scholarly journals The Neisseria meningitidis Capsule Is Important for Intracellular Survival in Human Cells

2007 ◽  
Vol 75 (7) ◽  
pp. 3594-3603 ◽  
Author(s):  
Maria Rita Spinosa ◽  
Cinzia Progida ◽  
Adelfia Talà ◽  
Laura Cogli ◽  
Pietro Alifano ◽  
...  
Keyword(s):  
Neisseria Meningitidis ◽  
Efflux Pump ◽  
Polymyxin B ◽  
Intracellular Survival ◽  
Outer Core ◽  
Human Cells ◽  
In Vitro Assays ◽  
Bacterial Survival ◽  
Innate Defense

ABSTRACT While much data exist in the literature about how Neisseria meningitidis adheres to and invades human cells, its behavior inside the host cell is largely unknown. One of the essential meningococcal attributes for pathogenesis is the polysaccharide capsule, which has been shown to be important for bacterial survival in extracellular fluids. To investigate the role of the meningococcal capsule in intracellular survival, we used B1940, a serogroup B strain, and its isogenic derivatives, which lack either the capsule or both the capsule and the lipooligosaccharide outer core, to infect human phagocytic and nonphagocytic cells and monitor invasion and intracellular growth. Our data indicate that the capsule, which negatively affects bacterial adhesion and, consequently, entry, is, in contrast, fundamental for the intracellular survival of this microorganism. The results of in vitro assays suggest that an increased resistance to cationic antimicrobial peptides (CAMPs), important components of the host innate defense system against microbial infections, is a possible mechanism by which the capsule protects the meningococci in the intracellular environment. Indeed, unencapsulated bacteria were more susceptible than encapsulated bacteria to defensins, cathelicidins, protegrins, and polymyxin B, which has long been used as a model compound to define the mechanism of action of CAMPs. We also demonstrate that both the capsular genes (siaD and lipA) and those encoding an efflux pump involved in resistance to CAMPs (mtrCDE) were up-regulated during the intracellular phase of the infectious cycle.

scholarly journals Bound To Shock: Protection from Lethal Endotoxemic Shock by a Novel, Nontoxic, Alkylpolyamine Lipopolysaccharide Sequestrant

2007 ◽  
Vol 51 (8) ◽  
pp. 2811-2819 ◽  
Author(s):  
Diptesh Sil ◽  
Anurupa Shrestha ◽  
Matthew R. Kimbrell ◽  
Thuan B. Nguyen ◽  
Ashok K. Adisechan ◽  
...  
Keyword(s):  
Polymyxin B ◽  
In Vitro Assays ◽  
Critically Ill Patient ◽  
Peptide Antibiotic ◽  
Outer Membranes ◽  
Wide Range ◽  
Endotoxemic Shock ◽  
Inflammatory Processes ◽  
Shock Protection

ABSTRACT Lipopolysaccharide (LPS), or endotoxin, a structural component of gram-negative bacterial outer membranes, plays a key role in the pathogenesis of septic shock, a syndrome of severe systemic inflammation which leads to multiple-system organ failure. Despite advances in antimicrobial chemotherapy, sepsis continues to be the commonest cause of death in the critically ill patient. This is attributable to the lack of therapeutic options that aim at limiting the exposure to the toxin and the prevention of subsequent downstream inflammatory processes. Polymyxin B (PMB), a peptide antibiotic, is a prototype small molecule that binds and neutralizes LPS toxicity. However, the antibiotic is too toxic for systemic use as an LPS sequestrant. Based on a nuclear magnetic resonance-derived model of polymyxin B-LPS complex, we had earlier identified the pharmacophore necessary for optimal recognition and neutralization of the toxin. Iterative cycles of pharmacophore-based ligand design and evaluation have yielded a synthetically easily accessible N 1,mono-alkyl-mono-homologated spermine derivative, DS-96. We have found that DS-96 binds LPS and neutralizes its toxicity with a potency indistinguishable from that of PMB in a wide range of in vitro assays, affords complete protection in a murine model of LPS-induced lethality, and is apparently nontoxic in vertebrate animal models.

