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 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 Evaluation of Accessory Gene Regulator (agr) Group and Function in the Proclivity towards Vancomycin Intermediate Resistance in Staphylococcus aureus

2006 ◽  
Vol 51 (3) ◽  
pp. 1089-1091 ◽  
Author(s):  
Brian T. Tsuji ◽  
Michael J. Rybak ◽  
Kerry L. Lau ◽  
George Sakoulas
Keyword(s):  
Staphylococcus Aureus ◽  
Wild Type ◽  
Accessory Gene ◽  
Time Curve ◽  
Unbound Fraction ◽  
Accessory Gene Regulator ◽  
Intermediate Resistance ◽  
And Function ◽  
Type Strains

ABSTRACT Simulated therapeutic vancomycin exposures were evaluated against agr wild-type and knockout Staphylococcus aureus groups I, II, III, and IV using an in vitro pharmacodynamic model. All agr groups developed intermediate resistance to vancomycin after subtherapeutic exposure. The free unbound fraction of the area under the concentration-time curve (fAUC/MIC) required to suppress resistance was fourfold higher (P < 0.001) in agr dysfunctional strains (112 to 169) than that in parent wild-type strains (28).

Isolation of Listeria monocytogenes mutants with high-level in vitro expression of host cytosol-induced gene products

2003 ◽  
Vol 48 (6) ◽  
pp. 1537-1551 ◽  
Author(s):  
Lynne M. Shetron-Rama ◽  
Kimberly Mueller ◽  
Juan M. Bravo ◽  
H. G. Archie Bouwer ◽  
Sing Sing Way ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Gene Products ◽  
In Vitro Expression ◽  
High Level

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 Recombinant Listeria monocytogenes Expressing a Cell Wall-Associated Listeriolysin O Is Weakly Virulent but Immunogenic

2009 ◽  
Vol 77 (10) ◽  
pp. 4371-4382 ◽  
Author(s):  
Javier A. Carrero ◽  
Boris Calderon ◽  
Hector Vivanco-Cid ◽  
Emil R. Unanue
Keyword(s):  
Listeria Monocytogenes ◽  
Listeriolysin O ◽  
Wild Type ◽  
Positive Bacterium ◽  
Cell Responses ◽  
A Cell ◽  
Weakly Virulent

ABSTRACT Listeriolysin O (LLO) is an essential virulence factor for the gram-positive bacterium Listeria monocytogenes. Our goal was to determine if altering the topology of LLO would alter the virulence and toxicity of L. monocytogenes in vivo. A recombinant strain was generated that expressed a surface-associated LLO (sLLO) variant secreted at 40-fold-lower levels than the wild type. In culture, the sLLO strain grew in macrophages, translocated to the cytosol, and induced cell death. However, the sLLO strain showed decreased infectivity, reduced lymphocyte apoptosis, and decreased virulence despite a normal in vitro phenotype. Thus, the topology of LLO in L. monocytogenes was a factor in the pathogenesis of the infection and points to a role of LLO secretion during in vivo infection. The sLLO strain was cleared by severe combined immunodeficient (SCID) mice. Despite the attenuation of virulence, the sLLO strain was immunogenic and capable of eliciting protective T-cell responses.

scholarly journals Intestinal P Glycoprotein Acts as a Natural Defense Mechanism against Listeria monocytogenes

2004 ◽  
Vol 72 (7) ◽  
pp. 3849-3854 ◽  
Author(s):  
Brien L. Neudeck ◽  
Jennifer M. Loeb ◽  
Nancy G. Faith ◽  
Charles J. Czuprynski
Keyword(s):  
Listeria Monocytogenes ◽  
Defense Mechanism ◽  
Transepithelial Transport ◽  
Bacterial Invasion ◽  
Wild Type ◽  
In Vivo Experiments ◽  
Natural Defense ◽  
P Glycoprotein

