Rapid Evolution Of Drug Resistance Research Articles

Synthesis of a tetralone derivative of ampicillin to control ampicillin-resistant Staphylococcusaureus

Due to the rapid emergence of antibiotic resistant new bacterial strains and new infections, there is an urgent need for novel or newly modified and efficient alternatives of treatment. However, conventional antibiotics are still used in therapeutic settings but their efficacy is uncertain due to the rapid evolution of drug resistance. In the present study, we have synthesized a new derivative of conventional antibiotic ampicillin using SN2-type substitution reaction. NMR and mass analysis of the newly synthesized derivative of ampicillin confirmed it as ampicillin-bromo-methoxy-tetralone (ABMT). Importantly, ABMT is revealed to have efficient activity against Staphylococcus aureus (S. aureus) with a MIC value of 32 μg ml−1 while ampicillin was not effective, even at 64 μg ml−1 of concentration. Electron microscopy results confirmed the membrane-specific killing of S. aureus at 1 h of treatment. Additionally, molecular docking analysis revealed a strong binding affinity of ABMT with β-lactamase via the formation of a closed compact bridge. Our findings, avail a new derivative of ampicillin that could be a potential alternative to fight ampicillin-resistant bacteria possibly by neutralizing the β-lactamase action.

Synthesis, Biological Evaluation, QSAR, Molecular Docking and ADMET Studies of N-aryl/N,N-dimethyl Substituted Sulphonamide Derivatives

<P>Background: Rapid evolution of drug resistance and side effects of currently used drugs develop more efficacious and newer antimicrobial agents. Further, for the management of Type II Diabetes, α-gulcosidase and α-amylase inhibitors play a very important role by inhibiting the postprandial hyperglycemia. </P><P> Objectives: The objective of this study was to synthesize N-aryl/N,N-dimethyl sulphonamides, investigate their antihyperglycemic and antimicrobial potential, develop QSAR model for identifying molecular descriptors and predict their binding modes and in silico ADMET properties. </P><P> Methods: Synthesized derivatives were subjected to in vitro studies for their antidiabetic activity against α-glucosidase and α-amylase enzymes and antimicrobial activity. Molecular docking studies were carried out to find out molecular binding interactions of the ligand molecules with their respective targets. QSAR studies were carried out to identify structural determinants responsible for antimicrobial activity. </P><P> Results: Antidiabetic study demonstrated the potent activity of two compounds 2 and 6 as α- glucosidase and α-amylase inhibitors, as well as compound 1 and 2, exhibited potent antimicrobial activity against all the tested microbes. All the compounds have more antifungal potential against Candida albicans. QSAR studies confirmed the role of molecular connectivity indices (valence first order and second order) in controlling the antimicrobial activity. Molecular docking studies supported the observed in vitro biological activities of the synthesized compounds. </P><P> Conclusion: The compounds with 2,3-dimethyl substitution were found to be antidiabetic agents and molecules having bromo and 2,3-dimethyl substituents on phenyl ring have established themselves as potent antimicrobial agents. The role of valence first and 2nd order molecular connectivity indices as molecular properties were identified for antimicrobial activity and various electrostatic, hydrogen bonding and hydrophobic interactions were found to be prominent in the binding of molecules at the target site.</P>

A Physical Model Overlay of Wild Type Influenza Virus A Neuraminidase and the His274Tyr Mutant Reveals the Basis of Drug Resistance and Catalysis

The influenza virus is the causative agent of the flu, a contagious respiratory illness that causes morbidity, loss of productivity, and, in some instances, death. Although the seasonal flu is typically only life threatening to high‐risk groups, exceptionally virulent forms of the virus that emerge during pandemics, can even threaten strong and otherwise healthy individuals. A strong arsenal of antiviral drugs is essential during a pandemic, but drug resistance threatens our preparedness. A key target for antivirals is neuraminidase, an enzyme that cleaves glycosidic bonds between sialic acid residues on cell surface glycoproteins so that the virus can infect or escape from host cells to repeat the cycle of infection. The enzyme exists as a homo‐tetramer with calcium ions stabilizing the protein structure. Antiviral medications, including Oseltamivir and Zanamivir, inhibit neuraminidase activity but resistance to Oseltamivir is most prevalent. The challenges posed by the rapid evolution of drug resistance have led Dr. Schiffer and her colleagues to develop more innovative ways, based on structural analyses to formulate drugs that are immune to resistance. We chose to focus on resistance of the His274Tyr neuraminidase mutant to the drug Oseltamivir using the crystal structure solved by Collins and colleagues that demonstrates that this resistance is due to a shift in the position of Glu276 into the hydrophobic pocket of the active site. Using the software application, Jmol, we designed physical models based on the overlaid crystal structures of the wild type and the His274Tyr mutant to visualize the shift in Glu276 and its impact on binding of each of three potential ligands: Oseltamivir, Zanamivir, and Sialic Acid. In addition, the catalytic residues Tyr406 and Glu277 were displayed to visualize the lack of impact on catalytic cleavage of the natural substrate, but continued inhibition by Zanamivir. By designing a physical model of Neuraminidase to emphasize the dimensional and catalytic residues, a better understanding of the protein’s function and potential inhibition by drugs can be obtained and may lead to a more effective way to design drugs in the future.Support or Funding InformationSupport for the CREST Project is through NSF‐IUSE #1725940.

