Use Of Antimicrobial Peptides Research Articles

Antibacterial activity of a short de novo designed peptide against fish bacterial pathogens

In the face of increasing antimicrobial resistance in aquaculture, researchers are exploring novel substitutes to customary antibiotics. One potential solution is the use of antimicrobial peptides (AMPs). We aimed to design and evaluate a novel, short, and compositionally simple AMP with potent activity against various bacterial pathogens in aquaculture. The resulting peptide, KK12YW, has an amphipathic nature and net charge of + 7. Molecular docking experiments disclosed that KK12YW has a strong affinity for aerolysin, a virulence protein produced by the bacterial pathogen Aeromonas sobria. KK12YW was synthesized using Fmoc chemistry and tested against a range of bacterial pathogens, including A. sobria, A. salmonicida, A. hydrophila, Edwardsiella tarda, Vibrio parahaemolyticus, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus epidermidis, and methicillin-resistant S. aureus. The AMP showed promising antibacterial activity, with MIC and MBC values ranging from 0.89 to 917.1 µgmL−1 and 3.67 to 1100.52 µgmL−1, respectively. In addition, KK12YW exhibited resistance to high temperatures and remained effective even in the presence of serum and salt, indicating its stability. The peptide also demonstrated minimal hemolysis toward fish RBCs, even at higher concentrations. Taken together, these findings indicate that KK12YW could be a highly promising and viable substitute for conventional antibiotics to combat microbial infections in aquaculture.

Immobilised antimicrobial peptides in downregulation of biofilm.

Colonisation of sessile bacterial species on biotic and abiotic surfaces is responsible for the development of various infections in humans. At present, biofilm-associated chronic infections have been a prime concern among the healthcare practitioners since they are impermeable to drugs, resulting in the development of antibiotic resistance or multi-drug resistance. For a few decades, a lot of research activity has been performed in the development of alternative therapeutics to combat biofilm-associated chronic infections. The presence of extracellular polymeric substance (EPS) prevents the permeation of most of the drugs rendering drug failures. The use of small molecules has been necessary to penetrate easily through the EPS and act on the targeted cells. In present days, the use of antimicrobial peptides (AMPs) has gained immense importance as alternative therapeutics since they exhibit a novel class of antibiotics exhibiting a wide spectrum of activity and possess a low rate of development of resistance. In the last few decades, a large number of AMPs have been identified from varied groups of organisms as effector molecules for innate immune system acting as an important line of defence. In this review, we will discuss the use of AMPs as effective agents to combat various biofilm-associated chronic infections.

In Silico Prediction and Molecular Simulation of Antimicrobial Peptide Variants From Lactobacillus sp. Against Porphyromonas gingivalis and Fusobacterium nucleatum in Oral Squamous Cell Carcinoma

ABSTRACTPorphyromonas gingivalis and Fusobacterium nucleatum are known to contribute to a variety of tumorigenic pathways linked to the progression of oral squamous cell carcinoma (OSCC). The growing global incidence of antibiotic resistance highlights the critical need to consider the use of antimicrobial peptides (AMPs) as a viable alternative to conventional antibiotics. The current study comprehensively tested Lactobacillus sp.−derived AMPs against bacterially exacerbated OSCC. A total of 52 AMPs were obtained from various databases, and an in silico analysis determined their potent antibacterial and anticancer characteristics after a rigorous screening and pruning approach. Twelve AMPs were tested for 3D structural alignment prediction and validation, with the GH12 synthetic AMP serving as a control. These candidate peptides were thoroughly screened against six important virulence proteins of P. gingivalis and four of F. nucleatum, with the lowest energy score of the docked complexes measuring binding affinity and interactions with active residues being chosen. plpl_18 was determined as the most efficient new AMP that interacted with the virulence protein RagB of P. gingivalis and Fap2 of F. nucleatum with docking scores of −238.24 and −254.27 kcal/mol, respectively. This AMP plpl_18 was docked against selective target OSCC regulatory proteins such as cytokines, metallomatrix proteinase, MAPK, E‐cadherin, and JAK‐1 proteins. Among these proteins, it docked against matrix metalloproteinase‐9 with the highest negative docking scores of −7.5, −260.956, and −1361.9 kcal/mol using AutoDock Vina, HPEPDOCK, and ClusPro 2.0, respectively. Molecular dynamic simulation was used to perform extrapolated validation. These computational studies provide an essential foundation for anticipated laboratory and clinical investigations concerning the possibility of adapting therapeutic peptides based on probiotics to combat the proliferation of OSCC, which is accelerated by F. nucleatum and P. gingivalis.

