Potent Broad-spectrum Antibiotic Research Articles

Arsinothricin Inhibits Plasmodium falciparum Proliferation in Blood and Blocks Parasite Transmission to Mosquitoes.

Malaria, caused by Plasmodium protozoal parasites, remains a leading cause of morbidity and mortality. The Plasmodium parasite has a complex life cycle, with asexual and sexual forms in humans and Anopheles mosquitoes. Most antimalarials target only the symptomatic asexual blood stage. However, to ensure malaria eradication, new drugs with efficacy at multiple stages of the life cycle are necessary. We previously demonstrated that arsinothricin (AST), a newly discovered organoarsenical natural product, is a potent broad-spectrum antibiotic that inhibits the growth of various prokaryotic pathogens. Here, we report that AST is an effective multi-stage antimalarial. AST is a nonproteinogenic amino acid analog of glutamate that inhibits prokaryotic glutamine synthetase (GS). Phylogenetic analysis shows that Plasmodium GS, which is expressed throughout all stages of the parasite life cycle, is more closely related to prokaryotic GS than eukaryotic GS. AST potently inhibits Plasmodium GS, while it is less effective on human GS. Notably, AST effectively inhibits both Plasmodium erythrocytic proliferation and parasite transmission to mosquitoes. In contrast, AST is relatively nontoxic to a number of human cell lines, suggesting that AST is selective against malaria pathogens, with little negative effect on the human host. We propose that AST is a promising lead compound for developing a new class of multi-stage antimalarials.

Polymeric Microparticles: Synthesis, Characterization and In Vitro Evaluation for Pulmonary Delivery of Rifampicin.

Rifampicin, a potent broad-spectrum antibiotic, remains the backbone of anti-tubercular therapy. However, it can cause severe hepatotoxicity when given orally. To overcome the limitations of the current oral therapy, this study designed inhalable spray-dried, rifampicin-loaded microparticles using aloe vera powder as an immune modulator, with varying concentrations of alginate and L-leucine. The microparticles were assessed for their physicochemical properties, in vitro drug release and aerodynamic behavior. The spray-dried powders were 2 to 4 µm in size with a percentage yield of 45 to 65%. The particles were nearly spherical with the tendency of agglomeration as depicted from Carr’s index (37 to 65) and Hausner’s ratios (>1.50). The drug content ranged from 0.24 to 0.39 mg/mg, with an association efficiency of 39.28 to 96.15%. The dissolution data depicts that the in vitro release of rifampicin from microparticles was significantly retarded with a higher L-leucine concentration in comparison to those formulations containing a higher sodium alginate concentration due to its hydrophobic nature. The aerodynamic data depicts that 60 to 70% of the aerosol mass was emitted from an inhaler with MMAD values of 1.44 to 1.60 µm and FPF of 43.22 to 55.70%. The higher FPF values with retarded in vitro release could allow sufficient time for the phagocytosis of synthesized microparticles by alveolar macrophages, thereby leading to the eradication of M. tuberculosis from these cells.

Dissociating antibacterial from ototoxic effects of gentamicin C-subtypes

Gentamicin is a potent broad-spectrum aminoglycoside antibiotic whose use is hampered by ototoxic side-effects. Hospital gentamicin is a mixture of five gentamicin C-subtypes and several impurities of various ranges of nonexact concentrations. We developed a purification strategy enabling assaying of individual C-subtypes and impurities for ototoxicity and antimicrobial activity. We found that C-subtypes displayed broad and potent in vitro antimicrobial activities comparable to the hospital gentamicin mixture. In contrast, they showed different degrees of ototoxicity in cochlear explants, with gentamicin C2b being the least and gentamicin C2 the most ototoxic. Structure-activity relationships identified sites in the C4'-C6' region on ring I that reduced ototoxicity while preserving antimicrobial activity, thus identifying targets for future drug design and mechanisms for hair cell toxicity. Structure-activity relationship data suggested and electrophysiological data showed that the C-subtypes both bind and permeate the hair cell mechanotransducer channel, with the stronger the binding the less ototoxic the compound. Finally, both individual and reformulated mixtures of C-subtypes demonstrated decreased ototoxicity while maintaining antimicrobial activity, thereby serving as a proof-of-concept of drug reformulation to minimizing ototoxicity of gentamicin in patients.

