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Antibiotics, Volume 7, Issue 1 (March 2018)

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Editorial

Jump to: Research, Review

Open AccessEditorial Acknowledgement to Reviewers of Antibiotics in 2017
Received: 25 January 2018 / Revised: 25 January 2018 / Accepted: 25 January 2018 / Published: 25 January 2018
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Abstract
Peer review is an essential part in the publication process, ensuring that Antibiotics maintains high quality standards for its published papers.[...] Full article

Research

Jump to: Editorial, Review

Open AccessArticle Sperm Quality during Storage Is Not Affected by the Presence of Antibiotics in EquiPlus Semen Extender but Is Improved by Single Layer Centrifugation
Received: 26 October 2017 / Revised: 15 December 2017 / Accepted: 18 December 2017 / Published: 21 December 2017
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Abstract
Contamination of semen with bacteria arises during semen collection and handling. This bacterial contamination is typically controlled by adding antibiotics to semen extenders but intensive usage of antibiotics can lead to the development of bacterial resistance and may be detrimental to sperm quality.
[...] Read more.
Contamination of semen with bacteria arises during semen collection and handling. This bacterial contamination is typically controlled by adding antibiotics to semen extenders but intensive usage of antibiotics can lead to the development of bacterial resistance and may be detrimental to sperm quality. The objective of this study was to determine the effects of antibiotics in a semen extender on sperm quality and to investigate the effects of removal of bacteria by modified Single Layer Centrifugation (MSLC) through a colloid. Semen was collected from six adult pony stallions (three ejaculates per male). Aliquots of extended semen were used for MSLC with Equicoll, resulting in four treatment groups: control and MSLC in extender with antibiotics (CA and SA, respectively); control and MSLC in extender without antibiotics (CW and SW, respectively). Sperm motility, membrane integrity, mitochondrial membrane potential and chromatin integrity were evaluated daily by computer-assisted sperm analysis (CASA) and flow cytometry. There were no differences in sperm quality between CA and CW, or between SA and SW, although progressive motility was negatively correlated to total bacterial counts at 0 h. However, MSLC groups showed higher mean total motility (P < 0.001), progressive motility (P < 0.05), membrane integrity (P < 0.0001) and mitochondrial membrane potential (P < 0.05), as well as better chromatin integrity (P < 0.05), than controls. Sperm quality remained higher in the MSLC groups than controls throughout storage. These results indicate that sperm quality was not adversely affected by the presence of antibiotics but was improved considerably by MSLC. Full article
(This article belongs to the Special Issue Top 35 of Antibiotics Travel Awards 2017)
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Open AccessArticle Evidence for Anti-Pseudogymnoascus destructans (Pd) Activity of Propolis
Received: 16 October 2017 / Revised: 5 December 2017 / Accepted: 20 December 2017 / Published: 21 December 2017
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Abstract
White-nose syndrome (WNS) in bats, caused by Pseudogymnoascus destructans (Pd), is a cutaneous infection that has devastated North American bat populations since 2007. At present, there is no effective method for controlling this disease. Here, we evaluated the effect of propolis
[...] Read more.
White-nose syndrome (WNS) in bats, caused by Pseudogymnoascus destructans (Pd), is a cutaneous infection that has devastated North American bat populations since 2007. At present, there is no effective method for controlling this disease. Here, we evaluated the effect of propolis against Pd in vitro. Using Sabouraud dextrose agar (SDA) medium, approximately 1.7 × 107 conidia spores of the Pd strain M3906-2/mL were spread on each plate and grown to form a consistent lawn. A Kirby–Bauer disk diffusion assay was employed using different concentrations of propolis (1%, 2%, 3%, 4%, 5%, 10%, 15%, 20%, 25%), in plates incubated at 8 °C and 15 °C. At 8 °C and 15 °C, as the concentration of propolis increased, there was an increasing zone of inhibition (ZOI), reaching the highest degree at 10% and 25% concentrations, respectively. A germule suppression assay showed a similar effect on Pd conidia germination. A MALDI-TOF-MS analysis of propolis revealed multiple constituents with a potential anti-Pd activity, including cinnamic acid, p-coumaric acid, and dihydrochalcones, which could be further tested for their individual effects. Our study suggests that propolis or its individual constituents might be suitable products against Pd. Full article
(This article belongs to the Special Issue Top 35 of Antibiotics Travel Awards 2017)
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Open AccessFeature PaperArticle Establishing a System for Testing Replication Inhibition of the Vibrio cholerae Secondary Chromosome in Escherichia coli
Received: 30 October 2017 / Revised: 5 December 2017 / Accepted: 20 December 2017 / Published: 23 December 2017
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Abstract
Regulators of DNA replication in bacteria are an attractive target for new antibiotics, as not only is replication essential for cell viability, but its underlying mechanisms also differ from those operating in eukaryotes. The genetic information of most bacteria is encoded on a
[...] Read more.
Regulators of DNA replication in bacteria are an attractive target for new antibiotics, as not only is replication essential for cell viability, but its underlying mechanisms also differ from those operating in eukaryotes. The genetic information of most bacteria is encoded on a single chromosome, but about 10% of species carry a split genome spanning multiple chromosomes. The best studied bacterium in this context is the human pathogen Vibrio cholerae, with a primary chromosome (Chr1) of 3 M bps, and a secondary one (Chr2) of about 1 M bps. Replication of Chr2 is under control of a unique mechanism, presenting a potential target in the development of V. cholerae-specific antibiotics. A common challenge in such endeavors is whether the effects of candidate chemicals can be focused on specific mechanisms, such as DNA replication. To test the specificity of antimicrobial substances independent of other features of the V. cholerae cell for the replication mechanism of the V. cholerae secondary chromosome, we establish the replication machinery in the heterologous E. coli system. We characterize an E. coli strain in which chromosomal replication is driven by the replication origin of V. cholerae Chr2. Surprisingly, the E. coli ori2 strain was not inhibited by vibrepin, previously found to inhibit ori2-based replication. Full article
(This article belongs to the Special Issue Bacterial DNA Replication and Replication Inhibitors)
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Open AccessArticle Characteristics of Pediatric Antimicrobial Stewardship Programs: Current Status of the Sharing Antimicrobial Reports for Pediatric Stewardship (SHARPS) Collaborative
Received: 20 December 2017 / Revised: 17 January 2018 / Accepted: 24 January 2018 / Published: 25 January 2018
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Abstract
In response to the growing epidemic of antibiotic-resistant bacterial infections, antimicrobial stewardship programs (ASP) have been rapidly implemented in the United States (US). This study examines the prevalence of the Centers for Disease Control and Prevention’s (CDC) seven core elements of a successful
[...] Read more.
