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Small colony variant

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https://www.readbyqxmd.com/read/29150501/glna-truncation-in-salmonella-enterica-results-in-a-small-colony-variant-phenotype-attenuated-host-cell-entry-and-reduced-expression-of-flagellin-and-spi-1-associated-effector-genes
#1
Philipp Aurass, Juliane Düvel, Susanne Karste, Ulrich Nübel, Wolfgang Rabsch, Antje Flieger
Many pathogenic bacteria use sophisticated survival strategies to overcome harsh environmental conditions. One is the formation of slow-growing subpopulations termed small colony variants (SCVs). Here we characterize an SCV, which spontaneously emerged from an axenic Salmonella enterica serovar Typhimurium water culture. We found that the SCV harbors a frameshift mutation in the glutamine synthetase gene glnA leading to a ∼90% truncation of the corresponding protein. Glutamine synthetase, a central enzyme in nitrogen assimilation, converts glutamate and ammonia to glutamine...
November 17, 2017: Applied and Environmental Microbiology
https://www.readbyqxmd.com/read/29143727/characterization-of-clinically-isolated-thymidine-dependent-small-colony-variants-of-escherichia-coli-producing-extended-spectrum-%C3%AE-lactamase
#2
Tatsuya Negishi, Takehisa Matsumoto, Kazuki Horiuchi, Eriko Kasuga, Tatsuya Natori, Mina Matsuoka, Naoko Ogiwara, Mitsutoshi Sugano, Takeshi Uehara, Noriyuki Nagano, Takayuki Honda
PURPOSE: Thymidine-dependent small-colony variants (TD-SCVs) are difficult to detect or test for antimicrobial susceptibility. We investigated the characteristics of clonal TD-SCVs of Escherichia coli, both with and without blaCTX-M-3, isolated from a patient. METHODOLOGY: Mutation in the thyA gene was analysed by sequencing, and morphological abnormalities in the colonies and cells of the isolates were examined. Additionally, conjugational transfer experiments were performed to prove the horizontal transferability of plasmids harbouring resistance genes...
November 16, 2017: Journal of Medical Microbiology
https://www.readbyqxmd.com/read/29130165/biosensors-for-the-detection-and-quantification-of-ai-2-class-quorum-sensing-compounds
#3
Sathish Rajamani, Richard Sayre
Intercellular small-molecular-weight signaling molecules modulate a variety of biological functions in bacteria. One of the more complex behaviors mediated by intercellular signaling molecules is the suite of activities regulated by quorum-sensing molecules. These molecules mediate a variety of population-dependent responses including the expression of genes that regulate bioluminescence, type III secretion, siderophore production, colony morphology, biofilm formation, and metalloprotease production. Given their central role in regulating these responses, the detection and quantification of QS molecules have important practical implications...
2018: Methods in Molecular Biology
https://www.readbyqxmd.com/read/29034850/pseudomonas-aeruginosa-variants-obtained-from-veterinary-clinical-samples-reveal-a-role-for-cyclic-di-gmp-in-biofilm-formation-and-colony-morphology
#4
Maria T Brock, Galya C Fedderly, Grace I Borlee, Michael M Russell, Liliana K Filipowska, Doreene R Hyatt, Ryan A Ferris, Bradley R Borlee
Overuse of antibiotics is contributing to an emerging antimicrobial resistance crisis. To better understand how bacteria adapt tolerance and resist antibiotic treatment, Pseudomonas aeruginosa isolates obtained from infection sites sampled from companion animals were collected and evaluated for phenotypic differences. Selected pairs of clonal isolates were obtained from individual infection samples and were assessed for antibiotic susceptibility, cyclic di-GMP levels, biofilm production, motility and genetic-relatedness...
October 16, 2017: Microbiology
https://www.readbyqxmd.com/read/28993457/the-electron-transport-chain-sensitises-staphylococcus-aureus-and-enterococcus-faecalis-to-the-oxidative-burst
#5
Kimberley L Painter, Alex Hall, Kam Pou Ha, Andrew M Edwards
Small colony variants (SCVs) of Staphylococcus aureus typically lack a functional electron transport chain and cannot produce virulence factors such as leukocidins, hemolysins or the anti-oxidant staphyloxanthin. Despite this, SCVs are associated with persistent infections of the bloodstream, bones and prosthetic devices. The survival of SCVs in the host has been ascribed to intracellular residency, biofilm formation and resistance to antibiotics. However, the ability of SCVs to resist host defences is largely uncharacterised...