Azithromycin-liposomes as a novel approach for localized therapy of cervicovaginal bacterial infections.

BackgroundEfficient localized cervicovaginal antibacterial therapy, enabling the delivery of antibiotic to the site of action at lower doses while escaping systemic drug effects and reducing the risk of developing microbial resistance, is attracting considerable attention. Liposomes have been shown to allow sustained drug release into vaginal mucosa and improve delivery of antibiotics to bacterial cells and biofilms. Azithromycin (AZI), a potent broad-spectrum macrolide antibiotic, has not yet been investigated for localized therapy of cervicovaginal infections, although it is administered orally for the treatment of sexually transmitted diseases. Encapsulation of AZI in liposomes could improve its solubility, antibacterial activity, and allow the prolonged drug release in the cervicovaginal tissue, while avoiding systemic side effects.PurposeThe objective of this study was to develop AZI-liposomes and explore their potentials for treating cervicovaginal infections.MethodsAZI-liposomes that differed in bilayer elasticity/rigidity and surface charge were prepared and evaluated under simulated cervicovaginal conditions to yield optimized liposomes, which were assessed for antibacterial activity against several planktonic and biofilm-forming Escherichia coli strains and intracellular Chlamydia trachomatis, ex vivo AZI vaginal deposition/penetration, and in vitro cytotoxicity toward cervical cells.ResultsNegatively charged liposomes with rigid bilayers (CL-3), propylene glycol liposomes (PGL-2) and deformable propylene glycol liposomes (DPGL-2) were efficient against planktonic E. coli ATCC 700928 and K-12. CL-3 was superior for preventing the formation of E. coli ATCC 700928 and K-12 biofilms, with IC50 values (concentrations that inhibit biofilm viability by 50%) up to 8-fold lower than those of the control (free AZI). DPGL-2 was the most promising for eradication of already formed E. coli biofilms and for treating C. trachomatis infections. All AZI-liposomes were biocompatible with cervical cells and improved localization of the drug inside vaginal tissue compared with the control.ConclusionThe performed studies confirm the potentials of AZI-liposomes for localized cervicovaginal therapy.

Synergistic efficacy of Bisbenzimidazole and Carbonyl Cyanide 3-Chlorophenylhydrazone combination against MDR bacterial strains

Activation of efflux systems and the formation of biofilm are majorly adapted by microbes to resist antimicrobial agents. PPEF (bisbenzimidazole) targeting topoisomerase IA is observed to be an effective bactericidal agent against both Gram-positive and Gram-negative bacterial strains and thus can be developed as potent broad-spectrum antibiotic against MDR strains. PPEF treatment did not cause target specific mutation instead it leads to up-regulation of efflux gene in E. coli K12 as a mechanism of resistance. Microscopy, fluorescence spectroscopy and flow cytometry result demonstrate higher accumulation of PPEF in efflux gene deleted E. coli K12 mutants, and also suggest that Carbonyl Cyanide 3-Chlorophenylhydrazone (CCCP), resist the efflux of PPEF, and thus increases efficacy of PPEF. Herein, we report, PPEF and CCCP synergistically killed the persistent bacterial cells, which are not killed by PPEF alone. The above two compounds together inhibited biofilm formation, eradicate preformed biofilms and kills the biofilm cells of P. aeruginosa. PPEF and CCCP together reduced bacterial load of E. coli ATCC25922 by 6 log10 in neutropenic thigh infection model of balb/c mice. Present study suggests that combination therapy could be a promising antimicrobial strategy to handle MDR pathogenic strains.

