Ensuring a sustained workforce to combat antibiotic resistance in the 21st century: the critical need for training the next-gen of scientists at the pre-doctoral level

Antibiotics revolutionized the treatment of bacterial infection and enhanced modern healthcare. While the current global antibiotic resistance crisis is widely acknowledged, the need for a highly trained cohort of scientists to continue and expand efforts to combat this threat has received less attention. We posit that training of pre-doctoral students in the antibiotic resistance field is critical for future efforts in combating this crisis and urge development of training programs that focus on this need.

Treatment of MRSA Infection: Where are We?

Staphylococcus aureus is a leading cause of septicemia, endocarditis, pneumonia, skin and soft tissue infections, bone and joint infections, and hospital-acquired infections. In particular, methicillin-resistant Staphylococcus aureus (MRSA) is associated with high morbidity and mortality, and continues to be a major public health problem. The emergence of multidrug-resistant MRSA strains along with the wide consumption of antibiotics has made anti-MRSA treatment a huge challenge. Novel treatment strategies (e.g., novel antimicrobials and new administrations) against MRSA are urgently needed. In the past decade, pharmaceutical companies have invested more in the research and development (R&D) of new antimicrobials and strategies, spurred by favorable policies. All research articles were collected from authentic online databases, including Google Scholar, PubMed, Scopus, and Web of Science, by using different combinations of keywords, including 'anti-MRSA', 'antibiotic', 'antimicrobial', 'clinical trial', 'clinical phase', clinical studies', and 'pipeline'. The information extracted from articles was compared to information provided on the drug manufacturer's website and Clinical Trials.gov (https://clinicaltrials.gov/) to confirm the latest development phase of anti-MRSA agents. The present review focuses on the current development status of new anti-MRSA strategies concerning chemistry, pharmacological target(s), indications, route of administration, efficacy and safety, pharmacokinetics, and pharmacodynamics, and aims to discuss the challenges and opportunities in developing drugs for anti-MRSA infections.

Efficacy of various extracting solvents on phytochemical composition, and biological properties of Mentha longifolia L. leaf extracts

The current work attempts to explore the influence of three extraction solvents on phytochemical composition, content of polyphenols, antioxidant potential, and antibacterial capacity of hydroethanolic, acetonic, and aqueous extracts from Moroccan Mentha longifolia leaves. To achieve this goal, the chemical composition was identified using an HPLC-DAD examination. The contents of polyphenols were assessed, while the total antioxidant capacity (TAC), the DPPH test, and the reducing power test (RP) were utilized to determine antioxidant capacity. To assess the antibacterial activity, the microdilution technique was carried out to calculate the minimum inhibitory (MIC) and minimum bactericidal concentrations (MBC) of extracts against four nosocomial bacteria (Bacillus cereus, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus). Additionally, the antibacterial and antioxidant activities of all tested extracts were examined in silico against the proteins NADPH oxidase and Bacillus cereus phospholipase C. Study reveals that M. longifolia extracts contain high phenolic and flavonoids. Additionally, the hydroethanolic extract contained the highest amounts of phenolic and flavonoid content, with values of 23.52 ± 0.14 mg Gallic acid equivalent/g dry weight and 17.62 ± 0.36 mg Quercetin Equivalent/g dry weight, respectively compared to the other two extracts. The same extract showed the best antioxidant capacity (IC50 = 39 µg/mL ± 0.00), and the higher RP (EC50 of 0.261 ± 0.00 mg/mL), compared to the acetonic and aqueous extract regarding these tests. Furthermore, the hydroethanolic and acetonic extracts expressed the highest TAC (74.40 ± 1.34, and 52.40 ± 0.20 mg EAA/g DW respectively), compared with the aqueous extract. Regarding antibacterial activity, the MIC value ranges between 1.17 and 12.50 mg/mL. The in-silico results showed that the antibacterial activity of all extracts is principally attributed to kaempferol and ferulic acid, while antioxidant capacity is attributed to ferulic acid.

Natural flavonols: actions, mechanisms, and potential therapeutic utility for various diseases

Background

Flavonols are phytoconstituents of biological and medicinal importance. In addition to functioning as antioxidants, flavonols may play a role in antagonizing diabetes, cancer, cardiovascular disease, and viral and bacterial diseases. Quercetin, myricetin, kaempferol, and fisetin are the major dietary flavonols. Quercetin is a potent scavenger of free radicals, providing protection from free radical damage and oxidation-associated diseases.

Main body of the abstract

An extensive literature review of specific databases (e.g., Pubmed, google scholar, science direct) were conducted using the keywords "flavonol," "quercetin," "antidiabetic," "antiviral," "anticancer," and "myricetin." Some studies concluded that quercetin is a promising antioxidant agent while kaempferol could be effective against human gastric cancer. In addition, kaempferol prevents apoptosis of pancreatic beta-cells via boosting the function and survival rate of the beta-cells, leading to increased insulin secretion. Flavonols also show potential as alternatives to conventional antibiotics, restricting viral infection by antagonizing the envelope proteins to block viral entry.

Short conclusion

There is substantial scientific evidence that high consumption of flavonols is associated with reduced risk of cancer and coronary diseases, free radical damage alleviation, tumor growth prevention, and insulin secretion improvement, among other diverse health benefits. Nevertheless, more studies are required to determine the appropriate dietary concentration, dose, and type of flavonol for a particular condition to prevent any adverse side effects.

Iron Acquisition Proteins of Pseudomonas aeruginosa as Potential Vaccine Targets: In Silico Analysis and In Vivo Evaluation of Protective Efficacy of the Hemophore HasAp

BACKGROUND

Pseudomonas aeruginosa (PA) is a Gram-negative pathogen responsible for fatal nosocomial infections worldwide. Iron is essential for Gram-negative bacteria to establish an infection. Therefore, iron acquisition proteins (IAPs) of bacteria are attractive vaccine targets.

METHODOLOGY

A "Reverse Vaccinology" approach was employed in the current study. Expression levels of 37 IAPs in various types of PA infections were analyzed in seven previously published studies. The IAP vaccine candidate was selected based on multiple criteria, including a high level of expression, high antigenicity, solubility, and conservation among PA strains, utilizing suitable bioinformatics analysis tools. The selected IAP candidate was recombinantly expressed in Escherichia coli and purified using metal affinity chromatography. It was further evaluated in vivo for protection efficacy. The novel immune adjuvant, naloxone (NAL), was used.

RESULTS AND DISCUSSION

HasAp antigen met all the in silico selection criteria, being highly antigenic, soluble, and conserved. In addition, it was the most highly expressed IAP in terms of average fold change compared to control. Although HasAp did excel in the in silico evaluation, subcutaneous immunization with recombinant HasAp alone or recombinant HasAp plus NAL (HasAP-NAL) did not provide the expected protection compared to controls. Immunized mice showed a low IgG2a/IgG1 ratio, indicating a T-helper type 2 (Th2)-oriented immune response that is suboptimal for protection against PA infections. Surprisingly, the bacterial count in livers of both NAL- and HasAp-NAL-immunized mice was significantly lower than the count in the HasAp and saline groups. The same trend was observed in kidneys and lungs obtained from these groups, although the difference was not significant. Such protection could be attributed to the enhancement of innate immunity by NAL.

CONCLUSIONS

We provided a detailed in silico analysis of IAPs of PA followed by in vivo evaluation of the best IAP, HasAp. Despite the promising in silico results, HasAp did not provide the anticipated vaccine efficacy. HasAp should be further evaluated as a vaccine candidate through varying the immunization regimens, models of infection, and immunoadjuvants. Combination with other IAPs might also improve vaccination efficacy. We also shed light on several highly expressed promising IAPs whose efficacy as vaccine candidates is worthy of further investigation.

