Development Of Broad-spectrum Antibiotics Research Articles

Antimicrobial profiling of coral reef and sponge associated bacteria from southeast coast of India

Culturable bacteria associated with marine sponges and coral mucus (collected from Gulf of Mannar and Palk Bay) were screened for their prospective antimicrobial compounds against 9 bacterial pathogens (Bacillus megaterium, B. cereus, Salmonella typhimurium, Staphylococcus aureus, Proteus vulgaris, Klebsillla pneumoniae, Escherichia coli, Pseudomonas aeruginosa and Acinetobacter baumannii) and a fungal pathogen (Candida albicans). Of the 263 bacterial isolates obtained during this study, 52 isolates displayed antimicrobial activity against one or more pathogens. 16S rRNA gene sequencing revealed that these 52 strains affiliated to 14 genera from three phyla Proteobacteria, Firmicutes and Actinobacteria. Sponge associated bacterial strains F-04, I-23, I-33 and G-03 inhibited the growth of all the bacterial pathogens tested in this study and significantly the former 2 strains inhibited the growth of fungal pathogen also. Majority of the potential strains (88.4% out of 52 strains) inhibited the growth of Bacillus cereus. Interestingly, an actinomycete strain F-04 (isolated from sponge Orina sagittaria) inhibited the growth of methicillin resistant Staphylococcus aureus. In total, 10 volatile organic compounds were determined from the ethyl acetate and hexane extract of the strain F-04 using GC-MS. Overall, marine bacteria isolated during this study demonstrate the potential for the development of broad spectrum antibiotics.

Cationic Anthraquinone Analogs as Selective Antimicrobials.

Development of new antibiotics is always needed in the fight against growing threat from multiple drug–resistant bacteria, such as resistant Gram-negative (G−) Escherichia coli and Klebsiella pneumoniae. While the development of broad-spectrum antibiotics has attracted great attention, careful administration of these antibiotics is important to avoid adverse effects, like Clostridium difficile infection (CDI). The use of broad-spectrum antibiotics, for example, quinolones, can increase the risk of CDI by eradicating the protective bacteria in intestine and encouraging C difficile spore germination. Many common intestine bacteria are G− or anaerobic, including Enterococcus faecalis, Bacteroides fragilis, and E coli. Hence, it may be advantageous in certain therapeutic practices to employ selective antimicrobials. For instance, Gram-positive (G+) methicillin-resistant Staphylococcus aureus (MRSA) that can cause life-threatening sepsis can be controlled with the use of selective antibiotic, vancomycin. Nevertheless, its effectiveness has been limited with the emerging of vancomycin-resistant Staphylococcus aureus (VRSA). A recent report on antimicrobial cationic anthraquinone analogs (CAAs) that show tunable activity and selectivity may provide new hope in the search for selective antimicrobials. In particular, the lead CAA displays prominent activity against MRSA while manifesting low activity against E coli and low cytotoxicity toward normal mammalian cells.

Diagnostic and Prognostic Values of Interferon Inducible Protein 10 in Occurrence and Outcome of Sepsis in Preterm Neonates

Background: Infection is still an important cause of neonatal morbidity and mortality despite development of broad-spectrum antibiotics and clinical advances in life support therapy. Aim of the work: To evaluate plasma interferon gamma inducible protein 10 (IP-10) in the diagnosis and prognosis of sepsis in preterm neonates and comparison with CRP and blood culture. Subjects and methods: Samples collected from 40 preterm neonates (20 with suspected infection and 20 with no suspicion of infection) from NICU of Elsayed Galal Hospital were subjected to blood culture, CRP, CBC and measurement of plasma interferon induced protein 10 using sandwich enzyme linked immunosorbent assay (ELISA). Results: The study recruited 40 neonates divided into two groups (20 neonates each). In our study, the mean gestational age was 32.7 weeks for patient cases. The mean birth weight was 1.557 kg for confirmed cases. CRP was found to be higher in septic than non-septic group with a range from 6 to 24 mg/dl. The blood culture in our study was positive in 18 cases (11 cases had klebsiella, 2 had acinetobacter, 2 had coagulase negative staph (cons), one had staph aureus, one had pseudomonas, and one had MRSA) while others were negative. In our study, IP-10 cut-off for diagnosing sepsis was 133 ng/ml. Our data revealed that there was significantly higher plasma IP-10 levels in preterm neonates with neonatal sepsis compared to healthy neonates. Conclusion and Recommendations: The level of IP-10 increased early in cases with suspicion of infection. Plasma IP10 is a valuable laboratory test in the assessment of preterm infants aged < 1 week with suspicion of sepsis and may serve as a better diagnostic marker of sepsis than CRP