The effects of LPS on the activity of Trp-containing antimicrobial peptides against Gram-negative bacteria and endotoxin neutralization

A series of synthesized Trp-containing antimicrobial peptides showed significantly different antimicrobial activity against Gram-negative bacteria despite having similar components and amino acid sequences and the same net positive charge and hydrophobicity. Lipopolysaccharide (LPS) in the outer membrane is a permeability barrier to prevent antimicrobial peptides from crossing into Gram-negative bacteria. We investigated the interaction of five Trp-containing peptides, I1W, I4W, L5W, L11W and L12W, with LPS using circular dichroism (CD), IR spectroscopy, isothermal titration calorimetry (ITC), dynamic light scattering (DLS), zeta-potential measurements and confocal laser scanning microscopy, to address whether bacterial LPS is responsible for the different susceptibilities of Gram-negative bacteria to Trp-containing peptides. Our data indicate that I1W and I4W penetrated the LPS layer and killed Gram-negative bacteria by a “self-promoted uptake” pathway in which the peptides first approach LPS by electrostatic forces and then dissociate LPS micelle. This process results in disorganization of the LPS leaflet and promotes the ability of the peptide to cross the outer membrane into the inner membrane and disrupt the cytoplasmic membrane. Although L5W, L11W and L12W strongly bind to LPS bilayers and depolarize bacterial cytoplasmic membranes, similar to I1W and I4W, they are unable to destabilize LPS aggregates and traverse through the tightly packed LPS molecules. This study increases our understanding of the mechanism of action of these peptides in the LPS outer membrane and will help in the development of a potent broad-spectrum antibiotic for future therapeutic purposes. Statement of SignificanceTryptophan (Trp) residues show a strong preference for the interfacial region of biological membranes, and this property endows Trp-containing peptides with the unique ability to interact with the surface of bacterial cell membranes. In this manuscript, we report the membrane interaction of Trp-containing peptide to address whether bacterial LPS is responsible for the different susceptibilities of Gram-negative bacteria to Trp-containing peptides. Based on the data collected, we propose a molecular mechanism for the peptide-LPS interactions that allows the peptides to traverse or prevents them from transversing the LPS layer and the target inner membrane. The data should help in the development of a potent broad-spectrum antibiotic for future therapeutic purposes.

Decontamination of ofloxacin: optimization of removal process onto sawdust using response surface methodology

Ofloxacin is one of the most used fluoroquinolones, a potent broad spectrum antibiotic class; it is also included in pharmaceutically active compounds that are considered as environmental pollutants. To clean the water systems sorption has been found as an effective way to remove these pollutants. Present study demonstrates the effect of different sawdust treatments on removal of ofloxacin from aqueous solutions. The sorption of ofloxacin by treated sawdust has been optimized by response surface methodology using central composite design. Set of 18 experiments was used and factors as pH, amount of sorbent, contact time, and concentration of sorbate were considered the critical factors to be studied for removal. HCl-treated sawdust was found to have maximum removal efficiency (96%) with the sorption capacity of 47 μmol g−1 as compared to other treated sorbents. Amount of sorbent have significantly positive impact on the removal for all three treated sorbents whereas concentration of sorbate has non-significant positive effect for HCl-treated sawdust. Further, sorption isotherms, kinetics, and thermodynamics studies onto HCl-treated sawdust showed that reaction is exothermic and spontaneous in nature and psuedo-second-order is predominant route. Complex sorption mechanism with simultaneous intraparticle diffusion as well as surface adsorption phenomena is responsible for sorption of ofloxacin onto sawdust.

Resurrecting Inactive Antimicrobial Peptides from the Lipopolysaccharide Trap

Host defense antimicrobial peptides (AMPs) are a promising source of antibiotics for the treatment of multiple-drug-resistant pathogens. Lipopolysaccharide (LPS), the major component of the outer leaflet of the outer membrane of Gram-negative bacteria, functions as a permeability barrier against a variety of molecules, including AMPs. Further, LPS or endotoxin is the causative agent of sepsis killing 100,000 people per year in the United States alone. LPS can restrict the activity of AMPs inducing aggregations at the outer membrane, as observed for frog AMPs, temporins, and also in model AMPs. Aggregated AMPs, "trapped" by the outer membrane, are unable to traverse the cell wall, causing their inactivation. In this work, we show that these inactive AMPs can overcome LPS-induced aggregations while conjugated with a short LPS binding β-boomerang peptide motif and become highly bactericidal. The generated hybrid peptides exhibit activity against Gram-negative and Gram-positive bacteria in high-salt conditions and detoxify endotoxin. Structural and biophysical studies establish the mechanism of action of these peptides in LPS outer membrane. Most importantly, this study provides a new concept for the development of a potent broad-spectrum antibiotic with efficient outer membrane disruption as the mode of action.

