Drug-resistant Diseases Research Articles

Structure and Biosynthesis of the Antibiotic Bottromycin D

Drug resistant infectious diseases are quickly becoming a global health crisis. While Streptomyces spp. have been a major source of antibiotics over the past 50 years, efficient methods are needed to identify new antibiotics and greatly improve the rate of discovery. LCMS-based metabolomics were applied to analyze extracts of 50 Streptomyes spp. Using this methodology, we discovered bottromycin D and used whole genome sequencing to determine its biosynthesis by a ribosomal pathway.

Antimicrobial activity of selected natural products against Gram-positive, Gram-negative and Acid-fast bacterial pathogens

Recurring epidemics of drug resistant bacterial diseases such as those caused by mycobacteria (tuberculosis and non-tuberculous infections), staphylococci (methicillin-resistant <em>Staphylococcus aureus</em> or MRSA infections) and various Gram-negative enterobacteria (enterobacterial infections) have reinforced the need to search for alternative antimicrobials. In this context, we investigated the anti-bacterial potential of nine different natural products and compared them with the antibiotic controls, using three test bacterial species, representing the Gram-negative (<em>Escherichia coli</em>), Gram-positive (<em>Staphylococcus epidermidis</em>), and Acid-fast (<em>Mycobacterium smegmatis</em>) pathogen groups. Six of the nine products showed detectable but variable zones of inhibition (mm2). The anti-bacterial activity (mm2 per 100 mg) of the extracts from the four solid natural products was in the following order for all three pathogen groups: Mint (<em>Mentha arvensis</em>) leaf extract, 264-930>Mushroom (<em>Agaricus bisporus</em>) cap extract, 112-241>Turmeric (<em>Curcuma longa</em>) root extract, 4-10>Ginger (<em>Zingiber officinale</em>) root extract, 3-9. For the liquid products, the activity measured on 100 μL aliquots was in the following order: Eucalyptus (<em>Eucalyptus globules</em>) oil, 264-1044>Mustard (<em>Brassica campestris</em> L. var. brown sarson) oil, 45-96. Taken together, these results indicated the highest activity in Mint extract and Eucalyptus oil against all three test organisms. However, the individual test strains showed the following variable order of susceptibility: Mint extract (<em>M. smegmatis</em>><em>E. coli</em>><em>S</em>. <em>epidermidis</em>); Eucalyptus oil (<em>M. smegmatis</em>><em>S. epidermidis</em>><em>E</em>. <em>coli</em>). Based on these results it can be concluded that Mint leaves and Eucalyptus oil have an unusually broad spectrum activity and may, therefore, be promising sources of new broad spectrum antimicrobials.

An In Vivo Platform for Rapid High-Throughput Antitubercular Drug Discovery

Treatment of tuberculosis, like other infectious diseases, is increasingly hindered by the emergence of drug resistance. Drug discovery efforts would be facilitated by facile screening tools that incorporate the complexities of human disease. Mycobacterium marinum-infected zebrafish larvae recapitulate key aspects of tuberculosis pathogenesis and drug treatment. Here, we develop a model for rapid in vivo drug screening using fluorescence-based methods for serial quantitative assessment of drug efficacy and toxicity. We provide proof-of-concept that both traditional bacterial-targeting antitubercular drugs and newly identified host-targeting drugs would be discovered through the use of this model. We demonstrate the model's utility for the identification of synergistic combinations of antibacterial drugs and demonstrate synergy between bacterial- and host-targeting compounds. Thus, the platform can be used to identify new antibacterial agents and entirely new classes of drugs that thwart infection by targeting host pathways. The methods developed here should be widely applicable to small-molecule screens for other infectious and noninfectious diseases.