In response to the growing epidemic of antibiotic-resistant bacterial infections, antimicrobial stewardship programs (ASP) have been rapidly implemented in the United States (US). This study examines the prevalence of the Centers for Disease Control and Prevention’s (CDC) seven core elements of a successful ASP within a large subset of US Children’s Hospitals. In 2016, a survey was conducted of 52 pediatric hospitals assessing the presence of the seven core elements: leadership commitment, accountability, drug expertise, action, tracking, reporting, and education. Forty-nine hospitals (94%) had established ASPs and 41 hospitals (79%) included all seven core elements. Physician accountability (87%) and a dedicated ASP pharmacist or drug expert (88%) were present in the vast majority of hospitals. However, substantial variability existed in the financial support allotted to these positions. This variability did not predict program actions, tracking, reporting, and education. When compared with previous surveys, these results document a dramatic increase in the prevalence and resources of pediatric stewardship programs, although continued expansion is warranted. Further research is required to understand the feasibility of various core stewardship activities and the impact on patient outcomes in the setting of finite resources. Full article
(This article belongs to the Special Issue Surveillance of Antimicrobial Use and Resistance in Children)
Open AccessArticle Screening of E. coli β-clamp Inhibitors Revealed that Few Inhibit Helicobacter pylori More Effectively: Structural and Functional Characterization
Received: 10 November 2017 / Revised: 9 January 2018 / Accepted: 10 January 2018 / Published: 11 January 2018
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Abstract
The characteristic of interaction with various enzymes and processivity-promoting nature during DNA replication makes β-clamp an important drug target. Helicobacter pylori (H. pylori) have several unique features in DNA replication machinery that makes it different from other microorganisms. To find out
[...] Read more.
The characteristic of interaction with various enzymes and processivity-promoting nature during DNA replication makes β-clamp an important drug target. Helicobacter pylori (H. pylori) have several unique features in DNA replication machinery that makes it different from other microorganisms. To find out whether difference in DNA replication proteins behavior accounts for any difference in drug response when compared to E. coli, in the present study, we have tested E. coli β-clamp inhibitor molecules against H. pylori β-clamp. Various approaches were used to test the binding of inhibitors to H. pylori β-clamp including docking, surface competition assay, complex structure determination, as well as antimicrobial assay. Out of five shortlisted inhibitor molecules on the basis of docking score, three molecules, 5-chloroisatin, carprofen, and 3,4-difluorobenzamide were co-crystallized with H. pylori β-clamp and the structures show that they bind at the protein-protein interaction site as expected. In vivo studies showed only two molecules, 5-chloroisatin, and 3,4-difluorobenzamide inhibited the growth of the pylori with MIC values in micro molar range, which is better than the inhibitory effect of the same drugs on E. coli. Therefore, the evaluation of such drugs against H. pylori may explore the possibility to use to generate species-specific pharmacophore for development of new drugs against H. pylori. Full article
(This article belongs to the Special Issue Bacterial DNA Replication and Replication Inhibitors)
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Open AccessArticle Reevaluation of the Acute Cystitis Symptom Score, a Self-Reporting Questionnaire. Part I. Development, Diagnosis and Differential Diagnosis
Received: 29 August 2017 / Revised: 8 January 2018 / Accepted: 8 January 2018 / Published: 15 January 2018
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Abstract
This study aimed to reevaluate the Acute Cystitis Symptom Score (ACSS). The ACSS is a simple and standardized self-reporting questionnaire for the diagnosis of acute uncomplicated cystitis (AC) assessing typical and differential symptoms, quality of life, and possible changes after therapy in female
[...] Read more.