Isoquinoline Antimicrobial Agent: Activity against Intracellular Bacteria and Effect on Global Bacterial Proteome

A new class of alkynyl isoquinoline antibacterial compounds, synthesized via Sonogashira coupling, with strong bactericidal activity against a plethora of Gram-positive bacteria including methicillin- and vancomycin-resistant Staphylococcus aureus (S. aureus) strains is presented. HSN584 and HSN739, representative compounds in this class, reduce methicillin-resistant S. aureus (MRSA) load in macrophages, whilst vancomycin, a drug of choice for MRSA infections, was unable to clear intracellular MRSA. Additionally, both HSN584 and HSN739 exhibited a low propensity to develop resistance. We utilized comparative global proteomics and macromolecule biosynthesis assays to gain insight into the alkynyl isoquinoline mechanism of action. Our preliminary data show that HSN584 perturb S. aureus cell wall and nucleic acid biosynthesis. The alkynyl isoquinoline moiety is a new scaffold for the development of potent antibacterial agents against fatal multidrug-resistant Gram-positive bacteria.

Pseudo-Tetrahedral Copper(I) Symmetrical Formamidine Dithiocarbamate-Phosphine Complexes: Antibacterial, Antioxidant and Pharmacokinetics Studies

Three copper(I) dithiocarbamate–phosphine complexes of the general formula Cu(PPh3)2L were synthesized by metathesis reactions of the potassium salt of the dithiocarbamate ligand L and the precursor complex Cu(PPh3)2NO3 in an equimolar ratio. L represents N,N′-bis(2,6-dimethylphenyl)formamidine dithiocarbamate L1 in complex 1, N,N′-bis(2,6-disopropylphenyl) formamidine dithiocarbamate L2 in complex 2, and N,N′-dimesitylformamidine dithiocarbamate L3 in complex 3. The single-crystal X-ray structure revealed the coordination of the copper atom to two sulfur atoms of the dithiocarbamates, as well as two phosphorus atoms of the PPh3 units, which resulted in distorted tetrahedral geometries. The calculated τ4 (tau factor) values for 1, 2 and 3 were 0.82, 0.81 and 0.85, respectively, confirming the pseudo-tetrahedral geometry proposed. Complexes 1–3 showed remarkable luminescent properties in CH2Cl2 at room temperature. All three complexes showed moderate-to-low antibacterial potential against Gram-negative bacteria, while none of the complexes were active against Gram-positive bacteria. The DPPH assay studies showed that complex 2 had the lowest IC50 (4.99 × 10−3 mM),and had higher DPPH free radical scavenging ability than 1 and 3. The pharmacological estimations of 1–3 showed that all of the complexes showed minimal violation of Lipinski’s rule.

Chitosan/cyclodextrin surface-adsorbed naringenin-loaded nanocapsules enhance bacterial quorum quenching and anti-biofilm activities

Pathogenic bacteria use quorum sensing (QS), a cell-to-cell communication process that relies on small signaling molecules, to regulate the genetic expression that leads to several essential virulence factors such as bioluminescence, biofilm formation, bacterial motility, among other. Naringenin (NAR), a bitter and colorless flavanone ubiquitous in herbs and fruits, has been shown to inhibit QS activity in P. aeruginosa by decreasing the production of pyocyanin and elastase. In this study, to evaluate the anti-QS activity of naringenin against an E. coli Top 10 biosensor, we developed a novel core-corona nanocapsule formulation comprising surface co-adsorbed β-cyclodextrin (Captisol®) and chitosan loaded with NAR. The results showed that both the nanocapsule (NC) and nanoemulsion (NE) formulations, NAR payload associated with high efficiency , namely ~ 92.88 and ~ 67.98%, respectively. These formulations remained stable for 24 h and showed a biphasic controlled release profile in bacterial M9 medium. Captisol® was effectively immobilized on the NC's surface, resulting in a surface charge inversion from positive (~ + 42 mV) to negative (~ -32 mV) ζ-potential. The biosensor assay revealed that NC outperformed NE in quenching the QS response and the incorporation of naringenin at the NC's multifunctional surface enhanced this bioactivity. Cytotoxicity assays showed that when NAR was associated in NC (188 µM) it was not cytotoxic to Caco2 cells, by contrast with its free form, thus highlighting the cytoprotective effect of the developed formulation. Biofilm formation was inhibited up to ~ 60% in NAR-loaded NC (188 μM), indicating the synergistic effect of positively charged chitosan with the bioactivity of NAR while harnessing the NC's high surface area-to-volume ratio.

Combating Multidrug-Resistant Bacteria by Integrating a Novel Target Site Penetration and Receptor Binding Assay Platform Into Translational Modeling

Multidrug-resistant bacteria are causing a serious global health crisis. A dramatic decline in antibiotic discovery and development investment by pharmaceutical industry over the last decades has slowed the adoption of new technologies. It is imperative that we create new mechanistic insights based on latest technologies, and use translational strategies to optimize patient therapy. Although drug development has relied on minimal inhibitory concentration testing and established in vitro and mouse infection models, the limited understanding of outer membrane permeability in Gram-negative bacteria presents major challenges. Our team has developed a platform using the latest technologies to characterize target site penetration and receptor binding in intact bacteria that inform translational modeling and guide new discovery. Enhanced assays can quantify the outer membrane permeability of β-lactam antibiotics and β-lactamase inhibitors using multiplex liquid chromatography tandem mass spectrometry. While β-lactam antibiotics are known to bind to multiple different penicillin-binding proteins (PBPs), their binding profiles are almost always studied in lysed bacteria. Novel assays for PBP binding in the periplasm of intact bacteria were developed and proteins identified via proteomics. To characterize bacterial morphology changes in response to PBP binding, high-throughput flow cytometry and time-lapse confocal microscopy with fluorescent probes provide unprecedented mechanistic insights. Moreover, novel assays to quantify cytosolic receptor binding and intracellular drug concentrations inform target site occupancy. These mechanistic data are integrated by quantitative and systems pharmacology modeling to maximize bacterial killing and minimize resistance in in vitro and mouse infection models. This translational approach holds promise to identify antibiotic combination dosing strategies for patients with serious infections.

Synergistic Quinolone Sensitization by Targeting the recA SOS Response Gene and Oxidative Stress

Suppression of the recA SOS response gene and reactive oxygen species (ROS) overproduction have been shown, separately, to enhance fluoroquinolone activity and lethality. Their putative synergistic impact as a strategy to potentiate the efficacy of bactericidal antimicrobial agents such as fluoroquinolones is unknown. We generated Escherichia coli mutants that exhibited a suppressed ΔrecA gene in combination with inactivated ROS detoxification system genes (ΔsodA, ΔsodB, ΔkatG, ΔkatE, and ΔahpC) or inactivated oxidative stress regulator genes (ΔoxyR and ΔrpoS) to evaluate the interplay of both DNA repair and detoxification systems in drug response. Synergistic sensitization effects, ranging from 7.5- to 30-fold relative to the wild type, were observed with ciprofloxacin in double knockouts of recA and inactivated detoxification system genes. Compared to recA knockout, inactivation of an additional detoxification system gene reduced MIC values up to 8-fold. In growth curves, no growth was evident in mutants doubly deficient for recA gene and oxidative detoxification systems at subinhibitory concentrations of ciprofloxacin, in contrast to the recA-deficient strain. There was a marked reduction of viable bacteria in a short period of time when the recA gene and other detoxification system genes (katG, sodA, or ahpC) were inactivated (using absolute ciprofloxacin concentrations). At 4 h, a bactericidal effect of ciprofloxacin was observed for ΔkatG ΔrecA and ΔahpC ΔrecA double mutants compared to the single ΔrecA mutant (Δ3.4 log₁₀ CFU/ml). Synergistic quinolone sensitization, by targeting the recA gene and oxidative detoxification stress systems, reinforces the role of both DNA repair systems and ROS in antibiotic-induced bacterial cell death, opening up a new pathway for antimicrobial sensitization.