Antibacterial effect of Allium sativum cloves and Zingiber officinale rhizomes against multiple-drug resistant clinical pathogens

ObjectiveTo evaluate the antibacterial properties of Allium sativum (garlic) cloves and Zingiber officinale (ginger) rhizomes against multi-drug resistant clinical pathogens causing nosocomial infection. MethodsThe cloves of garlic and rhizomes of ginger were extracted with 95% (v/v) ethanol. The ethanolic extracts were subjected to antibacterial sensitivity test against clinical pathogens. ResultsAnti-bacterial potentials of the extracts of two crude garlic cloves and ginger rhizomes were tested against five gram negative and two gram positive multi-drug resistant bacteria isolates. All the bacterial isolates were susceptible to crude extracts of both plants extracts. Except Enterobacter sp. and Klebsiella sp., all other isolates were susceptible when subjected to ethanolic extracts of garlic and ginger. The highest inhibition zone was observed with garlic (19.45 mm) against Pseudomonas aeruginosa (P. aeruginosa). The minimal inhibitory concentration was as low as 67.00 μg/mL against P. aeruginosa. ConclusionsNatural spices of garlic and ginger possess effective anti-bacterial activity against multi-drug clinical pathogens and can be used for prevention of drug resistant microbial diseases and further evaluation is necessary.

Multiplex De Novo Sequencing of Peptide Antibiotics

Proliferation of drug-resistant diseases raises the challenge of searching for new, more efficient antibiotics. Currently, some of the most effective antibiotics (i.e., Vancomycin and Daptomycin) are cyclic peptides produced by non-ribosomal biosynthetic pathways. The isolation and sequencing of cyclic peptide antibiotics, unlike the same activity with linear peptides, is time-consuming and error-prone. The dominant technique for sequencing cyclic peptides is nuclear magnetic resonance (NMR)-based and requires large amounts (milligrams) of purified materials that, for most compounds, are not possible to obtain. Given these facts, there is a need for new tools to sequence cyclic non-ribosomal peptides (NRPs) using picograms of material. Since nearly all cyclic NRPs are produced along with related analogs, we develop a mass spectrometry approach for sequencing all related peptides at once (in contrast to the existing approach that analyzes individual peptides). Our results suggest that instead of attempting to isolate and NMR-sequence the most abundant compound, one should acquire spectra of many related compounds and sequence all of them simultaneously using tandem mass spectrometry. We illustrate applications of this approach by sequencing new variants of cyclic peptide antibiotics from Bacillus brevis, as well as sequencing a previously unknown family of cyclic NRPs produced by marine bacteria. Supplementary Material is available online at www.liebertonline.com/cmb.

ChemInform Abstract: Antibacterials from the Sea

AbstractReview: 195 refs.

Remission of severe autoimmune bullous disorders induced by long-term extracorporeal photochemotherapy

Pemphigus vulgaris (PV) and epidermolysis bullosa acquisita (EBA) sometimes resist treatments. In drug-resistant cases, adjuvant treatment with extracorporeal photochemotherapy (ECP) has been reported to induce remission. However, limited numbers of patients have been reported up to date. Eleven patients with drug-resistant autoimmune bullous diseases have been treated with ECP (8 patients with PV, 3 patients with EBA). The introduction of ECP to systemic therapies of the patients with PV resulted in complete response (CR) after a limited cycle (2–6 cycles) in all, except one patient. Prednisolone doses could be tapered in all patients. ECP resulted in CR in two patients while improvement was partial in one patient with EBA after 3–6 cycles. Our patients demonstrate the efficacy of long-term ECP to be tried in the treatment of aggressive autoimmune bullous disorders. The treatment has produced a remarkable corticosteroid-sparing effect while inducing clinical remission.

(-)-Epigallocatechin-3-gallate downregulates Pg-P and BCRP in a tamoxifen resistant MCF-7 cell line