Natural Terpenoids Against Female Breast Cancer: A 5-year Recent Research.

The approval of Taxol® in 1993 marked the great entrance of terpenoids in the anti-cancer area and this drug is still highly important in the treatment of refractory ovarian, breast and other cancers. Over decades, other prominent natural terpenoids have become indispensable for the modern pharmacotherapy of breast cancer. However, given the rapid evolution of drug resistance, effective treatments for advanced breast cancers requiring cytotoxic chemotherapy represent a major unmet clinical need. Therefore, innovative agents effective in long-term chemotherapy are urgently needed. This review examines recent advances/research about natural terpenoids, and their mechanisms against female breast cancer over the period covering January 1st, 2012 to December 31st, 2016. Carcinogenesis constitutes a multistep process wherein each stage is characterized by distinct phenotypic changes. Numerous chemicals recorded in this review have been shown to significantly inhibit proliferation, migration, apoptosis resistance, tumor angiogenesis or metastasis in different breast cancer cells/tumours in vitro and in vivo. Targeting simultaneously several or all these aspects/steps of cancer progression could be an advantage. In line with this, phytochemicals such as thymoquinone (8), costunolide (46), tanshinone IIA (132), triptolide (136), cucurbitacin B (179), celastrol (226) and lycopene (238) had caught our attention. These compounds appear to be promising to overcome breast cancer treatment failure. However, despite the interesting activities, additional preclinical investigations are needed in further breast cancer cell/tumor models in vitro and in vivo.

An experimental evaluation of drug-induced mutational meltdown as an antiviral treatment strategy.

The rapid evolution of drug resistance remains a critical public health concern. The treatment of influenza A virus (IAV) has proven particularly challenging, due to the ability of the virus to develop resistance against current antivirals and vaccines. Here, we evaluate a novel antiviral drug therapy, favipiravir, for which the mechanism of action in IAV involves an interaction with the viral RNA-dependent RNA polymerase resulting in an effective increase in the viral mutation rate. We used an experimental evolution framework, combined with novel population genetic method development for inference from time-sampled data, to evaluate the effectiveness of favipiravir against IAV. Evaluating whole genome polymorphism data across 15 time points under multiple drug concentrations and in controls, we present the first evidence for the ability of IAV populations to effectively adapt to low concentrations of favipiravir. In contrast, under high concentrations, we observe population extinction, indicative of mutational meltdown. We discuss the observed dynamics with respect to the evolutionary forces at play and emphasize the utility of evolutionary theory to inform drug development.

Genetics-directed drug discovery for combating Mycobacterium tuberculosis infection

Mycobacterium tuberculosis (Mtb), the pathogen of tuberculosis (TB), is one of the most infectious bacteria in the world. The traditional strategy to combat TB involves targeting the pathogen directly; however, the rapid evolution of drug resistance lessens the efficiency of this anti-TB method. Therefore, in recent years, some researchers have turned to an alternative anti-TB strategy, which hinders Mtb infection through targeting host genes. In this work, using a theoretical genetic analysis, we identified 170 Mtb infection-associated genes from human genetic variations related to Mtb infection. Then, the agents targeting these genes were identified to have high potential as anti-TB drugs. In particular, the agents that can target multiple Mtb infection-associated genes are more druggable than the single-target counterparts. These potential anti-TB agents were further screened by gene expression data derived from connectivity map. As a result, some agents were revealed to have high interest for experimental evaluation. This study not only has important implications for anti-TB drug discovery, but also provides inspirations for streamlining the pipeline of modern drug discovery.