This study aimed to reevaluate the Acute Cystitis Symptom Score (ACSS). The ACSS is a simple and standardized self-reporting questionnaire for the diagnosis of acute uncomplicated cystitis (AC) assessing typical and differential symptoms, quality of life, and possible changes after therapy in female patients with AC. This paper includes literature research, development and evaluation of the ACSS, an 18-item self-reporting questionnaire including (a) six questions about “typical” symptoms of AC, (b) four questions regarding differential diagnoses, (c) three questions on quality of life, and (d) five questions on additional conditions that may affect therapy. The ACSS was evaluated in 228 women (mean age 31.49 ± 11.71 years) in the Russian and Uzbek languages. Measurements of reliability, validity, predictive ability, and responsiveness were performed. Cronbach’s alpha for ACSS was 0.89, split-half reliability was 0.76 and 0.79 for first and second halves, and the correlation between them was 0.87. Mann-Whitney U test revealed a significant difference in scores of the “typical” symptoms between patients and controls (10.50 vs. 2.07, p < 0.001). The optimal threshold score was 6 points, with a 94% sensitivity and 90% specificity to predict AC. The “typical” symptom score decreased significantly when comparing before and after therapy (10.4 and 2.5, p < 0.001). The reevaluated Russian and Uzbek ACSS are accurate enough and can be recommended for clinical studies and practice for initial diagnosis and monitoring the process of the treatment of AC in women. Evaluation in German, UK English, and Hungarian languages was also performed and in other languages evaluation of the ACSS is in progress Full article
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Open AccessArticle Phage-Bacterial Dynamics with Spatial Structure: Self Organization around Phage Sinks Can Promote Increased Cell Densities
Received: 27 December 2017 / Revised: 21 January 2018 / Accepted: 23 January 2018 / Published: 29 January 2018
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Abstract
Bacteria growing on surfaces appear to be profoundly more resistant to control by lytic bacteriophages than do the same cells grown in liquid. Here, we use simulation models to investigate whether spatial structure per se can account for this increased cell density in
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Bacteria growing on surfaces appear to be profoundly more resistant to control by lytic bacteriophages than do the same cells grown in liquid. Here, we use simulation models to investigate whether spatial structure per se can account for this increased cell density in the presence of phages. A measure is derived for comparing cell densities between growth in spatially structured environments versus well mixed environments (known as mass action). Maintenance of sensitive cells requires some form of phage death; we invoke death mechanisms that are spatially fixed, as if produced by cells. Spatially structured phage death provides cells with a means of protection that can boost cell densities an order of magnitude above that attained under mass action, although the effect is sometimes in the opposite direction. Phage and bacteria self organize into separate refuges, and spatial structure operates so that the phage progeny from a single burst do not have independent fates (as they do with mass action). Phage incur a high loss when invading protected areas that have high cell densities, resulting in greater protection for the cells. By the same metric, mass action dynamics either show no sustained bacterial elevation or oscillate between states of low and high cell densities and an elevated average. The elevated cell densities observed in models with spatial structure do not approach the empirically observed increased density of cells in structured environments with phages (which can be many orders of magnitude), so the empirical phenomenon likely requires additional mechanisms than those analyzed here. Full article
(This article belongs to the Special Issue Bacteriophages: Alternatives to Antibiotics and Beyond)
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Open AccessArticle Use of a Regression Model to Study Host-Genomic Determinants of Phage Susceptibility in MRSA
Received: 15 November 2017 / Revised: 20 January 2018 / Accepted: 24 January 2018 / Published: 29 January 2018
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Abstract
Staphylococcus aureus is a major agent of nosocomial infections. Especially in methicillin-resistant strains, conventional treatment options are limited and expensive, which has fueled a growing interest in phage therapy approaches. We have tested the susceptibility of 207 clinical S. aureus strains to 12
[...] Read more.
Staphylococcus aureus is a major agent of nosocomial infections. Especially in methicillin-resistant strains, conventional treatment options are limited and expensive, which has fueled a growing interest in phage therapy approaches. We have tested the susceptibility of 207 clinical S. aureus strains to 12 (nine monovalent) different therapeutic phage preparations and subsequently employed linear regression models to estimate the influence of individual host gene families on resistance to phages. Specifically, we used a two-step regression model setup with a preselection step based on gene family enrichment. We show that our models are robust and capture the data’s underlying signal by comparing their performance to that of models build on randomized data. In doing so, we have identified 167 gene families that govern phage resistance in our strain set and performed functional analysis on them. This revealed genes of possible prophage or mobile genetic element origin, along with genes involved in restriction-modification and transcription regulators, though the majority were genes of unknown function. This study is a step in the direction of understanding the intricate host-phage relationship in this important pathogen with the outlook to targeted phage therapy applications. Full article
(This article belongs to the Special Issue Bacteriophages: Alternatives to Antibiotics and Beyond)
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Open AccessArticle Assessing the Knowledge, Attitudes and Behaviors of Human and Animal Health Students towards Antibiotic Use and Resistance: A Pilot Cross-Sectional Study in the UK
Antibiotics 2018, 7(1), 10; https://doi.org/10.3390/antibiotics7010010
Received: 29 December 2017 / Revised: 23 January 2018 / Accepted: 25 January 2018 / Published: 30 January 2018
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Abstract
The Global Action Plan on Antimicrobial Resistance highlights the importance of training all healthcare professionals. No study has assessed patterns of students’ knowledge, attitudes and practices concerning antibiotic use simultaneously across different healthcare course types. We conducted a cross-sectional multi-center survey among UK
[...] Read more.
The Global Action Plan on Antimicrobial Resistance highlights the importance of training all healthcare professionals. No study has assessed patterns of students’ knowledge, attitudes and practices concerning antibiotic use simultaneously across different healthcare course types. We conducted a cross-sectional multi-center survey among UK students. The survey was advertised through local survey coordinators at 25 universities. The online survey was accessible from 10th October to 17th November 2016 (before European Antibiotic Awareness Day). A total of 255 students from 25 universities participated, including students on medicine, pharmacy, nursing, physician associate, dentistry and veterinary medicine courses. Antibiotic resistance was considered to be a more important global challenge than climate change, obesity or food security (p < 0.001). Most students (95%) believed that antibiotic resistance will be a problem for their future practice, but fewer (69%) thought that the antibiotics they will prescribe, administer or dispense will contribute to the problem. A fifth of students felt they had sufficient knowledge of antibiotic use for their future work. Our exploratory study suggests that UK human and animal healthcare students are aware of the importance of antibiotic resistance, but many still have certain misconceptions. Campaigns and improved educational efforts applying behavioral insights methodology could address these. Full article
(This article belongs to the Special Issue Top 35 of Antibiotics Travel Awards 2017)
Open AccessArticle Survey of Nonprescription Medication and Antibiotic Use in Patients with Stevens-Johnson Syndrome, Toxic Epidermal Necrolysis, and Overlap Syndrome
Antibiotics 2018, 7(1), 11; https://doi.org/10.3390/antibiotics7010011
Received: 16 December 2017 / Revised: 10 January 2018 / Accepted: 25 January 2018 / Published: 1 February 2018
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Abstract
Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and overlap syndrome (SJS-TEN) are rare, serious skin and mucosa break-down conditions frequently associated with antibiotic use. The role of nonprescription medications alone, or in combination with antibiotics in triggering SJS/TEN, is largely unknown. This study
[...] Read more.
Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and overlap syndrome (SJS-TEN) are rare, serious skin and mucosa break-down conditions frequently associated with antibiotic use. The role of nonprescription medications alone, or in combination with antibiotics in triggering SJS/TEN, is largely unknown. This study summarized data collected from patient surveys about nonprescription and antibiotic use prior to a SJS/TEN diagnosis. The survey was administered online to members of the U.S. SJS Foundation who had been diagnosed with SJS/TEN or were the parent of a child who had been diagnosed with SJS/TEN. Respondents were asked about nonprescription medications taken within the year before diagnosis, and the approximate point in time before diagnosis that they had taken them. They were also asked about specific prescription medications, including antibiotics, that they took before diagnosis. An estimated 4500 patients received an invitation to complete the survey. 251 patients completed it, resulting in a response rate of 5.6%. The mean age of respondents was 43 years (SD (standard deviation) = 17.3) and 70% were female. 32.3% of respondents indicated that a prescription antibiotic triggered their reaction. 14.1% indicated a nonprescription medication had triggered their SJS/TEN, and 18.1% said a nonprescription medication may have triggered their SJS/TEN. 85.5% of respondents said they took a nonprescription medication within three months of their SJS/TEN diagnosis. Of those respondents who reported that an antibiotic triggered their SJS/TEN, 35.2% reported taking a nonprescription medication within the three months prior to their diagnosis. This survey captured valuable information about nonprescription and antibiotic use in SJS/TEN patients. It is important for future studies to estimate the impact of antibiotics on SJS/TEN, and account for nonprescription medication use in that relationship. Full article
(This article belongs to the Special Issue Top 35 of Antibiotics Travel Awards 2017)
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Open AccessArticle Diversification of Secondary Metabolite Biosynthetic Gene Clusters Coincides with Lineage Divergence in Streptomyces
Antibiotics 2018, 7(1), 12; https://doi.org/10.3390/antibiotics7010012
Received: 11 January 2018 / Revised: 6 February 2018 / Accepted: 7 February 2018 / Published: 13 February 2018
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Abstract
We have identified Streptomyces sister-taxa which share a recent common ancestor and nearly identical small subunit (SSU) rRNA gene sequences, but inhabit distinct geographic ranges demarcated by latitude and have sufficient genomic divergence to represent distinct species. Here, we explore the evolutionary dynamics
[...] Read more.
We have identified Streptomyces sister-taxa which share a recent common ancestor and nearly identical small subunit (SSU) rRNA gene sequences, but inhabit distinct geographic ranges demarcated by latitude and have sufficient genomic divergence to represent distinct species. Here, we explore the evolutionary dynamics of secondary metabolite biosynthetic gene clusters (SMGCs) following lineage divergence of these sister-taxa. These sister-taxa strains contained 310 distinct SMGCs belonging to 22 different gene cluster classes. While there was broad conservation of these 22 gene cluster classes among the genomes analyzed, each individual genome harbored a different number of gene clusters within each class. A total of nine SMGCs were conserved across nearly all strains, but the majority (57%) of SMGCs were strain-specific. We show that while each individual genome has a unique combination of SMGCs, this diversity displays lineage-level modularity. Overall, the northern-derived (NDR) clade had more SMGCs than the southern-derived (SDR) clade (40.7 ± 3.9 and 33.8 ± 3.9, mean and S.D., respectively). This difference in SMGC content corresponded with differences in the number of predicted open reading frames (ORFs) per genome (7775 ± 196 and 7093 ± 205, mean and S.D., respectively) such that the ratio of SMGC:ORF did not differ between sister-taxa genomes. We show that changes in SMGC diversity between the sister-taxa were driven primarily by gene acquisition and deletion events, and these changes were associated with an overall change in genome size which accompanied lineage divergence. Full article
(This article belongs to the Special Issue Actinomycetes: The Antibiotics Producers)
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Open AccessArticle Efficacy of an Optimised Bacteriophage Cocktail to Clear Clostridium difficile in a Batch Fermentation Model
Antibiotics 2018, 7(1), 13; https://doi.org/10.3390/antibiotics7010013
Received: 31 December 2017 / Revised: 3 February 2018 / Accepted: 6 February 2018 / Published: 13 February 2018
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Abstract
Clostridium difficile infection (CDI) is a major cause of infectious diarrhea. Conventional antibiotics are not universally effective for all ribotypes, and can trigger dysbiosis, resistance and recurrent infection. Thus, novel therapeutics are needed to replace and/or supplement the current antibiotics. Here, we describe
[...] Read more.
Clostridium difficile infection (CDI) is a major cause of infectious diarrhea. Conventional antibiotics are not universally effective for all ribotypes, and can trigger dysbiosis, resistance and recurrent infection. Thus, novel therapeutics are needed to replace and/or supplement the current antibiotics. Here, we describe the activity of an optimised 4-phage cocktail to clear cultures of a clinical ribotype 014/020 strain in fermentation vessels spiked with combined fecal slurries from four healthy volunteers. After 5 h, we observed ~6-log reductions in C. difficile abundance in the prophylaxis regimen and complete C. difficile eradication after 24 h following prophylactic or remedial regimens. Viability assays revealed that commensal enterococci, bifidobacteria, lactobacilli, total anaerobes, and enterobacteria were not affected by either regimens, but a ~2-log increase in the enterobacteria, lactobacilli, and total anaerobe abundance was seen in the phage-only-treated vessel compared to other treatments. The impact of the phage treatments on components of the microbiota was further assayed using metagenomic analysis. Together, our data supports the therapeutic application of our optimised phage cocktail to treat CDI. Also, the increase in specific commensals observed in the phage-treated control could prevent further colonisation of C. difficile, and thus provide protection from infection being able to establish. Full article
(This article belongs to the Special Issue Bacteriophages: Alternatives to Antibiotics and Beyond)
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Open AccessArticle Fragment-Based Discovery of Inhibitors of the Bacterial DnaG-SSB Interaction
Antibiotics 2018, 7(1), 14; https://doi.org/10.3390/antibiotics7010014
Received: 15 January 2018 / Revised: 9 February 2018 / Accepted: 13 February 2018 / Published: 22 February 2018
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Abstract
In bacteria, the DnaG primase is responsible for synthesis of short RNA primers used to initiate chain extension by replicative DNA polymerase(s) during chromosomal replication. Among the proteins with which Escherichia coli DnaG interacts is the single-stranded DNA-binding protein, SSB. The C-terminal hexapeptide
[...] Read more.