DCAP: A Broad-Spectrum Antibiotic That Targets the Cytoplasmic Membrane of Bacteria

Persistent infections are frequently caused by dormant and biofilm-associated bacteria, which often display characteristically slow growth. Antibiotics that require rapid cell growth may be ineffective against these organisms and thus fail to prevent reoccurring infections. In contrast to growth-based antimicrobial agents, membrane-targeting drugs effectively kill slow-growing bacteria. Herein we introduce 2-((3-(3,6-dichloro-9H-carbazol-9-yl)-2-hydroxypropyl)amino)-2-(hydroxymethyl)propane-1,3-diol (DCAP), a potent broad-spectrum antibiotic that reduces the transmembrane potential of Gram-positive and Gram-negative bacteria and causes mislocalization of essential membrane-associated proteins, including MinD and FtsA. Importantly, DCAP kills nutrient-deprived microbes and sterilizes bacterial biofilms. DCAP is lethal against bacterial cells, has no effect on red blood cell membranes, and only decreases the viability of mammalian cells after ≥6 h. We conclude that membrane-active compounds are a promising solution for treating persistent infections. DCAP expands the limited number of compounds in this class of therapeutic small molecules and provides new opportunities for the development of potent broad-spectrum antimicrobial agents.

Synthesis of Streptolydigin

Streptolydigin is a highly potent broad-spectrum antibiotic isolated from Strep­tomyces lydicus. It displays inhibitory activity against bacterial RNA polymerase with a distinct mode of action compared with the rifamycins that are commonly used to treat tuberculosis.

Isolation and Structure of Platencin: A FabH and FabF Dual Inhibitor with Potent Broad‐Spectrum Antibiotic Activity

Two birds with one stone: Platencin (1) is a novel and potent broad-spectrum Gram-positive antibiotic. Whereas platensimycin is a selective inhibitor of FabF, platencin exerts its activity by a novel mode of action by dual inhibition of FabH and FabF. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2007/z701058_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Cephalexin-Mediated Synthesis of Quasi-Spherical and Anisotropic Gold Nanoparticles and Their in Situ Capping by the Antibiotic

Here we report, for the first time, synthesis of gold nanostructures in aqueous medium by reducing gold ions using cephalexin, a potent broad-spectrum antibiotic, where the morphology of the gold nanoparticles is found to be dependent on the concentration of chloroauric acid. The characterization techniques indicate that particle surfaces are coated with the robust layer of the antibiotic making them stable for a long time. Thus, cephalexin acts as both the reducing and the capping agent. NMR and XPS analysis indicate that the sulfur moiety is responsible for the reduction and binding process.

Experience with prophylactic oral ciprofloxacin in gynecological cancer patients developing severe chemotherapy-induced neutropenia.

The development of significant neutropenia is a relatively frequent complication of cytotoxic chemotherapy of malignant disease. In an effort to develop a cost-effective management strategy to prevent serious infectious events associated with severe chemotherapy-induced neutropenia, patients treated in the Gynecological Oncology Program of the Cleveland Clinic Taussig Cancer Center have been administered ciprofloxacin, a potent broad-spectrum antibiotic, 500 mg orally twice a day, beginning at the time of documentation of grade 4 neutropenia. The antibiotic is continued until granulocyte recovery. A total of 44 patients (57 treatment courses) have been treated in this manner. There have been no complications of therapy and no episodes of subsequent infections due to ciprofloxacin-resistant organisms. Two patients required hospital admission following the development of significant fever, despite the use of ciprofloxacin. While these results are encouraging and suggest that the use of prophylactic ciprofloxacin is a highly cost-effective management approach in this setting, randomized controlled trials are necessary to define the ultimate benefit of this clinical strategy.