October 9, 2017: Infection and Immunity
https://www.readbyqxmd.com/read/28987343/comparison-of-gene-co-expression-networks-in-pseudomonas-aeruginosa-and-staphylococcus-aureus-reveals-conservation-in-some-aspects-of-virulence
#6
Nazanin Hosseinkhan, Zaynab Mousavian, Ali Masoudi-Nejad
Pseudomonas aeruginosa and Staphylococcus aureus are two evolutionary distant bacterial species that are frequently isolated from persistent infections such as chronic infectious wounds and severe lung infections in cystic fibrosis patients. To the best of our knowledge no comprehensive genome scale co-expression study has been already conducted on these two species and in most cases only the expression of very few genes has been the subject of investigation. In this study, in order to investigate the level of expressional conservation between these two species, using heterogeneous gene expression datasets the weighted gene co-expression network analysis (WGCNA) approach was applied to study both single and cross species genome scale co-expression patterns of these two species...
October 4, 2017: Gene
https://www.readbyqxmd.com/read/28943172/staphylococcus-lugdunensis-small-colony-variant-conversion-resulting-in-chronic-prosthetic-joint-infection
#7
X Argemi, S Dahyot, J Lebeurre, Y Hansmann, C Ronde Oustau, G Prévost
No abstract text is available yet for this article.
November 2017: Médecine et Maladies Infectieuses
https://www.readbyqxmd.com/read/28915357/a-yigp-mutant-strain-is-a-small-colony-variant-of-e-coli-and-shows-pleiotropic-antibiotic-resistance
#8
Hui Xia, Qiongwei Tang, Jie Song, Jiang Ye, Haizhen Wu, Huizhan Zhang
Small colony variants (SCVs) are a commonly observed subpopulation of bacteria that have a small colony size and distinctive biochemical characteristics. SCVs are more resistant than the wild type to some antibiotics and usually cause persistent infections in the clinic. SCV studies have been very active during the past 2 decades, especially Staphylococcus aureus SCVs. However, fewer studies on Escherichia coli SCVs exist, so we studied an E. coli SCV during an experiment involving the deletion of the yigP locus...
September 15, 2017: Canadian Journal of Microbiology
https://www.readbyqxmd.com/read/28874369/transcriptional-and-mutational-profiling-of-an-aminoglycoside-resistant-pseudomonas-aeruginosa-small-colony-variant
#9
Monika Schniederjans, Michal Koska, Susanne Häussler
Pseudomonas aeruginosa is a major causative agent of both acute and chronic infections. Although aminoglycoside antibiotics are very potent drugs against such infections, antibiotic failure is steadily increasing mainly because of increasing resistance of the bacteria. Many molecular mechanisms that determine resistance, such as acquisition of genes encoding aminoglycoside-inactivating enzymes or overexpression of efflux pumps, have been elucidated. However, there are additional, less well-described mechanisms of aminoglycoside resistance...
November 2017: Antimicrobial Agents and Chemotherapy
https://www.readbyqxmd.com/read/28859444/evaluation-of-combinations-of-putative-anti-biofilm-agents-and-antibiotics-to-eradicate-biofilms-of-staphylococcus-aureus-and-pseudomonas-aeruginosa
#10
Katherine Belfield, Roger Bayston, Nadzieja Hajduk, Georgia Levell, John P Birchall, Matija Daniel
Objectives: To evaluate potential anti-biofilm agents for their ability to enhance the activity of antibiotics for local treatment of localized biofilm infections. Methods: Staphylococcus aureus and Pseudomonas aeruginosa in vitro biofilm models were developed. The putative antibiotic enhancers N-acetylcysteine, acetylsalicylic acid, sodium salicylate, recombinant human deoxyribonuclease I, dispersin B, hydrogen peroxide and Johnson's Baby Shampoo (JBS) were tested for their anti-biofilm activity alone and their ability to enhance the activity of antibiotics for 7 or 14 days, against 5 day old biofilms...