Production of antimicrobial metabolites against pathogenic bacteria and yeasts by Fusarium oxysporum in submerged culture processes

The antimicrobial activity of the metabolites produced by Fusarium oxysporum PR-33 in submerged culture was evaluated against Gram-positive and Gram-negative bacteria and yeasts. Metabolites were determined by HPLC-DAD-MS/MS. An extract was obtained following the removal of mycelium by centrifugation and lyophilisation of the supernatant. The compounds in this extract demonstrated broad-spectrum antimicrobial action, with rates of inhibition between 60 and 80%, depending on the species and extract tested. The major compounds of the extracts were identified as fusarinolic acid and its isomer [56.9% flask extract (FE)] and 59.2% bioreactor extract (BE), dehydrofusaric acid (35.7% FE and 31.6% BE), and fusaric acid (6.5% FE and 1.1% BE). Fusaric acid has been shown to be responsible for antimicrobial activity. The cytotoxicity of the extracts was evaluated in culture of HEK-293 and SH-SY5Y animal cells and toxicity of these extracts was verified even in the lowest tested concentrations. Therefore, our results indicate that the compounds identified exhibit potential as antimicrobial agents.

Unconventional Antibacterials and Adjuvants

The need for new classes of antibacterials is genuine in light of the dearth of clinical options for the treatment of bacterial infections. The prodigious discoveries of antibiotics during the 1940s to 1970s, a period wistfully referred to as the Golden Age of Antibiotics, have not kept up in the face of emergence of resistant bacteria in the past few decades. There has been a renewed interest in old drugs, the repurposing of the existing antibiotics and pairing of synergistic antibiotics or of an antibiotic with an adjuvant. Notwithstanding, discoveries of novel classes of these life-saving drugs have become increasingly difficult, calling for new paradigms. We describe, herein, three strategies from our laboratories toward discoveries of new antibacterials and adjuvants using computational and multidisciplinary experimental methods. One approach targets penicillin-binding proteins (PBPs), biosynthetic enzymes of cell-wall peptidoglycan, for discoveries of non-β-lactam inhibitors. Oxadiazoles and quinazolinones emerged as two structural classes out of these efforts. Several hundred analogs of these two classes of antibiotics have been synthesized and fully characterized in our laboratories. A second approach ventures into inhibition of allosteric regulation of cell-wall biosynthesis. The mechanistic details of allosteric regulation of PBP2a of Staphylococcus aureus, discovered in our laboratories, is outlined. The allosteric site in this protein is at 60 Å distance to the active site, whereby ligand binding at the former makes access to the latter by the substrate possible. We have documented that both quinazolinones and ceftaroline, a fifth-generation cephalosporin, bind to the allosteric site in manifestation of the antibacterial activity. Attempts at inhibition of the regulatory phosphorylation events identified three classes of antibacterial adjuvants and one class of antibacterials, the picolinamides. The chemical structures for these hits went through diversification by synthesis of hundreds of analogs. These analogs were characterized in various assays for identification of leads with adjuvant and antibacterial activities. Furthermore, we revisited the mechanism of bulgecins, a class of adjuvants discovered and abandoned in the 1980s. These compounds potentiate the activities of β-lactam antibiotics by the formation of bulges at the sites of septum formation during bacterial replication, which are points of structural weakness in the envelope. These bulges experience rupture, which leads to bacterial death. Bulgecin A inhibits the lytic transglycosylase Slt of Pseudomonas aeruginosa as a likely transition-state mimetic for its turnover of the cell-wall peptidoglycan. Once damage to cell wall is inflicted by a β-lactam antibiotic, the function of Slt is to repair the damage. When Slt is inhibited by bulgecin A, the organism cannot cope with it and would undergo rapid lysis. Bulgecin A is an effective adjuvant of β-lactam antibiotics. These discoveries of small-molecule classes of antibacterials or of adjuvants to antibacterials hold promise in strategies for treatment of bacterial infections.

An inventory of 44 qPCR assays using hydrolysis probes operating with a unique amplification condition for the detection and quantification of antibiotic resistance genes

Early antibiotic resistance determinants (ARDs) detection in humans or animals is crucial to counteract their propagation. The ARDs quantification is fundamental to understand the perturbation caused by disruptors, such as antibiotics, during therapies. Forty-three qPCRs on the most diffused ARDs and integrons among human and animal Enterobacterales, and one on the 16S rDNA for bacteria quantification, were developed. The qPCRs, using hydrolysis probes, operated with a unique amplification condition and were tested analytically and diagnostically performing 435 reactions on five positive and negative controls for each qPCR. Diagnostic sensitivity and specificity were confirmed by PCR and genome sequencing of control isolates, demonstrating 100% performance for all qPCRs. An easy and rapid discrimination method for the epidemiologically relevant bla_CTX-Ms is provided. This large, noncommercial qPCRs inventory could serve for precise quantification of ARDs, but also as a rapid screening tool for surveillance purposes, providing the basis for further high-throughput developments.

Exploring the future of infectious disease treatment in a post-antibiotic era: A comparative review of alternative therapeutics

Antibiotic resistance is projected to be one of the greatest healthcare challenges of the 21st century. As the efficacy of these critical drugs wanes and the discovery of new antibiotics stagnates, exploration of alternative therapies could offer a much needed solution. Although numerous alternative therapies are currently under investigation, three in particular appear poised for long-term success, namely antimicrobial oligonucleotides, monoclonal antibodies and phage therapy. Antimicrobial oligonucleotides could conceivably offer the greatest spectrum of activity while having the lowest chance of unrecoverable resistance. Bacteriophages, while most susceptible to resistance, are inexhaustible, inexpensive and exceptionally adept at eliminating biofilm-associated infections. And although monoclonal antibodies may have limited access to such recalcitrant bacteria, these agents are uniquely able to neutralise exotoxins and other diffusible virulence factors. This comparative review seeks to illuminate these promising therapies and to encourage the scientific and financial support necessary to usher in the next generation of infectious disease treatment.

Novel effective antibacterial small-molecules against Staphylococcus and Enterococcus strains

Background: Resistance developments against established antibiotics are an emerging problem for antibacterial therapies. Novel antibiotics are urgently needed. Materials & methods: We developed novel small-molecule antibacterials which are easily accessible in a simple one-pot synthesis. The central cyclopentaindole core is substituted with two indole residues. Various indole and cyclopentane substituents have been introduced. Additionally, first indole substituted propene compounds as ring-open variants of the cyclopentaindoles have been yielded and evaluated as antibacterials against Staphylococcus aureus and Enterococcus strains. Results: Most effective compounds have been those with a bromo cyclopentane and a chloro indole substitution. First lead compounds were identified with promising activities similar to that observed in vitro for last resort antibiotics, so that the novel compounds enriche the pool of perspective small-molecule antibacterial drug candidates.

