to phage resistance. Transcriptome analysis and quantitative reverse transcriptase PCR revealed that genes encoding lipopolysaccharide synthesis, ompK35, blaTEM-1, and type II and Hha-TomB toxin-antitoxin systems, were all downregulated in SWKP1711R. Taken together, the evidence presented here indicates that the phenotypic alterations and phage resistance displayed by the mutant may be related to the frameshift mutation of lpcA and altered gene expression. While evolution of phage resistance remains an issue, our study suggests that the reduced antibiotic resistance and virulence of phage-resistant strain derivatives might be beneficial in alleviating the burden caused by multidrug-resistant bacteria.

Role of CRISPR-Cas systems and anti-CRISPR proteins in bacterial antibiotic resistance

The emergence and development of antibiotic resistance in bacteria is a serious threat to global public health. Antibiotic resistance genes (ARGs) are often located on mobile genetic elements (MGEs). They can be transferred among bacteria by horizontal gene transfer (HGT), leading to the spread of drug-resistant strains and antibiotic treatment failure. CRISPR (clustered regularly interspaced short palindromic repeats)-Cas (CRISPR-associated genes) is one of the many strategies bacteria have developed under long-term selection pressure to restrict the HGT. CRISPR-Cas systems exist in about half of bacterial genomes and play a significant role in limiting the spread of antibiotic resistance. On the other hand, bacteriophages and other MGEs encode a wide range of anti-CRISPR proteins (Acrs) to counteract the immunity of the CRISPR-Cas system. The Acrs could decrease the CRISPR-Cas system's activity against phages and facilitate the acquisition of ARGs and virulence traits for bacteria. This review aimed to assess the relationship between the CRISPR-Cas systems and Acrs with bacterial antibiotic resistance. We also highlighted the CRISPR technology and Acrs to control and prevent antibacterial resistance. The CRISPR-Cas system can target nucleic acid sequences with high accuracy and reliability; therefore, it has become a novel gene editing and gene therapy tool to prevent the spread of antibiotic resistance. CRISPR-based approaches may pave the way for developing smart antibiotics, which could eliminate multidrug-resistant (MDR) bacteria and distinguish between pathogenic and beneficial microorganisms. Additionally, the engineered anti-CRISPR gene-containing phages in combination with antibiotics could be used as a cutting-edge treatment approach to reduce antibiotic resistance.

CRISPR-Cas System: A New Dawn to Combat Antibiotic Resistance

Antimicrobial resistance (AMR) can potentially harm global public health. Horizontal gene transfer (HGT), which speeds up the emergence of AMR and increases the burden of drug resistance in mobile genetic elements (MGEs), is the primary method by which AMR genes are transferred across bacterial pathogens. New approaches are urgently needed to halt the spread of bacterial diseases and antibiotic resistance. Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR), an RNA-guided adaptive immune system, protects prokaryotes from foreign DNA like plasmids and phages. This approach may be essential in limiting horizontal gene transfer and halting the spread of antibiotic resistance. The CRISPR-Cas system has been crucial in identifying and understanding resistance mechanisms and developing novel therapeutic approaches. This review article investigates the CRISPR-Cas system's potential as a tool to combat bacterial AMR. Antibiotic-resistant bacteria can be targeted and eliminated by the CRISPR-Cas system. It has been proven to be an efficient method for removing carbapenem-resistant plasmids and regaining antibiotic susceptibility. The CRISPR-Cas system has enormous potential as a weapon against bacterial AMR. It precisely targets and eliminates antibiotic-resistant bacteria, facilitates resistance mechanism identification, and offers new possibilities in diagnostics and therapeutics.