‘Lollipop’-shaped helical structure of a hybrid antimicrobial peptide of temporin B-lipopolysaccharide binding motif and mapping cationic residues in antibacterial activity

BackgroundTemporins are attractive templates for the development of antibiotics. However, many temporins are inactive against Gram-negative bacteria. Previously, we demonstrated conjugation of a lipopolysaccharide binding motif peptide to temporins yielded hybrid non-haemolytic AMPs that killed several Gram-negative bacteria. MethodsWe carried out a systematic Ala replacement of individual cationic and polar amino acid residues of LG21, a hybrid AMP consisted of temporin B (TB) and LPS binding motif. These Ala containing analogs of LG21 were examined for antibacterial activity, cell membrane permeabilization and liposome leakage assays using optical spectroscopic methods. Atomic resolution structure of LG21 was determined in zwitterionic dodecyl phosphocholine (DPC) micelles by NMR spectroscopy. ResultsCationic residues in the LPS binding motif of LG21 were critical for bactericidal and membrane permeabilization. Detergent bound structure of LG21 revealed helical conformation containing extensive sidechain/sidechain packing including cation/π interactions in the LPS binding motif. The helical structure of LG21 resembled a ‘lollipop’ like shape that was sustained by a compacted bulky aromatic/cationic head with a comparatively thinner ‘stick’ at the N-terminal region. The ‘head’ of the structure could be localized into micelle-water interfacial region whereas the ‘stick’ region may be inserted into the hydrophobic core of micelle. ConclusionsThe LPS binding motif of LG21 played dominant roles in broad spectrum activity and the 3-D structure provided plausible mechanistic insights for permeabilization of bacterial membrane. General significanceHybrid AMPs containing LPS binding motif could be useful for the structure based development of broad spectrum antibiotics.

Use of Enterobacterial Repetitive Intergenic Consensus PCR in Detecting Target(s) of Hapalindole-T, From a Cyanobacterium, in &lt;i&gt;Escherichia Coli&lt;/i&gt;: &lt;i&gt;In Silico&lt;/i&gt; Validation

Problem statement: Identification of newer biomolecule as well as targets are a rising concern because of increasing drug resistance in bacteria. We have isolated a broad spectrum antibiotic biomolecule Hapalindole-T from a cyanobacterium, Fisherella sp. growing on local Azadirachta indica tree bark. A model bacterium E. coli was screened spontaneously for Hap-T resistance. These resistant strains of E. coli were used to identify Hap-T target(s). Approach: These strains were subjected to Enterobacterial Repetitive Intergenic Consensus (ERIC) PCR analysis and compared with the sensitive one. We have used different bioinformatic tools like Clustalw, NJ Plot and Docking server. The Swiss-model server was used for homology modelling. Predicted 3D structure was refined by energy minimization and quality was assessed by Procheck. The model protein hailed from fimbrial biogenesis outer membrane usher protein (ADK89122.1). The interaction between the predicted structure of Model-1 protein and Hap-T biomolecule was analysed in silico using Autodock and Mopac parameters. Results: An additional band of DNA fragment (~500 base pairs) was found on agarose gel run after amplified genome of resistant strain. The results indicated that certain residues (Tyr-28), (Phe-54), (Leu-36) and (Val-52) were highly conserved and present in active sites. Conclusion/Recommendations: Thus understanding of microbial adhesion can act as an alternative approach in development of broad spectrum antibiotics.