In bacteria, the DnaG primase is responsible for synthesis of short RNA primers used to initiate chain extension by replicative DNA polymerase(s) during chromosomal replication. Among the proteins with which Escherichia coli DnaG interacts is the single-stranded DNA-binding protein, SSB. The C-terminal hexapeptide motif of SSB (DDDIPF; SSB-Ct) is highly conserved and is known to engage in essential interactions with many proteins in nucleic acid metabolism, including primase. Here, fragment-based screening by saturation-transfer difference nuclear magnetic resonance (STD-NMR) and surface plasmon resonance assays identified inhibitors of the primase/SSB-Ct interaction. Hits were shown to bind to the SSB-Ct-binding site using 15N–1H HSQC spectra. STD-NMR was used to demonstrate binding of one hit to other SSB-Ct binding partners, confirming the possibility of simultaneous inhibition of multiple protein/SSB interactions. The fragment molecules represent promising scaffolds on which to build to discover new antibacterial compounds. Full article
(This article belongs to the Special Issue Bacterial DNA Replication and Replication Inhibitors)
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Open AccessArticle Protective Effects of Bacteriophages against Aeromonas hydrophila Causing Motile Aeromonas Septicemia (MAS) in Striped Catfish
Antibiotics 2018, 7(1), 16; https://doi.org/10.3390/antibiotics7010016
Received: 28 December 2017 / Revised: 30 January 2018 / Accepted: 23 February 2018 / Published: 25 February 2018
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Abstract
To determine the effectivity of bacteriophages in controlling the mass mortality of striped catfish (Pangasianodon hypophthalmus) due to infections caused by Aeromonas spp. in Vietnamese fish farms, bacteriophages against pathogenic Aeromonas hydrophila were isolated. A. hydrophila-phage 2 and A. hydrophila
[...] Read more.
To determine the effectivity of bacteriophages in controlling the mass mortality of striped catfish (Pangasianodon hypophthalmus) due to infections caused by Aeromonas spp. in Vietnamese fish farms, bacteriophages against pathogenic Aeromonas hydrophila were isolated. A. hydrophila-phage 2 and A. hydrophila-phage 5 were successfully isolated from water samples from the Saigon River of Ho Chi Minh City, Vietnam. These phages, belonging to the Myoviridae family, were found to have broad activity spectra, even against the tested multiple-antibiotic-resistant Aeromonas isolates. The latent periods and burst size of phage 2 were 10 min and 213 PFU per infected host cell, respectively. The bacteriophages proved to be effective in inhibiting the growth of the Aeromonas spp. under laboratory conditions. Phage treatments applied to the pathogenic strains during infestation of catfish resulted in a significant improvement in the survival rates of the tested fishes, with up to 100% survival with MOI 100, compared to 18.3% survival observed in control experiments. These findings illustrate the potential for using phages as an effective bio-treatment method to control Motile Aeromonas Septicemia (MAS) in fish farms. This study provides further evidence towards the use of bacteriophages to effectively control disease in aquaculture operations. Full article
(This article belongs to the Special Issue Bacteriophages: Alternatives to Antibiotics and Beyond)
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Open AccessArticle Efflux Activity Differentially Modulates the Levels of Isoniazid and Rifampicin Resistance among Multidrug Resistant and Monoresistant Mycobacterium tuberculosis Strains
Antibiotics 2018, 7(1), 18; https://doi.org/10.3390/antibiotics7010018
Received: 8 February 2018 / Revised: 28 February 2018 / Accepted: 1 March 2018 / Published: 3 March 2018
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Abstract
With the growing body of knowledge on the contribution of efflux activity to Mycobacterium tuberculosis drug resistance, increased attention has been given to the use of efflux inhibitors as adjuvants of tuberculosis therapy. Here, we investigated how efflux activity modulates the levels of
[...] Read more.