Cefixime in the Treatment of Respiratory and Urinary Tract Infections

Cefixime is quickly establishing in Western countries as a potent broad-spectrum antibiotic with a variety of indications. A multinational, nonrandomized study in Central and Eastern Europe has confirmed the excellent efficacy of cefixime in both children and adults. In 45 children with acute sinusitis and 50 with acute otitis media, once-daily cefixime in oral suspension resulted in clinical cure or improvement in 45 (100%) and 48 (96%) patients, respectively. In 60 adult patients with acute exacerbations of chronic bronchitis and 12 with pneumonia, cefixime 400 mg resulted in cure or improvement in 59 (98%) and 12 (100%) patients, respectively. Similarly, excellent efficacy was found in adults with urinary tract infections (UTI), with cure in 80 (94%) patients, improvement in 4 (5%), and failure in 1 (1%). Very good efficacy of cefixime was also demonstrated microbiologically, with eradication in 35 of 36 isolates from children, including all Streptococcus pneumoniae isolates, 40 of 45 isolates from patients with respiratory tract infections, and 64 of 71 isolates from patients with UTI.

Ofloxacin Monotherapy for the Primary Treatment of Microbial Keratitis: A Double-masked, Randomized, Controlled Trial with Conventional Dual Therapy

Background: Ofloxacin is a potent broad-spectrum fluoroquinolone antibiotic commercially available as a topical ophthalmic preparation. The authors compared ofloxacin (0.3%) as a single therapy with their conventional dual therapy of specially prepared, fortified gentamicin (1.5%) and cefuroxime (5.0%) drops for the treatment of suspected microbial keratitis.Methods: The authors enrolled 122 patients with a clinical diagnosis of microbial keratitis in a prospective, randomized, controlled, double-masked study to compare the two therapies. The ofloxacin drops were decanted into identical-looking bottles to the conventional treatment and dispensed with a second bottle containing saline only. The initial and subsequent assessments noted any risk factors, the size and location of the ulcer, and any evidence of corneal and conjunctival toxicity. All ulcers were scraped for microbiologic culture, and isolated organisms were tested for sensitivity to the trial antibiotics. For statistical analysis, a “cure” was defined as complete healing of the ulcer (no epithelial defect). A ratio of the two outcome proportions and its confidence limits was used to compare the two treatment groups. Multiple regression analysis using Poisson models was used to adjust for confounding factors that may have modified the outcome ratios.Results: There was no difference in the treatment success between the two treatments, with 67.9% of the conventional treatment group and 62.1 % of the of loxacin group being cured within 14 days (ratio, 1.09; [95% confidence interval, 0.83-1.43]; P = 0.59). However, there was significantly more toxicity encountered with the conventional treatment group (50.8% vs. 10.2%; ratio, 5.00 [95% confidence interval, 2.25-11.11 ]; P < 0.0001). Poisson regression with adjustment for confounders did not materially change the ratio proportions for either treatment success or toxicity. There was at least a 90% chance to detect a 30% difference between the groups.Conclusions: The authors found that the treatment outcomes with ofloxacin monotherapy compared favorably with their conventional therapy and were associated with less toxicity.

Coordinate induction of two antibiotic genes in tracheal epithelial cells exposed to the inflammatory mediators lipopolysaccharide and tumor necrosis factor alpha.