ABSTRACT Mechanisms by which the intestinal epithelium resists invasion by food-borne pathogens such as Listeria monocytogenes are an evolving area of research. Intestinal P glycoprotein is well known to limit the absorption of xenobiotics and is believed to act as a cytotoxic defense mechanism. The aim of this study was to determine if intestinal P glycoprotein is involved in host defense against L. monocytogenes. Caco-2 cells and a P-glycoprotein-overexpressing subclone (Caco-2/MDR) were employed in addition to mdr1a−/− mice and wild-type controls. In vitro invasion assays and in vivo experiments were employed to measure bacterial invasion and dissemination. In addition, L. monocytogenes proteins were labeled with [35S]methionine, and the transepithelial transport across Caco-2 monolayers was characterized in both directions. Overexpression of P glycoprotein in Caco-2/MDR cells led to increased resistance to L. monocytogenes invasion, whereas P-glycoprotein inhibition led to increased invasion. Flux of [35S]methionine-labeled L. monocytogenes proteins was significantly greater in the basolateral-to-apical direction than in the apical-to-basolateral direction, indicating dependence on an apically located efflux transporter. Moreover, inhibiting P glycoprotein reduced the basolateral-to-apical flux of the proteins. Early dissemination of L. monocytogenes from the gastrointestinal tract was significantly greater in the mdr1a−/− mice than in wild-type controls. Expression and function of intestinal P glycoprotein is an important determinant in resistance to early invasion of L. monocytogenes.

scholarly journals Mycobacterium tuberculosis Dihydrofolate Reductase Is Not a Target Relevant to the Antitubercular Activity of Isoniazid

2010 ◽  
Vol 54 (9) ◽  
pp. 3776-3782 ◽  
Author(s):  
Feng Wang ◽  
Paras Jain ◽  
Gulcin Gulten ◽  
Zhen Liu ◽  
Yicheng Feng ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Dihydrofolate Reductase ◽  
Fold Increase ◽  
Antitubercular Activity ◽  
Experimental Sample ◽  
Wild Type ◽  
Negative Results ◽  
Sequencing Studies ◽  
Type Strains

ABSTRACT Mycobacterium tuberculosis enoyl-acyl-ACP reductase (InhA) has been demonstrated to be the primary target of isoniazid (INH). Recently, it was postulated that M. tuberculosis dihydrofolate reductase (DHFR) is also a target of INH, based on the findings that a 4R-INH-NADP adduct synthesized from INH by a nonenzymatic approach showed strong inhibition of DHFR in vitro, and overexpression of M. tuberculosis dfrA in M. smegmatis conferred a 2-fold increase of resistance to INH. In the present study, a plasmid expressing M. tuberculosis dfrA was transformed into M. smegmatis and M. tuberculosis strains, respectively. The transformant strains were tested for their resistance to INH. Compared to the wild-type strains, overexpression of dfrA in M. smegmatis and M. tuberculosis did not confer any resistance to INH based on the MIC values. Similar negative results were obtained with 14 other overexpressed proteins that have been proposed to bind some form of INH-NAD(P) adduct. An Escherichia coli cell-based system was designed that allowed coexpression of both M. tuberculosis katG and dfrA genes in the presence of INH. The DHFR protein isolated from the experimental sample was not found bound with any INH-NADP adduct by enzyme inhibition assay and mass spectroscopic analysis. We also used whole-genome sequencing to determine whether polymorphisms in dfrA could be detected in six INH-resistant clinical isolates known to lack mutations in inhA and katG, but no such mutations were found. The dfrA overexpression experiments, together with the biochemical and sequencing studies, conclusively demonstrate that DHFR is not a target relevant to the antitubercular activity of INH.

scholarly journals The Escherichia coli gabDTPC Operon: Specific γ-Aminobutyrate Catabolism and Nonspecific Induction

2002 ◽  
Vol 184 (24) ◽  
pp. 6976-6986 ◽  
Author(s):  
Barbara L. Schneider ◽  
Stephen Ruback ◽  
Alexandros K. Kiupakis ◽  
Hillary Kasbarian ◽  
Christine Pybus ◽  
...  
Keyword(s):  
Nitrogen Source ◽  
Nitrogen Limitation ◽  
Nitrogen Sources ◽  
Wild Type ◽  
Gaba A ◽  
Specific Induction ◽  
Related Compounds ◽  
Type Strains

