Antimicrobial treatment imprecision: an outcome-based model to close the data-to-action loop

Health-care systems, food supply chains, and society in general are threatened by the inexorable rise of antimicrobial resistance. This threat is driven by many factors, one of which is inappropriate antimicrobial treatment. The ability of policy makers and leaders in health care, public health, regulatory agencies, and research and development to deliver frameworks for appropriate, sustainable antimicrobial treatment is hampered by a scarcity of tangible outcome-based measures of the damage it causes. In this Personal View, a mathematically grounded, outcome-based measure of antimicrobial treatment appropriateness, called imprecision, is proposed. We outline a framework for policy makers and health-care leaders to use this metric to deliver more effective antimicrobial stewardship interventions to future patient pathways. This will be achieved using learning antimicrobial systems built on public and practitioner engagement; solid implementation science; advances in artificial intelligence; and changes to regulation, research, and development. The outcomes of this framework would be more ecologically and organisationally sustainable patterns of antimicrobial development, regulation, and prescribing. We discuss practical, ethical, and regulatory considerations involved in the delivery of novel antimicrobial drug development, and policy and patient pathways built on artificial intelligence-augmented measures of antimicrobial treatment imprecision.

Prevalence of multi-antimicrobial resistant non-typhoidal Salmonella isolated from filth flies at wet markets in Klang, Malaysia, and their survival in the simulated gastric fluid

Filth flies at wet markets can be a vector harbouring multiple antimicrobial-resistant (MAR) nontyphoidal Salmonella (NTS), and such strains are a significant threat to public health as they may cause severe infections in humans. This study aims to investigate the prevalence of antimicrobial-resistant NTS, especially Salmonella Enteritidis and S. Typhimurium harboured by filth flies at wet markets, and investigate their survival in the simulated gastric fluid (SGF). Filth flies (n = 90) were captured from wet markets in Klang, Malaysia, and processed to isolate Salmonella spp. The isolates (n = 16) were identified using the multiplex-touchdown PCR and assessed their antimicrobial susceptibility against 11 antimicrobial agents. Finally, three isolates with the highest MAR index were subjected to SGF survival tests. It was observed that 17.8 % of flies (n = 16/90) harbouring Salmonella, out of which 10 % (n = 9/90) was S. Enteritidis, 2.2 % (n = 2/90) was S. Typhimurium, and 5.6 % was unidentified serotypes of Salmonella enterica subsp. I. 43.8 % (n = 7/16) were confirmed as MAR, and they were observed to be resistant against ampicillin, chloramphenicol, kanamycin, streptomycin, and nalidixic acid. Three strains, F35, F75, and F85 demonstrated the highest MAR index and were able to survive (>6-log10) in the SGF (180 min), indicating their potential virulence and invasiveness. This study provides significant insights into the prevalence and severity of MAR nontyphoidal Salmonella harboured by filth flies in wet markets, which may help inform strategies for controlling the spread and outbreak of foodborne disease.

Discovery of Novel Small Molecule Growth Inhibitors to Manage Pseudomonas Leaf Spot Disease on Peppers (Capsicum sp.)

Pseudomonas leaf spot (PLS) disease in peppers caused by Pseudomonas syringae pv. syringae (Pss) is an emerging seedborne phytopathogen. Pss infection can severely reduce the marketable yield of peppers in favorable environmental conditions and cause significant economic losses. The intensive use of copper-sulfate and streptomycin-sulfate to control PLS and other bacterial diseases is associated with antimicrobial-resistant Pss strains, making these control methods less effective. So, there is an urgent need to develop novel antimicrobials effective against Pss in peppers. Several studies, including those done in our laboratory, have shown that small molecule (SM) antimicrobials are ideal candidates as they can be effective against multidrug resistant bacteria. Therefore, our study aims to identify novel SM growth inhibitors of Pss, assess their safety, and evaluate their efficacy on Pss-infected pepper seeds and seedlings. Using high-throughput screening, we identified 10 SMs (PC1 to PC10) that inhibited the growth of Pss strains at 200 µM or lower concentrations. These SMs were effective against both copper- and streptomycin-resistant as well as biofilm-embedded Pss. These SMs were effective against other plant pathogens (n = 22) at low concentrations (<200 μM) and had no impact on beneficial phytobacteria (n = 12). Furthermore, these SMs showed better or equivalent antimicrobial activity against Pss in infested pepper seeds and inoculated seedlings compared with copper-sulfate (200 μM) and streptomycin (200 μg/ml). Additionally, none of the SMs were toxic to pepper tissues (seeds, seedlings, or fruits), human Caco-2 cells, and pollinator honeybees at 200 μM. Overall, the SMs identified in this study are promising alternative antimicrobials for managing PLS in pepper production.