With the growing body of knowledge on the contribution of efflux activity to Mycobacterium tuberculosis drug resistance, increased attention has been given to the use of efflux inhibitors as adjuvants of tuberculosis therapy. Here, we investigated how efflux activity modulates the levels of efflux between monoresistant and multi- and extensively drug resistant (M/XDR) M. tuberculosis clinical isolates. The strains were characterized by antibiotic susceptibility testing in the presence/absence of efflux inhibitors, molecular typing, and genetic analysis of drug-resistance-associated genes. Efflux activity was quantified by real-time fluorometry. The results demonstrated that all the M. tuberculosis clinical strains, susceptible or resistant, presented a faster, rapid, and non-specific efflux-mediated short-term response to drugs. The synergism assays demonstrated that the efflux inhibitors were more effective in reducing the resistance levels in the M/XDR strains than in the monoresistant strains. This indicated that M/XDR strains presented a more prolonged response to drugs mediated by efflux compared to the monoresistant strains, but both maintain it as a long-term stress response. This work shows that efflux activity modulates the levels of drug resistance between monoresistant and M/XDR M. tuberculosis clinical strains, allowing the bacteria to survive in the presence of noxious compounds. Full article
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Open AccessArticle Genetic Determinants of Tetracycline Resistance in Clinical Streptococcus pneumoniae Serotype 1 Isolates from Niger
Antibiotics 2018, 7(1), 19; https://doi.org/10.3390/antibiotics7010019
Received: 17 June 2017 / Revised: 2 February 2018 / Accepted: 2 February 2018 / Published: 6 March 2018
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Abstract
Streptococcus pneumoniae serotype 1 is the first cause of pneumococcal meningitis Niger. To determine the underlying mechanism of resistance to tetracycline in serotype 1 Streptococcus pneumoniae, a collection of 37 isolates recovered from meningitis patients over the period of 2002 to 2009
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Streptococcus pneumoniae serotype 1 is the first cause of pneumococcal meningitis Niger. To determine the underlying mechanism of resistance to tetracycline in serotype 1 Streptococcus pneumoniae, a collection of 37 isolates recovered from meningitis patients over the period of 2002 to 2009 in Niger were analyzed for drug susceptibility, and whole genome sequencing (WGS) was performed for molecular analyses. MIC level was determined for 31/37 (83.8%) isolates and allowed detection of full resistance (MIC = 8 µg) in 24/31 (77.4%) isolates. No resistance was found to macrolides and quinolones. Sequence-types deduced from WGS were ST217 (54.1%), ST303 (35.1%), ST2206 (5.4%), ST2839 (2.7%) and one undetermined ST (2.7%). All tetracycline resistant isolates carried a Tn5253 like element, which was found to be an association of two smaller transposons of Tn916 and Tn5252 families. No tet(O) and tet(Q) genes were detected. However, a tet(M) like sequence was identified in all Tn5253 positive strains and was found associated to Tn916 composite. Only one isolate was phenotypically resistant to chloramphenicol, wherein a chloramphenicol acetyl transferase (cat) gene sequence homologous to catpC194 from the Staphylococcus aureus plasmid pC194 was detected. In conclusion, clinical Streptococcus pneumoniae type 1 isolated during 2002 to 2009 meningitis surveillance in Niger were fully susceptible to macrolides and quinolones but highly resistant to tetracycline (77.4%) through acquisition of a defective Tn5253 like element composed of Tn5252 and Tn916 transposons. Of the 31 tested isolates, only one was exceptionally resistant to chloramphenicol and carried a Tn5253 transposon that contained cat gene sequence. Full article
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Open AccessFeature PaperArticle Biosynthesis of Rishirilide B
Antibiotics 2018, 7(1), 20; https://doi.org/10.3390/antibiotics7010020
Received: 14 February 2018 / Revised: 1 March 2018 / Accepted: 1 March 2018 / Published: 7 March 2018
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Abstract
Rishirilide B was isolated from Streptomyces rishiriensis and Streptomyces bottropensis on the basis of its inhibitory activity towards alpha-2-macroglobulin. The biosynthesis of rishirilide B was investigated by feeding experiments with different 13C labelled precursors using the heterologous host Streptomyces albus J1074::cos4 containing
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Rishirilide B was isolated from Streptomyces rishiriensis and Streptomyces bottropensis on the basis of its inhibitory activity towards alpha-2-macroglobulin. The biosynthesis of rishirilide B was investigated by feeding experiments with different 13C labelled precursors using the heterologous host Streptomyces albus J1074::cos4 containing a cosmid encoding of the gene cluster responsible for rishirilide B production. NMR spectroscopic analysis of labelled compounds demonstrate that the tricyclic backbone of rishirilide B is a polyketide synthesized from nine acetate units. One of the acetate units is decarboxylated to give a methyl group. The origin of the starter unit was determined to be isobutyrate. Full article
(This article belongs to the Special Issue Actinomycetes: The Antibiotics Producers)
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Open AccessArticle Protein Expression Modifications in Phage-Resistant Mutants of Aeromonas salmonicida after AS-A Phage Treatment
Antibiotics 2018, 7(1), 21; https://doi.org/10.3390/antibiotics7010021
Received: 31 January 2018 / Revised: 1 March 2018 / Accepted: 6 March 2018 / Published: 8 March 2018
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Abstract
The occurrence of infections by pathogenic bacteria is one of the main sources of financial loss for the aquaculture industry. This problem often cannot be solved with antibiotic treatment or vaccination. Phage therapy seems to be an alternative environmentally-friendly strategy to control infections.