Peptides with potent broad-spectrum antibiotic activity have been identified in many animal species. Recent investigations have demonstrated that epithelial cells are a site of antibiotic peptide expression, suggesting that these peptides contribute to host defense at mucosal surfaces. Expression of tracheal antimicrobial peptide (TAP), a member of the beta-defensin family of peptides, is inducible in cultured tracheal epithelial cells (TEC) upon challenge with bacterial lipopolysaccharide (LPS) (G. Diamond, J.P. Russell, and C.L. Bevins, Proc. Natl. Acad. Sci. USA, in press). In this study, an anchored reverse transcriptase PCR strategy was used to determine if TAP was the sole beta-defensin isoform expressed upon stimulation of the cells with LPS. In addition to TAP, a second class of cDNA clones which encoded lingual antimicrobial peptide (LAP), a beta-defensin peptide recently isolated from a different mucosal site, the bovine tongue, was identified (B.S. Schonwetter, E.D. Stolzenberg, and M. Zasloff, Science 267:1645-1648, 1995). Northern (RNA) blot analysis demonstrated in vivo expression of LAP mRNA in tracheal mucosa. Levels of LAP mRNA were higher in cultured TEC challenged with either LPS or tumor necrosis factor alpha than in control cells. Thus, a response of TEC exposed to inflammatory mediators is induction of antibiotic-encoding genes, including both TAP and LAP. This work complements the in vivo studies of Schonwetter et al. (cited above), which showed elevated levels of LAP mRNA in squamous epithelial cells of the tongue near sites of tissue injury and inflammation, by suggesting possible mediators of the in vivo observation. Together these lines of investigations support the hypothesis that inducible expression of endogenous antibiotic peptides by inflammatory mediators characterizes local defense of mammalian mucosal surfaces.

Moxalactam (Moxam) in the Treatment of Experimental Staphylococcal Endophthalmitis

We investigated the intraocular penetration, retinal toxicity, clearance from the vitreous, and antibacterial activity of moxalactam (Moxam), a new third-generation cephalosporin with activity against aerobic and anaerobic gram positive organisms and many gram negative organisms. Seventy-four albino rabbits were used. Subconjunctival injection yielded therapeutic aqueous and vitreous levels for all hours studied. Intraocular penetration following single dose intravenous and intramuscular administration was poor. Two mg injected into the vitreous produced rare focal retinal toxicity. Eleven of the 11 eyes receiving intravitreal injections of 2 mg moxalactam eight hours after inoculation with S. aureus were sterile and free of morphologic changes. Moxalactam appears to be a potent broad spectrum antibiotic with a low degree of toxicity to rabbit retinal tissue.

Treatment Pattern of Acute Respiratory Tract Infections in General Practice with 3rd generation Oral Cefixime in Bangladesh

Respiratory tract infections (RTIs) are a major health problem in developing countries. RTIs are the most common reason for physician visits and prescription of antibiotics. Cefixime is quickly establishing as a potent broad-spectrum antibiotic with a variety of indications. This observational study was designed to describe the treatment pattern of third generation oral cefixime in managing RTIs in general practice. This noncontrolled, multicenter, observational registry was carried out from March 2009 to July 2010. During this period 2400 patients aged 3 years to 76 years suffering from RTIs were enrolled by general physicians throughout the country. Study variable were socio demographic, signs and symptoms, clinical diagnosis, investigations, antimicrobial prescribed and clinical outcome. Clinical outcome was determined based on improvement of signs and symptoms. Compliance, efficacy and tolerance were assessed on days 7 and 10. The enrolled patients were considered for analysis. The mean age was 26.59 (± 18.10) years and 62% of patients were male. Common presenting signs and symptoms were fever, cough, shortness of breath and increased sputum volume in 80%, 75%, 39%, and 12% respectively. From prescriptions, pneumonia, acute bronchitis, acute exacerbation of chronic bronchitis and lung abscess were the diagnosis in 42%, 26%, 24% and 3% of the prescriptions, respectively. Following the treatment with cefixime clinically cured, much improved and better were obtained in 77%, 21% and 2% respectively. Furthermore, the rate of adverse events were insignificant. The study showed clinical symptoms improved rapidly and high rates of clinical cure were achieved. More over, the rate of adverse events were relatively quite low. The results supports the use of cefixime for a variety of respiratory infections in adult and pediatric patients in Bangladesh. DOI: http://dx.doi.org/10.3329/bmj.v40i1.9962 BMJ 2011; 40(1): 39-42