Hsp90: A Global Regulator of the Genotype-to-Phenotype Map in Cancers.

Cancer cells have the unusual capacity to limit the cost of the mutation load that they harbor and simultaneously harness its evolutionary potential. This property fuels drug resistance, a key failure mode in oncogene-directed therapy. However, the factors that regulate this capacity might also provide an Achilles' heel that could be exploited therapeutically. Recently, insight has come from a seemingly distant field: protein folding. It is now clear that protein homeostasis broadly supports malignancy and fuels the rapid evolution of drug resistance. Among protein homeostatic mechanisms that influence cancer biology, the essential ATP-driven molecular chaperone heat-shock protein 90 (Hsp90) is especially important. Hsp90 catalyzes folding of many proteins that regulate growth and development. These "client" kinases, transcription factors, and ubiquitin ligases often play critical roles in human disease, especially cancer. Studies in a wide range of systems-from single-celled organisms to human tumor samples-suggest that Hsp90 can broadly reshape the map between genotype and phenotype, acting as a "capacitor" and "potentiator" of genetic variation. Indeed, it has likely done so to such a degree that it has left an impress on diverse genome sequences. Hsp90 can constitute as much as 5% of total protein in transformed cells and increased levels of heat-shock activation correlate with poor prognosis in breast cancer. These findings and others have motivated a flurry of interest in Hsp90 inhibitors as cancer therapeutics, which have met with rather limited success as single agents, but may eventually prove invaluable in limiting the emergence of resistance to other chemotherapeutics, both genotoxic and molecularly targeted. Here, we provide an overview of Hsp90 function, review its relationship to genetic variation and the evolution of new traits, and discuss the importance of these findings for cancer biology and future efforts to drug this pathway.

ISOLATION AND PRESENCE OF ANTIMALARIAL ACTIVITIES OF MARINE SPONGE <i>Xestospongia</i> sp.

Plasmodium falciparum, the agent of malignant malaria, is one of mankind's most severe scourges, mainly in the tropic world. Efforts to develop preventive vaccines or remedial drugs are handicapped by the parasite's rapid evolution of drug resistance. Here, we presented an advance work on examination of antimalarial component from marine life of Xestospongia sp., the study is based on hexane extraction method. The premier result, we obtained five fractions. Among these five fractions, the fourth has the most potent inhibitory against the growth of P. falciparum 3D7 with an IC50: 7.13 µg/mL. A compiled spectrum analysis, FTIR, 1H-NMR and GC-MS, revealed that the fourth fraction consisted abundantly of two secondary metabolites such as flavonoids and triterpenoids. Finally, our results suggest a plausible structure rooted to the base of ibuprofen.

Bacteria Evolve to Go Against the Grain

Since Alexander Fleming discovered in 1928 that a substance secreted by a mold could kill bacteria, we have become used to the ease of administering cocktails of antibiotics to fight bacterial infections. However, the use and misuse of antibiotics in human medicine and livestock farming over many decades has had the serious side effect of selecting for bacteria that survive drug attack: many bacterial strains have emerged that are resistant to antibiotics, most famously the multi-drug-resistant Staphylococcus aureus strain, the source of Staph infections, that represents a major threat to hospital patients. The pool of effective antibiotics is running out, and finding new strategies to prevent the rapid evolution of drug resistance has become a pressing challenge for global health. Now, two independent theoretical studies, one published in Physical Review Letters by Philip Greulich at the University of Edinburgh, UK, and colleagues [1], and the other by Rutger Hermsen at the Center for Theoretical Biological Physics, San Diego, and colleagues in Proceedings of the National Academy of Sciences[2], address how the evolution of drug resistance can be profoundly influenced by how drugs are distributed in biological tissues. Once administered, drugs do not spread evenly throughout the human body, which is compartmentalized and composed of tissues that have different affinity for retaining the drugs. The new research suggests that variations in the drug concentration may play an important role in selecting bacterial strains that are able to survive exposure to antibiotics. The rapid evolution of drug resistance is an impressive demonstration of the efficiency of bacterial adaptation. Bacterial populations are large and cells are able to replicate rapidly (sometimes in minutes) and to exchange genetic material. These are ideal conditions for Darwinian evolution to act: slight changes, or mutations, in the genomes arise by chance from one bacterial generation to the next. While most of these changes are deleterious, some, such as resistance to an antibiotic substance, may confer an advantage to bacteria living in human tissues, allowing the population of resistant mutant strains to rapidly increase. As a consequence, unless a bacterial infection is completely wiped out by a large dose of antibiotics, drug resistant strains emerge. Yet when a mix of antibiotics is administered, the buildup of drug resistance requires multiple mutations and becomes harder to explain [3]; in this case, the bacterial population should be driven to extinction, unless a resistant multimutant arises. This, however, becomes prohibitively unlikely for just a handful of required mutations. Why then does drug resistance evolve so readily? The work of Greulich et al. and Hermsen et al. could solve this puzzle because it demonstrates that spatial variations in drug concentrations allow for a gradual selection of drug resistant mutants. Heterogeneities in drug concentrations have been previously recognized as a potential driver of drug resistance [4, 5], as was demonstrated in a recent microfluidic experiment [6]. Yet quantitative models have been lacking so far. The new theoretical studies fill this gap and help identify parameters that may be key to controlling drug resistance evolution. In a gradient of drug concentration, resistance can evolve following the stepwise dynamics illustrated in Fig. 1. Initially, only a small population of wild-type (i.e., nonmutant) cells can be sustained in the regions where drug concentration is low. The growth of bacteria in this suitable habitat is balanced by the death of bacteria that move by chance into less hospitable regions of higher drug concentration. During this continual population turnover, a mutant will eventually appear that is slightly more resistant than the wild type. This mutant will then be able to endure higher drug concentration and move up the concentration gradient. Thereby the mutant population can overgrow the wild type and reach a steadystate distribution that covers a slightly larger region than

