Peptide Therapeutics Versus Superbugs: Highlight on Current Research and Advancements

Analysis of extracellular and intracellular antibiotic resistance genes in commercial organic fertilizers reveals a non-negligible risk posed by extracellular genes

Livestock manure is known to be a significant reservoir of antibiotic resistance genes (ARGs), posing a major threat to human health and animal safety. ARGs are found in both intracellular and extracellular DNA fractions. However, there has been no comprehensive analysis of these fractions in commercial organic fertilizers (COFs). The present study conducted a systematic survey of the profiles of intracellular ARGs (iARGs) and extracellular ARGs (eARGs) and their contributing factor in COFs in Northern China. Results showed that the ARG diversity in COFs (i.e., 57 iARGs and 53 eARGs) was significantly lower than that in cow dung (i.e., 68 iARGs and 69 eARGs). The total abundance of iARGs and eARGs decreased by 85.7% and 75.8%, respectively, after compost processing, and there were no significant differences between iARGs and eARGs in COFs (P > 0.05). Notably, the relative abundance of Campilobacterota decreased significantly (99.1-100.0%) after composting, while that of Actinobacteriota and Firmicutes increased by 21.1% and 29.7%, respectively, becoming the dominant bacteria in COFs. Co-occurrence analysis showed that microorganisms and mobile genetic elements (MGEs) were more closely related to eARGs than iARGs in COFs. And structural equation models (SEMs) further verified that microbial community was an essential factor regulating iARGs and eARGs variation in COFs, with a direct influence (λ = 0.74 and 0.62, P < 0.01), following by similar effects of MGEs (λ = 0.59 and 0.43, P < 0.05). These findings indicate the need to separate eARGs and iARGs when assessing the risk of dissemination and during removal management in the environment.

Antimicrobial Peptides in Early-Life Host Defense, Perinatal Infections, and Necrotizing Enterocolitis—An Update

Host defense against early-life infections such as chorioamnionitis, neonatal sepsis, or necrotizing enterocolitis (NEC) relies primarily on innate immunity, in which antimicrobial peptides (AMPs) play a major role. AMPs that are important for the fetus and neonate include α and β defensins, cathelicidin LL-37, antiproteases (elafin, SLPI), and hepcidin. They can be produced by the fetus or neonate, the placenta, chorioamniotic membranes, recruited neutrophils, and milk-protein ingestion or proteolysis. They possess antimicrobial, immunomodulating, inflammation-regulating, and tissue-repairing properties. AMPs are expressed as early as the 13th week and increase progressively through gestation. Limited studies are available on AMP expression and levels in the fetus and neonate. Nevertheless, existing evidence supports the role of AMPs in pathogenesis of chorioamnionitis, neonatal sepsis, and NEC, and their association with disease severity. This suggests a potential role of AMPs in diagnosis, prevention, prognosis, and treatment of sepsis and NEC. Herein, we present an overview of the antimicrobial and immunomodulating properties of human AMPs, their sources in the intrauterine environment, fetus, and neonate, and their changes during pre- and post-natal infections and NEC. We also discuss emerging data regarding the potential utility of AMPs in early-life infections, as diagnostic or predictive biomarkers and as therapeutic alternatives or adjuncts to antibiotic therapy considering the increase of antibiotic resistance in neonatal intensive care units.

Fate of Antibiotic Resistance Genes and Changes in Bacterial Community With Increasing Breeding Scale of Layer Manure

The use of antimicrobials in intensive poultry production is becoming increasingly common because of its high throughput of meat and egg products. However, the profile of antibiotic resistance genes (ARGs) and the underlying mechanisms in different breeding scale farms were not fully explored. The study examined the profiles of ARGs in layer manure from three free-range and 12 intensive layer farms with different scales (N500, N5000, N10000, and N20000). A quantitative PCR (qPCR) array was used to quantify ARGs, and microbial community structure was analyzed by 16S rRNA gene sequencing. A total of 48 ARGs, belonging to seven major types, were identified in the layer manure samples, with sul2, tetM-01, and ermB being the predominant ones. The abundance, diversity, and mobility potential of ARGs in layer manure changed significantly with the increasing of the breeding scale. The abundances of total ARGs had significantly positive correlations with mobile genetic elements (MGEs), suggesting the mobility potential of ARGs in layer manure samples. Bacterial abundance did not show significant differences among the five group manure samples. However, bacterial diversity showed an increasing trend along the breeding scale. Pathogenic Bacteroidetes increased in the largest-scale layer manure samples and showed significant positive correlations with most ARGs. Network analysis revealed significant co-occurrence patterns between ARGs and microbial taxa, indicating ARGs had a wide range of bacterial hosts. Proteobacteria and Firmicutes were potential hosts for tetracycline and macrolide-lincosamide-streptogramin B (MLSB) resistant genes. Our results indicated that the expansion of the breeding scale of a farm promotes the abundance, diversity, and mobility potential of ARGs in layer manure.

