Inhibition Of Cell Wall Synthesis Research Articles

Human Milk Oligosaccharides (HMOs) Sensitize Group B Streptococcus to Clindamycin, Erythromycin, Gentamicin, and Minocycline on a Strain Specific Basis.

Human milk oligosaccharides (HMOs) possess antimicrobial and antibiofilm activity against Group B Streptococcus (GBS). HMOs were screened for their ability to potentiate antibiotic activity. We observed that HMOs potentiate the function of aminoglycosides, lincosamides, macrolides, and tetracyclines on a strain specific basis but not β-lactams or glycopeptides that inhibit cell wall synthesis. These findings are notable as GBS has evolved high levels of resistance toward aminoglycosides, macrolides, and tetracyclines. Finally, HMOs potentiate the function of aminoglycosides against both Staphylococcus aureus and Acinetobacter baumannii. On the basis of these observations, we hypothesized that HMOs act by increasing membrane permeability. This hypothesis was evaluated using a bacterial membrane permeability assay which revealed that HMOs increase membrane permeability toward propidium iodide.

Modifying the Lantibiotic Mutacin 1140 for Increased Yield, Activity, and Stability.

Mutacin 1140 belongs to the epidermin family of type AI lantibiotics. This family has a broad spectrum of activity against Gram-positive bacteria. The binding of mutacin 1140 to lipid II leads to the inhibition of cell wall synthesis. Pharmacokinetic experiments with type AI lantibiotics are generally discouraging for clinical applications due to the short half-life of these compounds. The unprotected dehydrated and protease-susceptible residues outside the lanthionine rings may play a role in the short half-life in physiological settings. Previous mutagenesis work on mutacin 1140 has been limited to the lanthionine-forming residues, the C-terminally decarboxylated residue, and single amino acid substitutions at residues Phe1, Trp4, Dha5, and Arg13. To study the importance of the dehydrated (Dha5 and Dhb14) and protease-susceptible (Lys2 and Arg13) residues within mutacin 1140 for stability and bioactivity, each of these residues was evaluated for its impact on production and inhibitory activity. More than 15 analogs were purified, enabling direct comparison of the activities against a select panel of Gram-positive bacteria. The efficiency of the posttranslational modification (PTM) machinery of mutacin 1140 is highly restricted on its substrate. Analogs in the various intermediate stages of PTMs were observed as minor products following single point mutations at the 2nd, 5th, 13th, and 14th positions. The combination of alanine substitutions at the Dha5 and Dhb14 positions abolished mutacin 1140 production, while the production was restored by substitution of a Gly residue at one of these positions. Analogs with improved activity, productivity, and proteolytic stability were identified.IMPORTANCE Our findings show that the efficiency of mutacin 1140 PTMs is highly dependent on the core peptide sequence. Analogs in various intermediate stages of PTMs can be transported by the bacterium, which indicates that PTMs and transport are finely tuned for the native mutacin 1140 core peptide. Only certain combinations of amino acid substitutions at the Dha5 and Dhb14 dehydrated residue positions were tolerated. Observation of glutamylated core peptide analogs shows that dehydrations occur in a glutamate-dependent manner. Interestingly, mutations at positions outside rings A and B, the lipid II binding domain, would interfere with lipid II binding. Purified mutacin 1140 analogs have various activities and selectivities against different genera of bacteria, supporting the effort to generate analogs with higher specificity against pathogenic bacteria. The discovery of analogs with improved inhibitory activity against pathogenic bacteria, increased stability in the presence of protease, and higher product yields may promote the clinical development of this unique antimicrobial compound.

Ex vivo penetration of fosfomycin into healthy and Lawsonia intracellularis-colonized swine intestinal mucosa.