Phosphonopeptides Revisited, in an Era of Increasing Antimicrobial Resistance

Given the increase in resistance to antibacterial agents, there is an urgent need for the development of new agents with novel modes of action. As an interim solution, it is also prudent to reinvestigate old or abandoned antibacterial compounds to assess their efficacy in the context of widespread resistance to conventional agents. In the 1970s, much work was performed on the development of peptide mimetics, exemplified by the phosphonopeptide, alafosfalin. We investigated the activity of alafosfalin, di-alanyl fosfalin and β-chloro-L-alanyl-β-chloro-L-alanine against 297 bacterial isolates, including carbapenemase-producing Enterobacterales (CPE) (n = 128), methicillin-resistant Staphylococcus aureus (MRSA) (n = 37) and glycopeptide-resistant enterococci (GRE) (n = 43). The interaction of alafosfalin with meropenem was also examined against 20 isolates of CPE. The MIC₅₀ and MIC₉₀ of alafosfalin for CPE were 1 mg/L and 4 mg/L, respectively and alafosfalin acted synergistically when combined with meropenem against 16 of 20 isolates of CPE. Di-alanyl fosfalin showed potent activity against glycopeptide-resistant isolates of Enterococcus faecalis (MIC₉₀; 0.5 mg/L) and Enterococcus faecium (MIC₉₀; 2 mg/L). Alafosfalin was only moderately active against MRSA (MIC₉₀; 8 mg/L), whereas β-chloro-L-alanyl-β-chloro-L-alanine was slightly more active (MIC₉₀; 4 mg/L). This study shows that phosphonopeptides, including alafosfalin, may have a therapeutic role to play in an era of increasing antibacterial resistance.

A Review on Onychine and its Analogs: Synthesis and Biological Activity

BACKGROUND

Onychine is a 4-azafluorenone alkaloid isolated from the Annonaceae family, in low concentrations. Onychine and its analogs exhibit a wide range of pharmacological activities such as antifungal, antibacterial, anticancer, and antimalarial. Because of the high bioactivity of some 4-azafluorenone derivatives, several synthetic methods have been developed for their procurement.

OBJECTIVE

Considering the importance of these alkaloids, we aim to present the main synthetic approaches to onychines and its derivatives and the biological activity of some 4-azafluorenones.

METHODS

The most prominent methodologies for the synthesis of onychines were reviewed.

RESULTS

In this work, we cover many synthetic approaches for the synthesis of onychine and 4-azafluorenone derivatives including intramolecular cyclizations, multicomponent reactions, microwave-assisted multicomponent reactions, Diels-alder reactions, among others. Moreover, we also review the biological activity of 4-azafluorenones.

CONCLUSION

4-azafluorenones have risen as prominent structures in medicinal chemistry; however, most of the time, access to new derivatives involves toxic catalysts, harsh reaction conditions, and long-step procedures. Therefore, the development of new synthetic routes with more operational simplicity, simple purification procedure, good yields, and low environmental impact, is desirable.

Discovery of sulfone-resistant dihydropteroate synthase (DHPS) as a target enzyme for kaempferol, a natural flavanoid

Kaempferol is a ubiquitous flavonoid, found in various plants having a wide range of known pharmacological activities, including antioxidant, antiinflammatory, anticancer, antiallergic, antidiabetic, neuroprotective, cardioprotective and antimicrobial activities. Nonetheless various evidence suggest that kaempferol is also able to interact with many unknown therapeutic targets modulating signalling pathways, thus providing an opportunity to explore the potential target space of kaempferol. In this study, we have employed various ligand-based approaches to identify the potential targets of kaempferol, followed by validations using modelling and docking studies. Molecular dynamics, free energy calculations, volume and residue contact map analyses were made to delineate the cause of drug-resistance among mutants. We have discovered dihydropteroate synthase (DHPS) as a novel potential therapeutic target for kaempferol. Further studies employing molecular dynamics simulations and binding free energies indicate that kaempferol has potential to inhibit even the sulfone-resistant DHPS mutants, which makes it a very attractive antibiotic agent. The identification of natural-product based kaempferol opens up the door for the design of antibiotics in a quick and high throughput fashion for identifying antibiotic leads.

Chlorpromazine-impregnated catheters as a potential strategy to control biofilm-associated urinary tract infections

Aim: This study proposes the impregnation of Foley catheters with chlorpromazine (CPZ) to control biofilm formation by Escherichia coli, Proteus mirabilis and Klebsiella pneumoniae. Materials & methods: The minimum inhibitory concentrations (MICs) for CPZ and the effect of CPZ on biofilm formation were assessed. Afterward, biofilm formation and the effect of ciprofloxacin and meropenem (at MIC) on mature biofilms grown on CPZ-impregnated catheters were evaluated. Results: CPZ MIC range was 39.06-625 mg/l. CPZ significantly reduced (p < 0.05) biofilm formation in vitro and on impregnated catheters. In addition, CPZ-impregnation potentiated the antibiofilm activity of ciprofloxacin and meropenem. Conclusion: These findings bring perspectives for the use of CPZ as an adjuvant for preventing and treating catheter-associated urinary tract infections.

Structure-Activity Relationship of Peptide-Conjugated Chloramphenicol for Inhibiting Escherichia coli

Intravenous administration of a prodrug, chloramphenicol succinate (CLsu), is ineffective. Recently, we have shown that conjugation of diglycine of CLsu (CLsuGG) not only increases the antibiotic efficacy against Escherichia coli but also reduces adverse drug effects against bone marrow stromal cells. Here, we report the synthesis of structural analogues of CLsuGG and their activities against E. coli. These analogues reveal several trends: (i) except the water-insoluble analogues, the attachment of peptides to CLsu enhances the efficacy of the prodrugs; (ii) negative charges, high steric hindrance in the side chains, or a rigid diester decreases the activities of prodrugs in comparison to CLsuGG; (iii) dipeptides apparently increase the efficacy of the prodrugs most effectively; and so forth. This work suggests that conjugating peptides to CLsu effectively modulates the properties of prodrugs. The structure-activity relationship of these new conjugates may provide useful insights for expanding the pool of antibiotics.

FSE-Ag complex NS: preparation and evaluation of antibacterial activity

Silver (Ag) complexes of drugs and their nanosystems have great potential as antibacterials. Recently, an Ag complex of furosemide (Ag-FSE) has shown to be a promising antimicrobial. However, poor solubility of Ag-FSE could hamper its introduction into clinics. Therefore, the authors developed a nanosuspension of Ag-FSE (Ag-FSE_NS) for its solubility and antibacterial activity enhancement. The aim of this study was to introduce a novel nanoantibiotic with enhanced antibacterial efficacy. Ag-FSE_NS was prepared by precipitation-ultrasonication technique. Size, polydispersity index (PI) and zeta potential (ZP) of prepared Ag-FSE_NS were measured by dynamic light scattering, whereas surface morphology was determined using scanning electron microscopy (SEM). In vitro antibacterial activity was evaluated against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa using broth microdilution method. Size, PI and ZP of optimised Ag-FSE_NS1 were 191.2 ± 19.34 nm, 0.465 ± 0.059 and -55.7 ± 8.18 mV, respectively. SEM revealed that Ag-FSE_NS1 particles were rod or needle-like with smooth surfaces. Saturation solubility of Ag-FSE in NS increased eight-fold than pure Ag-FSE. Ag-FSE_NS1 exhibited two-fold and eight-fold enhancements in activity against E. coli and S. aureus, respectively. The results obtained showed that developed Ag-FSE_NS1 holds a promise as a topical antibacterial.

Antibiotic-Induced Genetic Variation: How It Arises and How It Can Be Prevented

By targeting essential cellular processes, antibiotics provoke metabolic perturbations and induce stress responses and genetic variation in bacteria. Here we review current knowledge of the mechanisms by which these molecules generate genetic instability. They include production of reactive oxygen species, as well as induction of the stress response regulons, which lead to enhancement of mutation and recombination rates and modulation of horizontal gene transfer. All these phenomena influence the evolution and spread of antibiotic resistance. The use of strategies to stop or decrease the generation of resistant variants is also discussed.