Recombinant Tandem Repeated Expression of S3 and SΔ3 Antimicrobial Peptides

Background

Antimicrobial peptides (AMPs) are promising candidates for new generations of antibiotics to overcome the threats of multidrug-resistant infections as well as other industrial applications. Recombinant expression of small peptides is challenging due to low expression rates and high sensitivity to proteases. However, recombinant multimeric or fusion expression of AMPs facilitates cost-effective large-scale production of AMPs. In This project, S3 and SΔ3 AMPs were expressed as fusion partners. S3 peptide is a 34 amino acid linear antimicrobial peptide derived from lipopolysaccharide (LPS) binding site of factor C of horseshoe crab hemolymph and SΔ3 is a modified variant of S3 possessing more positive charges.

Methods

Two copy tandem repeat of the fusion protein (named as SΔ3S3-2mer-GS using glycine- serine linker was expressed in E. coli. BL21 (DE3). After cell disruption and solubilization of inclusion bodies, the protein was purified by Ni -NTA affinity chromatography. Antimicrobial activity and cytotoxic properties of purified SΔ3S3-2mer-GS were compared with a previously produced tetramer of S3 with the same glycine- serine linker (S3-4mer-GS) and each of monomeric blocks of S3 and SΔ3.

Results

SΔ3S3-2mer-GS was successfully expressed with an expression rate of 26%. The geometric average of minimum inhibitory concentration (MIC GM) of SΔ3S3-2mer-GS was 28%, 34%, and 57% lower than SΔ3, S3-4mer-GS, and S3, respectively. SΔ3S3-2mer-GS had no toxic effect on eukaryotes human embryonic kidney cells at its MIC concentration.

Conclusion

tandem repeated fusion expression strategy could be employed as an effective technique for recombinant production of AMPs.

Addressing Antimicrobial Resistance Through Nanoantibiotics

In recent years, the irrational use of antibiotics has escalated the evolution of multidrug-resistant (MDR) bacterial strains. The infectious diseases caused by these MDR bacterial strains remain a major threat to human health and have emerged as the leading cause of morbidity and mortality. The WHO and CDC have expressed serious concern regarding the continued increase in the development of multidrug resistance among bacteria. The antimicrobial resistance (AMR) poses a severe global threat of growing concern to human health and economic burden. Bacteria have developed the ability to resist antimicrobials by altering target site/enzyme, inactivation of the enzyme, decreasing cell permeability, increasing efflux due to over-expression of efflux pumps, target protection, target overproduction, and many other ways. The shortage of new antimicrobials and rapid rise in antibiotic resistance demands pressing need to develop alternate antibacterial agents.

A New Era of Antibiotics: The Clinical Potential of Antimicrobial Peptides

Antimicrobial resistance is a multifaceted crisis, imposing a serious threat to global health. The traditional antibiotic pipeline has been exhausted, prompting research into alternate antimicrobial strategies. Inspired by nature, antimicrobial peptides are rapidly gaining attention for their clinical potential as they present distinct advantages over traditional antibiotics. Antimicrobial peptides are found in all forms of life and demonstrate a pivotal role in the innate immune system. Many antimicrobial peptides are evolutionarily conserved, with limited propensity for resistance. Additionally, chemical modifications to the peptide backbone can be used to improve biological activity and stability and reduce toxicity. This review details the therapeutic potential of peptide-based antimicrobials, as well as the challenges needed to overcome in order for clinical translation. We explore the proposed mechanisms of activity, design of synthetic biomimics, and how this novel class of antimicrobial compound may address the need for effective antibiotics. Finally, we discuss commercially available peptide-based antimicrobials and antimicrobial peptides in clinical trials.

Family livestock waste: An ignored pollutant resource of antibiotic resistance genes

The random discharge of livestock waste from family farms without utilization and treatment has caused great pressure on the rural ecological environment and gravely increased the environmental pollution. In this study, we targeted 26 family livestock farms to assess the occurrence characteristics of antibiotic resistance genes (ARGs) in livestock waste and its receiving farmland environment in Erhai Lake basin of China by real-time fluorescence quantitative PCR. The results showed that various common ARGs and some high-risk ARGs (i.e., bla_ampC, bla_OXA-1 and bla_TEM-1) were prevalent in family livestock waste, and the pollution of tetracycline resistance genes was the most serious in these family livestock farms. Meanwhile, we also found that the ARG levels were higher in family chicken farms than that in pig and cattle farms, and ARGs pollution in layer waste and sow waste was more severe than that in broiler waste and piglet/fattening pig waste, respectively. Troublesomely, significant ARGs levels could be discharged via manure application, further causing the increase of ARGs abundance in soil environment (approximately 11-36 times). This study demonstrated the high prevalence and severity of ARGs contamination in family livestock farms, also emphasizing that family livestock waste was a non-ignored important pollutant resource of ARGs in the environment.