A South African Perspective on the Microbiological and Chemical Quality of Meat: Plausible Public Health Implications

Meat comprises proteins, fats, vitamins, and trace elements, essential nutrients for the growth and development of the body. The increased demand for meat necessitates the use of antibiotics in intensive farming to sustain and raise productivity. However, the high water activity, the neutral pH, and the high protein content of meat create a favourable milieu for the growth and the persistence of bacteria. Meat serves as a portal for the spread of foodborne diseases. This occurs because of contamination. This review presents information on animal farming in South Africa, the microbial and chemical contamination of meat, and the consequential effects on public health. In South Africa, the sales of meat can be operated both formally and informally. Meat becomes exposed to contamination with different categories of microbes, originating from varying sources during preparation, processing, packaging, storage, and serving to consumers. Apparently, meat harbours diverse pathogenic microorganisms and antibiotic residues alongside the occurrence of drug resistance in zoonotic pathogens, due to the improper use of antibiotics during farming. Different findings obtained across the country showed variations in prevalence of bacteria and multidrug-resistant bacteria studied, which could be explained by the differences in the manufacturer practices, handling processes from producers to consumers, and the success of the hygienic measures employed during production. Furthermore, variation in the socioeconomic and political factors and differences in bacterial strains, geographical area, time, climatic factors, etc. could be responsible for the discrepancy in the level of antibiotic resistance between the provinces. Bacteria identified in meat including Escherichia coli, Listeria monocytogenes, Staphylococcus aureus, Campylobacter spp., Salmonella spp., etc. are incriminated as pathogenic agents causing serious infections in human and their drug-resistant counterparts can cause prolonged infection plus long hospital stays, increased mortality and morbidity as well as huge socioeconomic burden and even death. Therefore, uncooked meat or improperly cooked meat consumed by the population serves as a risk to human health.

Recent Progress in the Characterization, Synthesis, Delivery Procedures, Treatment Strategies, and Precision of Antimicrobial Peptides

Infectious diseases are constantly evolving to bypass antibiotics or create resistance against them. There is a piercing alarm for the need to improve the design of new effective antimicrobial agents such as antimicrobial peptides which are less prone to resistance and possess high sensitivity. This would guard public health in combating and overcoming stubborn pathogens and mitigate incurable diseases; however, the emergence of antimicrobial peptides' shortcomings ranging from untimely degradation by enzymes to difficulty in the design against specific targets is a major bottleneck in achieving these objectives. This review is aimed at highlighting the recent progress in antimicrobial peptide development in the area of nanotechnology-based delivery, selectivity indices, synthesis and characterization, their doping and coating, and the shortfall of these approaches. This review will raise awareness of antimicrobial peptides as prospective therapeutic agents in the medical and pharmaceutical industries, such as the sensitive treatment of diseases and their utilization. The knowledge from this development would guide the future design of these novel peptides and allow the development of highly specific, sensitive, and accurate antimicrobial peptides to initiate treatment regimens in patients to enable them to have accommodating lifestyles.