September 1, 2017: Journal of Antimicrobial Chemotherapy
https://www.readbyqxmd.com/read/28845425/having-your-cake-and-eating-it-staphylococcus-aureus-small-colony-variants-can-evolve-faster-growth-rate-without-losing-their-antibiotic-resistance
#11
COMMENT
Gerrit Brandis, Sha Cao, Douglas L Huseby, Diarmaid Hughes
Staphylococcus aureus can produce small colony variants (SCVs) during infections. These cause significant clinical problems because they are difficult to detect in standard microbiological screening and are associated with persistent infections. The major causes of the SCV phenotype are mutations that inhibit respiration by inactivation of genes of the menadione or hemin biosynthesis pathways. This reduces the production of ATP required to support fast growth. Importantly, it also decreases cross-membrane potential in SCVs, resulting in decreased uptake of cationic compounds, with reduced susceptibility to aminoglycoside antibiotics as a consequence...
August 1, 2017: Microbial Cell
https://www.readbyqxmd.com/read/28843820/multiple-paths-towards-reduced-membrane-potential-and-concomitant-reduction-in-aminoglycoside-susceptibility-in-staphylococcus-aureus
#12
Martin Vestergaard, Katrine Nøhr-Meldgaard, Hanne Ingmer
Staphylococcus aureus confers life-threatening and difficult to treat infections worldwide and antimicrobial resistance is an increasing concern. While acquired resistance has been widely studied, little is known of the contributions from chromosomal determinants that upon inactivation may reduce the susceptibility towards antibiotics. The aim of this study was to identify genetic determinants that upon inactivation reduce aminoglycoside susceptibility in Staphylococcus aureus. We screened the Nebraska Transposon Mutant Library of 1920 single-gene inactivations in S...
August 23, 2017: International Journal of Antimicrobial Agents
https://www.readbyqxmd.com/read/28820897/persistent-infection-due-to-a-small-colony-variant-of-burkholderia-pseudomallei-leads-to-pd-1-upregulation-on-circulating-immune-cells-and-mononuclear-infiltration-in-viscera-of-experimental-balb-c-mice
#13
Jia-Xiang See, Samudi Chandramathi, Mahmood Ameen Abdulla, Jamuna Vadivelu, Esaki M Shankar
BACKGROUND: Melioidosis is a neglected tropical disease endemic across South East Asia and Northern Australia. The etiological agent, Burkholderia pseudomallei (B.pseudomallei), is a Gram-negative, rod-shaped, motile bacterium residing in the soil and muddy water across endemic regions of the tropical world. The bacterium is known to cause persistent infections by remaining latent within host cells for prolonged duration. Reactivation of the recrudescent disease often occurs in elders whose immunity wanes...
August 2017: PLoS Neglected Tropical Diseases
https://www.readbyqxmd.com/read/28769913/intracellular-survival-of-staphylococcus-aureus-in-endothelial-cells-a-matter-of-growth-or-persistence
#14
Guillaume Rollin, Xin Tan, Fabiola Tros, Marion Dupuis, Xavier Nassif, Alain Charbit, Mathieu Coureuil
The Gram-positive human pathogen Staphylococcus aureus is a leading cause of severe bacterial infections. Recent studies have shown that various cell types could readily internalize S. aureus and infected cells have been proposed to serve as vehicle for the systemic dissemination of the pathogen. Here we focused on the intracellular behavior of the Community-Associated Methicillin-Resistant S. aureus strain USA300. Supporting earlier observations, we found that wild-type S. aureus strain USA300 persisted for longer period within endothelial cells than within macrophages and that a mutant displaying the small colony variant phenotype (ΔhemDBL) had increased intracellular persistence...
2017: Frontiers in Microbiology
https://www.readbyqxmd.com/read/28750619/the-practical-use-of-genome-sequencing-data-in-the-management-of-a-feline-colony-pedigree
#15
Fabiana H G Farias, Chad Tomlinson, Jeffrey Labuda, Gerardo Perez-Camargo, Rondo Middleton, Wesley C Warren
BACKGROUND: A higher prevalence of inherited disorders among companion animals are often rooted in their historical restricted artificial selection for a variety of observed phenotypes that eventually decreased genetic diversity. Cats have been afflicted with many inherited diseases due to domestication and intense breed selection. Advances in sequencing technology have generated a more comprehensive way to access genetic information from an individual, allowing identification of putative disease-causing variants and in practice a means to avoid their spread and thus better pedigree management...