We investigated the anticancer effect of EGCG treatment on a breast carcinoma cell line resistant to tamoxifen (MCF-7Tam cells). As there are no reports about the molecular mechanisms implicated in EGCG treatment of tamoxifen resistant breast carcinoma cells, we studied the effects of EGCG treatment on three plasma membrane proteins that are involved in the mechanism of drug-resistance: Multidrug Resistance Protein (MRP1), P-glycoprotein (P-gp) and Breast Cancer Resistance Protein (BCRP). EGCG treatment (10-100 microg/ml for 24-72 hours) caused cell growth inhibition and dose-dependent apoptosis: after 100 microg/ml EGCG treatment for 24 hours, Bax expression increased and Bcl2 expression decreased (p<0.05). Coherently, Annexin V-FITC apoptosis assay detected a significant increase in labelled cells (p<0.05). EGCG did not affect MRP1: in contrast, 100 microg/ml EGCG administration caused P-gp decrease to 53% of control cells (p<0.001) and this effect was not due to downregulation of P-gp gene expression. EGCG induced P-gp decrease even when MG132, a strong proteasome inhibitor, was given together with EGCG to MCF-7Tam cells. EGCG treatment also inhibited BCRP activity: mRNA transcription and protein level did not change after treatment, but mitoxantrone test demonstrated a strong inhibition of BCRP activity (p<0.001). In conclusion, the present results showed that EGCG could down-regulate the activity of two molecules that play a key role in drug metabolism and transport and that are highly expressed in tamoxifen resistant breast carcinoma cells. The interaction of EGCG and drugs used in the therapy of estrogen sensitive breast carcinoma ought to be subject of studies and the potential use of EGCG in drug-resistant diseases ought to be better considered.

The Tumor Necrosis Factor-α-blocking Agent Infliximab Inhibits Interleukin 1ß (IL-1ß) and IL-6 Gene Expression in Human Osteoblastic Cells

Objective.Tumor necrosis factor-α (TNF-α) is a proinflammatory cytokine involved in the pathogenesis of several rheumatic diseases, including rheumatoid arthritis (RA), associated with systemic bone loss and subchondral bone erosions. TNF-α-blocking agents such as infliximab have been successful in treatment of disease-modifying antirheumatic drug-resistant rheumatic diseases. Infliximab therapy in RA also had beneficial effects on local bone destruction and bone mineral density. We assessed effects of infliximab treatment on the bone tissue compartment and cytokine profile expression in vitro.Methods.Osteoblast-like cells were exposed for 24 h to sera of RA patients collected at baseline and after 1 month (T1) and 3 years (T2) of infliximab treatment. Total RNA was extracted, and expression of interleukin 1ß (IL-1ß), IL-6, and osteoprotegerin (OPG) was measured by RT-PCR.Results.IL-1ß gene expression was significantly reduced by the T1 serum, and the same decrease was elicited by the T2 serum. IL-6 downregulation was evident with the T2 serum. OPG was unaffected.Conclusion.The finding of downregulation of inflammatory cytokines was interesting, particularly IL-6, which plays a crucial role in arthritis-related bone loss due to its involvement in osteoclast recruitment and activation. These results may represent a biological explanation and a link for the clinical observation of the beneficial effects of anti-TNF-α agents on the progression of rheumatic diseases at the bone level.

Polyether ionophores: broad-spectrum and promising biologically active molecules for the control of drug-resistant bacteria and parasites

Background: As multidrug-resistant (MDR) pathogens continue to emerge, there is a substantial amount of pressure to identify new drug candidates. Carboxyl polyethers, also referred to as polyether antibiotics, are a unique class of compounds with outstanding potency against a variety of critical infectious disease targets including protozoa, bacteria and viruses. The characteristics of these molecules that are of key interest are their selectivity and high potency against several MDR etiological agents. Objective: Although many studies have been published about carboxyl polyether antibiotics, there are no recent reviews of this class of drugs. The purpose of this review is to provide the reader with an overview of the spectrum of activity of polyether antibiotics, their mechanism of action, toxicity and potential as drug candidates to combat drug-resistant infectious diseases. Conclusion: Polyether ionophores show a high degree of promise for the potential control of drug-resistant bacterial and parasitic infections. Despite the long history of use of this class of drugs, very limited medicinal chemistry and drug optimization studies have been reported, thus leaving the door open to these opportunities in the future. Scifinder and PubMed were the main search engines used to locate articles relevant to the topic presented in the present review. Keywords used in our search were specific names of each of the 88 compounds presented in the review as well as more general terms such as polyethers, ionophores, carboxylic polyethers and polyether antibiotics.

