In vitro activity and killing effect of uperin 3.6 against gram-positive cocci isolated from immunocompromised patients

The sources of antimicrobial peptides against Gram-positives and Gramnegatives: our research experience

Antibiotic resistance of Gram-positive and Gramnegative bacteria is becoming increasingly prevalent. For this reason, the search for new molecules that can overcome current resistance and also recover antibiotics that are no longer effective is becoming increasingly urgent. Our research group at the 'Polytechnic University of Marche' managed to study the effectiveness of certain antimicrobial peptides (AMPs). We decided to review our experience with AMPs by classifying them according to their origin and evaluating their effect on Gram-negative and Gram-positive bacteria. AMPs can derive from mammals, amphibians, microorganisms, and insects. In conclusion, our research experience shows that the richest source of AMPs are amphibians. However, the studies done are mainly in vitro or in animal models, requiring further human studies to assess the efficacy and safety of these molecules. AMPs may be a new therapeutic option for infections sustained by multi-resistant micro-organisms and for overcoming the mechanisms of resistance to antibiotics currently used. In particular, combining AMPs with antibiotics, including those with limited antimicrobial activity due to antimicrobial resistance, has often shown a synergistic effect, increasing or restoring their efficacy. The possibility of using manageable and relatively safe antibiotics again is crucial, considering the widespread increase in bacterial resistance in hospitals and the community. Despite a plethora of research on AMPs and their application as potential treatment on infectious diseases, this area needs further exploration. There is evidence that the characteristics of AMPs can seriously improve through structural chemical modifications and different delivery systems to become alternatives drugs to conventional antibiotics. The aim is to provide an overview of the possible sources from which AMPs are extracted, evaluating their action exclusively on Gram-positive and negative bacteria. This is to determine, based on our experience, which might be the most promising sources of AMPs for future research as well.

Our Experience over 20 Years: Antimicrobial Peptides against Gram Positives, Gram Negatives, and Fungi

Antibiotic resistance is rapidly increasing, and new anti-infective therapies are urgently needed. In this regard, antimicrobial peptides (AMPs) may represent potential candidates for the treatment of infections caused by multiresistant microorganisms. In this narrative review, we reported the experience of our research group over 20 years. We described the AMPs we evaluated against Gram-positive, Gram-negative, and fungi. In conclusion, our experience shows that AMPs can be a key option for treating multiresistant infections and overcoming resistance mechanisms. The combination of AMPs allows antibiotics and antifungals that are no longer effective to exploit the synergistic effect by restoring their efficacy. A current limitation includes poor data on human patients, the cost of some AMPs, and their safety, which is why studies on humans are needed as soon as possible.

In Vitro Efficiency of Antimicrobial Peptides against Staphylococcal Pathogens Associated with Canine Pyoderma

Simple Summary

Coagulase-positive staphylococci (CoPS) are predominant pathogens in canine pyoderma, especially S. pseudintermedius and S. aureus. The antimicrobial resistance of CoPS has a key role in the management of canine skin infections. The vast majority of those diseases have a chronic character with a tendency to recur, which is reflected by recurrent systemic antibiotic therapy, associated with an alarming increase in the proportion of antibiotic-resistant staphylococci. Antimicrobial peptides (AMPs) seem to be a promising alternative to conventional antibiotics. The aim of this in vitro study was to evaluate the antimicrobial activity of selected AMPs against pathogenic staphylococcal strains, including multidrug- and methicillin-resistant strains isolated from canine pyoderma cases. The tested AMPs were shown to be equally efficient antimicrobial agents against resistant- and susceptible pathogenic staphylococcal strains associated with canine pyoderma. AMPs were more efficient against S. pseudintermedius than against S. aureus strains. Our findings seem to be particularly interesting from a clinical perspective, as a starting point from which to perform in vivo experiments to estimate the usefulness of these peptides as topical drug molecules for the treatment of canine pyoderma.

Abstract

The emergence of staphylococcal canine pathogens resistant to multiple antimicrobial agents is a growing and urgent problem in veterinary practice. Antimicrobial peptides (AMPs) seem to be a promising alternative to conventional antibiotics. The aim of this in vitro study was to evaluate the antimicrobial activity of selected AMPs against pathogenic staphylococcal strains, including multidrug- and methicillin-resistant strains isolated from canine pyoderma cases. Seven antimicrobial peptides (aurein 1.2, CAMEL, citropin 1.1, protegrin-1, pexiganan, temporin A and uperin 3.6) synthesized by the 9-fluorenylmethoxycarbonyl (Fmoc) solid-phase method were tested. The minimal inhibitory and minimal bactericidal concentrations (MIC and MBC) were determined by the broth microdilution method. The study showed that analyzed AMPs exerted an extensive effect against canine pathogens, with the most active peptide being uperin 3.6. The tested AMPs were equally efficient against both resistant- and susceptible staphylococcal strains and were more efficient against Staphylococcus pseudintermedius than against Staphylococcus aureus strains. Our findings are particularly interesting from a clinical perspective, as they point to AMPs as potential therapeutic topical agents in canine pyoderma cases associated with antimicrobial resistance of staphylococci.