On the rapidity of antibiotic resistance evolution facilitated by a concentration gradient

The rapid emergence of bacterial strains resistant to multiple antibiotics is posing a growing public health risk. The mechanisms underlying the rapid evolution of drug resistance are, however, poorly understood. The heterogeneity of the environments in which bacteria encounter antibiotic drugs could play an important role. E.g., in the highly compartmentalized human body, drug levels can vary substantially between different organs and tissues. It has been proposed that this could facilitate the selection of resistant mutants, and recent experiments support this. To study the role of spatial heterogeneity in the evolution of drug resistance, we present a quantitative model describing an environment subdivided into relatively isolated compartments with various antibiotic concentrations, in which bacteria evolve under the stochastic processes of proliferation, migration, mutation and death. Analytical and numerical results demonstrate that concentration gradients can foster a mode of adaptation that is impossible in uniform environments. It allows resistant mutants to evade competition and circumvent the slow process of fixation by invading compartments with higher drug concentrations, where less resistant strains cannot subsist. The speed of this process increases sharply with the sensitivity of the growth rate to the antibiotic concentration, which we argue to be generic. Comparable adaptation rates in uniform environments would require a high selection coefficient (s>0.1) for each forward mutation. Similar processes can occur if the heterogeneity is more complex than just a linear gradient. The model may also be applicable to other adaptive processes involving environmental heterogeneity and range expansion.

Genomewide Analysis of Divergence of Antibiotic Resistance Determinants in Closely Related Isolates of Acinetobacter baumannii

Multidrug resistance has emerged as a significant concern with infections caused by Acinetobacter baumannii. Ample evidence supports the involvement of mobile genetic elements in the transfer of antibiotic resistance genes, but the extent of variability and the rate of genetic change associated with the acquisition of antibiotic resistance have not been studied in detail. Whole-genome sequence analysis of six closely related clinical isolates of A. baumannii, including four from the same hospital, revealed extensive divergence of the resistance genotype that correlated with observed differences in antimicrobial susceptibility. Resistance genes associated with insertion sequences, plasmids, and a chromosomal resistance gene island all showed variability. The highly dynamic resistance gene repertoire suggests rapid evolution of drug resistance.

Highlights of the Third International Workshop on HIV and Hepatitis Coinfection

Apart from a highly productive lifecycle, HCV is genetically highly diverse, far more so than HIV-1 and HBV. Quasi species rapidly evolve after infection with HCV. This evolution is driven by the host HLA-system and by antiHCV drugs, but also by functional constraints in terms of reversion of sequences towards consensus. Ray presented interesting data demonstrating that evolution of the virus occurs rapidly within weeks after infection. Over the course of years to decades, his group has demonstrated that within a particular host the virus may evolve to genetically distinct subtypes. Recently, another mechanism of genetic diversification, not previously described for HCV, has been discovered. Ray presented data on the recombination of two different HCVs, which may confound genotyping and lead to rapid evolution of drug resistance. The high variability of HCV clearly suggests that future drug therapy with HCV-polymerase and protease inhibitors will have to take into account the rapid evolution of drug resistance. Combination therapy as currently approached, for instance by telaprevir, which is tested together with concomitant pegylated interferon/ribavirin combination therapy, will probably be the only way to circumvent the issue of the rapid evolution of drug resistance.