Panning for chemical gold: marine bacteria as a source of new therapeutics

Marine bacteria are emerging as an exciting resource for the discovery of new classes of therapeutics. The promising anticancer clinical candidates salinosporamide A and bryostatin only hint at the incredible wealth of drug leads hidden just beneath the ocean surface. For example, if properly developed, marine bacteria could provide the drugs needed to sustain us for the next 100 years in our battle against drug-resistant infectious diseases. This review will focus on several recently discovered compounds, primarily from cyanobacteria and actinobacteria, that illustrate the tremendous potential of marine bacteria as a source of new therapeutics within the areas of oncology and infectious diseases.

Cancer stem cells: Beyond Koch’s postulates

Until the last century, infectious diseases were the leading cause of human mortality. Therefore, our current medical reasoning is profoundly influenced by views that originated from medical microbiology. The notion that cancer growth is sustained by a sub-population of particular cells, the cancer stem cells, is highly reminiscent of the germ theory of disease as exemplified by Koch’s postulates in the XIX th century. However, accumulating data underscore the importance of cell-cell interactions and tumor environment. Hence it is essential to critically review the basic tenets of the cancer stem cell concept on the light of their relationships with Koch’s postulates. Shifting the pathogenic element from a special cellular entity (cancer stem cell or microorganism) to a “pathogenic field” could be critical for curing both cancer and drug-resistant infectious diseases.

Immunomodulation of autoimmunity in MRL/lpr mice with syngeneic bone marrow transplantation (SBMT).

MRL-lpr/lpr mice spontaneously develop a severe autoimmune syndrome, characterized by massive generalized lymphadenopathy, arthritis, arteritis, dermatitis and immune complex-mediated glomerulonephritis. Bone marrow transplantation (BMT) from MHC-matched systemic lupus erythematosus (SLE)-resistant donors to susceptible recipients has proved effective in correcting autoimmune manifestations in autoimmune-prone mice. We investigated the effect of syngeneic BMT from MRL/lpr (donor) to immunocompromised MRL/lpr (recipient), after purging the bone marrow inoculum with MoAbs against mature T cells (anti-Thy 1.2). All the untreated mice developed lymphadenopathy and by the age of 36 weeks five of the eight were dead; in contrast, all the mice which underwent syngeneic BMT following acute immunosuppression with total body irradiation (900 cGy) (TBI) remained disease-free. In an additional experiment, it was found that conditioning with cyclophosphamide (CY) before BMT was more effective than TBI in inhibiting delayed-onset autoimmune manifestations (mean survival 350 days in the CY group and 305 days in the TBI group, versus 197 days in untreated controls). Under both immunosuppressive regimens T cell-depleted bone marrow grafts produced far better results than did unmanipulated BMT. Following syngeneic BMT the incidence of proteinuria and the level of serum anti-DNA (dd) antibodies were significantly reduced, compared with that of the age-matched untreated controls. CY was more effective than TBI in reducing the anti-DNA titres. Likewise, T depletion of bone marrow inocula before BMT induced a more drastic drop in autoantibodies, following both CY and TBI conditioning protocols. After syngeneic BMT (either CY or TBI) no signs of lymphadenopathy were observed even at an advanced age. Upon histopathological examination, the BMT-treated mice displayed normal glomeruli with occasional minimal signs of glomerulonephritis. Syngeneic T cell-depleted BMT following acute cytoreduction of anti-self immune lymphocytes may represent a new therapeutic approach for drug-resistant autoimmune diseases.

Novel paradigms for drug discovery: computational multitarget screening

An established paradigm in current drug development is (i) to identify a single protein target whose inhibition is likely to result in the successful treatment of a disease of interest; (ii) to assay experimentally large libraries of small-molecule compounds in vitro and in vivo to identify promising inhibitors in model systems; and (iii) to determine whether the findings are extensible to humans. This complex process, which is largely based on trial and error, is risk-, time- and cost-intensive. Computational (virtual) screening of drug-like compounds simultaneously against the atomic structures of multiple protein targets, taking into account protein-inhibitor dynamics, might help to identify lead inhibitors more efficiently, particularly for complex drug-resistant diseases. Here we discuss the potential benefits of this approach, using HIV-1 and Plasmodium falciparum infections as examples. We propose a virtual drug discovery 'pipeline' that will not only identify lead inhibitors efficiently, but also help minimize side-effects and toxicity, thereby increasing the likelihood of successful therapies.