Mini Review on Antimicrobial Peptides, Sources, Mechanism and Recent Applications

Antimicrobial peptides in recent years have gained increased interest among scientists, health professionals and the pharmaceutical companies owing to their therapeutic potential. These are low molecular weight proteins with broad range antimicrobial and immuno modulatory activities against infectious bacteria (Gram positive and Gram negative), viruses and fungi. Inability of micro-organisms to develop resistance against most of the antimicrobial peptide has made them as an efficient product which can greatly impact the new era of antimicrobials. In addition to this these peptides also demonstrates increased efficacy, high specificity, decreased drug interaction, low toxicity, biological diversity and direct attacking properties. Pharmaceutical industries are therefore conducting appropriate clinical trials to develop these peptides as potential therapeutic drugs. More than 60 peptide drugs have already reached the market and several hundreds of novel therapeutic peptides are in preclinical and clinical development. Rational designing can be used further to modify the chemical and physical properties of existing peptides. This mini review will discuss the sources, mechanism and recent therapeutic applications of antimicrobial peptides in treatment of infectious diseases.

Targeted and MMP-2/9 responsive peptides for the treatment of rheumatoid arthritis

Bioactive peptides are attractive candidates for drug development. QAW is a tripeptide that is obtained from an anti-inflammatory protein-Annexin A1 (ANXA1). Previous studies showed that QAW alleviated inflammation in experimental colitis and inflammatory bowel disease via NF-κB inhibition. This study establishes adjuvant-induced arthritis (AIA) mouse models and explores the anti-inflammatory efficacy of QAW in AIA mice. To enhance the targeting, responsiveness, and efficacy of QAW to inflammation, QAW (Q) is modified with a cell penetrating peptide (T), a matrix metalloproteases-2/9 (MMP-2/9) digestive peptide (M), and an inflammation targeting peptide-RGD (R). The designed RMTQ demonstrates enhanced delivery to cytoplasm, higher reduction of pro-inflammatory factors, and better efficacy than QAW. The anti-inflammatory efficacy of RMTQ is similar to that of DEX in this study whereas RMTQ treatment shows a higher safety than that of DEX. In sum, this study demonstrates that RMTQ can be a potential therapeutic for inflammatory arthritis.

Broad-spectrum Antimicrobial Activity of Purified Hemocyanin Subunit IIIA Isolated from Asian Horseshoe Crab, Tachypleus gigas

BACKGROUND AND OBJECTIVES

Hemocyanin Subunit IIIA is believed to possess antimicrobial properties, but its efficacy against microbial pathogens is still unclarified. Thus, this study aimed to determine antimicrobial activities of hemocyanin subunit IIIA and to identify the best activator of this protein.

MATERIALS AND METHODS

The hemocyanin was partially purified using spin column affinity, its fraction was applied to Hi-Prep Sephacryl Exclusion 26/60 2-200 HR column, followed by Hi-Prep 26/10 Desalting Column on fast protein liquid chromatography. The purity of hemocyanin was validated by Matrix Assisted Laser Desorption Ionization-Time of Flight/Mass Spectrometry. The antimicrobial activity was performed by Disc Diffusion Test.

RESULTS

Purified hemocyanin subunit IIIA was identified to have a molecular weight of 72.9 kDa. SDS was found to be the best activator of hemocyanin, as indicated by elevated level of phenoloxidase. As for antimicrobial activity, hemocyanin was minimally inhibited by all bacteria strains tested (Escherichia coli, Staphylococcus aureus and Klebsiella pneumoniae), with relatively lower Minimum Inhibitory Concentration (MIC) at 0.005 g mL-1, than recorded MIC for fungal test strains. Two fungal strains (Penicillium sp. and A. niger) show susceptible response to phenoloxidase using MgSO4 as inducer. Whereas, lysate-treated CaCl2 induced susceptibility only to A. niger.

CONCLUSION

Hemocyanin shows better antimicrobial activity than phenoloxidase because of its broad-spectrum activity against bacterial and fungal strains tested. Hence, the hemocyanin may potentially become a new antimicrobial candidate to be discovered for a future use in treatment of resistant bacteria.