scholarly journals Nisin Resistance of Listeria monocytogenes Is Increased by Exposure to Salt Stress and Is Mediated via LiaR

2013 ◽  
Vol 79 (18) ◽  
pp. 5682-5688 ◽  
Author(s):  
Teresa M. Bergholz ◽  
Silin Tang ◽  
Martin Wiedmann ◽  
Kathryn J. Boor
Keyword(s):  
Salt Stress ◽  
Listeria Monocytogenes ◽  
Safety Concern ◽  
Response Regulator ◽  
Brain Heart Infusion ◽  
Control Measures ◽  
Protective Effects ◽  
Wild Type ◽  
Content Type ◽  
Type Strains

ABSTRACTGrowth ofListeria monocytogeneson refrigerated, ready-to-eat food is a significant food safety concern. Natural antimicrobials, such as nisin, can be used to control this pathogen on food, but little is known about how other food-related stresses may impact how the pathogen responds to these compounds. Prior work demonstrated that exposure ofL. monocytogenesto salt stress at 7°C led to increased expression of genes involved in nisin resistance, including the response regulatorliaR. We hypothesized that exposure to salt stress would increase subsequent resistance to nisin and that LiaR would contribute to increased nisin resistance. Isogenic deletion mutations inliaRwere constructed in 7 strains ofL. monocytogenes, and strains were exposed to 6% NaCl in brain heart infusion broth and then tested for resistance to nisin (2 mg/ml Nisaplin) at 7°C. For the wild-type strains, exposure to salt significantly increased subsequent nisin resistance (P< 0.0001) over innate levels of resistance. Compared to the salt-induced nisin resistance of wild-type strains, ΔliaRstrains were significantly more sensitive to nisin (P< 0.001), indicating that induction of LiaFSR led to cross-protection ofL. monocytogenesagainst subsequent inactivation by nisin. Transcript levels of LiaR-regulated genes were induced by salt stress, and lmo1746 andtelAwere found to contribute to LiaR-mediated salt-induced nisin resistance. These data suggest that environmental stresses similar to those on foods can influence the resistance ofL. monocytogenesto antimicrobials such as nisin, and potential cross-protective effects should be considered when selecting and applying control measures for this pathogen on ready-to-eat foods.

scholarly journals Pharmacodynamics of Itraconazole against Aspergillus fumigatus in anIn VitroModel of the Human Alveolus: Perspectives on the Treatment of Triazole-Resistant Infection and Utility of Airway Administration

2012 ◽  
Vol 56 (8) ◽  
pp. 4146-4153 ◽  
Author(s):  
Zaid Al-Nakeeb ◽  
Ajay Sudan ◽  
Adam R. Jeans ◽  
Lea Gregson ◽  
Joanne Goodwin ◽  
...  
Keyword(s):  
Aspergillus Fumigatus ◽  
Therapeutic Strategies ◽  
Wild Type ◽  
Content Type ◽  
Exposure Response ◽  
Prevention And Treatment ◽  
Resistant Infection ◽  
Resistant Strains ◽  
Type Strains

ABSTRACTItraconazole is used for the prevention and treatment of infections caused byAspergillus fumigatus. An understanding of the pharmacodynamics of itraconazole against wild-type and triazole-resistant strains provides a basis for innovative therapeutic strategies for treatment of infections. Anin vitromodel of the human alveolus was used to define the pharmacodynamics of itraconazole. Galactomannan was used as a biomarker. The effect of systemic and airway administration of itraconazole was assessed, as was a combination of itraconazole administered to the airway and systemically administered 5FC. Systemically administered itraconazole against the wild type induced a concentration-dependent decline in galactomannan in the alveolar and endothelial compartments. No exposure-response relationships were apparent for the L98H, M220T, or G138C mutant. The administration of itraconazole to the airway resulted in comparable exposure-response relationships to those observed with systemic therapy. This was achieved without detectable concentrations of drug within the endothelial compartment. The airway administration of itraconazole resulted in a definite but submaximal effect in the endothelial compartment against the L98H mutant. The administration of 5FC resulted in a concentration-dependent decline in galactomannan in both the alveolar and endothelial compartments. The combination of airway administration of itraconazole and systemically administered 5FC was additive. Systemic administration of itraconazole is ineffective against Cyp51 mutants. The airway administration of itraconazole is effective for the treatment of wild-type strains and appears to have some activity against the L98H mutants. Combination with other agents, such as 5FC, may enable the attainment of near-maximal antifungal activity.