The role of the public toilet: pathogen transmitter or health facilitator?

This paper discusses the role of public toilets, as transmitters of disease, but also of their importance in contributing to the health and well-being of society. Research has shown that public toilets are vital components in creating sustainable, accessible, inclusive cities. But there is no mandatory legislation requiring local authorities to provide them. Over 40% have been closed in the UK in the last 10 years. The promotion of the 24 hour city, characterized by a male youth drinking culture, along with toilet closure, has resulted in increased street urination, creating the conditions for the spread of previously-eradicated, water borne diseases in city streets. Less visible, but as virulent, has been the effect of toilet closure for women. Women, in response to lack of toilet provision, are likely to ‘hold on’ resulting in urine (and pathogen) retention, and bladder distension increasing the propensity for continence problems. The elderly and people with disabilities may simply not go out for fear of there being no toilet when they need one. Those toilets that are available may be unusable. Lack of regulation or compulsory standards result in poor toilet design, inadequate maintenance and management, and unhygienic conditions, resulting in the spread of MRSA and other drug-resistant diseases. Recommendations are summarized for the provision of a spatial hierarchy of toilet provision that would both meet user needs and reduce the chances of the public toilets acting as epicentres of germ transmission. Unless compulsory legislation, increased funding, and improved management, maintenance and cleaning regimes are instigated, public toilet provision will continue to be a source of disease.

Blood-Brain Barrier Active Efflux Transporters: ATP-Binding Cassette Gene Family

The blood-brain barrier (BBB) contributes to brain homeostasis by protecting the brain from potentially harmful endogenous and exogenous substances. BBB active drug efflux transporters of the ATP-binding cassette (ABC) gene family are increasingly recognized as important determinants of drug distribution to, and elimination from, the CNS. The ABC efflux transporter P-glycoprotein (Pgp) has been demonstrated as a key element of the BBB that can actively transport a huge variety of lipophilic drugs out of the brain capillary endothelial cells that form the BBB. In addition to Pgp, other ABC efflux transporters such as members of the multidrug resistance protein (MRP) family and breast cancer resistance protein (BCRP) seem to contribute to BBB function. Consequences of ABC efflux transporters in the BBB include minimizing or avoiding neurotoxic adverse effects of drugs that otherwise would penetrate into the brain. However, ABC efflux transporters may also limit the central distribution of drugs that are beneficial to treat CNS diseases. Furthermore, neurological disorders such as epilepsy may be associated with overexpression of ABC efflux transporters at the BBB, resulting in pharmacoresistance to therapeutic medication. Therefore, modulation of ABC efflux transporters at the BBB forms a novel strategy to enhance the penetration of drugs into the brain and may yield new therapeutic options for drug-resistant CNS diseases.

Blood-brain barrier active efflux transporters: ATP-binding cassette gene family

The blood-brain barrier (BBB) contributes to brain homeostasis by protecting the brain from potentially harmful endogenous and exogenous substances. BBB active drug efflux transporters of the ATP-binding cassette (ABC) gene family are increasingly recognized as important determinants of drug distribution to, and elimination from, the CNS. The ABC efflux transporter P-glycoprotein (Pgp) has been demonstrated as a key element of the BBB that can actively transport a huge variety of lipophilic drugs out of the brain capillary endothelial cells that form the BBB. In addition to Pgp, other ABC efflux transporters such as members of the multidrug resistance protein (MRP) family and breast cancer resistance protein (BCRP) seem to contribute to BBB function. Consequences of ABC efflux transporters in the BBB include minimizing or avoiding neurotoxic adverse effects of drugs that otherwise would penetrate into the brain. However, ABC efflux transporters may also limit the central distribution of drugs that are beneficial to treat CNS diseases. Furthermore, neurological disorders such as epilepsy may be associated with overexpression of ABC efflux transporters at the BBB, resulting in pharmacoresistance to therapeutic medication. Therefore, modulation of ABC efflux transporters at the BBB forms a novel strategy to enhance the penetration of drugs into the brain and may yield new therapeutic options for drug-resistant CNS diseases.