The Medicinal Phage-Regulatory Roadmap for Phage Therapy under EU Pharmaceutical Legislation

Bacteriophage therapy is a promising approach to treating bacterial infections. Research and development of bacteriophage therapy is intensifying due to the increase in antibiotic resistance and the faltering development of new antibiotics. Bacteriophage therapy uses bacteriophages (phages), i.e., prokaryotic viruses, to specifically target and kill pathogenic bacteria. The legal handling of this type of therapy raises several questions. These include whether phage therapeutics belong to a specially regulated class of medicinal products, and which legal framework should be followed with regard to the various technical ways in which phage therapeutics can be manufactured and administered. The article shows to which class of medicinal products phage therapeutics from wild type phages and from genetically modified (designer) phages do or do not belong. Furthermore, the article explains which legal framework is relevant for the manufacture and administration of phage therapeutics, which are manufactured in advance in a uniform, patient-independent manner, and for tailor-made patient-specific phage therapeutics. For the systematically coherent, successful translation of phage therapy, the article considers pharmaceutical law and related legal areas, such as genetic engineering law. Finally, the article shows how the planned legislative revisions of Directive 2001/83/EC and Regulation (EC) No 726/2004 may affect the legal future of phage therapy.

The overlooked bacterial pandemic

The COVID-19 pandemic had a significant economic and health impact worldwide. It also reinforced the misperception that only viruses can pose a threat to human existence, overlooking that bacteria (e.g., plague and cholera) have severely haunted and shaped the course of human civilization. While the world is preparing for the next viral pandemic, it is again overlooking a silent one: antimicrobial resistance (AMR). This review proposes to show the impact of bacterial infections on civilization to remind the pandemic potential. The work will also discuss a few examples of how bacteria can mutate risking global spread and devastating outcomes, the effect on the global burden, and the prophylactic and therapeutic measures. Indeed, AMR is dramatically increasing and if the trend is not reversed, it has the potential to quickly turn into the most important health problem worldwide.

Size and charge effects of metal nanoclusters on antibacterial mechanisms

Nanomaterials, specifically metal nanoclusters (NCs), are gaining attention as a promising class of antibacterial agents. Metal NCs exhibit antibacterial properties due to their ultrasmall size, extensive surface area, and well-controlled surface ligands. The antibacterial mechanisms of metal NCs are influenced by two primary factors: size and surface charge. In this review, we summarize the impacts of size and surface charge of metal NCs on the antibacterial mechanisms, their interactions with bacteria, and the factors that influence their antibacterial effects against both gram-negative and gram-positive bacteria. Additionally, we highlight the mechanisms that occur when NCs are negatively or positively charged, and provide examples of their applications as antibacterial agents. A better understanding of relationships between antibacterial activity and the properties of metal NCs will aid in the design and synthesis of nanomaterials for the development of effective antibacterial agents against bacterial infections. Based on the remarkable achievements in the design of metal NCs, this review also presents conclusions on current challenges and future perspectives of metal NCs for both fundamental investigations and practical antibacterial applications.

Application of CRISPR/Cas9-based genome editing in ecotoxicology

Chemicals are widely used and released into the environment, and their degradation, accumulation, migration, and transformation processes in the environment can pose a threat to the ecosystem. The advancement in analytical methods with high-throughput screening of biomolecules has revolutionized the way toxicologists used to explore the effects of chemicals on organisms. CRISPR/Cas is a newly developed tool, widely used in the exploration of basic science and biologically engineered products given its high efficiency and low cost. For example, it can edit target genes efficiently, and save loss of the crop yield caused by environmental pollution as well as gain a better understanding of the toxicity mechanisms from various chemicals. This review briefly introduces the development history of CRISPR/Cas and summarizes the current application of CRISPR/Cas in ecotoxicology, including its application on improving crop yield and drug resistance towards agricultural pollution, antibiotic pollution and other threats. The benefits by applying the CRISPR/Cas9 system in conventional toxicity mechanism studies are fully demonstrated here together with its foreseeable expansions in other area of ecotoxicology. Finally, the prospects and disadvantages of CRISPR/Cas system in the field of ecotoxicology are also discussed.

Application of CRISPR-Cas system in the diagnosis and therapy of ESKAPE infections

Antimicrobial-resistant ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) pathogens represent a global threat to human health. ESKAPE pathogens are the most common opportunistic pathogens in nosocomial infections, and a considerable number of their clinical isolates are not susceptible to conventional antimicrobial therapy. Therefore, innovative therapeutic strategies that can effectively deal with ESKAPE pathogens will bring huge social and economic benefits and ease the suffering of tens of thousands of patients. Among these strategies, CRISPR (clustered regularly interspaced short palindromic repeats) system has received extra attention due to its high specificity. Regrettably, there is currently no direct CRISPR-system-based anti-infective treatment. This paper reviews the applications of CRISPR-Cas system in the study of ESKAPE pathogens, aiming to provide directions for the research of ideal new drugs and provide a reference for solving a series of problems caused by multidrug-resistant bacteria (MDR) in the post-antibiotic era. However, most research is still far from clinical application.