scholarly journals Molecular Analysis of Resistance and Detection of Non-Wild-Type Strains Using Etest Epidemiological Cutoff Values for Amphotericin B and Echinocandins for Bloodstream Candida Infections from a Tertiary Hospital in Qatar

2018 ◽  
Vol 62 (9) ◽  
Author(s):  
Saad J. Taj-Aldeen ◽  
Husam Salah ◽  
Winder B. Perez ◽  
Muna Almaslamani ◽  
Mary Motyl ◽  
...  
Keyword(s):  
Amphotericin B ◽  
Hot Spot ◽  
Antifungal Susceptibility ◽  
Tertiary Hospital ◽  
Wild Type ◽  
Content Type ◽  
Cutoff Values ◽  
Echinocandin Resistance ◽  
Candida Infections ◽  
Type Strains

ABSTRACT A total of 301 Candida bloodstream isolates collected from 289 patients over 5 years at a tertiary hospital in Qatar were evaluated. Out of all Candida infections, 53% were diagnosed in patients admitted to the intensive care units. Steady increases in non-albicans Candida species were reported from 2009 to 2014 (30.2% for Candida albicans versus 69.8% for the other Candida species). Etest antifungal susceptibility testing was performed on all recovered clinical isolates to determine echinocandin (micafungin and anidulafungin) and amphotericin B susceptibilities and assess non-wild-type (non-WT) strains (strains for which MICs were above the epidemiological cutoff values). DNA sequence analysis was performed on all isolates to assess the presence of FKS mutations, which confer echinocandin resistance in Candida species. A total of 3.9% of isolates (12/301) among strains of C. albicans and C. orthopsilosis contained FKS hot spot mutations, including heterozygous mutations in FKS1. For C. tropicalis, the Etest appeared to overestimate strains non-WT for micafungin, anidulafungin, and amphotericin B, as 14%, 11%, and 35% of strains, respectively, had values above the epidemiological cutoff value. However, no FKS mutations were identified in this species. For all other species, micafungin best reported the echinocandin non-WT strains relative to the FKS genotype, as anidulafungin tended to overestimate non-wild-type strains. Besides C. tropicalis, few strains were classified as non-WT for amphotericin B.

scholarly journals Avoidance of Autophagy Mediated by PlcA or ActA Is Required for Listeria monocytogenes Growth in Macrophages

2015 ◽  
Vol 83 (5) ◽  
pp. 2175-2184 ◽  
Author(s):  
Gabriel Mitchell ◽  
Liang Ge ◽  
Qiongying Huang ◽  
Chen Chen ◽  
Sara Kianian ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Wild Type Strain ◽  
Fold Increase ◽  
Host Cells ◽  
Listeriolysin O ◽  
Wild Type ◽  
Conjugation System ◽  
Content Type ◽  
A Cell ◽  
Gain Access

Listeria monocytogenesis a facultative intracellular pathogen that escapes from phagosomes and grows in the cytosol of infected host cells. Most of the determinants that govern its intracellular life cycle are controlled by the transcription factor PrfA, including the pore-forming cytolysin listeriolysin O (LLO), two phospholipases C (PlcA and PlcB), and ActA. We constructed a strain that lacked PrfA but expressed LLO from a PrfA-independent promoter, thereby allowing the bacteria to gain access to the host cytosol. This strain did not grow efficiently in wild-type macrophages but grew normally in macrophages that lacked ATG5, a component of the autophagy LC3 conjugation system. This strain colocalized more with the autophagy marker LC3 (42% ± 7%) at 2 h postinfection, which constituted a 5-fold increase over the colocalization exhibited by the wild-type strain (8% ± 6%). While mutants lacking the PrfA-dependent virulence factor PlcA, PlcB, or ActA grew normally, a double mutant lacking both PlcA and ActA failed to grow in wild-type macrophages and colocalized more with LC3 (38% ± 5%). Coexpression of LLO and PlcA in a PrfA-negative strain was sufficient to restore intracellular growth and decrease the colocalization of the bacteria with LC3. In a cell-free assay, purified PlcA protein blocked LC3 lipidation, a key step in early autophagosome biogenesis, presumably by preventing the formation of phosphatidylinositol 3-phosphate (PI3P). The results of this study showed that avoidance of autophagy byL. monocytogenesprimarily involves PlcA and ActA and that either one of these factors must be present forL. monocytogenesgrowth in macrophages.

scholarly journals Increased Vancomycin Susceptibility in Mycobacteria: a New Approach To Identify Synergistic Activity against Multidrug-Resistant Mycobacteria