Fosfomycin (FOS) is an antibiotic used, mostly in Latin America, for the treatment of lung and enteric infections of pigs. Intracellular fluids of enterocytes can act as biophase for Lawsonia intracellularis, the causative agent of porcine proliferative enteropathy (PPE). The aim of this study was to determine whether the presence of L.intracellularis in the enterocytes modifies FOS penetration. Eight healthy pigs in growth-finishing stage were used to produce healthy (group A) and L.intracellularis-colonized (group B) intestinal explants. For both groups, treatment consisted of a 580μg/ml concentration of calcium FOS, which was added to each explant (0.5-6hr). For group B, the Enterisol Ileitis® vaccine was used as source of the micro-organism. Previously to the assay, the time necessary for L.intracellularis to colonize the enterocytes was defined. Also, a PCR protocol was optimized to determine the presence of the pathogen in the explants. There were nonstatistical differences for the penetration of the antibiotic into healthy and L.intracellularis-colonized enterocytes. MIC90 of FOS for L.intracellularis is unknown; nevertheless, MIC90 of various antibiotics ranges between 0.125 and 128μg/ml. FOS reaches inside the enterocyte concentrations which surpass the MICs90 of other antibiotics that also act by the inhibition of cell wall synthesis; however, further studies should be carried out to determine fosfomycin MIC90 for L.intracellularis to discern the usefulness of this antibiotic in the treatment of PPE.

Intravenous Fosfomycin: An Assessment of Its Potential for Use in the Treatment of Systemic Infections in Canada.

Fosfomycin is a bactericidal agent that inhibits cell wall synthesis using a mechanism of action distinct from β-lactams or other antimicrobial agents. It is a broad-spectrum agent that is frequently active against antimicrobial-resistant bacterial pathogens including methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), multidrug-resistant (MDR) Enterobacteriaceae, and some isolates of MDR Pseudomonas aeruginosa. Intravenous fosfomycin has been prescribed for a wide variety of infections in many countries for >40 years. It is most frequently used in combination with other antimicrobial agents (e.g., β-lactams, carbapenems, and aminoglycosides) and has an excellent safety profile, including in neonates and children, even with long-term administration (weeks). Fosfomycin achieves extensive tissue distribution including difficult to reach compartments such as aqueous humor, vitreous humor, abscess fluid, and CSF. Available data, to date, suggest no clinically relevant pharmacological interactions between fosfomycin and other agents, including drugs, stimulants, or food. Intravenous fosfomycin's role in therapy in Canada is likely as an agent used alone or in combination for complicated urinary tract infections in hospitalized patients as well as hospitalized patients with MDR infections who have not responded to first-, and potentially, second-line antimicrobials or in patients who cannot tolerate (due to adverse effects) first- and second-line antimicrobials.

Design, Synthesis, Characterisation and Biological Evaluation of some Novel 1, 3, 4 Thiadiazole Derivatives as Anti-tubercular agents Targeting Decaprenyl Phosphoryl Beta-D-Ribose 2 ’Epimerase-1