The Antistaphylococcal Activity of Citropin 1.1 and Temporin A against Planktonic Cells and Biofilms Formed by Isolates from Patients with Atopic Dermatitis: An Assessment of Their Potential to Induce Microbial Resistance Compared to Conventional Antimicrobials

Staphylococcus aureus (SA) colonizes the vast majority of patients with atopic dermatitis (AD). Its resistance to antibiotics and ability to form biofilms are the main origins of therapeutic complications. Endogenous antimicrobial peptides (AMPs) exhibit strong activity against SA, including antibiotic resistant strains as well as bacteria existing in biofilm form. The purpose of the present work was to determine the antistaphylococcal activity of two amphibian peptides against SA isolated from patients with AD. The AMPs demonstrated permanent activity towards strains exposed to sublethal concentrations of the compounds and significantly stronger antibiofilm activity in comparison to that of conventional antimicrobials. The results suggest the potential application of amphibian AMPs as promising antistaphylococcal agents for the management of skin infections.

Host-defense peptides of Australian anurans. Part 2. Structure, activity, mechanism of action, and evolutionary significance

A previous review summarized research prior to 2004 carried out on the bioactive host-defense peptides contained in the skin secretions of Australian anurans (frogs and toads). This review covers the extension of that research from 2004 to 2012, and includes membrane-active peptides (including antibacterial, anticancer, antifungal and antiviral peptides) together with the mechanisms by which these peptides interact with model membranes, peptides that may be classified as "neuropeptides" (including smooth muscle active peptides, opioids and immunomodulators) and peptides which inhibit the formation of nitric oxide from neuronal nitric oxide synthase. The review discusses the outcome of cDNA sequencing of signal-spacer-active peptides from an evolutionary viewpoint, and also lists those peptides for which activities have not been found to this time.

Activity of short lipopeptides and conventional antimicrobials against planktonic cells and biofilms formed by clinical strains of Staphylococcus aureus

Background: The therapy for staphylococcal skin diseases is facing several difficulties caused by the growth of biofilms and development of resistant strains. Short synthetic lipopeptides designed on the basis of antimicrobial peptide structure seem to provide an alternative to conventional therapy. The purpose of this study was to synthesize a group of lipopeptides and evaluate their antistaphylococcal activity against biofilms formed by clinical strains of Staphylococcus aureus. Results: The compounds exhibited a strong antibiofilm activity against all the isolates. The maturity of the biofilms has shown a well-defined influence on antimicrobial activity of conventional antimicrobials. Discussion: Results showed that the lipopeptides were promising agents as the time of the culture did not greatly affect their activity.

In vitro potential of equine DEFA1 and eCATH1 as alternative antimicrobial drugs in rhodococcosis treatment

Rhodococcus equi, the causal agent of rhodococcosis, is a severe pathogen of foals but also of immunodeficient humans, causing bronchopneumonia. The pathogen is often found together with Klebsiella pneumoniae or Streptococcus zooepidemicus in foals. Of great concern is the fact that some R. equi strains are already resistant to commonly used antibiotics. In the present study, we evaluated the in vitro potential of two equine antimicrobial peptides (AMPs), eCATH1 and DEFA1, as new drugs against R. equi and its associated pathogens. The peptides led to growth inhibition and death of R. equi and S. zooepidemicus at low micromolar concentrations. Moreover, eCATH1 was able to inhibit growth of K. pneumoniae. Both peptides caused rapid disruption of the R. equi membrane, leading to cell lysis. Interestingly, eCATH1 had a synergic effect together with rifampin. Furthermore, eCATH1 was not cytotoxic against mammalian cells at bacteriolytic concentrations and maintained its high killing activity even at physiological salt concentrations. Our data suggest that equine AMPs, especially eCATH1, may be promising candidates for alternative drugs to control R. equi in mono- and coinfections.

A biochemical characterization of the major peptides from the Venom of the giant Neotropical hunting ant Dinoponera australis

Venom from the "false tocandira"Dinoponera australis, a giant Neotropical hunting ant, paralyzes small invertebrate prey and induces a myriad of systemic effects in large vertebrates. HPLC/DAD/MS analyses revealed that the venom has over 75 unique proteinaceous components with a large diversity of properties ranging in size, hydrophobicity, and overall abundance. The six most abundant peptides, demonstrative of this diversity and hereafter referred to as Dinoponeratoxins, were de novo sequenced by exact mass precursor ion selection and Edman degradation. The smallest peptide characterized, Da-1039, is hydrophilic and has similarities to vasoactive peptides like kinin and bombesin. The two largest and most abundant peptides, Da-3105 and Da-3177, have a 92.9% identity in a 28 residue overlap and share approximately 50 of their sequence with ponericin G2 (an antimicrobial from another ponerine ant Pachycondyla goeldii). One peptide, Da-1585, is a hydrophilic cleavage product of an amphipathic peptide, Da-2501. The most hydrophobic peptide, Da-1837, is amidated (a PTM observed in one half of the major peptides) and shares homology with poneratoxin, a sodium channel modifier found in the bullet ant Paraponera clavata. This study is the first examination of potential pharmacophores from venom of the genus Dinoponera (Order: Hymenoptera).