scholarly journals Assessment of Minocycline and Polymyxin B Combination against Acinetobacter baumannii

2015 ◽  
Vol 59 (5) ◽  
pp. 2720-2725 ◽  
Author(s):  
Dana R. Bowers ◽  
Henry Cao ◽  
Jian Zhou ◽  
Kimberly R. Ledesma ◽  
Dongxu Sun ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Clinical Utility ◽  
Efflux Pump ◽  
Polymyxin B ◽  
Intracellular Concentration ◽  
Bacterial Cells ◽  
Efflux Pump Inhibitor ◽  
Content Type

ABSTRACTAntimicrobial resistance amongAcinetobacter baumanniiis increasing worldwide, often necessitating combination therapy. The clinical utility of using minocycline with polymyxin B is not well established. In this study, we investigated the activity of minocycline and polymyxin B against 1 laboratory isolate and 3 clinical isolates ofA. baumannii. Minocycline susceptibility testing was performed with and without an efflux pump inhibitor, phenylalanine-arginine β-naphthylamide (PAβN). The intracellular minocycline concentration was determined with and without polymyxin B (0.5 μg/ml). Time-kill studies were performed over 24 h using approximately 106CFU/ml of each strain with clinically relevant minocycline concentrations (2 μg/ml and 8 μg/ml), with and without polymyxin B (0.5 μg/ml). Thein vivoefficacy of the combination was assessed in a neutropenic murine pneumonia model. Infected animals were administered minocycline (50 mg/kg), polymyxin B (10 mg/kg), or both to achieve clinically equivalent exposures in humans. A reduction in the minocycline MIC (≥4×) was observed in the presence of PAβN. The intracellular concentration andin vitrobactericidal effect of minocycline were both enhanced by polymyxin B. With 2 minocycline-susceptible strains, the bacterial burden in lung tissue at 24 h was considerably reduced by the combination compared to monotherapy with minocycline or polymyxin B. In addition, the combination prolonged survival of animals infected with a minocycline-susceptible strain. Polymyxin B increased the intracellular concentration of minocycline in bacterial cells and enhanced the bactericidal activity of minocycline, presumably due to efflux pump disruption. The clinical utility of this combination should be further investigated.

O V A.1 Nucleotide excision repair mechanism in human cells: Analysis by in vitro assays

1997 ◽  
Vol 379 (1) ◽  
pp. S33
Author(s):  
Bernard Salles ◽  
Patrick Calsou ◽  
Philippe Frit ◽  
Ruo-Ya Li ◽  
Catherine Muller ◽  
...  
Keyword(s):  
Nucleotide Excision Repair ◽  
Excision Repair ◽  
Human Cells ◽  
In Vitro Assays ◽  
Repair Mechanism ◽  
Nucleotide Excision

scholarly journals NorB, an Efflux Pump in Staphylococcus aureus Strain MW2, Contributes to Bacterial Fitness in Abscesses

2008 ◽  
Vol 190 (21) ◽  
pp. 7123-7129 ◽  
Author(s):  
Yanpeng Ding ◽  
Yoshikuni Onodera ◽  
Jean C. Lee ◽  
David C. Hooper
Keyword(s):  
Gene Expression ◽  
Staphylococcus Aureus ◽  
Efflux Pump ◽  
Efflux Pumps ◽  
Single Copy ◽  
Aureus Strain ◽  
Bacterial Survival ◽  
Bacterial Fitness