Effect of tryptophan position and lysine/arginine substitution in antimicrobial peptides on antifungal action

Every year, the overprescription, misuse, and improper disposal of antibiotics have led to the rampant development of drug-resistant pathogens and, in turn, a significant increase in the number of patients who die of drug-resistant fungal infections. Recently, researchers have begun investigating the use of antimicrobial peptides (AMPs) as next-generation antifungal agents to inhibit the growth of drug-resistant fungi. The antifungal activity of alpha-helical peptides designed using the cationic amino acids containing lysine and arginine and the hydrophobic amino acids containing isoleucine and tryptophan were evaluated using 10 yeast and mold fungi. Among these peptides, WIK-14, which is composed of a 14-mer with tryptophan sequences at the amino terminus, showed the best antifungal activity via transient pore formation and ROS generation. In addition, the in vivo antifungal effects of WIK-14 were investigated in a mouse model infected with drug-resistant Candida albicans. The results demonstrate the potential of AMPs as antifungal agents.

Treatment and Management of Acinetobacter Pneumonia: Lessons Learned from Recent World Event.

Acinetobacter pneumonia is a significant healthcare-associated infection that poses a considerable challenge to clinicians due to its multidrug-resistant nature. Recent world events, such as the COVID-19 pandemic, have highlighted the need for effective treatment and management strategies for Acinetobacter pneumonia. In this review, we discuss lessons learned from recent world events, particularly the COVID-19 pandemic, in the context of the treatment and management of Acinetobacter pneumonia. We performed an extensive literature review to uncover studies and information pertinent to the topic. The COVID-19 pandemic underscored the importance of infection control measures in healthcare settings, including proper hand hygiene, isolation protocols, and personal protective equipment use, to prevent the spread of multidrug-resistant pathogens like Acinetobacter. Additionally, the pandemic highlighted the crucial role of antimicrobial stewardship programs in optimizing antibiotic use and curbing the emergence of resistance. Advances in diagnostic techniques, such as rapid molecular testing, have also proven valuable in identifying Acinetobacter infections promptly. Furthermore, due to the limited availability of antibiotics for treating infections caused A. baumannii, alternative strategies are needed like the use of antimicrobial peptides, bacteriophages and their enzymes, nanoparticles, photodynamic and chelate therapy. Recent world events, particularly the COVID-19 pandemic, have provided valuable insights into the treatment and management of Acinetobacter pneumonia. These lessons emphasize the significance of infection control, antimicrobial stewardship, and early diagnostics in combating this challenging infection.

Managing Helicobacter pylori infection: transitioning from conventional to alternative treatment approaches

Helicobacter pylori, an essential constituent of the gastric microbiome in those infected, is commonly associated with medical conditions such as chronic gastritis, peptic ulcer disease, and gastric cancer. In recent years, the growing resistance to antibiotics worldwide has emerged as a substantial hurdle in the effective treatment of H. pylori infection. Consequently, it has necessitated the exploration of innovative treatment strategies aimed at bolstering the potency of existing antibiotic-based eradication therapies. Such avant-garde strategies include the incorporation of probiotics and prebiotics as complementary measures to H. pylori treatment, the use of antimicrobial peptides as potential replacements for traditional antibiotics, and the application of photodynamic therapy via ingestible devices. Other advanced methodologies entail deploying drug delivery systems that utilize microparticles and nanoparticles, the invention of vaccines, the exploration of natural products, and the potential use of phage therapy. This review offers a contemporary synopsis of these burgeoning strategies designed to suppress H. pylori, delving into their strengths, hurdles, and aspects to consider during their development. A significant achievement would be the creation of an efficient human vaccine; however, previous attempts at developing such vaccines have met with obstacles or even cessation. Numerous natural products have displayed anti-H. pylori properties, predominantly in laboratory environments. Nonetheless, a requirement remains for more extensive clinical studies to fully comprehend their role in exterminating H. pylori. Finally, phage therapy, while demonstrating potential as a suitable alternative, grapples with considerable challenges, chiefly the isolation of highly virulent bacteriophages that specifically target H. pylori.