Biochemical, biological characteristics and antibacterial activity of glycoprotein extracted from the epidermal mucus of African catfish (Clarias gariepinus)

Catfish glycoprotein (CFG) was extracted from the cutaneous mucus of Egyptian catfish by ammonium sulphate precipitation and purified on gel filtration column (sephadex G-50). After purification, CFG produced one band on SDS-PAGE (22 kDa). Urea-PAGE and the pH-solubility of CFG indicated its positive charge (IEP 8). CFG contained 12 saccharides. FTIR spectrum shows 3 groups of bands at 1800-2900, 1100-1700 and 700-1100 cm^-1. CFG exhibited antibacterial activity against 9 pathogenic bacteria with low MIC (50 μg/mL), where two Gram+ bacteria, i.e.; Streptococcus pyogenes (St. pyogenes) and Listeria ivanovii (L. ivanovii) were the most sensitive. The growth curves of the bacteria subjected to 1 MIC of CFG during 30 h showed general growth inhibition, particularly in case of Gram^- bacteria such as E. coli. TEM images showed evidently reduced relative content of the intact cells and clear incurred cellular malformations. Combining CFG with specific antibiotic at equal ratios induced synergistic antibacterial actions, amounting to 40% of the mathematical sum of the combination. Substituting the antibiotic chloramphenicol with gradual increasing ratios of CFG of its starting concentration (30 μg/mL), produced proportionally bigger antibacterial actions against St. pyogenes growth and increasing synergistic effect up to 37% at 80% of CFG substitution.

Antibiotic resistance profile in eye infections in a reference centre in Floridablanca, Colombia

BACKGROUND AND OBJECTIVE

In view of the increasing bacterial resistance to antibiotics, it is necessary to determine it locally in order to serve as a guide in clinical management. The purpose of this study was to characterise the pattern of antibiotic sensitivity in cases of eye infections in a third level ophthalmological institution in Floridablanca (Colombia).

MATERIALS AND METHODS

An observational cross-sectional study in which an analysis was made of the culture and antibiogram reports of specimens taken from cases of conjunctivitis, infectious keratitis, and endophthalmitis between January 2013 and June 2016.

RESULTS

A total of 833 specimens were positive for bacteria. Considering both gram-positive and gram-negative microorganisms gentamicin, tobramycin, and ciprofloxacin showed high resistance rates (64.4%, 40.3%, and 29.1%, respectively). Moxifloxacin, vancomycin, imipenem, and gatifloxacin showed low percentages of resistance: 2.6%, 2.1%, 0.6%, and 0.4%, respectively. When comparing the results with previous studies in our institution, there was a decrease in sensitivity to the fourth-generation quinolones and imipenem, especially within the gram-negative ones.

CONCLUSION

Fourth generation quinolones, imipenem and vancomycin continue to have a low in vitro resistance to bacteria that cause eye infections. However, there was a tendency to an increase in the resistance of gram-negative bacteria. Measures should be taken to try to control this phenomenon, and consider possible antimicrobial therapy alternatives to infections caused by these microorganisms.

Mutations Utilize Dynamic Allostery to Confer Resistance in TEM-1 β-lactamase

β-lactamases are enzymes produced by bacteria to hydrolyze β-lactam antibiotics as a common mechanism of resistance. Evolution in such enzymes has been rendering a wide variety of antibiotics impotent, therefore posing a major threat. Clinical and in vitro studies of evolution in TEM-1 β-lactamase have revealed a large number of single point mutations that are responsible for driving resistance to antibiotics and/or inhibitors. The distal locations of these mutations from the active sites suggest that these allosterically modulate the antibiotic resistance. We investigated the effects of resistance driver mutations on the conformational dynamics of the enzyme to provide insights about the mechanism of their long-distance interactions. Through all-atom molecular dynamics (MD) simulations, we obtained the dynamic flexibility profiles of the variants and compared those with that of the wild type TEM-1. While the mutational sites in the variants did not have any direct van der Waals interactions with the active site position S70 and E166, we observed a change in the flexibility of these sites, which play a very critical role in hydrolysis. Such long distance dynamic interactions were further confirmed by dynamic coupling index (DCI) analysis as the sites involved in resistance driving mutations exhibited high dynamic coupling with the active sites. A more exhaustive dynamic analysis, using a selection pressure for ampicillin and cefotaxime resistance on all possible types of substitutions in the amino acid sequence of TEM-1, further demonstrated the observed mechanism. Mutational positions that play a crucial role for the emergence of resistance to new antibiotics exhibited high dynamic coupling with the active site irrespective of their locations. These dynamically coupled positions were neither particularly rigid nor particularly flexible, making them more evolvable positions. Nature utilizes these sites to modulate the dynamics of the catalytic sites instead of mutating the highly rigid positions around the catalytic site.

Mutational Evolution of Pseudomonas aeruginosa Resistance to Ribosome-Targeting Antibiotics

The present work examines the evolutionary trajectories of replicate Pseudomonas aeruginosa cultures in presence of the ribosome-targeting antibiotics tobramycin and tigecycline. It is known that large number of mutations across different genes - and therefore a large number of potential pathways - may be involved in resistance to any single antibiotic. Thus, evolution toward resistance might, to a large degree, rely on stochasticity, which might preclude the use of predictive strategies for fighting antibiotic resistance. However, the present results show that P. aeruginosa populations evolving in parallel in the presence of antibiotics (either tobramycin or tigecycline) follow a set of trajectories that present common elements. In addition, the pattern of resistance mutations involved include common elements for these two ribosome-targeting antimicrobials. This indicates that mutational evolution toward resistance (and perhaps other properties) is to a certain degree deterministic and, consequently, predictable. These findings are of interest, not just for P. aeruginosa, but in understanding the general rules involved in the evolution of antibiotic resistance also. In addition, the results indicate that bacteria can evolve toward higher levels of resistance to antibiotics against which they are considered to be intrinsically resistant, as tigecycline in the case of P. aeruginosa and that this may confer cross-resistance to other antibiotics of therapeutic value. Our results are particularly relevant in the case of patients under empiric treatment with tigecycline, which frequently suffer P. aeruginosa superinfections.

Identification and screening of potent antimicrobial peptides in arthropod genomes

Using tBLASTn and BLASTp searches, we queried recently sequenced arthropod genomes and expressed sequence tags (ESTs) using a database of known arthropod cecropins, defensins, and attacins. We identified and synthesized 6 potential AMPs and screened them for antimicrobial activity. Using radial diffusion assays and microtiter antimicrobial assays, we assessed the in vitro antimicrobial effects of these peptides against several human pathogens including Gram-positive and Gram-negative bacteria and fungi. We also conducted hemolysis assays to examine the cytotoxicity of these peptides to mammalian cells. Four of the six peptides identified showed antimicrobial effects in these assays. We also created truncated versions of these four peptides to assay their antimicrobial activity. Two cecropins derived from the monarch butterfly genome (Danaus plexippus), DAN1 and DAN2, showed minimum inhibitory concentrations (MICs) in the range of 2-16 μg/ml when screened against Gram-negative bacteria. HOLO1 and LOUDEF1, two defensin-like peptides derived from red flour beetle (Tribolium castaneum) and human body louse (Pediculus humanus humanus), respectively, exhibited MICs in the range of 13-25 μg/ml against Gram-positive bacteria. Furthermore, HOLO1 showed an MIC less than 5 μg/ml against the fungal species Candida albicans. These peptides exhibited no hemolytic activity at concentrations up to 200 μg/ml. The truncated peptides derived from DAN2 and HOLO1 showed very little antimicrobial activity. Our experiments show that the peptides DAN1, DAN2, HOLO1, and LOUDEF1 showed potent antimicrobial activity in vitro against common human pathogens, did not lyse mammalian red blood cells, and indicates their potential as templates for novel therapeutic agents against microbial infection.