2015 ◽  
Vol 59 (8) ◽  
pp. 5057-5060 ◽  
Author(s):  
Karine Soetaert ◽  
Céline Rens ◽  
Xiao-Ming Wang ◽  
Jacqueline De Bruyn ◽  
Marie-Antoinette Lanéelle ◽  
...  
Keyword(s):  
Lipid Synthesis ◽  
Multidrug Resistant ◽  
Screening Strategy ◽  
Synergistic Activity ◽  
Wild Type ◽  
New Approach ◽  
Content Type ◽  
Phthiocerol Dimycocerosates ◽  
Type Strains ◽  
Phenolic Glycolipids

ABSTRACTMycobacterium tuberculosisis wrapped in complex waxes, impermeable to most antibiotics. ComparingMycobacterium bovisBCG andM. tuberculosismutants that lack phthiocerol dimycocerosates (PDIM) and/or phenolic glycolipids with wild-type strains, we observed that glycopeptides strongly inhibited PDIM-deprived mycobacteria. Vancomycin together with a drug targeting lipid synthesis inhibited multidrug-resistant (MDR) and extensively drug-resistant (XDR) clinical isolates. Our study puts glycopeptides in the pipeline of potential antituberculosis (TB) agents and might provide a new antimycobacterial drug-screening strategy.

scholarly journals Cwp19 Is a Novel Lytic Transglycosylase Involved in Stationary-Phase Autolysis Resulting in Toxin Release inClostridium difficile

mBio ◽  
2018 ◽  
Vol 9 (3) ◽  
Author(s):  
Sandra Wydau-Dematteis ◽  
Imane El Meouche ◽  
Pascal Courtin ◽  
Audrey Hamiot ◽  
René Lai-Kuen ◽  
...  
Keyword(s):  
Health Care ◽  
Clostridium Difficile ◽  
Stationary Phase ◽  
Catalytic Domain ◽  
Brain Heart Infusion ◽  
Surface Protein ◽  
Wild Type ◽  
Content Type ◽  
Lytic Transglycosylase ◽  
Cell Autolysis

ABSTRACTClostridium difficileis the major etiologic agent of antibiotic-associated intestinal disease. Pathogenesis ofC. difficileis mainly attributed to the production and secretion of toxins A and B. Unlike most clostridial toxins, toxins A and B have no signal peptide, and they are therefore secreted by unusual mechanisms involving the holin-like TcdE protein and/or autolysis. In this study, we characterized the cell surface protein Cwp19, a newly identified peptidoglycan-degrading enzyme containing a novel catalytic domain. We purified a recombinant His6-tagged Cwp19 protein and showed that it has lytic transglycosylase activity. Moreover, we observed that Cwp19 is involved in cell autolysis and that aC. difficilecwp19mutant exhibited delayed autolysis in stationary phase compared to the wild type when bacteria were grown in brain heart infusion (BHI) medium. Wild-type cell autolysis is correlated to strong alterations of cell wall thickness and integrity and to release of cytoplasmic material. Furthermore, we demonstrated that toxins were released into the extracellular medium as a result of Cwp19-induced autolysis when cells were grown in BHI medium. In contrast, Cwp19 did not induce autolysis or toxin release when cells were grown in tryptone-yeast extract (TY) medium. These data provide evidence for the first time that TcdE and bacteriolysis are coexisting mechanisms for toxin release, with their relative contributionsin vitrodepending on growth conditions. Thus, Cwp19 is an important surface protein involved in autolysis of vegetative cells ofC. difficilethat mediates the release of the toxins from the cell cytosol in response to specific environment conditions.IMPORTANCEClostridium difficile-associated disease is mainly known as a health care-associated infection. It represents the most problematic hospital-acquired infection in North America and Europe and exerts significant economic pressure on health care systems. Virulent strains ofC. difficilegenerally produce two toxins that have been identified as the major virulence factors. The mechanism for release of these toxins from bacterial cells is not yet fully understood but is thought to be partly mediated by bacteriolysis. Here we identify a novel peptidoglycan hydrolase inC. difficile, Cwp19, exhibiting lytic transglycosylase activity. We show that Cwp19 contributes toC. difficilecell autolysis in the stationary phase and, consequently, to toxin release, most probably as a response to environmental conditions such as nutritional signals. These data highlight that Cwp19 constitutes a promising target for the development of new preventive and curative strategies.