Recalculating the Route: Repositioning Antimicrobial Peptides for Cancer Treatment.

Resistance to antimicrobial drugs has been considered a public health problem. Likewise, the increasing resistance of cancer cells to drugs currently used in therapy has also become a problem. Therefore, the research and development of synthetic peptides bring a new perspective on the emergence of new drugs for treating this resistance since bioinformatics provides a means to optimize these molecules and save time and costs in research. Peptides have several mechanisms of action, such as forming pores on the cell membrane and inhibiting protein synthesis. Some studies report the use of antimicrobial peptides with the potential for action against cancer cells, suggesting a repositioning of antimicrobial peptides to fight back cancer resistance. There is an alteration in the microenvironment, making its net charge negative for the survival and growth of cancer cells. The changes in glycoproteins favor the membrane to have a more negative charge, favoring the interaction between the cells and the peptide, thus making possible the repositioning of these antimicrobial peptides against cancer. Here, we will discuss the mechanism of action, targets and effects of peptides, comparison between microbial and cancer cells, and proteomic changes caused by the interaction of peptides and cells.

Antimicrobial peptide LL-37 disrupts plasma membrane and calcium homeostasis in Candida albicans via the Rim101 pathway.

Antimicrobial peptides play an important role in human innate defense against microbial pathogens. LL-37 is the only member of the human cathelicidin family of antimicrobial peptides. We previously showed that LL-37 targets the cell wall of Candida albicans, thereby reducing cell adhesion to plastic surfaces, oral epidermoid cells, and urinary bladders of mice. Moreover, LL-37 also induces cell wall and endoplasmic reticulum stress responses. Here, we found that LL-37 alters plasma membrane properties. In addition, LL-37 affected calcium homeostasis and induced the generation of reactive oxygen species associated with mitochondria and vacuoles. Finally, the Rim101 pathway was linked to the cellular response to LL-37. Together, these findings provide new insights into anti-C. albicans actions of LL-37 and highlight the complex cellular responses induced by LL-37.IMPORTANCECandida albicans is a major human fungal pathogen, and antimicrobial peptides are key components of innate immunity. Studying the interplay between C. albicans and human antimicrobial peptides would enhance a better understanding of pathogen-host interactions. Moreover, potential applications of antimicrobial peptides in antifungal therapy have aroused great interest. This work explores new mechanisms of LL-37 against C. albicans and reveals the complex connection among calcium homeostasis, oxidative stress, signaling, and possibly organelle interaction. Notably, these findings support the possible use of antimicrobial peptides to prevent and treat fungal infections.

Impact of C- and N-terminal protection on the stability, metal chelation and antimicrobial properties of calcitermin

The main limitation to the use of antimicrobial peptides (AMPs) as regular drugs, against antibiotic and antifungal resistance, mainly relates to their rapid degradation by proteolytic enzymes. The introduction of suitable structural changes in the peptide chain can make the peptide less susceptible to the action of proteases, thus overcoming this problem. To improve the plasma stability of calcitermin, a metal-chelating AMP present in the human respiratory tract and investigated in the present study, C- and/or N- terminal modifications have been introduced in the native sequence. Evaluation of peptide stability has been performed to determine the half-life times in human plasma of both native calcitermin and its derivatives. However, the protection of the peptide termini can also affect its metal coordination behaviour. Thus, the characterization of Zn2+ and Cu2+ complexes has been performed by means of several techniques, including potentiometry, high-resolution mass spectrometry, UV–Vis, circular dichroism and EPR. On the basis of the obtained results, it was possible to compare the biological activity of the studied systems, taking into account both the metal-binding ability and the peptide stability to search for a link among them. A significant result of this study is that the N-terminal protection increases the calcitermin half-life over seven times and the formation of metal complexes confers resistance towards degradation almost doubling its half-life.