INTRODUCTION:Tuberculosis [TB] is caused by mycobacterium tuberculosis that most often affect the lungs. Tuberculosis is curable and preventable. In 1882, the German physician Robert Koch isolated the bacterium. Tuberculosis is contagious and airborne disease. In 1944, streptomycin was to treat tuberculosis [TB]. This amino glycoside interferes with protein biosynthesis through an interaction with the small 30s subunit of the ribosome. The discovery of Para amino salicylic acid in 1946 was quickly followed by the important discovery of Isoniazid [INH], as one of the most active anti-TB drugs used today. Inhibition of mycolic acids biosynthesis, one of the essential components of the mycobacterium cell wall was determined as the mechanism of action. Pyrazinamide [PZA] appeared as a potential Anti-TB drug in 1952. The TB treatment in the 1980s was a great success as it allowed to shorten the duration of the therapy from 9 to 6 months. Ethambutol [EMB] and Rifampin [RIF], the two last derivatives used in the TB first-line treatment, were discovered during the 60s. Ethambutol is an ethylenediamine discovered in 1961, which affects the cell wall by specifically targeting the polymerization of arabinogalactan and lipoarabinomannan. Finally, Rifampin appeared as a drug of choice for TB treatment around 1970, by acting on replicating and non-replicating mycobacteria. This derivative belongs to the rifampicin family and inhibits bacterial RNA synthesis by binding to the b-subunit of the DNA-dependent polymerase. AIM: The aim of this project is to design molecules with potential anti-tubercular activity that is capable of inhibiting cell wall synthesis by inhibiting Decaprenylphosphoryl-beta-D-ribose2-epimerase-1. The designed compounds will be synthesized, characterized and evaluated for biological activity and toxicity. OBJECTIVE:The compounds are designed and docked against a specific crucial target, Decaprenylphosphoryl-beta-D-ribose2epimerase-1.This is involved in the cell wall biosynthesis and Lipid metabolism. The synthesized compounds are expected to act on the same.SUMMARY:Decaprenylphosphoryl-beta-D-ribose 2-epimerase a critical enzyme for the growth of Mycobacterium tuberculosis was chosen for our study after review of literature. It belongs to the Oxidoreductase family. A database of 200 molecules with high prospects of inhibiting the target Dpre1 were carefully chosen by making changes to the known hit molecules, here the thiadiazole nucleus was chosen. Selected molecules were designed and docked against Dpre1 using Argus lab® software. Six molecules with good docking score [lower binding energy] and interactions were shortlisted for synthesis. Reaction conditions were optimized. The selected molecules were subjected to toxicity prediction assessment by OSIRIS® property explorer developed by Acetilon Pharmaceuticals limited which is available online. The results are color coded as green color which predicts the drug likeness and possibly better activity. The molecules were labelled as SDK1, SDK2, SDK3, SDK5, PAA, HA, and were synthesized with satisfactory yield. The purity of the synthesized compounds was ensured by repeated recrystallization. Further the compounds were evaluated by TLC and Melting point determination. The characterization of the synthesized compounds was done using Infra-red, Nuclear Magnetic Resonance [H1 NMR] and Mass spectrometric methods [LC-MS, GC-MS]. All the Synthesized compounds exhibited molecular ion peak (M+) of varying intensities. The final pure compounds were screened for Anti-mycobacterial activity by in vitro method called Micro plate Alamar Blue Assay [MABA]. The synthesized compounds showed sensitivity [Minimum inhibitory concentration] at 3.12mcg/ml. The standard drugs Pyrazinamide, Streptomycin, Ciprofloxacin exhibited anti mycobacterial activity at 3.125mcg/ml, 6.25mcg/ml, and 3.125mcg/ml concentrations respectively. This indicates that the synthesized compounds are as Potent as the standard drugs.CONCLUSION:All the compounds gave Docking score between -8.73 to 11.37 kcal/mol Pyrazinamide gave docking score 11.55kcal/mol for 4P8Y, Streptomycin gave docking score of 10.87kcal/mol for 4P8Y and Ciprofloxacin gave docking score of 11.25kcal/mol for 4P8Y. There is a correlation between the score and activities of all the compounds which were tested and compared with the standard drugs. This goes to prove that Decaprenyl phosphoryl beta-D-ribose 2’ epimerase-1’ (PDBID: 4P8Y) is a critical enzyme for anti-mycobacterial activity. So the fine tuning the structures of these compounds will yield molecules with better anti mycobacterial activity. Further structural modifications of the synthesized compounds will aid in the development of potential molecules against the tuberculosis pathogen.