Pathogenicity and Production of Virulence Factors by Listeria monocytogenes Isolates from Channel Catfish

2000 ◽  
Vol 63 (5) ◽  
pp. 613-619 ◽  
Author(s):  
SEVIL ERDENLIG ◽  
A. JERALD AINSWORTH ◽  
FRANK W. AUSTIN
Keyword(s):  
Listeria Monocytogenes ◽  
Virulence Factors ◽  
Channel Catfish ◽  
Type Strain ◽  
Specific Activity ◽  
Brain Heart Infusion ◽  
Virulent Strains ◽  
Virulent Type ◽  
Type Strains ◽  
Comparative Manner

Pathogenicity of four channel catfish Listeria monocytogenes isolates (CCF1, CCF4, HCC7, and HCC23) was examined in a comparative manner with virulent type strains L. monocytogenes ATCC 19115 and EGD and avirulent type strain ATCC 15313 in BDF and A/J mice. Isolates HCC7 and CCF1 (both serovar 1) caused similar percent mortalities and 50% lethal concentration values when compared with virulent type strains and were therefore considered pathogenic. The presence of the virulence factors listeriolysin (LLO), phosphotidylcholine-phospholipase (PC-PLC), and phosphotidylinositol-phospholipase (PI-PLC) was determined using specific activity tests. The virulent catfish isolates were positive for production of LLO, PCPLC, and PI-PLC. However, catfish isolate HCC23 was not virulent in mice despite being hemolytic, suggesting that not every hemolytic L. monocytogenes strain is virulent. With the exception of HCC7, all virulent strains displayed enhanced LLO production in a special stress medium, whereas almost undetectable LLO activity was present when catfish isolates and virulent type strain L. monocytogenes were grown in a rich medium such as brain heart infusion. Avirulent strains were found to lack or have decreased expression of LLO, PC-PLC, or PI-PLC.

scholarly journals Mutants of Listeria monocytogenes Defective in In Vitro Invasion and Cell-to-Cell Spreading Still Invade and Proliferate in Hepatocytes of Neutropenic Mice

2000 ◽  
Vol 68 (2) ◽  
pp. 912-914 ◽  
Author(s):  
Rui Appelberg ◽  
Irene S. Leal
Keyword(s):  
Monoclonal Antibody ◽  
Listeria Monocytogenes ◽  
Cell Spreading ◽  
Histologic Examination ◽  
Gene Products ◽  
Wild Type ◽  
In Vitro Invasion ◽  
Parenchymal Cells ◽  
Type Strains

ABSTRACT Listeria monocytogenes mutants defective in theactA gene, the plcB gene, and theinlA and inlB genes were less virulent when injected intravenously into BALB/c mice. The growth of these strains as well as of the virulent wild-type strains was increased by treating mice with a neutrophil-specific depleting monoclonal antibody, RB6-8C5. Histologic examination of the livers of the treated animals showed intrahepatocytic proliferation of the listeriae in all cases. Our data show that more than one pathway exists that allows L. monocytogenes to invade parenchymal cells. One pathway most likely involves the actA and plcB gene products, and a second one probably involves the internalins.

scholarly journals The Type IX Secretion System Is Required for Virulence of the Fish Pathogen Flavobacterium columnare

2017 ◽  
Vol 83 (23) ◽  
Author(s):  
Nan Li ◽  
Yongtao Zhu ◽  
Benjamin R. LaFrentz ◽  
Jason P. Evenhuis ◽  
David W. Hunnicutt ◽  
...  
Keyword(s):  
Secretion System ◽  
Gliding Motility ◽  
Control Measures ◽  
Flavobacterium Columnare ◽  
Wild Type ◽  
Secretion Systems ◽  
Content Type ◽  
Freshwater Aquaculture ◽  
Columnaris Disease ◽  
Spent Media