Marine Invertebrate Antimicrobial Peptides and Their Potential as Novel Peptide Antibiotics.

Marine invertebrates constantly interact with a wide range of microorganisms in their aquatic environment and possess an effective defense system that has enabled their existence for millions of years. Their lack of acquired immunity sets marine invertebrates apart from other marine animals. Invertebrates could rely on their innate immunity, providing the first line of defense, survival, and thriving. The innate immune system of marine invertebrates includes various biologically active compounds, and specifically, antimicrobial peptides. Nowadays, there is a revive of interest in these peptides due to the urgent need to discover novel drugs against antibiotic-resistant bacterial strains, a pressing global concern in modern healthcare. Modern technologies offer extensive possibilities for the development of innovative drugs based on these compounds, which can act against bacteria, fungi, protozoa, and viruses. This review focuses on structural peculiarities, biological functions, gene expression, biosynthesis, mechanisms of antimicrobial action, regulatory activities, and prospects for the therapeutic use of antimicrobial peptides derived from marine invertebrates.

Are Antimicrobial Peptides a 21st-Century Solution for Atopic Dermatitis?

Atopic dermatitis (AD) is a chronic inflammatory skin disorder that is the result of various environmental, bacterial and genetic stimuli, which culminate in the disruption of the skin's barrier function. Characterized by highly pruritic skin lesions, xerosis and an array of comorbidities among which skin infections are the most common, this condition results in both a significant loss of quality of life and in the need for life-long treatments (e.g., corticosteroids, monoclonal antibodies and regular antibiotic intake), all of which may have harmful secondary effects. This, in conjunction with AD's rising prevalence, made the development of alternative treatment strategies the focus of both the scientific community and the pharmaceutical industry. Given their potential to both manage the skin microbiome, fight infections and even modulate the local immune response, the use of antimicrobial peptides (AMPs) from more diverse origins has become one of the most promising alternative solutions for AD management, with some being already used with some success towards this end. However, their production and use also exhibit some limitations. The current work seeks to compile the available information and provide a better understanding of the state of the art in the understanding of AMPs' true potential in addressing AD.

Immunomodulation, Bioavailability and Safety of Bacteriocins.

The rise of antibiotic-resistant bacteria and the emergence of new pathogens have created a need for new strategies to fight against infectious diseases. One promising approach is the use of antimicrobial peptides produced by a certain species of bacteria, known as bacteriocins, which are active against other strains of the same or related species. Bacteriocins can help in the treatment and prevention of infectious diseases. Moreover, bacteriocins can be obtained in prokaryotic organisms, and contribute s to their widespread use. While the use of bacteriocins is currently limited to the food industry (for example, nisin is used as a preservative, E234), a large number of studies on their microbicidal properties suggest that their use in medicine may increase in the foreseeable future. However, for the successful use of bacteriocins in medicine, it is necessary to understand their effect on the immune system, especially in cases where immunity is weakened due to infectious processes, oncological, allergic, or autoimmune diseases. Studies on the immuno-modulatory activity of bacteriocins in animal models and human cells have revealed their ability to induce both pro-inflammatory and anti-inflammatory factors involved in the implementation of innate immunity. The influence of bacteriocins on acquired immunity is revealed by an increase in the number of T-lymphocytes with a simultaneous decrease in B-lymphocyte levels, which makes them attractive substances for reducing inflammation. The widespread use of bacteriocins in the food industry, their low toxicity, and their broad and narrow specificity are reasons for researchers to pay attention to their immunomodulatory properties and explore their medical applications. Inflammation regulation by bacteriocins can be used in the treatment of various pathologies. The aim of the review was to analyze scientific publications on the immunomodulatory activity, bioavailability, and safety of bacteriocins in order to use the data obtained to organize preclinical and clinical studies.