Exploring Conformations of the Teixobactin-Lipid II Complex in Membrane

Teixobactin is a recently discovered antibiotic that works against gram-positive bacteria without detectable resistance. The bactericidal mechanism of teixobactin is believed to be the inhibition of cell wall synthesis due to the binding to lipid II and lipid III, which likely takes place at the pyrophosphate moiety that shared by both targets. Despite numerous chemical analogs of teixobactin have been synthesized and functionally assessed, and the pharmacophore of one analog has been identified, detailed structural information is still lacking for the conformations of teixobactin and lipid II in their complex. Here we use molecular modeling and multiple sets of microsecond-scale molecular dynamics simulations to create atomic models of teixobactin-lipid II complex at the membrane surface. Two major lipid II binding conformations of teixobactin have been captured, and both show pyrophosphate binding by the backbone amides near the C-terminal cyclic depsipeptide (D-Thr8—Ile11) ring, as well as by the side chains of Ser7 and the unique allo-enduracididine. Interestingly, the major difference between the two conformations is the swapping of two groups of hydrogen bond donors that coordinate one of the lipid II phosphates, which results in opposite orientations of lipid II binding between two conformations. In addition, regardless of the detailed phosphate-binding interactions, residues D-allo-Ile5 and Ile6 always function as membrane anchors in both conformations. Based on the teixobactin-lipid II interactions captured in their complexes, as well as their partition depths at the membrane surface, we propose that the bactericidal mechanism of teixobactin is to arrest cell wall synthesis by selectively inhibiting the transglycosylation of peptidoglycan, while the transpeptidation is possibly unaffected. This pyrophosphate caging mechanism of lipid II inhibition appears to be similar to some lantibiotics, but different from that of vancomycin or bacitracin.

In vitro activities of carbapenems in combination with amikacin, colistin, or fosfomycin against carbapenem-resistant Acinetobacter baumannii clinical isolates

Carbapenem-resistant Acinetobacter baumannii clinical isolates (n=23) were investigated for carbapenem resistance mechanisms and in vitro activities of carbapenems in combination with amikacin, colistin, or fosfomycin. Major carbapenem resistance mechanism was OXA-23 production. The vast majority of these isolates were OXA-23–producing A. baumannii ST195 and ST542, followed by novel STs, ST1417, and ST1423. The interuption of carO by a novel insertion sequence, ISAba40, was found in two isolates. The combinations of imipenem and fosfomycin, meropenem and amikacin, imipenem and amikacin, and imipenem and colistin were synergistic against carbapenem-resistant A. baumannii by 65.2%, 46.2%, 30.8%, and 17.4%, respectively. Surprisingly, the combination of imipenem and fosfomycin was the most effective in this study against A. baumannii, which is intrinsically resistant to fosfomycin. Imipenem and fosfomycin inhibit cell wall synthesis; therefore, fosfomycin may be an adjuvant and enhance the inhibition of cell wall synthesis of carbapenem-resistant A. baumannii when combined with imipenem.

Development of Candida albicans Biofilms Is Diminished by Paeonia lactiflora via Obstruction of Cell Adhesion and Cell Lysis.

Candida albicans infections are often problematic to treat owing to antifungal resistance, as such infections are mostly associated with biofilms. The ability of C. albicans to switch from a budding yeast to filamentous hyphae and to adhere to host cells or various surfaces supports biofilm formation. Previously, the ethanol extract from Paeonia lactiflora was reported to inhibit cell wall synthesis and cause depolarization and permeabilization of the cell membrane in C. albicans. In this study, the P. lactiflora extract was found to significantly reduce the initial stage of C. albicans biofilms from 12 clinical isolates by 38.4%. Thus, to assess the action mechanism, the effect of the P. lactiflora extract on the adhesion of C. albicans cells to polystyrene and germ tube formation was investigated using a microscopic analysis. The density of the adherent cells was diminished following incubation with the P. lactiflora extract in an acidic medium. Additionally, the P. lactiflora-treated C. albicans cells were mostly composed of less virulent pseudohyphae, and ruptured debris was found in the serum-containing medium. A quantitative real-time PCR analysis indicated that P. lactiflora downregulated the expression of C. albicans hypha-specific genes: ALS3 by 65% (p = 0.004), ECE1 by 34.9% (p = 0.001), HWP1 by 29.2% (p = 0.002), and SAP1 by 37.5% (p = 0.001), matching the microscopic analysis of the P. lactiflora action on biofilm formation. Therefore, the current findings demonstrate that the P. lactiflora ethanol extract is effective in inhibiting C. albicans biofilms in vitro, suggesting its therapeutic potential for the treatment of biofilm-associated infections.