CRISPR-Cas-Based Adaptive Immunity Mediates Phage Resistance in Periodontal Red Complex Pathogens

Periodontal diseases are polymicrobial immune-inflammatory diseases that can severely destroy tooth-supporting structures. The critical bacteria responsible for this destruction include red complex bacteria such as Porphoromonas gingivalis, Tanerella forsythia and Treponema denticola. These organisms have developed adaptive immune mechanisms against bacteriophages/viruses, plasmids and transposons through clustered regularly interspaced short palindromic repeats (CRISPR) and their associated proteins (Cas). The CRISPR-Cas system contributes to adaptive immunity, and this acquired genetic immune system of bacteria may contribute to moderating the microbiome of chronic periodontitis. The current research examined the role of the CRISPR-Cas system of red complex bacteria in the dysbiosis of oral bacteriophages in periodontitis. Whole-genome sequences of red complex bacteria were obtained and investigated for CRISPR using the CRISPR identification tool. Repeated spacer sequences were analyzed for homologous sequences in the bacteriophage genome and viromes using BLAST algorithms. The results of the BLAST spacer analysis for T. denticola spacers had a 100% score (e value with a bacillus phage), and the results for T. forsthyia and P. gingivalis had a 56% score with a pectophage and cellulophage (e value: 0.21), respectively. The machine learning model of the identified red complex CRISPR sequences predicts with area an under the curve (AUC) accuracy of 100 percent, indicating phage inhibition. These results infer that red complex bacteria could significantly inhibit viruses and phages with CRISPR immune sequences. Therefore, the role of viruses and bacteriophages in modulating sub-gingival bacterial growth in periodontitis is limited or questionable.

CRISPR-Based Gene Editing in Acinetobacter baumannii to Combat Antimicrobial Resistance

Antimicrobial resistance (AMR) poses a significant threat to the health, social, environment, and economic sectors on a global scale and requires serious attention to addressing this issue. Acinetobacter baumannii was given top priority among infectious bacteria because of its extensive resistance to nearly all antibiotic classes and treatment options. Carbapenem-resistant A. baumannii is classified as one of the critical-priority pathogens on the World Health Organization (WHO) priority list of antibiotic-resistant bacteria for effective drug development. Although available genetic manipulation approaches are successful in A. baumannii laboratory strains, they are limited when employed on newly acquired clinical strains since such strains have higher levels of AMR than those used to select them for genetic manipulation. Recently, the CRISPR-Cas (Clustered regularly interspaced short palindromic repeats/CRISPR-associated protein) system has emerged as one of the most effective, efficient, and precise methods of genome editing and offers target-specific gene editing of AMR genes in a specific bacterial strain. CRISPR-based genome editing has been successfully applied in various bacterial strains to combat AMR; however, this strategy has not yet been extensively explored in A. baumannii. This review provides detailed insight into the progress, current scenario, and future potential of CRISPR-Cas usage for AMR-related gene manipulation in A. baumannii.

Unlocking the potential of phages: Innovative approaches to harnessing bacteriophages as diagnostic tools for human diseases

Phages, viruses that infect bacteria, have been explored as promising tools for the detection of human disease. By leveraging the specificity of phages for their bacterial hosts, phage-based diagnostic tools can rapidly and accurately detect bacterial infections in clinical samples. In recent years, advances in genetic engineering and biotechnology have enabled the development of more sophisticated phage-based diagnostic tools, including those that express reporter genes or enzymes, or target specific virulence factors or antibiotic resistance genes. However, despite these advancements, there are still challenges and limitations to the use of phage-based diagnostic tools, including concerns over phage safety and efficacy. This review aims to provide a comprehensive overview of the current state of phage-based diagnostic tools, including their advantages, limitations, and potential for future development. By addressing these issues, we hope to contribute to the ongoing efforts to develop safe and effective phage-based diagnostic tools for the detection of human disease.