Global phylogenetic analysis of Escherichia coli and plasmids carrying the mcr-1 gene indicates bacterial diversity but plasmid restriction

To understand the dynamics behind the worldwide spread of the mcr-1 gene, we determined the population structure of Escherichia coli and of mobile genetic elements (MGEs) carrying the mcr-1 gene. After a systematic review of the literature we included 65 E. coli whole genome sequences (WGS), adding 6 recently sequenced travel related isolates, and 312 MLST profiles. We included 219 MGEs described in 7 Enterobacteriaceae species isolated from human, animal and environmental samples. Despite a high overall diversity, 2 lineages were observed in the E. coli population that may function as reservoirs of the mcr-1 gene, the largest of which was linked to ST10, a sequence type known for its ubiquity in human faecal samples and in food samples. No genotypic clustering by geographical origin or isolation source was observed. Amongst a total of 13 plasmid incompatibility types, the IncI2, IncX4 and IncHI2 plasmids accounted for more than 90% of MGEs carrying the mcr-1 gene. We observed significant geographical clustering with regional spread of IncHI2 plasmids in Europe and IncI2 in Asia. These findings point towards promiscuous spread of the mcr-1 gene by efficient horizontal gene transfer dominated by a limited number of plasmid incompatibility types.

Diastereoselective synthesis and biological evaluation of enantiomerically pure tricyclic indolines

Tricyclic indolines are common in both natural products and synthetic chemical probes. In this study we demonstrated that enantiomerically pure tricyclic indolines can be prepared from an inexpensive commercially available chiral starting material, pyroglutamic acid. The synthesis features a highly diastereoselective gold-catalyzed cyclization of alkyne-tethered indoles and subsequent diastereoselective reductive ring-opening reaction. Using this approach, we synthesized analogs of our previously discovered tricyclic indoline probes that possess antibacterial and resistance-modifying activity. The biological activity against methicillin-resistant Staphylococcus aureus (MRSA) of these analogues was evaluated and reported. The synthetic approach reported may be leveraged in the future to prepare diastereopure chemical probes for the determination of biological targets for drug discovery.

Effect of iNOS inhibitor LNMMA along with antibiotics Chloramphenicol or Ofloxacin in murine peritoneal macrophages regulates S.aureus infection as well as inflammation: An in vitro study

Death due to sepsis by S. aureus is rapidly increasing because of their potent weaponries against macrophage mediated killing. Macrophages serve as intracellular reservoirs of S. aureus. Although significant resources have been invested during the last decade in new treatments for sepsis, only antibiotic therapy has failed to improve outcomes. Moreover the host pathogen interaction resulted in host cell death triggering inflammation. So, successful therapy requires amalgamation of therapies to delineate pathogen along with providing protection to host cell. With this idea, LNMMA, the iNOS inhibitor is used along with antibiotics Ofloxacin or Chloramphenicol on S. aureus infected mouse peritoneal macrophage. ROS like H₂O₂, O₂^- production has been measured. NO inhibition by iNOS inhibitor and antioxidant levels has been analysed. COX2, TLR2 and iNOS expression along with proinflammatory cytokine level was studied. It was found that the use of iNOS inhibitor LNMMA along with antibiotics not only enhances bacterial clearance but also decreases proinflammatory responses in Staphylococcus aureus infected macrophages. Inhibition of TLR2 as well as COX2 has also been found in combined treatment groups. The use of iNOS inhibitor LNMMA plus Ofloxacin or Chloramphenicol pretreatment enhanced bacterial clearance by increasing ROS. Decreases in NO protect the cell from harmful peroxynitril as well as inflammatory damage by changes in iNOS, COX2 activity along with reduced proinflammatory cytokines like TNFα, IFNγ, IL1-β etc. Changes in antioxidant level has been found. This in-vitro realm of augmented bacterial clearance and regulated inflammation may be considered as a novel and important therapeutic intervention.

Quorum Sensing Inhibitors from the Sea Discovered Using Bacterial N-acyl-homoserine Lactone-Based Biosensors

Marine natural products with antibiotic activity have been a rich source of drug discovery; however, the emergence of antibiotic-resistant bacterial strains has turned attention towards the discovery of alternative innovative strategies to combat pathogens. In many pathogenic bacteria, the expression of virulence factors is under the regulation of quorum sensing (QS). QS inhibitors (QSIs) present a promising alternative or potential synergistic treatment since they disrupt the signaling pathway used for intra- and interspecies coordination of expression of virulence factors. This review covers the set of molecules showing QSI activity that were isolated from marine organisms, including plants (algae), animals (sponges, cnidarians, and bryozoans), and microorganisms (bacteria, fungi, and cyanobacteria). The compounds found and the methods used for their isolation are the emphasis of this review.

Does the presence of Klebsiella pneumoniae carbapenemase and New Delhi metallo-β-lactamase-1 genes in pathogens lead to fatal outcome?

INTRODUCTION

Infections due to multidrug-resistant (MDR) pathogens are a medical challenge. There is considerable apprehension among clinicians regarding pathogens reported as carrying New Delhi metallo-β-lactamase-1 (NDM) and Klebsiella pneumoniae carbapenemase (KPC) genes from their patients. In the face of extremely high rates of antimicrobial resistance, it is essential to gauge the clinical significance of isolation of pathogens carrying these genes from clinical samples. This study compares the outcome of patients infected with pathogens carrying NDM/KPC genes versus those without these genes.

METHODS

The study was conducted over a 1-year period at a Level-1 trauma centre. Hospital-acquired infections were diagnosed on the basis of CDC's criteria. The correlation of isolation of a multi-resistant pathogen carrying KPC or NDM genes with the clinical outcome was ascertained.

RESULTS

A total of 276 consecutive patients admitted to the Intensive Care Units/wards of the JPNA Trauma Centre were included in this study. Of the 371 isolates recovered from these patients, 116 were from patients who had a fatal outcome. The difference in prevalence of blaNDMand blaKPCwas not significant in any genera of Gram-negative pathogens isolated from patients who survived versus those who had a fatal outcome.

CONCLUSION

Isolation of MDR pathogens carrying NDM/KPC genes from clinical samples is not always a harbinger of a fatal outcome. Efforts should be made to prevent cross-transmission of these pathogens.

An assessment of the future impact of alternative technologies on antibiotics markets

BACKGROUND

The increasing threat of antimicrobial resistance combined with the paucity of new classes of antibiotics represents a serious public health challenge. New treatment technologies could, in theory, have a significant impact on the future use of traditional antibiotics, be it by facilitating rational and responsible use or by product substitution in the existing antibiotics markets, including by reducing the incidence of bacterial infections through preventative approaches. The aim of this paper is to assess the potential of alternative technologies in reducing clinical use of and demand for antibiotics, and to briefly indicate which segments of the antibiotics market that might be impacted by these technologies.

METHODS

An initial mapping exercise to identify the alternative technologies was followed by a review of relevant published and grey literature (n = 52). We also carried out stakeholder engagement activities by a round-table discussion with infectious disease specialists and a multi-criteria decision analysis exercise with pharmaceutical industry experts.