The synergistic bactericidal effect of vancomycin on UTMD treated biofilm involves damage to bacterial cells and enhancement of metabolic activities

In this study, the synergistic effect of vancomycin, a cell wall synthesis inhibitor, and ultrasound-targeted microbubble destruction (UTMD), on cell viability of Staphylococcus epidermidis, embedded in biofilm, was investigated. Biofilms are the leading causes of antibiotic-resistant bacterial infections of medical implants and prosthetics worldwide. The antibiotic-resistant nature of biofilm-embedded pathogens poses a critical challenge to the medical community. Previously, studies have demonstrated the efficacy of using ultrasound waves and UTMD in circumventing this problem. However, the mechanism(s) underlying this phenomenon was not clear. Here, the present study showed that both ultrasound and UTMD damaged the cell wall structure of S. epidermidis, and floccules and fragments from damaged cells were observed on transmission electron microscope micrograph. However, the cell membrane integrity was not seriously affected by treatments, and the treatment increased the metabolic activity levels of the dormant biofilm-embedded bacteria, detected by confocal laser scanning microscope and flow cytometry, which could make them susceptible to the effect of the antibiotic. Thus, the biological mechanism underlying the efficacy of the combined treatment involving UTMD and vancomycin in the case of S. epidermidis biofilm was dissected, which may be utilized for further investigations on other biofilm pathogens before clinical use.

Influence of Extremely Low frequency Magnetic Field on Proteus mirabilis bacteria

Urinary tract infections (UTI) due to Proteus mirabilis strains represented nearly 90% of Urinary tract infection cases. In this study the effect of applying extremely low frequency square magnetic pulses ELF-SMP on P. mirabilis was investigated. While, it interferes with the bioelectric signals generated during the cell division process. Also, the effect of exposure on bacterial antibiotic susceptibility and morphological cellular structure was studied. The results indicated that there was a significant inhibition effect for P. mirabilis exposed to 0.6 Hz SMP for one hour and significant increase in antibiotic susceptibility to DNA, proteins, β-lactamase enzyme and cell-wall synthesis inhibitors. Additionally, results of dielectric relaxation and TEM indicated molecular and morphological changes. According to these aforementioned results, it was concluded that treatment of P. mirabilis cells with SMP at mentioned frequency acts on its cellular activity and structure of the bacteria which can make this method is a promising one in further in vivo applications.

Interplay between Antibiotic Efficacy and Drug-Induced Lysis Underlies Enhanced Biofilm Formation at Subinhibitory Drug Concentrations.

ABSTRACTSubinhibitory concentrations of antibiotics have been shown to enhance biofilm formation in multiple bacterial species. While antibiotic exposure has been associated with modulated expression of many biofilm-related genes, the mechanisms of drug-induced biofilm formation remain a focus of ongoing research efforts and may vary significantly across species. In this work, we investigate antibiotic-induced biofilm formation in Enterococcus faecalis, a leading cause of nosocomial infections. We show that biofilm formation is enhanced by subinhibitory concentrations of cell wall synthesis inhibitors but not by inhibitors of protein, DNA, folic acid, or RNA synthesis. Furthermore, enhanced biofilm is associated with increased cell lysis, increases in extracellular DNA (eDNA) levels, and increases in the density of living cells in the biofilm. In addition, we observe similar enhancement of biofilm formation when cells are treated with nonantibiotic surfactants that induce cell lysis. These findings suggest that antibiotic-induced biofilm formation is governed by a trade-off between drug toxicity and the beneficial effects of cell lysis. To understand this trade-off, we developed a simple mathematical model that predicts changes in antibiotic-induced biofilm formation due to external perturbations, and we verified these predictions experimentally. Specifically, we demonstrate that perturbations that reduce eDNA (DNase treatment) or decrease the number of living cells in the planktonic phase (a second antibiotic) decrease biofilm induction, while chemical inhibitors of cell lysis increase relative biofilm induction and shift the peak to higher antibiotic concentrations. Overall, our results offer experimental evidence linking cell wall synthesis inhibitors, cell lysis, increased eDNA levels, and biofilm formation in E. faecalis while also providing a predictive quantitative model that sheds light on the interplay between cell lysis and antibiotic efficacy in developing biofilms.