ABSTRACT While remaining a major problem in hospitals, Staphylococcus aureus is now spreading in communities. Strain MW2 (USA400 lineage) and other community methicillin-resistant S. aureus strains most commonly cause skin infections with abscess formation. Multidrug resistance (MDR) efflux pumps contribute to antimicrobial resistance but may also contribute to bacterial survival by removal of environmental toxins. In S. aureus, NorA, NorB, NorC, and Tet38 are chromosomally encoded efflux pumps whose overexpression can confer MDR to quinolones and other compounds (Nor pumps) or tetracyclines alone (Tet38), but the natural substrates of these pumps are not known. To determine the role of these efflux pumps in a natural environment in the absence of antibiotics, we used strain MW2 in a mouse subcutaneous abscess model and compared pump gene expression as determined by reverse transcription-PCR in the abscesses and in vitro. norB and tet38 were selectively upregulated in vivo more than 171- and 24-fold, respectively, whereas norA and norC were downregulated. These changes were associated with an increase in expression of mgrA, which encodes a transcriptional regulator known to affect pump gene expression. In competition experiments using equal inocula of a norB or tet38 mutant and parent strain MW2, each mutant exhibited growth defects of about two- to threefold in vivo. In complementation experiments, a single-copy insertion of norB (but not a single-copy insertion of tet38) in the attB site within geh restored the growth fitness of the norB mutant in vivo. Our findings indicate that some MDR pumps, like NorB, can facilitate bacterial survival when they are overexpressed in a staphylococcal abscess and may contribute to the relative resistance of abscesses to antimicrobial therapy, thus linking bacterial fitness and resistance in vivo.

Transposon-Derived Brucella abortusRough Mutants Are Attenuated and Exhibit Reduced Intracellular Survival

1998 ◽  
Vol 66 (3) ◽  
pp. 1008-1016 ◽  
Author(s):  
Chris A. Allen ◽  
L. Garry Adams ◽  
Thomas A. Ficht
Keyword(s):  
Sequence Analysis ◽  
Polymyxin B ◽  
Intracellular Survival ◽  
Phagocytic Cells ◽  
Gene Encoding ◽  
Amphipathic Peptide ◽  
O Antigen ◽  
Genes Encoding ◽  
Definition Of

ABSTRACT The O antigen of Brucella abortus has been described as a major virulence determinant based on the attenuated survival of fortuitously isolated rough variants. However, the lack of genetic definition of these mutants and the virulence of naturally occurring rough species, Brucella ovis and Brucella canis, has confused interpretation. To better characterize the role of O antigen in virulence and survival, transposon mutagenesis was used to generate B. abortus rough mutants defective in O-antigen presentation. Sequence analysis of DNA flanking the site of Tn5 insertion was used to verify insertion in genes encoding lipopolysaccharide (LPS) biosynthetic functions. Not surprisingly, each of the rough mutants was attenuated for survival in mice, but unexpected differences among the mutants were observed. In an effort to define the basis for the observed differences, the structure of the rough LPS and the sensitivity of these mutants to individual killing mechanisms were examined in vitro. All of the B. abortus rough mutants exhibited a 4- to 5-log-unit increase, compared to the smooth parental strain, in sensitivity to complement-mediated lysis. Little change was evident in the sensitivity of these organisms to hydrogen peroxide, consistent with an inability of O antigen to exclude relatively small molecules. Sensitivity to polymyxin B, which was employed as a model cationic, amphipathic peptide similar to defensins found in phagocytic cells, revealed survival differences among the rough mutants similar to those observed in the mouse. One mutant in particular exhibited hypersensitivity to polymyxin B and reduced survival in mice. This mutant was characterized by a truncated rough LPS. DNA sequence analysis of this mutant revealed a transposon interruption in the gene encoding phosphomannomutase (pmm), suggesting that this activity may be required for the synthesis of a full-length core polysaccharide in addition to O antigen. B. abortus O antigen appears to be essential for extra- and intracellular survival in mice.

scholarly journals Pulmonary Surfactant Promotes Virulence Gene Expression and Biofilm Formation inKlebsiella pneumoniae

2018 ◽  
Vol 86 (7) ◽  
Author(s):  
Graham G. Willsey ◽  
Sebastian Ventrone ◽  
Kristin C. Schutz ◽  
Aaron M. Wallace ◽  
John W. Ribis ◽  
...  
Keyword(s):  
Biofilm Formation ◽  
Pulmonary Surfactant ◽  
De Novo ◽  
Efflux Pump ◽  
Initial Point ◽  
Bacterial Survival ◽  
Content Type ◽  
Insight Into