Human Salmonellosis: A Continuous Global Threat in the Farm-to-Fork Food Safety Continuum

Salmonella is one of the most common zoonotic foodborne pathogens and a worldwide public health threat. Salmonella enterica is the most pathogenic among Salmonella species, comprising over 2500 serovars. It causes typhoid fever and gastroenteritis, and the serovars responsible for the later disease are known as non-typhoidal Salmonella (NTS). Salmonella transmission to humans happens along the farm-to-fork continuum via contaminated animal- and plant-derived foods, including poultry, eggs, fish, pork, beef, vegetables, fruits, nuts, and flour. Several virulence factors have been recognized to play a vital role in attaching, invading, and evading the host defense system. These factors include capsule, adhesion proteins, flagella, plasmids, and type III secretion systems that are encoded on the Salmonella pathogenicity islands. The increased global prevalence of NTS serovars in recent years indicates that the control approaches centered on alleviating the food animals' contamination along the food chain have been unsuccessful. Moreover, the emergence of antibiotic-resistant Salmonella variants suggests a potential food safety crisis. This review summarizes the current state of the knowledge on the nomenclature, microbiological features, virulence factors, and the mechanism of antimicrobial resistance of Salmonella. Furthermore, it provides insights into the pathogenesis and epidemiology of Salmonella infections. The recent outbreaks of salmonellosis reported in different clinical settings and geographical regions, including Africa, the Middle East and North Africa, Latin America, Europe, and the USA in the farm-to-fork continuum, are also highlighted.

Antifungal medicines in the terrestrial environment: Levels in biosolids from England and Wales

Antifungals are used widely in clinical and agricultural practice to control fungal growth, either treating or preventing infection. There are reports of increasing prevalence of resistance to antifungals in human pathogens and concern that their use in agriculture is driving clinical resistance in patients. While crop protection products are the most obvious source in agriculture, a further source may be biosolids from wastewater treatment. In the UK, these are applied to land to provide nutrients and improve soil structure for crops. In this study, biosolids from ten sites in England and one in Wales were analysed for clinical antifungals. Ketoconazole and miconazole were detected in all samples with a median concentration of 0.87 and 0.54 mg kg^-1 dry weight (DW), respectively. Clotrimazole was detected at seven of eleven sites at a median level of 1.32 mg kg^-1 DW and its absence at four others was considered treatment related. Two prescription-only and systemic medications, itraconazole and posaconazole, were frequently detected with median concentrations of 0.14 mg kg^-1 DW and 0.09 mg kg^-1 DW, respectively. The biosolid levels of itraconazole found in this study were two orders of magnitude higher than an indicative Predicted No Effect Concentration for resistance selection (PNEC-R) in soil. Neither fluconazole, griseofulvin, and voriconazole nor flucytosine and nystatin were found above the limit of detection of 0.01 or 0.1 mg kg^-1 as received, respectively. The findings show that biosolids represent a viable pathway for antifungal agents to reach soil.

MALDI-TOF MS Indirect Beta-Lactamase Detection in Ampicillin-Resistant Haemophilus influenzae

Rapid identification of beta-lactamase-producing strains of Haemophilus influenzae plays key role in diagnostics in clinical microbiology. Therefore, the aim of this study was the rapid determination of beta-lactamase's presence in H. influenzae isolates via indirect detection of degradation ampicillin products using MALDI-TOF MS. H. influenzae isolates were subjected to antibiotic resistance testing using disk diffusion and MIC methodologies. Beta-lactamase activity was tested using MALDI-TOF MS, and results were compared to spectral analysis of alkaline hydrolysis. Resistant and susceptible strains of H. influenzae were distinguished, and strains with a high MIC level were identified as beta-lactamase-producing. Results indicate that MALDI-TOF mass spectrometry is also suitable for the rapid identification of beta-lactamase-producing H. influenzae. This observation and confirmation can accelerate identification of beta-lactamase strains of H. influenzae in clinical microbiology, which can have an impact on health in general.

Antibiotic Resistance and Food Safety: Perspectives on New Technologies and Molecules for Microbial Control in the Food Industry

Antibiotic resistance (ABR) has direct and indirect repercussions on public health and threatens to decrease the therapeutic effect of antibiotic treatments and lead to more infection-related deaths. There are several mechanisms by which ABR can be transferred from one microorganism to another. The risk of transfer is often related to environmental factors. The food supply chain offers conditions where ABR gene transfer can occur by multiple pathways, which generates concerns regarding food safety. This work reviews mechanisms involved in ABR gene transfer, potential transmission routes in the food supply chain, the prevalence of antibiotic residues in food and ABR organisms in processing lines and final products, and implications for public health. Finally, the paper will elaborate on the application of antimicrobial peptides as new alternatives to antibiotics that might countermeasure ABR and is compatible with current food trends.