Pseudomonas aeruginosa Alters Staphylococcus aureus Sensitivity to Vancomycin in a Biofilm Model of Cystic Fibrosis Infection.

ABSTRACTThe airways of cystic fibrosis (CF) patients have thick mucus, which fosters chronic, polymicrobial infections. Pseudomonas aeruginosa and Staphylococcus aureus are two of the most prevalent respiratory pathogens in CF patients. In this study, we tested whether P. aeruginosa influences the susceptibility of S. aureus to frontline antibiotics used to treat CF lung infections. Using our in vitro coculture model, we observed that addition of P. aeruginosa supernatants to S. aureus biofilms grown either on epithelial cells or on plastic significantly decreased the susceptibility of S. aureus to vancomycin. Mutant analyses showed that 2-n-heptyl-4-hydroxyquinoline N-oxide (HQNO), a component of the P. aeruginosa Pseudomonas quinolone signal (PQS) system, protects S. aureus from the antimicrobial activity of vancomycin. Similarly, the siderophores pyoverdine and pyochelin also contribute to the ability of P. aeruginosa to protect S. aureus from vancomycin, as did growth under anoxia. Under our experimental conditions, HQNO, P. aeruginosa supernatant, and growth under anoxia decreased S. aureus growth, likely explaining why this cell wall-targeting antibiotic is less effective. P. aeruginosa supernatant did not confer additional protection to slow-growing S. aureus small colony variants. Importantly, P. aeruginosa supernatant protects S. aureus from other inhibitors of cell wall synthesis as well as protein synthesis-targeting antibiotics in an HQNO- and siderophore-dependent manner. We propose a model whereby P. aeruginosa causes S. aureus to shift to fermentative growth when these organisms are grown in coculture, leading to reduction in S. aureus growth and decreased susceptibility to antibiotics targeting cell wall and protein synthesis.

Microbiology: Diversity breeds tolerance.

A gene has been identified that underpins the capacity of mycobacterial cells to divide to produce physiologically different daughter cells. This finding has implications for drug treatment of tuberculosis. See Letter p.153 Here the authors report the discovery of a new protein (LamA) that functions as part of the 'divisome' in mycobacteria. The authors report that LamA functions as an inhibitor of cell wall synthesis at the nascent cell pole, contributing to asymmetry in polar growth. Asymmetric growth and division increases population heterogeneity, which has been linked to antibiotic tolerance and persistent infection. Here they show that removal of LamA leads to a more uniform cell population that is more effectively killed by antibiotics. Thus, LamA represents a much-needed new target for the development of anti-tuberculosis therapies.

Peripheral modifications of [Ψ[CH2NH]Tpg4]vancomycin with added synergistic mechanisms of action provide durable and potent antibiotics

Subsequent to binding pocket modifications designed to provide dual d-Ala-d-Ala/d-Ala-d-Lac binding that directly overcome the molecular basis of vancomycin resistance, peripheral structural changes have been explored to improve antimicrobial potency and provide additional synergistic mechanisms of action. A C-terminal peripheral modification, introducing a quaternary ammonium salt, is reported and was found to provide a binding pocket-modified vancomycin analog with a second mechanism of action that is independent of d-Ala-d-Ala/d-Ala-d-Lac binding. This modification, which induces cell wall permeability and is complementary to the glycopeptide inhibition of cell wall synthesis, was found to provide improvements in antimicrobial potency (200-fold) against vancomycin-resistant Enterococci (VRE). Furthermore, it is shown that this type of C-terminal modification may be combined with a second peripheral (4-chlorobiphenyl)methyl (CBP) addition to the vancomycin disaccharide to provide even more potent antimicrobial agents [VRE minimum inhibitory concentration (MIC) = 0.01-0.005 μg/mL] with activity that can be attributed to three independent and synergistic mechanisms of action, only one of which requires d-Ala-d-Ala/d-Ala-d-Lac binding. Finally, it is shown that such peripherally and binding pocket-modified vancomycin analogs display little propensity for acquired resistance by VRE and that their durability against such challenges as well as their antimicrobial potency follow now predictable trends (three > two > one mechanisms of action). Such antibiotics are expected to display durable antimicrobial activity not prone to rapidly acquired clinical resistance.