Recombination in HIV and the evolution of drug resistance: for better or for worse?

The rapid evolution of drug resistance remains a major obstacle for HIV therapy. The capacity of the virus for recombination is widely believed to facilitate the evolution of drug resistance. Here, we challenge this intuitive view. We develop a population genetic model of HIV replication that incorporates the processes of mutation, cellular superinfection, and recombination. We show that cellular superinfection increases the abundance of low fitness viruses at the expense of the fittest strains due to the mixing of viral proteins during virion assembly. Moreover, we argue that whether recombination facilitates the evolution of drug resistance depends critically on how resistance mutations interact to determine viral fitness. Contrary to the commonly held belief, we find that, under the most plausible biological assumptions, recombination is expected to slow down the rate of evolution of multi-drug-resistant virus during therapy.

Bacterial genomics as a potential tool for discovering new antimicrobial agents.

The past 30 years have witnessed the emergence of new infectious diseases as well as the re-emergence of those thought to be defeated or under control. It is likely that this threat will continue and that infectious micro-organisms will be found to be responsible for numerous diseases whose etiology had been previously unknown. Compounding this threat is the rapid evolution of drug resistance by micro-organisms that is rendering many existing antimicrobial agents obsolete. Thus, there is an urgent need for the development of new classes of antimicrobial agents and the identification of new drug targets. Over the past decade, advances in high-throughput automated DNA sequencing have delivered a wealth of genetic information in the form of whole genome sequences of microbial pathogens. Coupled with this advancement has been the development of new genetic tools and computational advances capable of selecting genes of particular interest as well as testing for the effects of candidate drugs. While no new drugs have yet been developed, further study into the application and limitations of these new approaches to the identification of novel targets will aid in overcoming the current problem of antimicrobial drug resistance.

Plasmodium falciparum antigenic diversity: evidence of clonal population structure.

Plasmodium falciparum, the agent of malignant malaria, is one of mankind's most severe scourges. Efforts to develop preventive vaccines or remedial drugs are handicapped by the parasite's rapid evolution of drug resistance and protective antigens. We examine 25 DNA sequences of the gene coding for the highly polymorphic antigenic circumsporozoite protein. We observe total absence of silent nucleotide variation in the two nonrepeated regions of the gene. We propose that this absence reflects a recent origin (within several thousand years) of the world populations of P. falciparum from a single individual; the amino acid polymorphisms observed in these nonrepeat regions would result from strong natural selection. Analysis of these polymorphisms indicates that: (i) the incidence of recombination events does not increase with nucleotide distance; (ii) the strength of linkage disequilibrium between nucleotides is also independent of distance; and (iii) haplotypes in the two nonrepeat regions are correlated with one another, but not with the central repeat region they span. We propose two hypotheses: (i) variation in the highly polymorphic central repeat region arises by mitotic intragenic recombination, and (ii) the population structure of P. falciparum is clonal--a state of affairs that persists in spite of the necessary stage of physiological sexuality that the parasite must sustain in the mosquito vector to complete its life cycle.

1993 Sir Henry Wellcome Medal and Prize Recipient

Mefloquine is an antimalarial drug developed by the U.S. Army Antimalarial Drug Program in conjunction with the World Health Organization and Hoffmann-La Roche to address the problem of chloroquine-resistant falciparum malaria encountered during the Vietnam War. Despite the expenditure of millions of dollars over a 20-year period, it is unlikely that mefloquine will ever be used for U.S. soldiers deployed to South East Asia. Although mefloquine met the specifications set by its developers, its usefulness is now limited by the rapid evolution of drug resistance following its release to the civilian population. Drug development for particular military needs was compromised by a rapid biological response from the parasite and commercial concerns. In an era of shrinking military budgets, military drug development programs will by necessity be more resource constrained, thus yielding fewer new drugs per decade. In the short-term, emphasis should be directed toward adapting available antimicrobial drugs for antimalarial purposes.