Microbial Contamination and Antibiotic Resistance in Marketed Food in Bangladesh: Current Situation and Possible Improvements

Antimicrobial resistance (AMR) is a public health problem worldwide. Bangladesh, like its neighboring countries, faces many public health challenges, including access to safe food, inadequate food surveillance, as well as increasing AMR. This study investigated bacterial contamination and the AMR profile of pathogens in marketed food in Bangladesh and explored barriers to reducing AMR in the country. We collected 366 tomatoes, 359 chicken and 249 fish samples from 732 vendors in traditional markets in urban, peri-urban and rural areas in Bangladesh, as well as from 121 modern retails in Dhaka capital to analyse Vibrio cholerae and Escherichia coli in fish, Salmonella in chicken, and Salmonella and E. coli in tomatoes. Antibiotic susceptibility against 11 antibiotics was tested using a disc diffusion test and interpreted by an automated zone inhibition reader. In addition, a qualitative study using key informant interviews was conducted to explore antimicrobial use and AMR reduction potential in Bangladesh. We found E. coli in 14.21% of tomatoes and 26.91% of fish samples, while 7.38% of tomatoes and 17.27% of chicken were positive for Salmonella, and 44.98% of fish were positive for Vibrio cholerae. In total 231/319 (72.4%) of all pathogens isolated were multidrug-resistant (MDR) (resistant to three or more antibiotic groups). Qualitative interviews revealed an inadequate surveillance system for antibiotic use and AMR in Bangladesh, especially in the agriculture sector. To be able to fully understand the human health risks from bacterial hazards in the food and the AMR situation in Bangladesh, a nationwide study with a one health approach should be conducted, within all sectors, including AMR testing as well as assessment of the antimicrobial use and its drivers.

Rational design of stapled antimicrobial peptides

The global increase in antimicrobial drug resistance has dramatically reduced the effectiveness of traditional antibiotics. Structurally diverse antibiotics are urgently needed to combat multiple-resistant bacterial infections. As part of innate immunity, antimicrobial peptides have been recognized as the most promising candidates because they comprise diverse sequences and mechanisms of action and have a relatively low induction rate of resistance. However, because of their low chemical stability, susceptibility to proteases, and high hemolytic effect, their usage is subject to many restrictions. Chemical modifications such as D-amino acid substitution, cyclization, and unnatural amino acid modification have been used to improve the stability of antimicrobial peptides for decades. Among them, a side-chain covalent bridge modification, the so-called stapled peptide, has attracted much attention. The stapled side-chain bridge stabilizes the secondary structure, induces protease resistance, and increases cell penetration and biological activity. Recent progress in computer-aided drug design and artificial intelligence methods has also been used in the design of stapled antimicrobial peptides and has led to the successful discovery of many prospective peptides. This article reviews the possible structure-activity relationships of stapled antimicrobial peptides, the physicochemical properties that influence their activity (such as net charge, hydrophobicity, helicity, and dipole moment), and computer-aided methods of stapled peptide design. Antimicrobial peptides under clinical trial: Pexiganan (NCT01594762, 2012-05-07). Omiganan (NCT02576847, 2015-10-13).

Derivation of a Precise and Consistent Timeline for Antibiotic Development

Antibiotic resistance is a global health crisis. New classes of antibiotics that can treat drug-resistant infections are urgently needed. To communicate this message, researchers have used antibiotic development timelines, but these are often contradictory or imprecise. We conducted a systematic literature review to produce an antibiotic timeline that incorporates the dates of discovery, first use, and initial reports of the emergence of resistance for the 38 classes of clinically used antibiotics. From our timeline, we derive lessons for identifying new antibiotics that are less prone to resistance. These include a required focus on molecules that exhibit multiple modes of action, possess unusually long 'resistance windows', or those that engage cellular targets whose molecular architectures are at least in part decoupled from evolutionary pressures. Our analysis also further highlights the importance of safeguarding antibiotics as a mechanism for mitigating the development of resistance. We have made our data and sources freely available so that the research community can adapt them to their own needs.