ABSTRACTThe interactions betweenKlebsiella pneumoniaeand the host environment at the site of infection are largely unknown. Pulmonary surfactant serves as an initial point of contact for inhaled bacteria entering the lung and is thought to contain molecular cues that aid colonization and pathogenesis. To gain insight into this ecological transition, we characterized the transcriptional response ofK. pneumoniaeMGH 78578 to purified pulmonary surfactant. This work revealed changes within theK. pneumoniaetranscriptome that likely contribute to host colonization, adaptation, and virulencein vivo. Notable transcripts expressed under these conditions include genes involved in capsule synthesis, lipopolysaccharide modification, antibiotic resistance, biofilm formation, and metabolism. In addition, we tested the contributions of other surfactant-induced transcripts toK. pneumoniaesurvival using engineered isogenic KPPR1 deletion strains in a murine model of acute pneumonia. In these infection studies, we identified the MdtJI polyamine efflux pump and the ProU glycine betaine ABC transporter to be significant mediators ofK. pneumoniaesurvival within the lung and confirmed previous evidence for the importance ofde novoleucine synthesis to bacterial survival during infection. Finally, we determined that pulmonary surfactant promoted type 3 fimbria-mediated biofilm formation inK. pneumoniaeand identified two surfactant constituents, phosphatidylcholine and cholesterol, that drive this response. This study provides novel insight into the interactions occurring betweenK. pneumoniaeand the host at an important infection site and demonstrates the utility of purified lung surfactant preparations for dissecting host-lung pathogen interactionsin vitro.

scholarly journals Effects of combined drug treatments on Plasmodium falciparum: In vitro assays with doxycycline, ivermectin and efflux pump inhibitors

PLoS ONE ◽  
2020 ◽  
Vol 15 (4) ◽  
pp. e0232171
Author(s):  
Riccardo Nodari ◽  
Yolanda Corbett ◽  
Ilaria Varotto-Boccazzi ◽  
Daniele Porretta ◽  
Donatella Taramelli ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Efflux Pump ◽  
In Vitro Assays ◽  
Drug Treatments ◽  
Efflux Pump Inhibitors

scholarly journals Pseudomonas aeruginosa Induces Membrane Blebs in Epithelial Cells, Which Are Utilized as a Niche for Intracellular Replication and Motility

2008 ◽  
Vol 76 (5) ◽  
pp. 1992-2001 ◽  
Author(s):  
Annette A. Angus ◽  
Amanda Ackerman Lee ◽  
Danielle K. Augustin ◽  
Ellen J. Lee ◽  
David J. Evans ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Epithelial Cells ◽  
Real Time ◽  
Cell Types ◽  
Intracellular Survival ◽  
Bacterial Survival ◽  
Intracellular Replication ◽  
Membrane Blebs ◽  
Cell Niche

ABSTRACT Pseudomonas aeruginosa is known to invade epithelial cells during infection and in vitro. However, little is known of bacterial or epithelial factors modulating P. aeruginosa intracellular survival or replication after invasion, except that it requires a complete lipopolysaccharide core. In this study, real-time video microscopy revealed that invasive P. aeruginosa isolates induced the formation of membrane blebs in multiple epithelial cell types and that these were then exploited for intracellular replication and rapid real-time motility. Further studies revealed that the type three secretion system (T3SS) of P. aeruginosa was required for blebbing. Mutants lacking either the entire T3SS or specific T3SS components were instead localized to intracellular perinuclear vacuoles. Most T3SS mutants that trafficked to perinuclear vacuoles gradually lost intracellular viability, and vacuoles containing those bacteria were labeled by the late endosomal marker lysosome-associated marker protein 3 (LAMP-3). Interestingly, mutants deficient only in the T3SS translocon structure survived and replicated within the vacuoles that did not label with LAMP-3. Taken together, these data suggest two novel roles of the P. aeruginosa T3SS in enabling bacterial intracellular survival: translocon-dependent formation of membrane blebs, which form a host cell niche for bacterial growth and motility, and effector-dependent bacterial survival and replication within intracellular perinuclear vacuoles.

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