Site-Directed Mutagenesis of N5-Carboxyaminoimidazole Ribonucleotide Mutase (Class I PurE) in Bacillus anthracis

Anthrax, the infection caused by the Gram-positive pathogen Bacillus anthracis (B. anthracis), is fatal if untreated, and some strains of B. anthracis have been found to be resistant to currently available antibiotics. The development of broad spectrum antibiotics is needed to treat the resistive strains. In antibiotic development, we have targeted B. anthracis Class I PurE enzyme (Ba PurE) as a unique and necessary enzyme in the de novo purine biosynthesis pathway, since the inactivation of this gene prevents B. anthraci growth in human serum, resulting in decreased bacterial proliferation. To identify inhibitors to $Ba$PurE, structural information on the substrate binding to its active site is needed. However, it is difficult to obtain crystals of Ba PurE with the substrate molecule in its binding site since upon binding to PurE, the substrate molecule is converted to the product molecule. An alternative approach is to create mutants of PurE that exhibit no enzymatic activity and do not convert the substrate to product, but still allow the substrate to bind to the active site. Then, the structure of mutant PurE with bound substrate can be obtained. We have identified a histidine residue at position 70 as the target of mutation to give an inactive enzyme. After successfully preparing the recombinant protein H70N, we have found that it exhibited no enzyme activity. This mutant will be useful in future experimentation to identify inhibitors of Ba PurE.

Myxopyronin induced bacterial RNA polymerase dynamics and computer aided drug discovery

Bacterial DNA‐dependent RNA polymerase (RNAP) is composed of a core of five subunits with the composition, 2α, β, β′, and ω. Each subunit has a highly conserved sequence among bacteria that is not shared among eukaryotes, characteristics that allow development of broad‐spectrum antibiotics. Here, we use two 175ns molecular dynamics simulations of MYX‐bound and unbound RNAP to show that MYX binding likely leads to an overall decrease in RNAP mobility and shortens the average distance and root mean square fluctuations between the β and β′ domains by one angstrom. These results are consistent with the view that MYX binding prevents opening of the DNA binding gate formed by the β and β′ domains, disallowing DNA binding and leading to inhibition. Additionally, we report a set of computationally predicted inhibitors found by integrating the molecular dynamics generated RNAP conformational distributions with a physics‐based virtual screen of the NCI diversity set.

Rapid Diagnostic Testing for Community-Acquired Pneumonia: Can Innovative Technology for Clinical Microbiology Be Exploited?

Two nonsynchronous events have affected the management of community-acquired pneumonia (CAP): spiraling empiricism for CAP and the “golden era” of clinical microbiology. The development of broad-spectrum antibiotics has led to widespread empiric use without ascertaining the etiology of the infecting microbe. Unfortunately, this approach clashes with the second event, which is the advent of molecular-based microbiology that can identify the causative pathogen rapidly at the point of care. The urinary antigen is a most effective rapid test that has allowed targeted therapy for Legionnaire disease at the point of care. The high specificity (> 90%) allows the clinician to administer appropriate anti-Legionella therapy based on a single rapid test; however, its low sensitivity (76%) means that a notable number of cases of Legionnaire disease will go undiagnosed if other tests, especially culture, are not performed. Further, culture for Legionella is not readily available. If a culture is not performed, epidemiologic identification of the source of the bacterium cannot be ascertained by molecular fingerprinting of the patient and the putative source strain. We recommend resurrection of the basic principles of infectious disease, which are to identify the microbial etiology of the infection and to use narrow, targeted antimicrobial therapy. To reduce antimicrobial overuse with subsequent antimicrobial resistance, these basic principles must be applied in concert with traditional and newer tests in the clinical microbiology laboratory.

Management of non-tuberculous mycobacteria in patients with cystic fibrosis.

Patients with CF are living longer with the present median survival close to 32 years of age. The increase in survival rates is attributed to better management of airway disease, including airway clearance techniques, better nutrition, new and innovative therapeutic approaches, and the development of broad-spectrum antibiotics. With improved survival, new pulmonary issues have developed. These include the emergence of multiresistant strains of Pseudomonas aeruginosa and as well as the emergence of organisms with increased virulence such as Burkholderia cepacia. Over the past few years several organisms have been identified with increasing frequency in the sputum of CF patients. These include Stenotrophomonas maltophilia, Achromobacter (Alcaligenes) xylosoxidans and nontuberculous mycobacteria (NTM). The clinical ramifications of these organisms are not entirely clear. The emergence of these organisms may be due to selection pressure from the increased use of antibiotics, improved culture techniques and/or the changing flora of an aging population. NTM have been recognised since the 1950s as potential pulmonary pathogens. NTM organisms are routinely found in the environment and are easily aerosolised. There have been documented cases of nosocomial outbreaks from medical equipment that utilises water. Person to person transmission is unlikely.