Molecular characterization of blaNDM, blaOXA-48, mcr-1 and blaTEM-52 positive and concurrently carbapenem and colistin resistant and extended spectrum beta-lactamase producing Escherichia coli in chicken in Malaysia

Background

Antimicrobial resistance (AMR) is a global public health threat and the use of antibiotics growth promoters in food animals has been implicated as a potential contributing factor in the emergence and spread of AMR. This study was conducted to investigate colistin and carbapenem resistance and extended spectrum beta-lactamase producing E. coli from live broiler chicken and chicken meat in Kelantan, Malaysia.

Results

Among the E. coli isolates, 37.5% (27/72 were positive for at least one of the resistance genes and one isolate was positive for mcr-1, bla_TEM-52, bla_NDM and bla_OXA-48 whereas 4.17% (3/72) and 2.78% (2/72) were positive for mcr-1, bla_TEM-52 and bla_OXA-48, and mcr-1, bla_TEM-52 and bla_IMP. Multilocus sequence typing (MLST) results revealed the presence of widespread E. coli strains belonging to the sequence types ST410 and ST155 and other extra-intestinal E. coli (ExPEC) strains. Phylogroup A made up the majority 51.85% (14/27) followed by phylogroup B1 22.22% (6/27).

Conclusions

The findings imply the potential threats of colistin, extended-spectrum beta-lactamase producing and carbapenem resistant E. coli in food animals to the public health and underscores the need for judicious use of antibiotics in animal production and good hygiene practices to curb the rising risks of AMR.

AMR-meta: a k-mer and metafeature approach to classify antimicrobial resistance from high-throughput short-read metagenomics data

BACKGROUND

Antimicrobial resistance (AMR) is a global health concern. High-throughput metagenomic sequencing of microbial samples enables profiling of AMR genes through comparison with curated AMR databases. However, the performance of current methods is often hampered by database incompleteness and the presence of homology/homoplasy with other non-AMR genes in sequenced samples.

RESULTS

We present AMR-meta, a database-free and alignment-free approach, based on k-mers, which combines algebraic matrix factorization into metafeatures with regularized regression. Metafeatures capture multi-level gene diversity across the main antibiotic classes. AMR-meta takes in reads from metagenomic shotgun sequencing and outputs predictions about whether those reads contribute to resistance against specific classes of antibiotics. In addition, AMR-meta uses an augmented training strategy that joins an AMR gene database with non-AMR genes (used as negative examples). We compare AMR-meta with AMRPlusPlus, DeepARG, and Meta-MARC, further testing their ensemble via a voting system. In cross-validation, AMR-meta has a median f-score of 0.7 (interquartile range, 0.2-0.9). On semi-synthetic metagenomic data-external test-on average AMR-meta yields a 1.3-fold hit rate increase over existing methods. In terms of run-time, AMR-meta is 3 times faster than DeepARG, 30 times faster than Meta-MARC, and as fast as AMRPlusPlus. Finally, we note that differences in AMR ontologies and observed variance of all tools in classification outputs call for further development on standardization of benchmarking data and protocols.

CONCLUSIONS

AMR-meta is a fast, accurate classifier that exploits non-AMR negative sets to improve sensitivity and specificity. The differences in AMR ontologies and the high variance of all tools in classification outputs call for the deployment of standard benchmarking data and protocols, to fairly compare AMR prediction tools.