Detection of molecular changes induced by antibiotics in Escherichia coli using vibrational spectroscopy

This study aimed to test Raman (400–1800cm−1) and Infra-red (1900–500cm−1) spectroscopies followed by statistical analysis (principal component analysis) to detect molecular changes induced by antibiotics (ampicillin, cefotaxime – cell wall synthesis inhibitors, tetracycline – protein synthesis inhibitor, ciprofloxacin – DNA synthesis inhibitor) against Escherichia coli TOP10. In case of ampicillin and cefotaxime, a decrease in protein bands in both Raman (1240, 1660cm−1), and IR spectra (1230, 1530, 1630cm−1), and an increase in carbohydrate bands (1150, 1020cm−1) in IR spectra were observed. Tetracycline addition caused an increase in nucleic acid bands (775, 1478, 1578cm−1), a sharp decrease in phenylalanine (995cm−1) in Raman spectra and the amide I and amide II bands (1630, 1530cm−1) in IR spectra, an increase in DNA in both Raman (1083cm−1) and IR spectra (1080cm−1). Regarding ciprofloxacin, an increase in nucleic acids (775, 1478, 1578cm−1) in Raman spectra and in protein bands (1230, 1520, 1630cm−1), in DNA (1080cm−1) in IR spectra were detected. Clear discrimination of antibiotic-treated samples compared to the control was recorded, showing that Raman and IR spectroscopies, coupled to principal component analysis for data, could be used to detect molecular modifications in bacteria exposed to different classes of antibiotics. These findings contribute to the understanding of the mechanisms of action of antibiotics in bacteria.

YENİ BİR DOĞAL ANTİBİYOTİK: “TEİKSOBAKTİN”

Antibiotic resistance is spreading faster than the introduction of new antimicrobials into clinical practice, causing a public health crisis. Most antibiotics were produced by screening soil microorganisms. This limited resource of cultivable bacteria was overmined by the 1960s. It is reported that uncultured bacteria by in vitro conditions make up approximately 99% of all species in external environments, and are a source of new antibiotics which could not be explored yet. The new technology for growing uncultured organisms by cultivation in situ or by using specific growth factors have been developed. As a result, it is reported that a new antibiotic termed as teixobactin has been discovered in the screening of the new soil bacterium named as Eleftheria terrae. Teixobactin has bactericidal effects in Grampositive bacteria inhibiting cell wall synthesis by binding to lipid II which is a a highly conserved precursor of peptidoglycan and lipid III which is a precursor of cell wall teichoic acid. It has been tested in two animal infection models: blood infections of methicillin-resistant Staphylococcus aureus and lung infections of Streptococcus pneumoniae. As a result, all animals were treated successfully and none developed resistance. If teixobactin is approved, it will be the first of a new class of antibiotics.

Antimicrobial peptide cWFW kills by combining lipid phase separation with autolysis

The synthetic cyclic hexapeptide cWFW (cyclo(RRRWFW)) has a rapid bactericidal activity against both Gram-positive and Gram-negative bacteria. Its detailed mode of action has, however, remained elusive. In contrast to most antimicrobial peptides, cWFW neither permeabilizes the membrane nor translocates to the cytoplasm. Using a combination of proteome analysis, fluorescence microscopy, and membrane analysis we show that cWFW instead triggers a rapid reduction of membrane fluidity both in live Bacillus subtilis cells and in model membranes. This immediate activity is accompanied by formation of distinct membrane domains which differ in local membrane fluidity, and which severely disrupts membrane protein organisation by segregating peripheral and integral proteins into domains of different rigidity. These major membrane disturbances cause specific inhibition of cell wall synthesis, and trigger autolysis. This novel antibacterial mode of action holds a low risk to induce bacterial resistance, and provides valuable information for the design of new synthetic antimicrobial peptides.