Two novel antimicrobial peptides against vegetative cells, spores and biofilm of Bacillus cereus

Bacillus cereus is a ubiquitous bacterium that causes food-associated gastrointestinal diseases. The ability to form spores and biofilm makes this bacterium highly resistant to antimicrobial agents and food preservatives, posing persistent risks to consumers and the food industry. The excessive use of antibiotics and chemical preservatives has led to the emergence of resistant B. cereus strains, impacting the safety of food. Therefore, there is demand for new antimicrobial agents to combat B. cereus. The use of antimicrobial peptides (AMPs) for food preservation has attracted attention because they can preserve food quality with low possibility of bacteria acquiring resistance. In this research, a series of peptide derivatives based on the previously reported peptide D51 (sequence FLFRVASKVFPALIGKFKKK) was designed and synthesized. Two of the peptides, D51-P11G and D51-P11K, exhibited satisfactory antimicrobial (MICs: 8 μg/mL) activities toward B. cereus, including diarrheal and emetic reference strains. Peptides D51-P11G and D51-P11K showed good physiological stability, high safety and a low tendency to induce bacterial resistance. Meanwhile, at 16 μg/mL, D51-P11G and D51-P11K could inhibit spore germination and biofilm formation. Studies of the antibacterial mechanism suggested that D51-P11G and D51-P11K exert their antibacterial activities mainly via a membrane-lytic mechanism, but they also bound to genome DNA of the bacteria. Notably, D51-P11G and D51-P11K (32 μg/mL) could control the growth of B. cereus in boiled rice and minced meat, the antimicrobial activities were almost the same as or even better than nisin A (300 μg/mL). These findings suggest that D51-P11G and D51-P11K are ideal candidates for application against vegetative cells, spores, and biofilm of B. cereus.

Antimicrobial Peptide Nanoparticle-Based Microneedle Patches for the Treatment of Bacteria-Infected Wounds

To avoid the production of drug resistance during the antibiotic treatment of wound infection, the use of antimicrobial peptides (AMPs) has been strongly developed. However, its application is limited by low bioavailability, rapid degradation of AMP, and the difficulty of deep-tissue bacterial elimination. To solve this problem, AMP and recombinant type III humanized collagen (Col III)-contained microneedle patches were designed to achieve slow and controlled release of AMP and Col III to effectively eliminate the bacteria in the deep wound tissue and promote wound healing. AMP (KKLRLKIAFK) coupled with Cy3 was encapsulated in the nanogel (CGA-NPs), which was formed by chitosan (CS) and gum arabic (GA) through electrostatic interactions. Microneedle (MN) patches were dissolved after penetrating the infected skin and biofilm formed by Staphylococcus aureus to release CGA-NPs. AMPs was released responding to the infected microenvironment to efficiently kill bacteria, and Col III was beneficial to promote wound healing. This is a strategy for the design and application of a microneedle-based antimicrobial drug delivery system.

Combined Use of Antimicrobial Peptides with Antiseptics against Multidrug-Resistant Bacteria: Pros and Cons.

Antimicrobial peptides (AMPs) are acknowledged as a promising template for designing new antimicrobials. At the same time, existing toxicity issues and limitations in their pharmacokinetics make topical application one of the less complicated routes to put AMPs-based therapeutics into actual medical practice. Antiseptics are one of the common components for topical treatment potent against antibiotic-resistant pathogens but often with toxicity limitations of their own. Thus, the interaction of AMPs and antiseptics is an interesting topic that is also less explored than combined action of AMPs and antibiotics. Herein, we analyzed antibacterial, antibiofilm, and cytotoxic activity of combinations of both membranolytic and non-membranolytic AMPs with a number of antiseptic agents. Fractional concentration indices were used as a measure of possible effective concentration reduction achievable due to combined application. Cases of both synergistic and antagonistic interaction with certain antiseptics and surfactants were identified, and trends in the occurrence of these types of interaction were discussed. The data may be of use for AMP-based drug development and suggest that the topic requires further attention for successfully integrating AMPs-based products in the context of complex treatment. AMP/antiseptic combinations show promise for creating topical formulations with improved activity, lowered toxicity, and, presumably, decreased chances of inducing bacterial resistance. However, careful assessment is required to avoid AMP neutralization by certain antiseptic classes in either complex drug design or AMP application alongside other therapeutics/care products.