ABSTRACT Nitrogen limitation induces the nitrogen-regulated (Ntr) response, which includes proteins that assimilate ammonia and scavenge nitrogen. Nitrogen limitation also induces catabolic pathways that degrade four metabolically related compounds: putrescine, arginine, ornithine, and γ-aminobutyrate (GABA). We analyzed the structure, function, and regulation of the gab operon, whose products degrade GABA, a proposed intermediate in putrescine catabolism. We showed that the gabDTPC gene cluster constitutes an operon based partially on coregulation of GabT and GabD activities and the polarity of an insertion in gabT on gabC. A ΔgabDT mutant grew normally on all of the nitrogen sources tested except GABA. The unexpected growth with putrescine resulted from specific induction of gab-independent enzymes. Nac was required for gab transcription in vivo and in vitro. Ntr induction did not require GABA, but various nitrogen sources did not induce enzyme activity equally. A gabC (formerly ygaE) mutant grew faster with GABA and had elevated levels of gab operon products, which suggests that GabC is a repressor. GabC is proposed to reduce nitrogen source-specific modulation of expression. Unlike a wild-type strain, a gabC mutant utilized GABA as a carbon source and such growth required σS. Previous studies showing σS-dependent gab expression in stationary phase involved gabC mutants, which suggests that such expression does not occur in wild-type strains. The seemingly narrow catabolic function of the gab operon is contrasted with the nonspecific (nitrogen source-independent) induction. We propose that the gab operon and the Ntr response itself contribute to putrescine and polyamine homeostasis.

scholarly journals Replication kinetics of a CHIKV Asian strain with 76 aa duplication in the nsP3 HVD, in comparison to the wild-type Asian and ECSA strains

2020 ◽  
Vol 2 (7A) ◽  
Author(s):  
Nurshariza Abdullah ◽  
Hong Wai Tham ◽  
Nafees Abdullah ◽  
Vinod RMT Balasubramaniam ◽  
I-Ching Sam ◽  
...  
Keyword(s):  
Amino Acid ◽  
Preliminary Finding ◽  
Wild Type ◽  
Replication Rate ◽  
Asian Strain ◽  
Genotypic Analysis ◽  
The Indian Ocean ◽  
Kinetics Of ◽  
Type Strains

Introduction: Chikungunya virus (CHIKV) is a mosquito-borne alphavirus which causes fever, rash and polyarthralgia. CHIKV has expanded its circulating regions to the Indian Ocean islands, Europe, Americas and Southeast Asia. Two CHIKV lineages, the ASIAN and ECSA are circulating in Malaysia. In 2009, a CHIKV strain with a 76 amino acid (aa) duplication in its nsP3 hypervariable domain (HVD), identified as CHIKvASIAN09MUM-Dup+ was isolated from a patient co-infected with DENV-2. Indels and duplication have been found in many other alphaviruses, and suggested to play a role in the survivality of the viruses. Objectives: We aim to compare and relate the replication kinetics and virulency in-vitro of CHIKvASIAN09MUM-Dup+ with the wild-type Asian and ECSA strains. Methods & Results: Genotypic analysis was conducted on three CHIKV strains in Malaysia, the CHIKvASIAN06UM-Dup-, CHIKvECSA08UM-Dup- and CHIKvASIAN09MUM-Dup+. We found that CHIKvASIAN09MUM-Dup+ has significant low replication rates in Vero, C6/36 and Rhabdosarcoma cells as compared to the wild-type strains. The highest titers were reached by CHIKvASIAN09MUM-Dup+ in all cells are 6.5 to 6.75 log10 TCID50/mL, which is 100 fold lower compared to the wild-type strains. Conclusion: The significantly low replication rate of Dup+ strain in all the cells, maybe suggestive to be due to co-infection and co-existence with DENV, where the aa duplication may play a role in overcoming competitive suppression. This preliminary finding agrees with reported events, where alphaviruses use insertion, deletion and duplication of amino acid in nsP3 HVD as strategies to influence replication in host, viral virulency, pathogenesis and survivality for evolution adaptation.

scholarly journals Characteristics of morphogenetic responses of Nicotiana langsdorffii on transformation with wild type strains of Agrobacterium in vitro

2007 ◽  
Vol 5 (3) ◽  
pp. 21-24 ◽  
Author(s):  
Tatyana V Matveeva ◽  
Tatiana Yu Pigichka ◽  
Ludmila A Lutova
Keyword(s):  
Agrobacterium Tumefaciens ◽  
Shoot Formation ◽  
Wild Type ◽  
Model Object ◽  
Nicotiana Langsdorffii ◽  
Type Strains ◽  
Morphogenetic Responses ◽  
Leaf Disks

Ability to transformation by wt strains of Agrobacterium tumefaciens (T37, C58, A6) and A. rhizogenes (15834, 8196, A4) was characterized for Nicotiana langsdorffii. It was shown that effectivity of transformation of this species by strains T37, A6,15834, 8196, A4 was lower comparing to the model object N. tabacum. Tumors induced by A. tumefaciens on leaf disks of N. langsdorffii, tend to shoot formation.

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