Optimization of CRISPR-Cas system for clinical cancer therapy

Cancer is a genetic disease caused by alterations in genome and epigenome and is one of the leading causes for death worldwide. The exploration of disease development and therapeutic strategies at the genetic level have become the key to the treatment of cancer and other genetic diseases. The functional analysis of genes and mutations has been slow and laborious. Therefore, there is an urgent need for alternative approaches to improve the current status of cancer research. Gene editing technologies provide technical support for efficient gene disruption and modification in vivo and in vitro, in particular the use of clustered regularly interspaced short palindromic repeats (CRISPR)-Cas systems. Currently, the applications of CRISPR-Cas systems in cancer rely on different Cas effector proteins and the design of guide RNAs. Furthermore, effective vector delivery must be met for the CRISPR-Cas systems to enter human clinical trials. In this review article, we describe the mechanism of the CRISPR-Cas systems and highlight the applications of class II Cas effector proteins. We also propose a synthetic biology approach to modify the CRISPR-Cas systems, and summarize various delivery approaches facilitating the clinical application of the CRISPR-Cas systems. By modifying the CRISPR-Cas system and optimizing its in vivo delivery, promising and effective treatments for cancers using the CRISPR-Cas system are emerging.

CRISPR-Cas System: A Tool to Eliminate Drug-Resistant Gram-Negative Bacteria

Rapidly emerging drug-resistant superbugs, especially Gram-negative bacteria, pose a serious threat to healthcare systems all over the globe. Newer strategies are being developed to detect and overcome the arsenal of weapons that these bacteria possess. The development of antibiotics is time-consuming and may not provide full proof of action on evolving drug-resistant pathogens. The clustered regularly interspaced short palindromic repeats/CRISPR-associated protein (CRISPR/Cas) systems are promising in curbing drug-resistant bacteria. This review focuses on the pathogenesis of Gram-negative bacteria, emergence of antimicrobial drug resistance, and their treatment failures. It also draws attention to the present status of the CRISPR-Cas system in diagnosisand treatment of Gram-negative bacterial infections.

The resurgence of phage-based therapy in the era of increasing antibiotic resistance: From research progress to challenges and prospects

Phage therapy was implemented almost a century ago but was subsequently abandoned when antibiotics emerged. However, the rapid emergence of drug-resistant, which has brought to the limelight situation reminiscent of the pre-antibiotic era, coupled with the unavailability of new drugs, has triggered the quest for an alternative therapeutic approach, and this has led to the rebirth of phage-derived therapy. Phages are viruses that infect and replicate in bacterial cells. Phage therapy, especially phage-derived proteins, is being given considerable attention among scientists as an antimicrobial agent. They are used alone or in combination with other biomaterials for improved biological activity. Over the years, much has been learned about the genetics and diversity of bacteriophages. Phage cocktails are currently being exploited for treating several infectious diseases as preliminary studies involving animal models and clinical trials show promising therapeutic efficacy. However, despite its numerous advantages, this approach has several challenges and unaddressed limitations. Addressing these issues requires lots of creativity and innovative ideas from interdisciplinary fields. However, with all available indications, phage therapy could hold the solution in this era of increasing antibiotic resistance. This review discussed the potential use of phages and phage-derived proteins in treating drug-resistant bacterial infections. Finally, we highlight the progress, challenges, and knowledge gaps and evaluate key questions requiring prompt attention for the full clinical application of phage therapy.

Combating antimicrobial resistance: an evidence-based overview of bacteriophage therapy

Antimicrobial resistance (AMR) problems cause an enormous challenge to our world in medicine and in agriculture and many other fields. The current situation makes bacteriophage therapy an attractive therapeutic candidate. Nevertheless, very limited clinical trials on bacteriophage therapy were performed and completed as of presence. Bacteriophage therapy alludes to infecting bacteria with a virus, this often results in a bactericidal effect. The compiled studies support the feasibility of treating AMR with bacteriophage. However, the efficacy of specific bacteriophage strains and the accurate dosage have to be further studied and tested rigorously.