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The occurrence of infections by pathogenic bacteria is one of the main sources of financial loss for the aquaculture industry. This problem often cannot be solved with antibiotic treatment or vaccination. Phage therapy seems to be an alternative environmentally-friendly strategy to control infections. Recognizing the cellular modifications that bacteriophage therapy may cause to the host is essential in order to confirm microbial inactivation, while understanding the mechanisms that drive the development of phage-resistant strains. The aim of this work was to detect cellular modifications that occur after phage AS-A treatment in A. salmonicida, an important fish pathogen. Phage-resistant and susceptible cells were subjected to five successive streak-plating steps and analysed with infrared spectroscopy, a fast and powerful tool for cell study. The spectral differences of both populations were investigated and compared with a phage sensitivity profile, obtained through the spot test and efficiency of plating. Changes in protein associated peaks were found, and these results were corroborated by 1-D electrophoresis of intracellular proteins analysis and by phage sensitivity profiles. Phage AS-A treatment before the first streaking-plate step clearly affected the intracellular proteins expression levels of phage-resistant clones, altering the expression of distinct proteins during the subsequent five successive streak-plating steps, making these clones recover and be phenotypically more similar to the sensitive cells. Full article
(This article belongs to the Special Issue Bacteriophages: Alternatives to Antibiotics and Beyond)
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Open AccessArticle Potentially Important Therapeutic Interactions between Antibiotics, and a Specially Engineered Emulsion Drug Vehicle Containing Krill-Oil-Based Phospholipids and Omega-3 Fatty Acids
Antibiotics 2018, 7(1), 22; https://doi.org/10.3390/antibiotics7010022
Received: 8 February 2018 / Revised: 5 March 2018 / Accepted: 9 March 2018 / Published: 10 March 2018
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Abstract
The incidence of antimicrobial resistance (AMR) worldwide is increasing as the pipeline for the development of new chemotherapeutic entities is decreasing. Clearly, overexposure to antibiotics, including excessive dosing, is a key factor that fuels AMR. In fact, most of the new antibacterial agents
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The incidence of antimicrobial resistance (AMR) worldwide is increasing as the pipeline for the development of new chemotherapeutic entities is decreasing. Clearly, overexposure to antibiotics, including excessive dosing, is a key factor that fuels AMR. In fact, most of the new antibacterial agents under development are derivatives of existing classes of antibiotics. Novel approaches involving unique antimicrobial combinations, targets, and/or delivery systems are under intense investigation. An innovative combination of active pharmaceutical ingredients (APIs) consisting of antimicrobial drug(s), krill-oil-based phospholipids, and omega-3 fatty acid triglycerides, that may extend the therapeutic viability of currently effective antibiotics, at least until new chemical entities are introduced, is described. Full article
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Open AccessArticle Parallel Colorimetric Quantification of Choline and Phosphocholine as a Method for Studying Choline Kinase Activity in Complex Mixtures
Antibiotics 2018, 7(1), 24; https://doi.org/10.3390/antibiotics7010024
Received: 27 February 2018 / Revised: 12 March 2018 / Accepted: 14 March 2018 / Published: 17 March 2018
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Abstract
Choline kinase (Chok) is an enzyme found in eukaryotes and Gram-positive bacteria. Chok catalyzes the production of phosphocholine from choline and ATP. This enzyme has been validated as a drug target in Streptococcus pneumonia, but the role Chok enzymatic activity plays in
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Choline kinase (Chok) is an enzyme found in eukaryotes and Gram-positive bacteria. Chok catalyzes the production of phosphocholine from choline and ATP. This enzyme has been validated as a drug target in Streptococcus pneumonia, but the role Chok enzymatic activity plays in bacterial cell growth and division is not well understood. Phosphocholine production by Chok and its attenuation by inhibitors in the context of complex samples such as cell extracts can currently be quantified by several methods. These include choline depletion measurements, radioactive methods, mass-spectrometry, and nuclear magnetic resonance. The first does not measure phosphocholine directly, the second requires elaborate safety procedures, and the third and fourth require significant capital investments and technical expertise. For these reasons, a less expensive, higher throughput, more easily accessible assay is needed to facilitate further study in Gram-positive Choks. Here, we present the development of a triiodide/activated charcoal/molybdenum blue system for detecting and quantifying choline and phosphocholine in parallel. We demonstrate that this system can reliably quantify changes in choline and phosphocholine concentrations over time in Chok enzymatic assays using cell extracts as the source of the enzyme. This is an easily accessible, convenient, robust, and economical method for studying Chok activity in complex samples. The triiodide/activated charcoal/molybdenum blue system opens new doors into the study choline kinase in Gram-positive pathogens. Full article
(This article belongs to the Special Issue Top 35 of Antibiotics Travel Awards 2017)
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Open AccessArticle Geographic Variation in Antibiotic Consumption—Is It Due to Doctors’ Prescribing or Patients’ Consulting?
Antibiotics 2018, 7(1), 26; https://doi.org/10.3390/antibiotics7010026
Received: 23 January 2018 / Revised: 11 March 2018 / Accepted: 19 March 2018 / Published: 20 March 2018
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Abstract
Antibiotic consumption varies greatly between Norwegian municipalities. We examine whether this variation is associated with inhabitants’ consultation rates or general practitioners’ (GP) prescription rates. Our study comprises consultations and antibiotic prescriptions for respiratory tract infections (RTIs) in general practice in all Norwegian municipalities
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Antibiotic consumption varies greatly between Norwegian municipalities. We examine whether this variation is associated with inhabitants’ consultation rates or general practitioners’ (GP) prescription rates. Our study comprises consultations and antibiotic prescriptions for respiratory tract infections (RTIs) in general practice in all Norwegian municipalities with over 5000 inhabitants in 2014. Data was collected from The Norwegian Prescription Database, The Directorate of Health’s system for control and payment of health reimbursements registry and Norway Statistics. Consultation rates and prescription rates were categorised in age- and gender specific quintiles and the effect on antibiotic consumption was analysed using a Poisson regression model. We found that inhabitants with RTIs received 42% more prescriptions if they belonged to a municipality with high consultation rates compared to low consultation rates [incidence rate ratio (IRR) 1.42 (95% CI 1.41–1.44)] and 48% more prescriptions if they belonged to a municipality with high prescription rates versus low prescription rates [IRR 1.48 (95% KI 1.47–1.50)]. Our results demonstrate that inhabitants’ consultation rates and GPs’ prescription rates have about equal impact on the number of RTI antibiotics prescribed at municipality level. These findings highlight the importance of interventions targeting patients as well as doctors in efforts to reduce unnecessary antibiotic consumption. Full article