Infectious disease in Haiti. HIV/AIDS, tuberculosis and social inequalities.

More than 50 years after the introduction of chemotherapy for the treatment of tuberculosis (TB), the disease is far from being under control. Among curable infectious diseases, TB remains the number‐one killer—each year, 2 million people still die of the disease and 8.4 million more fall ill (World Health Organization (WHO), 2002a). And future projections are grim. Fewer than half of all TB cases are diagnosed, and of those that are, fewer than 30% have access to the care recommended by the WHO (WHO, 2002a). The increase in TB worldwide is due, in part, to the expansion of the HIV/AIDS pandemic (WHO, 2001): at least one‐third of people with HIV die of TB (WHO, 2002a). HIV/AIDS now causes more than 3 million deaths per year (UNAIDS, 2002). More than 90% of HIV/AIDS deaths and new infections occur in poor countries where less than 5% of those who need antiretroviral treatment have access to these therapies (WHO, 2002b). If we consider that, on average, 10% of people with HIV need antiretroviral treatment, the 5% figure comes down to less than 1% in sub‐Saharan Africa, the region most affected by the pandemic. > The social contexts in which our patients became infected are an integral part of their stories Large‐scale social forces, such as racism, sexism, political violence, poverty and other social inequalities, are rooted in historical and economic processes and sculpt the distribution and outcome of HIV/AIDS and TB. We refer to these social forces as ‘structural violence’ (Castro & Farmer, 2002, 2003a,b; Farmer, 2003), which predisposes the human body to pathogenic vulnerability by shaping the risk of infection and subsequent disease reactivation. After infection, structural violence also determines who has access to diagnostics and effective therapy. Drugs that could stop or slow down these epidemics, such as …

Encyclopedia of plague and pestilence: from ancient times to the present

Epidemic disease has decimated populations and caused great suffering all over the world - and continues to do so, despite the availability of advanced medical treatments. While once life-threatening diseases such as polio, smallpox and cholera have been virtually eliminated, other epidemics have taken their place, posing an equal, if not greater, threat. This encyclopedia traces the roles that diseases have played throughout world history and offers information on more than 700 epidemics and their effects on civilization. Listed alphabetically by location of the outbreak, each entry includes when and where a particular epidemic began, how and why it happened, who it affected, how it spread and ran its course and its outcome and significance. Additional coverage includes information on the factors contributing to the spread of new epidemics and the growing problem of drug-resistant diseases, a foreword written by an expert on infectious diseases, and an appendix listing the entries alphabetically by disease. Diseases and epidemics covered include: smallpox (France, 580); black death (Europe, 1347-1380s); yellow fever (Philadelphia, 1973); Congolese sleeping sickness (Congo, 1895-1906); anthrax, (Russia, 1979/United States, 2001); Malaria (Madagascar, 1987-1988); HIV/AIDS pandemic (worldwide-present); hantavirus (United States, 1993); onchocerciasis (river blindness) (Brazil, 1996); and ebola (Uganda, 2000).

A New Ring-Forming Methodology for the Synthesis of Bioactive Pyrroloquinoline Derivatives

A new, efficient, two-step method for the synthesis of bioactive pyrroloquinolines is described. Readily available nitroquinolines, bearing the nitro moiety in the carbocyclic ring, are treated with 4-chlorophenoxyacetonitrile in the presence of potassium tert-butoxide/THF to give the analogous vicarious nucleophilic substitution products (5, 8 and 11). These, in turn, are subjected to catalytic hydrogenation to produce 1H-pyrrolo[2,3-f]quinoline (6), 3H-pyrrolo[3,2-f]quinoline (9) and 1H-pyrrolo[3,2-h]quinoline (12) in good yields and relatively short reaction times. The differential activity of two N-alkylated 1H-pyrrolo[2,3-f]quinolines (1) in cisplatin resistant cell lines compared to the corresponding parent lines suggests that these might be useful leads for developing agents for use in drug resistant diseases.