A review on cell wall synthesis inhibitors with an emphasis on glycopeptide antibiotics.

Cell wall biosynthesis inhibitors (CBIs) have historically been one of the most effective classes of antibiotics. They are the most extensively used class of antibiotics and their importance is exemplified by the β-lactams and glycopeptide antibiotics. However, this class of antibiotics has not received impunity from resistance development. In the wake of this predicament, this review presents the progress of CBIs, especially glycopeptide derivatives as antibiotics to confront antibacterial resistance. The various strategies used for the development of CBIs, their clinical status and possible directions in which this field can evolve have also been discussed.

Fosfomycin (FOS) Plus Meropenem (MER) Suppresses Resistance Emergence Against P. aeruginosa (PA) PAO1 in the Hollow Fiber Infection Model (HFIM)

BackgroundFOS (ZTI-01, fosfomycin for injection) is an epoxide antibiotic that covalently binds MurA, an earlier step in cell wall synthesis inhibition. FOS has demonstrated synergistic killing with other classes of agents, including carbapenems. PA, among other non-fermentors, are difficult to treat pathogens and combination therapy is important to ensure killing and suppress emergence of resistance. Here, we examine the combination of FOS + MER in the HFIM against PA.MethodsThe experimental design was fully factorial (3 FOS and 3 MER arms and all combinations). Simulated FOS doses were 4, 6 and 8 g 8 hourly (Q8). MER doses were 0.5, 1 and 2 g Q8. The experiment lasted 10 days. Concentrations from the central compartment were measured in all arms by LC/MS/MS. Total bacterial burden and resistant subpopulations for both drugs were measured. Resistance plates were infused with 3XBaseline MIC. Starting inoculum was 6.86 Logs.ResultsFOS/MER MIC’s were 64 mg/L (broth) and 0.5 mg/L. Mutational frequency to resistance were -5.27 (FOS) and -6.7 (MER). There were 15 drug-containing arms and a no-treatment control. All drug arms had concentration-time profiles accurately reproduced. All FOS alone arms had rapid resistance emergence. MER 0.5 gm alone had resistance emerge at Day1. FOS 4 g + MER 0.5 g allowed resistance to both agents as did FOS 6g + MER 0.5 g. FOS 6 g + MER 1 g allowed MER resistance, but not FOS. All other combination regimens fully suppressed all resistant mutants. The effect of combination therapy is shown in Figures 1–3. MIC’s for MER-resistant isolates were 2 mg/L early and up to 16 mg/L late (day4 and after). FOS-resistant isolates generally had MIC values between 128 and >1024 mg/L.ConclusionThe combination of FOS + MER is promising for therapy of a wild-type PA. Doses of FOS of 6 and 8 g Q8 tended to suppress resistance emergence to either agent when combined with 1 or 2 g Q8 of MER. We intend on examining the impact of resistance mutations to MER (oprD downregulated and MexAB upregulated) with this combination to identify any potential therapeutic advantage of this combination regimenDisclosures G. L. Drusano, Zavante: Scientific Advisor, Consulting fee

Delamanid and its Role in Drug-Resistant Tuberculosis

The World Health Organisation estimates that one-third of the world's population are currently infected with Tuberculosis bacillus, 10% of whom will develop the disease at some point in their lifetime. Poverty-Stricken countries of Africa and Asia bear the brunt of the disease partly due to an ominous synergy between mycobacterium bacteria and HIV. The recent recognition of MDR-TB and strains with more complex resistance patterns has stimulated the development of new TB medications including fluoroquinolones, oxazolidinones, diarylquinolines, nitroimidazopyrans. Delamanid, a newer mycobacterial cell wall synthesis inhibitor, received a conditional approval from European medicines agency (EMA) for the treatment of MDR‑TB. Preclinical and clinical studies have shown that delamanid has high potency, least risk for drug‑drug interactions and better tolerability. The purpoe of this article is to bring forward, the various roles played by Delamanid in order to curb the problem of Multi-drug resistant Tuberculosis.