The Resilience of Pseudomonas aeruginosa to Antibiotics and the Designing of Antimicrobial Peptides to Overcome Microbial Resistance.

Pseudomonas aeruginosa (P. aeruginosa) is a bacterium of medical concern known for its potential to persist in diverse environments due to its metabolic capacity. Its survival ability is linked to its relatively large genome of 5.5-7 Mbp, from which several genes are employed in overcoming conventional antibiotic treatments and promoting resistance. The worldwide prevalence of antibiotic-resistant clones of P. aeruginosa necessitates novel approaches to researching their multiple resistance mechanisms, such as the use of antimicrobial peptides (AMPs). In this review, we briefly discuss the epidemiology of the resistant strains of P. aeruginosa and then describe their resistance mechanisms. Next, we explain the biology of AMPs, enlist the present database platforms that describe AMPs, and discuss their usefulness and limitations in treating P. aeruginosa strains. Finally, we present 13 AMPs with theoretical action against P. aeruginosa, all of which we evaluated in silico in this work. Our results suggest that the AMPs we evaluated have a carpet-like mode of action with a membranolytic function in Gram-positive and Gramnegative bacteria, with a clear potential of synthesis for in vitro evaluation.

Nanoparticles associated with antimicrobial peptides (AMPs)  promising combination for biomedical and veterinary applications

Bacterial resistance to classical antibiotics is a growing concern, and scientists are seeking alternative methods to combat bacterial infections. One promising option is the use of antimicrobial peptides (AMPs) with strong antibacterial activity provided with diverse mechanisms, including membrane disruption, intracellular interference, and inhibition of bacterial metabolic processes. They can also modulate inflammation, enhancing antimicrobial effects. Compared to antibiotics, AMPs can have a broader range of activity and are less prone to bacterial resistance. However, their use has limitations, such as a short half-life and proteolytic degradation. To address these challenges, researchers are developing strategies to enhance the stability and efficacy of AMPs, including the use of nanocarriers. Nanocarriers, such as inorganic particles, liposomes, polymeric particles, cubosomes, and quantum dots can improve the stability of AMPs, protect them from degradation, enhance their penetration into bacterial cells, and increase their antibacterial activity. Nanocarriers can also boost AMPs absorption by bacteria and stimulate their enzymatic function. While nanocarriers show promise in enhancing AMPs efficacy and stability, further research is necessary to determine their safety and effectiveness in practical medical applications. This review offers a succinct exploration of specific nanoparticles, their function as carriers for AMPs, and their potential significance in both medical and veterinary contexts.

Chitosan and HPMCAS double-coating as protective systems for alginate microparticles loaded with Ctx(Ile21)-Ha antimicrobial peptide to prevent intestinal infections

The incorrect use of conventional drugs for both prevention and control of intestinal infections has contributed to a significant spread of bacterial resistance. In this way, studies that promote their replacement are a priority. In the last decade, the use of antimicrobial peptides (AMP), especially Ctx(Ile21)-Ha AMP, has gained strength, demonstrating efficient antimicrobial activity (AA) against pathogens, including multidrug-resistant bacteria. However, gastrointestinal degradation does not allow its direct oral application. In this research, double-coating systems using alginate microparticles loaded with Ctx(Ile21)-Ha peptide were designed, and in vitro release assays simulating the gastrointestinal tract were evaluated. Also, the AA against Salmonella spp. and Escherichia coli was examined. The results showed the physicochemical stability of Ctx(Ile21)-Ha peptide in the system and its potent antimicrobial activity. In addition, the combination of HPMCAS and chitosan as a gastric protection system can be promising for peptide carriers or other low pH-sensitive molecules, adequately released in the intestine. In conclusion, the coated systems employed in this study can improve the formulation of new foods or biopharmaceutical products for specific application against intestinal pathogens in animal production or, possibly, in the near future, in human health.

Therapeutic potential of antimicrobial peptides for treatment of wound infection.