RESULTS

Ten alternative technologies were identified and analyzed for their potential impact on the antibiotics market. Of these, rapid point-of-care diagnostics, vaccines, fecal microbiota transplantation, and probiotics were considered to have a "high" or "medium" potential impact over a 10-20 year horizon. Therapeutic antibodies, antibiotic biomaterials, bacteriophages, antimicrobial nanoparticles, antimicrobial peptides, and anti-virulence materials were rated as having "low" potential impact.

CONCLUSION

Despite the apparent potential of the most promising alternative technologies to reduce demand, that reduction will likely only happen in limited segments of the antibiotics market or, in the case of preventing community acquired streptococcal infections by vaccination, in a low-price generics market segment. Thus, alternative technologies are not expected to represent any disincentive to antibiotics developers. Finally, it is unlikely that alternative technologies will displace the need for new classes, and sub-classes, of antibiotics in the short and medium terms.

Import and spread of extended-spectrum β-lactamase-producing Enterobacteriaceae by international travellers (COMBAT study): a prospective, multicentre cohort study

BACKGROUND

International travel contributes to the dissemination of antimicrobial resistance. We investigated the acquisition of extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-E) during international travel, with a focus on predictive factors for acquisition, duration of colonisation, and probability of onward transmission.

METHODS

Within the prospective, multicentre COMBAT study, 2001 Dutch travellers and 215 non-travelling household members were enrolled. Faecal samples and questionnaires on demographics, illnesses, and behaviour were collected before travel and immediately and 1, 3, 6, and 12 months after return. Samples were screened for the presence of ESBL-E. In post-travel samples, ESBL genes were sequenced and PCR with specific primers for plasmid-encoded β-lactamase enzymes TEM, SHV, and CTX-M group 1, 2, 8, 9, and 25 was used to confirm the presence of ESBL genes in follow-up samples. Multivariable regression analyses and mathematical modelling were used to identify predictors for acquisition and sustained carriage, and to determine household transmission rates. This study is registered with ClinicalTrials.gov, number NCT01676974.

FINDINGS

633 (34·3%) of 1847 travellers who were ESBL negative before travel and had available samples after return had acquired ESBL-E during international travel (95% CI 32·1-36·5), with the highest number of acquisitions being among those who travelled to southern Asia in 136 of 181 (75·1%, 95% CI 68·4-80·9). Important predictors for acquisition of ESBL-E were antibiotic use during travel (adjusted odds ratio 2·69, 95% CI 1·79-4·05), traveller's diarrhoea that persisted after return (2·31, 1·42-3·76), and pre-existing chronic bowel disease (2·10, 1·13-3·90). The median duration of colonisation after travel was 30 days (95% CI 29-33). 65 (11·3%) of 577 remained colonised at 12 months. CTX-M enzyme group 9 ESBLs were associated with a significantly increased risk of sustained carriage (median duration 75 days, 95% CI 48-102, p=0·0001). Onward transmission was found in 13 (7·7%) of 168 household members. The probability of transmitting ESBL-E to another household member was 12% (95% CI 5-18).

INTERPRETATION

Acquisition and spread of ESBL-E during and after international travel was substantial and worrisome. Travellers to areas with a high risk of ESBL-E acquisition should be viewed as potential carriers of ESBL-E for up to 12 months after return.

FUNDING

Netherlands Organisation for Health Research and Development (ZonMw).

Synthesis and Biological Activity of Highly Cationic Dendrimer Antibiotics

The development of pathogenic bacteria resistant to current treatments is a major issue facing the world today. Here, the synthesis and biological activity of fourth generation poly(amidoamine) dendrimers decorated with 1-hexadecyl-azoniabicylo[2.2.2]octane (C₁₆-DABCO), a quaternary ammonium compound known to have antibacterial activity, are described. This highly cationic dendrimer antibiotic was tested against several Gram positive and Gram negative strains of pathogenic bacteria and exhibited activity against both. Higher activity toward the Gram positive strains that were tested was observed. After the antimicrobial activity was assessed, E. coli and B. cereus were subjected to a resistance selection study. This study demonstrated that a multivalent approach to antimicrobial design significantly reduces the likelihood of developing bacterial resistance. Highly cationic dendrimers were also used as pretreatment of a membrane to prevent biofilm formation.

Population Pharmacokinetics of Fixed Dose Combination of Ceftriaxone and Sulbactam in Healthy and Infected Subjects

Increased antibacterial resistance (ABR) and limited drug discovery warrant optimized use of available antibiotics. One option is to rationally combine two antibiotics (fixed dose combination (FDC)) that may delay or prevent emergence of ABR in notorious pathogen. Major concern with FDC is the mutual interaction of its components that might influence their pharmacokinetic (PK) profile, requiring reassessing of whole formulation (adding cost and time). The interaction can be identified by comparing PK profile of a drug present in FDC with its independent entity. An open-label, crossover, single-dose comparative PK study of FDC (ceftriaxone and sulbactam) with their individual reference formulations was performed in 24 healthy adult subjects. No mutual PK interactions between ceftriaxone and sulbactam were observed. Pharmacokinetic data was used to develop a population-PK model to understand between-subject variability (BSV). Pharmacokinetics of ceftriaxone/sulbactam was explained by one and two compartment models, respectively. The subject's "weight" was identified as a covariate explaining BSV. Both internal and external validations (healthy/infected subjects) were done. The model-derived population-PK parameters of FDC's active components in infected subjects were similar to literature reported values of individual components. Efficacies of various FDC dosage regimens over a range of minimum inhibitory concentrations (MICs) were assessed by Monte Carlo simulations using population-PK parameters of infected/healthy subjects. In infected subjects, 3 g FDC/24 h can treat bacteria with MIC ≤8 μg/mL, while for MIC 8-32 μg/mL, 3 g FDC/12 h is recommended. Lastly, the developed population-PK model was successfully used to predict drug exposure in pediatric population.

Does antibiotic resistance impair plasma susceptibility of multi-drug resistant clinical isolates of enterococci in vitro?

Background

Cold atmospheric plasma could constitute an alternative against multi-drug resistant pathogens. Susceptibility of enterococci to cold atmospheric plasma was investigated in vitro.

Methods

39 clinical isolates of enterococci were grouped dependent on the most important resistance patterns and treated on agar using dielectric barrier discharge plasma. These included enterococci with combined vancomycin- and high-level gentamicin resistance, high-level resistance to gentamicin (HLGR) only, vancomycin resistance alone (VRE), and enterococci susceptible to both. Susceptibility to cold atmospheric plasma was evaluated based on the zones of inhibition and examined in terms of the enterococcal group and the “degree” of drug resistance.

Results

Cold atmospheric plasma treatment killed all groups. Comparison of VRE and HLGR strains with non-VRE and non-HLGR isolates concerning zones of inhibition revealed that enterococci with special resistance patterns (VRE and HLGR) showed significantly smaller zones of inhibition than the sensitive ones. The mean of all isolates, irrespective of belonging to groups, showed smaller zones of inhibition with increasing “degree” of drug resistance.

Conclusions

Cold atmospheric plasma treatment killed all isolates of enterococci, but its efficacy depended on the “degree” of drug resistance and on membership in special resistance groups with particular clinical-outbreak importance. However, a possible role of the different genetic lineages, which might be prone to acquiring more or less resistance phenotypes, may also play a role in this context.

Electronic supplementary material

The online version of this article (doi:10.1186/s13099-016-0122-4) contains supplementary material, which is available to authorized users.