Antimicrobial resistance management in Pacific Island countries: Current status, challenges, and strategic solutions

Antimicrobial resistance (AMR) is currently recognized as a major emerging threat to human and animal health. The burden of antimicrobial-resistant infections affects the economy in developed and developing countries. There is a rapid rise in AMR in human and veterinary medicine globally. AMR profiles are poorly documented in Fiji, and limited data are accessible. Fiji currently has no national veterinary antibiotic resistance surveillance network or regulations and guidelines on veterinary drug use. However, available literature shows that although human drugs are better managed than veterinary drugs, the knowledge is still constrained and dispersed. Furthermore, Fiji was chosen as a case study to develop a prototype AMR surveillance and control in the Pacific region. Pacific Island countries share similar geographic and climatic conditions. Currently, the Australian Centre for International Agricultural Research has funded an AMR project that addresses some gaps in managing AMR in the region. The project is the first to adopt the One Health approach to research the AMR in humans, animals, and the Pacific region's environment. Combating AMR needs human health and veterinary personnel to work with all other stakeholders. Continuous surveillance for resistant clinical isolates in humans and animals and the development of appropriate policy intervention measures in human and veterinary drug use are necessary to alleviate AMR burden. Therefore, there is a need to educate farmers, human patients, and the public on the fight against AMR. In addition, AMR data are necessary to develop effective AMR control strategies. This review gives a comprehensive information assessment on AMR in Fiji and the other South Pacific Islands in relation to global trends. Suggestions on the most appropriate ways of effectively managing AMR in Fiji have been made.

Farm Animal Veterinarians' Knowledge and Attitudes toward Antimicrobial Resistance and Antimicrobial Use in the Republic of Serbia

Antimicrobial resistance (AMR) is considered one of the most prevalent global health issues in both veterinarian and human medicine. This complex problem requires a "One Health" approach with the cooperation of all healthcare sectors, as well as agriculture, finance, and consumers. We conducted a survey with the objective to assess the knowledge and attitudes of farm animal veterinarians toward AMR and antimicrobial use in the Republic of Serbia with a small focus on mastitis therapy. A total of 110 respondents completed the questionnaire, which represents a response rate of 27.3%. The majority of our respondents (n = 102, 92.7%) completely agreed that AMR currently represents severe concern in the health sector. Unfortunately, less than one-third (n = 34, 30.9%) of the respondents had only heard about antimicrobial stewardship. Participants showed a positive attitude toward prudent antimicrobial use and were open to solutions to the AMR crisis. We noticed a certain gap between farm veterinarians' desire to improve and perform better in daily practice, while at the same time feeling like they did not have enough guidance, help, and resources.

Finding a Balance in the Vaginal Microbiome: How Do We Treat and Prevent the Occurrence of Bacterial Vaginosis?

Bacterial vaginosis (BV) has been reported in one-third of women worldwide at different life stages, due to the complex balance in the ecology of the vaginal microbiota. It is a common cause of abnormal vaginal discharge and is associated with other health issues. Since the first description of anaerobic microbes associated with BV like Gardnerella vaginalis in the 1950s, researchers have stepped up the game by incorporating advanced molecular tools to monitor and evaluate the extent of dysbiosis within the vaginal microbiome, particularly on how specific microbial population changes compared to a healthy state. Moreover, treatment failure and BV recurrence rate remain high despite the standard antibiotic treatment. Consequently, researchers have been probing into alternative or adjunct treatments, including probiotics or even vaginal microbiota transplants, to ensure successful treatment outcomes and reduce the colonization by pathogenic microbes of the female reproductive tract. The current review summarizes the latest findings in probiotics use for BV and explores the potential of vaginal microbiota transplants in restoring vaginal health.

Exploring Prediction of Antimicrobial Resistance Based on Protein Solvent Accessibility Variation

Antimicrobial resistance (AMR) is a significant and growing public health threat. Sequencing of bacterial isolates is becoming more common, and therefore automatic identification of resistant bacterial strains is of pivotal importance for efficient, wide-spread AMR detection. To support this approach, several AMR databases and gene identification algorithms have been recently developed. A key problem in AMR detection, however, is the need for computational approaches detecting potential novel AMR genes or variants, which are not included in the reference databases. Toward this direction, here we study the relation between AMR and relative solvent accessibility (RSA) of protein variants from an in silico perspective. We show how known AMR protein variants tend to correspond to exposed residues, while on the contrary their susceptible counterparts tend to be buried. Based on these findings, we develop RSA-AMR, a novel relative solvent accessibility-based AMR scoring system. This scoring system can be applied to any protein variant to estimate its propensity of altering the relative solvent accessibility, and potentially conferring (or hindering) AMR. We show how RSA-AMR score can be integrated with existing AMR detection algorithms to expand their range of applicability into detecting potential novel AMR variants, and provide a ten-fold increase in Specificity. The two main limitations of RSA-AMR score is that it is designed on single point changes, and a limited number of variants was available for model learning.