Healing of cutaneous wounds is a fundamental process required to re-establish tissue integrity, repair skin barrier function, and restore skin homeostasis. Chronic wound infection, exacerbated by the growing development of resistance to conventional therapies, hinders the skin repair process and is a serious clinical problem affecting millions of people worldwide. In the past decade, the use of antimicrobial peptides (AMPs) has attracted increasing attention as a potential novel strategy for the treatment of chronic wound infections due to their unique multifaceted mechanisms of action, and AMPs have been demonstrated to function as potent host-defense molecules that can control microbial proliferation, modulate host-immune responses, and act as endogenous mediators of wound healing. To date over 3,200 AMPs have been discovered either from living organisms or through synthetic derivation, some of which have progressed to clinical trials for the treatment of burn and wound injuries. However, progress to routine clinical use has been hindered due to AMPs' susceptibility to wound and environmental factors including changes in pH, proteolysis, hydrolysis, oxidation, and photolysis. This review will discuss the latest research focused on the development and applications of AMPs for wound infections using the latest nanotechnological approaches to improve AMP delivery, and stability to present effective combinatorial treatment for clinical applications.

Evaluation of the Bactericidal Activity of Gramicidin S Against <i>Streptococcus pneumoniae</i> and <i>Staphylococcus aureus</i> Clinical Isolates with Single and Multiple Exposure

Background . Sore throat of infectious and inflammatory origin is one of the most common reasons for the prescription of antimicrobial drugs. The use of antimicrobial peptides (AMPs) for topical therapy may be a promising solution, due to the peculiarities of AMPs’ mechanism of action, taking into account the high importance of microbial resistance spread problem in relation to systemic etiotropic drugs. The aim of the study was to assess the formation of resistance to AMP Gramicidin S (GS) of clinical isolates of Streptococcus pneumoniae and Staphylococcus aureus , including strains resistant to antimicrobial drugs during repeated exposure, in the setting close to their actual use in clinical practice. Materials and methods . The object under study is AMP GS. The test microorganisms are reference strains of S.pneumoniae (ATCC 6303), S.aureus (ATCC 6538–P), and 10 strains of clinical isolates of each type of microorganisms, types with antimicrobial resistance (including MRSA). At the first stage, the antimicrobial activity of GS was evaluated by the method of microdilutions in plates by estimating the value of the minimum inhibitory and the minimum bactericidal concentrations (MIC and MBC, respectively). At the second stage, using reference strains and 4 clinical isolates of each microorganism, including types with antimicrobial resistance, resistance was formed in two ways simultaneously (with liquid and solid media) for 7 consecutive passages over 7 days with GS at concentrations equal to 0.5 and 1.0 MIC. The number of surviving microorganisms was estimated and the MIC and MBC were determined at each passage. Results . At the first stage, the MIC of GS in relation to S.pneumoniae was 8 µg/ml for 5 strains, 16 µg/ml for 5 strains, and 4 µg/ml for one. For 10 out of 11 strains of S.aureus , including MRSA, the MIC of GS was 4 µg/ml (for 1 strain — 8 µg/ml). For 4 strains of S.pneumoniae , MBC of GS was equal to MIC (16 µg/ml), for 7 strains MBC was 4–8 times higher than MIC, and mostly amounted to 32 µg/ml (for 1 strain — 64 µg/ml). MBC for 6 strains of S.aureus was equal to MIC (4 µg/ml), for the 5 remaining strains MBC was 2–8 times higher than MIC, but did not exceed 64 µg/ml. At the second stage, it was found that the estimated values of GS MIC and MBC with repeated exposure to GS remained at the same level for 7 passages in all strains, including those resistant to antibiotics in liquid and solid media. Conclusions . Gramicidin S demonstrated high bactericidal activity against reference strains and clinical isolates of leading pathogenic microorganisms S.pneumoniae and S.aureus , including strains resistant to systemic antimicrobial drugs, while MIC and MBC did not exceed concentrations contained in single doses of drugs used in clinical practice. During repeated exposure (7 passages in 7 days), there were no signs of the formation of resistance of test strains of pathogens, including those resistant to systemic antimicrobial medicines from the groups of beta-lactams, macrolides, fluoroquinolones, tetracyclines, aminoglycosides, etc.