ABSTRACT Flavobacterium columnare, a member of the phylum Bacteroidetes, causes columnaris disease in wild and aquaculture-reared freshwater fish. The mechanisms responsible for columnaris disease are not known. Many members of the phylum Bacteroidetes use type IX secretion systems (T9SSs) to secrete enzymes, adhesins, and proteins involved in gliding motility. The F. columnare genome has all of the genes needed to encode a T9SS. gldN, which encodes a core component of the T9SS, was deleted in wild-type strains of F. columnare. The F. columnare ΔgldN mutants were deficient in the secretion of several extracellular proteins and lacked gliding motility. The ΔgldN mutants exhibited reduced virulence in zebrafish, channel catfish, and rainbow trout, and complementation restored virulence. PorV is required for the secretion of a subset of proteins targeted to the T9SS. An F. columnare ΔporV mutant retained gliding motility but exhibited reduced virulence. Cell-free spent media from exponentially growing cultures of wild-type and complemented strains caused rapid mortality, but spent media from ΔgldN and ΔporV mutants did not, suggesting that soluble toxins are secreted by the T9SS. IMPORTANCE Columnaris disease, caused by F. columnare, is a major problem for freshwater aquaculture. Little is known regarding the virulence factors produced by F. columnare, and control measures are limited. Analysis of targeted gene deletion mutants revealed the importance of the type IX protein secretion system (T9SS) and of secreted toxins in F. columnare virulence. T9SSs are common in members of the phylum Bacteroidetes and likely contribute to the virulence of other animal and human pathogens.

scholarly journals High-Salt Stress Conditions Increase the pAW63 Transfer Frequency in Bacillus thuringiensis

2012 ◽  
Vol 78 (19) ◽  
pp. 7128-7131 ◽  
Author(s):  
Elise Beuls ◽  
Pauline Modrie ◽  
Cédric Deserranno ◽  
Jacques Mahillon
Keyword(s):  
Salt Stress ◽  
Bacillus Thuringiensis ◽  
Positive Impact ◽  
Brain Heart Infusion ◽  
Luria Bertani ◽  
Plasmid Transfer ◽  
High Salt ◽  
Content Type ◽  
Luria Bertani Broth ◽  
High Salt Stress

ABSTRACTConjugation experiments withBacillus thuringiensisand transfer kinetics demonstrated that salt stress has a positive impact on plasmid transfer efficiency. Compared to standard osmotic conditions (0.5% NaCl), plasmid transfer occurred more rapidly, and at higher frequencies (>100-fold), when bacteria were exposed to a high-salt stress (5% NaCl) in liquid brain heart infusion (BHI). Under milder salt conditions (2.5% NaCl), only a 10-fold effect was observed in Luria-Bertani broth and no difference was detected in BHI. These observations are particularly relevant in the scope of potential gene exchanges among members of theBacillus cereusgroup, which includes food-borne contaminants and pathogens.

scholarly journals The Atypical Response Regulator AtvR Is a New Player in Pseudomonas aeruginosa Response to Hypoxia and Virulence

2017 ◽  
Vol 85 (8) ◽  
Author(s):  
Gilberto Hideo Kaihami ◽  
Leandro Carvalho Dantas Breda ◽  
José Roberto Fogaça de Almeida ◽  
Thays de Oliveira Pereira ◽  
Gianlucca Gonçalves Nicastro ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Type Strain ◽  
Wild Type Strain ◽  
Environmental Changes ◽  
Response Regulator ◽  
Classical Pathway ◽  
Wild Type ◽  
Macrophage Infection ◽  
Content Type ◽  
Successful Infection

ABSTRACT Two-component systems are widespread in bacteria, allowing adaptation to environmental changes. The classical pathway is composed of a histidine kinase that phosphorylates an aspartate residue in the cognate response regulator (RR). RRs lacking the phosphorylatable aspartate also occur, but their function and contribution during host-pathogen interactions are poorly characterized. AtvR (PA14_26570) is the only atypical response regulator with a DNA-binding domain in the opportunistic pathogen Pseudomonas aeruginosa. Macrophage infection with the atvR mutant strain resulted in higher levels of tumor necrosis factor alpha secretion as well as increased bacterial clearance compared to those for macrophages infected with the wild-type strain. In an acute pneumonia model, mice infected with the atvR mutant presented increased amounts of proinflammatory cytokines, increased neutrophil recruitment to the lungs, reductions in bacterial burdens, and higher survival rates in comparison with the findings for mice infected with the wild-type strain. Further, several genes involved in hypoxia/anoxia adaptation were upregulated upon atvR overexpression, as seen by high-throughput transcriptome sequencing (RNA-Seq) analysis. In addition, atvR was more expressed in hypoxia in the presence of nitrate and required for full expression of nitrate reductase genes, promoting bacterial growth under this condition. Thus, AtvR would be crucial for successful infection, aiding P. aeruginosa survival under conditions of low oxygen tension in the host. Taken together, our data demonstrate that the atypical response regulator AtvR is part of the repertoire of transcriptional regulators involved in the lifestyle switch from aerobic to anaerobic conditions. This finding increases the complexity of regulation of one of the central metabolic pathways that contributes to Pseudomonas ubiquity and versatility.

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