July 27, 2017: BMC Veterinary Research
https://www.readbyqxmd.com/read/28720732/pseudomonas-aeruginosa-alters-staphylococcus-aureus-sensitivity-to-vancomycin-in-a-biofilm-model-of-cystic-fibrosis-infection
#16
Giulia Orazi, George A O'Toole
The 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...
July 18, 2017: MBio
https://www.readbyqxmd.com/read/28717043/tandem-amplification-of-the-staphylococcal-cassette-chromosome-mec-element-can-drive-high-level-methicillin-resistance-in-methicillin-resistant-staphylococcus-aureus
#17
Laura A Gallagher, Simone Coughlan, Nikki S Black, Pierce Lalor, Elaine M Waters, Bryan Wee, Mick Watson, Tim Downing, J Ross Fitzgerald, Gerard T A Fleming, James P O'Gara
Hospital-associated methicillin-resistant Staphylococcus aureus (MRSA) strains typically express high-level, homogeneous (HoR) β-lactam resistance, whereas community-associated MRSA (CA-MRSA) more commonly express low-level heterogeneous (HeR) resistance. Expression of the HoR phenotype typically requires both increased expression of the mecA gene, carried on the staphylococcal cassette chromosome mec element (SCCmec), and additional mutational event(s) elsewhere on the chromosome. Here the oxacillin concentration in a chemostat culture of the CA-MRSA strain USA300 was increased from 8 μg/ml to 130 μg/ml over 13 days to isolate highly oxacillin-resistant derivatives...
September 2017: Antimicrobial Agents and Chemotherapy
https://www.readbyqxmd.com/read/28714889/staphylococcus-aureus-regulator-sigma-b-is-important-to-develop-chronic-infections-in-hematogenous-murine-osteomyelitis-model
#18
Lorena Tuchscherr, Jennifer Geraci, Bettina Löffler
Staphylococcus aureus is a major pathogen causing bone infections that can become chronic and difficult to treat. Recently, we described the mechanism employed by S. aureus to switch to small colony variants (SCVs) and trigger intracellular bacterial persistence through the global stress regulator SigB. Here, we studied the role of SigB in the formation of chronic osteomyelitis. We used a murine hematogenous osteomyelitis model, where the mice were infected via the tail vein and subsequently developed chronic osteomyelitis...
July 15, 2017: Pathogens
https://www.readbyqxmd.com/read/28699877/isolation-and-characterization-of-kingella-negevensis-sp-nov-a-novel-kingella-species-detected-in-a-healthy-paediatric-population
#19
Nawal El Houmami, Sofiane Bakour, Janek Bzdrenga, Jaishiram Rathored, Hervé Seligmann, Catherine Robert, Nicholas Armstrong, Jacques Schrenzel, Didier Raoult, Pablo Yagupsky, Pierre-Edouard Fournier
We herein report the isolation and characterization of 21 Gram-stain-negative strains cultivated from the oropharynx of healthy children in Israel and Switzerland. Initially described as small colony variants of Kingella kingae, phenotypic analysis, biochemical analysis, phylogenetic analysis based on sequencing of the partial 16S rRNA gene and five housekeeping genes (abcZ, adk, G6PD, groEL and recA), and whole genome sequencing and comparison between members of the genera Kingella and Neisseria provided evidence for assigning them to the genus Kingella...
July 2017: International Journal of Systematic and Evolutionary Microbiology
https://www.readbyqxmd.com/read/28690982/deferiprone-and-gallium-protoporphyrin-have-the-capacity-to-potentiate-the-activity-of-antibiotics-in-staphylococcus-aureus-small-colony-variants
#20
Katharina Richter, Nicky Thomas, Guimin Zhang, Clive A Prestidge, Tom Coenye, Peter-John Wormald, Sarah Vreugde
Small colony variants (SCVs) of bacteria like Staphylococcus aureus are characterized by a reduced colony size and are linked to increased antibiotic tolerance and resistance. Their altered expression of virulence factors, slow growing properties and their ability to form biofilms make the eradication of SCVs challenging. In the context of biofilm-related infectious diseases involving S. aureus SCVs, a therapy targeting bacterial iron metabolism was evaluated. The combination of the iron-chelator deferiprone (Def) and the heme-analog gallium-protoporphyrin (GaPP), in solution and incorporated in a surgical wound gel, was tested for activity against planktonic and sessile SCVs...
2017: Frontiers in Cellular and Infection Microbiology
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