Phytogreen synthesis of multifunctional nano selenium with antibacterial and antioxidant implications

The exploitation of plant extracts for the synthesis of nano selenium having antibacterial and antioxidant activities is an exciting approach to counteract the prevalence of infections caused by antibiotic-resistant bacteria, which holds relevance for medical and food industries. In the present work, a green and facile method for the preparation of nano selenium (nSe) using the fruit extract of Indian gooseberry (Phyllanthus Emblica) has been reported. The optical and structural properties of the as-synthesized nSe were studied through various characterization techniques. Eventually, the antioxidant potential of nSe was investigated via 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl free radical scavenging assays. Parallely, the antibacterial activity of nSe against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa was evaluated. The antioxidant assays indicated that even low dosage of nSe showed excellent activity with EC50 values of 0.21 μg ml−1 and 3.34 μg ml−1, respectively. Moreover, nSe exhibited significant inhibition in bacterial growth at low minimum inhibitory concentration (MIC) values against Escherichia coli (16 μg ml−1), Staphylococcus aureus (32 μg ml−1) and Pseudomonas aeruginosa (48 μg ml−1) compared to MIC values for standard drug ampicillin. Importantly, nSe did not induce any cytotoxic effects on normal human keratinocytes (HaCaT) at the tested concentrations; representing their biocompatible nature. The data obtained demonstrated the versatility of phytogreen nSe as a potent antioxidant and antibacterial agent to effectively prevent as well as treat multidrug-resistant bacterial infections.

Effect of helical kink in antimicrobial peptides on membrane pore formation

Every cell is protected by a semipermeable membrane. Peptides with the right properties, for example Antimicrobial peptides (AMPs), can disrupt this protective barrier by formation of leaky pores. Unfortunately, matching peptide properties with their ability to selectively form pores in bacterial membranes remains elusive. In particular, the proline/glycine kink in helical peptides was reported to both increase and decrease antimicrobial activity. We used computer simulations and fluorescence experiments to show that a kink in helices affects the formation of membrane pores by stabilizing toroidal pores but disrupting barrel-stave pores. The position of the proline/glycine kink in the sequence further controls the specific structure of toroidal pore. Moreover, we demonstrate that two helical peptides can form a kink-like connection with similar behavior as one long helical peptide with a kink. The provided molecular-level insight can be utilized for design and modification of pore-forming antibacterial peptides or toxins.

Therapeutic lipid-coated hybrid nanoparticles against bacterial infections

One of the most important health concerns in society is the development of pathogen-causing nosocomial infections. Since the first discovery of antibiotics, bacterial infections have been highly treatable. However, with evolution and the nondiscretionary usage of antibiotics, pathogens have also found new ways to survive the onslaught of antibiotics by surviving intracellularly or through the formation of obstinate biofilms, and through these, the outcomes of regular antibiotic treatments may now be unsatisfactory. Lipid-coated hybrid nanoparticles (LCHNPs) are the next-generation core–shell structured nanodelivery system, where an inorganic or organic core, loaded with antimicrobials, is enveloped by lipid layers. This core–shell structure, with multifarious decorations, not only improves the loading capabilities of therapeutics but also has the potential to improve therapeutic delivery, especially for targeting biofilm-based and intracellular bacterial infections. Although there has been significant interest in the development of LCHNPs, they have yet to be widely exploited for bacterial infections. In this review, we will provide an overview on the latest development of LCHNPs and the various approaches in synthesizing this nano-delivery system. In addition, a discussion on future perspectives of LCHNPs, in combination with other novel anti-bacterial technologies, will be provided towards the end of this review.

Lipid-coated hybrid nanoparticles are next-generation core–shell structured nanodelivery systems, which improve the loading capabilities of therapeutics and can improve therapeutic delivery, especially for targeting biofilm-based and intracellular bacterial infections.