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Open AccessReview Bacteriophage Interactions with Marine Pathogenic Vibrios: Implications for Phage Therapy
Antibiotics 2018, 7(1), 15; https://doi.org/10.3390/antibiotics7010015
Received: 1 February 2018 / Revised: 19 February 2018 / Accepted: 21 February 2018 / Published: 24 February 2018
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Abstract
A global distribution in marine, brackish, and freshwater ecosystems, in combination with high abundances and biomass, make vibrios key players in aquatic environments, as well as important pathogens for humans and marine animals. Incidents of Vibrio-associated diseases (vibriosis) in marine aquaculture are
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A global distribution in marine, brackish, and freshwater ecosystems, in combination with high abundances and biomass, make vibrios key players in aquatic environments, as well as important pathogens for humans and marine animals. Incidents of Vibrio-associated diseases (vibriosis) in marine aquaculture are being increasingly reported on a global scale, due to the fast growth of the industry over the past few decades years. The administration of antibiotics has been the most commonly applied therapy used to control vibriosis outbreaks, giving rise to concerns about development and spreading of antibiotic-resistant bacteria in the environment. Hence, the idea of using lytic bacteriophages as therapeutic agents against bacterial diseases has been revived during the last years. Bacteriophage therapy constitutes a promising alternative not only for treatment, but also for prevention of vibriosis in aquaculture. However, several scientific and technological challenges still need further investigation before reliable, reproducible treatments with commercial potential are available for the aquaculture industry. The potential and the challenges of phage-based alternatives to antibiotic treatment of vibriosis are addressed in this review. Full article
(This article belongs to the Special Issue Bacteriophages: Alternatives to Antibiotics and Beyond)
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Open AccessReview Potential for Bacteriophage Endolysins to Supplement or Replace Antibiotics in Food Production and Clinical Care
Antibiotics 2018, 7(1), 17; https://doi.org/10.3390/antibiotics7010017
Received: 21 December 2017 / Revised: 6 February 2018 / Accepted: 23 February 2018 / Published: 27 February 2018
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Abstract
There is growing concern about the emergence of bacterial strains showing resistance to all classes of antibiotics commonly used in human medicine. Despite the broad range of available antibiotics, bacterial resistance has been identified for every antimicrobial drug developed to date. Alarmingly, there
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There is growing concern about the emergence of bacterial strains showing resistance to all classes of antibiotics commonly used in human medicine. Despite the broad range of available antibiotics, bacterial resistance has been identified for every antimicrobial drug developed to date. Alarmingly, there is also an increasing prevalence of multidrug-resistant bacterial strains, rendering some patients effectively untreatable. Therefore, there is an urgent need to develop alternatives to conventional antibiotics for use in the treatment of both humans and food-producing animals. Bacteriophage-encoded lytic enzymes (endolysins), which degrade the cell wall of the bacterial host to release progeny virions, are potential alternatives to antibiotics. Preliminary studies show that endolysins can disrupt the cell wall when applied exogenously, though this has so far proven more effective in Gram-positive bacteria compared with Gram-negative bacteria. Their potential for development is furthered by the prospect of bioengineering, and aided by the modular domain structure of many endolysins, which separates the binding and catalytic activities into distinct subunits. These subunits can be rearranged to create novel, chimeric enzymes with optimized functionality. Furthermore, there is evidence that the development of resistance to these enzymes may be more difficult compared with conventional antibiotics due to their targeting of highly conserved bonds. Full article
(This article belongs to the Special Issue Bacteriophages: Alternatives to Antibiotics and Beyond)
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Open AccessReview The Macromolecular Machines that Duplicate the Escherichia coli Chromosome as Targets for Drug Discovery
Antibiotics 2018, 7(1), 23; https://doi.org/10.3390/antibiotics7010023
Received: 1 February 2018 / Revised: 6 March 2018 / Accepted: 6 March 2018 / Published: 14 March 2018
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Abstract
DNA replication is an essential process. Although the fundamental strategies to duplicate chromosomes are similar in all free-living organisms, the enzymes of the three domains of life that perform similar functions in DNA replication differ in amino acid sequence and their three-dimensional structures.
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DNA replication is an essential process. Although the fundamental strategies to duplicate chromosomes are similar in all free-living organisms, the enzymes of the three domains of life that perform similar functions in DNA replication differ in amino acid sequence and their three-dimensional structures. Moreover, the respective proteins generally utilize different enzymatic mechanisms. Hence, the replication proteins that are highly conserved among bacterial species are attractive targets to develop novel antibiotics as the compounds are unlikely to demonstrate off-target effects. For those proteins that differ among bacteria, compounds that are species-specific may be found. Escherichia coli has been developed as a model system to study DNA replication, serving as a benchmark for comparison. This review summarizes the functions of individual E. coli proteins, and the compounds that inhibit them. Full article
(This article belongs to the Special Issue Bacterial DNA Replication and Replication Inhibitors)
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Open AccessReview Novel Aspects of Polynucleotide Phosphorylase Function in Streptomyces
Antibiotics 2018, 7(1), 25; https://doi.org/10.3390/antibiotics7010025
Received: 14 February 2018 / Revised: 13 March 2018 / Accepted: 16 March 2018 / Published: 18 March 2018
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Abstract
Polynucleotide phosphorylase (PNPase) is a 3′–5′-exoribnuclease that is found in most bacteria and in some eukaryotic organelles. The enzyme plays a key role in RNA decay in these systems. PNPase structure and function have been studied extensively in Escherichia coli, but there
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Polynucleotide phosphorylase (PNPase) is a 3′–5′-exoribnuclease that is found in most bacteria and in some eukaryotic organelles. The enzyme plays a key role in RNA decay in these systems. PNPase structure and function have been studied extensively in Escherichia coli, but there are several important aspects of PNPase function in Streptomyces that differ from what is observed in E. coli and other bacterial genera. This review highlights several of those differences: (1) the organization and expression of the PNPase gene in Streptomyces; (2) the possible function of PNPase as an RNA 3′-polyribonucleotide polymerase in Streptomyces; (3) the function of PNPase as both an exoribonuclease and as an RNA 3′-polyribonucleotide polymerase in Streptomyces; (4) the function of (p)ppGpp as a PNPase effector in Streptomyces. The review concludes with a consideration of a number of unanswered questions regarding the function of Streptomyces PNPase, which can be examined experimentally. Full article
(This article belongs to the Special Issue Actinomycetes: The Antibiotics Producers)
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