The clinical management of lower respiratory tract infections

The 2010 Global Burden of Disease Study reported that lower respiratory tract infections, including pneumonia, are the fourth most common cause of death globally. The etiology of acute bronchitis and asthma exacerbations is mostly viral and the therapy is symptomatic. Management decisions in community acquired pneumonia regarding site of care, extent of assessment, and level of treatment are based primarily on disease severity (outpatient, inpatient, ICU admission). Antibiotics are the main choice of treatment for patients with pneumonia, acute exacerbations (AE) of COPD (including increased sputum purulence and worsening shortness of breath) and AE of non-CF bronchiectasis. Inhaled antibiotics may represent a more optimal approach for the treatment and prevention of AE of non-CF bronchiectasis. Approved strategies for the prevention of exacerbations include smoking cessation and rehabilitation programs, drug therapy and vaccination.

Consolidating Russia and Eurasia Antibiotic Resistance Data for 1992-2014 Using Search Engine

Background: The World Health Organization recognizes the antibiotic resistance problem as a major health threat in the twenty first century. The paper describes an effort to fight it undertaken at the verge of two industries—healthcare and Data Science. One of the major difficulties in monitoring antibiotic resistance is low availability of comprehensive research data. Our aim is to develop a nation-wide antibiotic resistance database using Internet search and data processing algorithms using Russian language publications.

Materials and Methods: An interdisciplinary team built an intelligent Internet search filter to locate all publicly available research data on antibiotic resistance in Russia and Eurasia countries, extracted it, and collated it for analysis. A database was constructed using data from 850 original studies conducted at 153 locations in 12 countries between 1992 and 2014. The studies contained susceptibility and resistance rates of 156 microorganisms to 157 antibiotic drugs.

Results: The applied search methodology was highly robust in that it yielded search precision of 58 vs. 20% in a typical Internet search. It allowed finding and collating within the database the following data items (among many others): publication details including title, source, date, authors, etc.; study details: time period, locations, research organization, therapy area, etc.; microorganisms and antibiotic drugs included in the study along with prevalence values of resistant and susceptible strains, and numbers of isolates. The next stage in project development will try to validate the data by matching it to major benchmark studies; in addition, a panel of experts will be convened to evaluate the outcomes.

Conclusions: The work provides a supplementary tool to national surveillance systems in antibiotic resistance, and consolidates fragmented research data available for 12 countries for a period of more than 20 years.

Carriage of Enterobacteria Producing Extended-Spectrum β-Lactamases and Composition of the Gut Microbiota in an Amerindian Community

Epidemiological and individual risk factors for colonization by enterobacteria producing extended-spectrum beta-lactamases (E-ESBL) have been studied extensively, but whether such colonization is associated with significant changes in the composition of the rest of the microbiota is still unknown. To address this issue, we assessed in an isolated Amerindian Guianese community whether intestinal carriage of E-ESBL was associated with specificities in gut microbiota using metagenomic and metatranscriptomic approaches. While the richness of taxa of the active microbiota of carriers was similar to that of noncarriers, the taxa were less homogeneous. In addition, species of four genera, Desulfovibrio, Oscillospira, Parabacteroides, and Coprococcus, were significantly more abundant in the active microbiota of noncarriers than in the active microbiota of carriers, whereas such was the case only for species of Desulfovibrio and Oscillospira in the total microbiota. Differential genera in noncarrier microbiota could either be associated with resistance to colonization or be the consequence of the colonization by E-ESBL.

Specific chemical modification of bacterial type I dehydroquinase – opportunities for drug discovery

Type I dehydroquinase (DHQ1) is a class I aldolase enzyme that catalyzes the reversible dehydration of 3-dehydroquinic acid to form 3-dehydroshikimic acid by multistep mechanism that involves the formation of Schiff-base species. DHQ1 is present in plants and several bacterial sources but it does not have any counterpart in human cells. It has been suggested that DHQ1 may act as a virulence factor in vivo and therefore a promising target in the search for new antivirulence agents to combat widespread antibiotic resistance. This review covers recent progress in the structure-based design and chemical modifications caused by selective irreversible inhibitors. Computational studies aimed at understanding the experimentally obtained covalent modifications and inhibitory potencies of these inhibitors are also described.

Environmental dissemination of antibiotic resistance genes and correlation to anthropogenic contamination with antibiotics

Antibiotic resistance is a growing problem which threatens modern healthcare globally. Resistance has traditionally been viewed as a clinical problem, but recently non-clinical environments have been highlighted as an important factor in the dissemination of antibiotic resistance genes (ARGs). Horizontal gene transfer (HGT) events are likely to be common in aquatic environments; integrons in particular are well suited for mediating environmental dissemination of ARGs. A growing body of evidence suggests that ARGs are ubiquitous in natural environments. Particularly, elevated levels of ARGs and integrons in aquatic environments are correlated to proximity to anthropogenic activities. The source of this increase is likely to be routine discharge of antibiotics and resistance genes, for example, via wastewater or run-off from livestock facilities and agriculture. While very high levels of antibiotic contamination are likely to select for resistant bacteria directly, the role of sub-inhibitory concentrations of antibiotics in environmental antibiotic resistance dissemination remains unclear. In vitro studies have shown that low levels of antibiotics can select for resistant mutants and also facilitate HGT, indicating the need for caution. Overall, it is becoming increasingly clear that the environment plays an important role in dissemination of antibiotic resistance; further studies are needed to elucidate key aspects of this process. Importantly, the levels of environmental antibiotic contamination at which resistant bacteria are selected for and HGT is facilitated at should be determined. This would enable better risk analyses and facilitate measures for preventing dissemination and development of antibiotic resistance in the environment.

Focus on ceftazidime-avibactam for optimizing outcomes in complicated intra-abdominal and urinary tract infections

INTRODUCTION

Complicated intra-abdominal infections and urinary tract infections are frequently associated with Gram-negative bacteria and treatment can be hampered by the involvement of resistant organisms. A common resistance mechanism is β-lactamase production which confers resistance to β-lactam antibiotics.

AREAS COVERED

This article summarizes β-lactamases found among Gram-negative bacteria as well as providing an overview of complicated intra-abdominal infections and urinary tract infections and the impact inappropriate antibiotic therapy and antibiotic resistance has in their treatment. The author reviews the activity of ceftazidime-avibactam , including animal model data and microbiological data from Phase II clinical trials. This article also highlights Phase III clinical trials of ceftazidime-avibactam that are ongoing or completed and briefly discusses other β-lactamase inhibitor combinations currently in development.

EXPERT OPINION

The increasing problem and complexity of β-lactamase resistance has been met by resurgence in the development of β-lactamase inhibitor combinations. These show promise in the treatment of resistant infections. One β-lactamase inhibitor in advanced development with a broad spectrum of activity is avibactam, covering class A, class C and some class D enzymes. Importantly, the activity of avibactam also includes carbapenemases such as the KPC and OXA-48. The combination of avibactam with the cephalosporin ceftazidime is attractive, given the spectrum of antimicrobial activity and the low toxicity of the cephalosporin class.

Targets for Combating the Evolution of Acquired Antibiotic Resistance

Bacteria possess a remarkable ability to rapidly adapt and evolve in response to antibiotics. Acquired antibiotic resistance can arise by multiple mechanisms but commonly involves altering the target site of the drug, enzymatically inactivating the drug, or preventing the drug from accessing its target. These mechanisms involve new genetic changes in the pathogen leading to heritable resistance. This recognition underscores the importance of understanding how such genetic changes can arise. Here, we review recent advances in our understanding of the processes that contribute to the evolution of antibiotic resistance, with a particular focus on hypermutation mediated by the SOS pathway and horizontal gene transfer. We explore the molecular mechanisms involved in acquired resistance and discuss their viability as potential targets. We propose that additional studies into these adaptive mechanisms not only can provide insights into evolution but also can offer a strategy for potentiating our current antibiotic arsenal.