scholarly journals Antibiotic-Resistant Acinetobacter baumannii Is Susceptible to the Novel Iron-Sequestering Anti-infective DIBI In Vitro and in Experimental Pneumonia in Mice

2019 ◽  
Vol 63 (9) ◽  
Author(s):  
Maria del Carmen Parquet ◽  
Kimberley A. Savage ◽  
David S. Allan ◽  
M. Trisha C. Ang ◽  
Wangxue Chen ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Iron Acquisition ◽  
Microbial Infection ◽  
Content Type ◽  
Bacterial Physiology ◽  
New Treatment ◽  
Conventional Antibiotics ◽  
Hospital Acquired

ABSTRACT Acinetobacter baumannii is a major cause of nosocomial infections especially hospital-acquired pneumonia. This bacterium readily acquires antibiotic resistance traits and therefore, new treatment alternatives are urgently needed. The virulence of A. baumannii linked to iron acquisition suggests a potential for new anti-infectives that target its iron acquisition. DIBI, a 3-hydroxypyridin-4-one chelator, is a purpose-designed, iron-sequestering antimicrobial that has shown promise for treating microbial infection. DIBI was investigated for its in vitro and in vivo activities against clinical A. baumannii isolates. DIBI was inhibitory for all isolates tested with very low MICs (2 μg/ml, equivalent to 0.2 μM), i.e., at or below the typical antibiotic MICs reported for antibiotic-sensitive strains. DIBI inhibition is Fe specific, and it caused an iron-restricted bacterial physiology that led to enhanced antibiotic killing by several discrete antibiotics. DIBI also strongly suppressed recovery growth of the surviving population following antibiotic exposure. A low intranasal dose (11 μmol/kg) of DIBI after intranasal challenge with hypervirulent ciprofloxacin (CIP)-resistant A. baumannii LAC-4 significantly reduced bacterial burdens in mice, and DIBI also suppressed the spread of the infection to the spleen. Treatment of infected mice with CIP alone (20 mg/kg, equivalent to 60 μmol/kg) was ineffective given LAC-4’s CIP resistance, but if combined with DIBI, the treatment efficacy improved significantly. Our evidence suggests that DIBI restricts host iron availability to A. baumannii growing in the respiratory tract, bolstering the host innate iron restriction mechanisms. DIBI has potential as a sole anti-infective or in combination with conventional antibiotics for the treatment of A. baumannii pneumonia.

scholarly journals Ferric Uptake Regulator Fur Control of Putative Iron Acquisition Systems in Clostridium difficile

2015 ◽  
Vol 197 (18) ◽  
pp. 2930-2940 ◽  
Author(s):  
Theresa D. Ho ◽  
Craig D. Ellermeier
Keyword(s):  
Clostridium Difficile ◽  
Oxidative Damage ◽  
Iron Acquisition ◽  
Infectious Diarrhea ◽  
Intracellular Iron ◽  
Common Cause ◽  
Content Type ◽  
Hospital Acquired

ABSTRACTClostridium difficileis an anaerobic, Gram-positive, spore-forming opportunistic pathogen and is the most common cause of hospital-acquired infectious diarrhea. Although iron acquisition in the host is a key to survival of bacterial pathogens, high levels of intracellular iron can increase oxidative damage. Therefore, expression of iron acquisition mechanisms is tightly controlled by transcriptional regulators. We identified aC. difficilehomologue of the master bacterial iron regulator Fur. Using targetron mutagenesis, we generated afurinsertion mutant ofC. difficile. To identify the genes regulated by Fur inC. difficile, we used microarray analysis to compare transcriptional differences between thefurmutant and the wild type when grown in high-iron medium. Thefurmutant had increased expression of greater than 70 transcriptional units. Using quantitative reverse transcriptase PCR (qRT-PCR), we analyzed several of the Fur-regulated genes identified by the microarray and verified that they are both iron and Fur regulated inC. difficile. Among those Fur- and iron-repressed genes wereC. difficilegenes encoding 7 putative cation transport systems of different classes. We found that Fur was able to bind the DNA upstream of three Fur-repressed genes in electrophoretic mobility shift assays. We also demonstrate that expression of Fur-regulated putative iron acquisition systems was increased duringC. difficileinfection using the hamster model. Our data suggest thatC. difficileexpresses multiple iron transport mechanisms in response iron depletionin vitroandin vivo.IMPORTANCEClostridium difficileis the most common cause of hospital-acquired infectious diarrhea and has been recently classified as an “urgent” antibiotic resistance threat by the CDC. To survive and cause disease, most bacterial pathogens must acquire the essential enzymatic cofactor iron. While import of adequate iron is essential for most bacterial growth, excess intracellular iron can lead to extensive oxidative damage. Thus, bacteria must regulate iron import to maintain iron homeostasis. We demonstrate here thatC. difficileregulates expression of several putative iron acquisition systems using the transcriptional regulator Fur. These import mechanisms are induced under iron-limiting conditionsin vitroand duringC. difficileinfection of the host. This suggests that during aC. difficileinfection, iron availability is limitedin vivo.

scholarly journals Iron/Heme Metabolism-Targeted Gallium(III) Nanoparticles Are Active against Extracellular and Intracellular Pseudomonas aeruginosa and Acinetobacter baumannii

2019 ◽  
Vol 63 (4) ◽  
Author(s):  
Seoung-ryoung Choi ◽  
Bradley E. Britigan ◽  
Prabagaran Narayanasamy
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Acinetobacter Baumannii ◽  
Iron Acquisition ◽  
Antimicrobial Activities ◽  
Antibiofilm Activity ◽  
Content Type ◽  
Gallium Concentration ◽  
Iron Heme

ABSTRACT Iron/heme acquisition systems are critical for microorganisms to acquire iron from the human host, where iron sources are limited due to the nutritional immune system and insolubility of the ferric form of iron. Prior work has shown that a variety of gallium compounds can interfere with bacterial iron acquisition. This study explored the intra- and extracellular antimicrobial activities of gallium protoporphyrin (GaPP), gallium mesoporphyrin (GaMP), and nanoparticles encapsulating GaPP or GaMP against the Gram-negative pathogens Pseudomonas aeruginosa and Acinetobacter baumannii, including clinical isolates. All P. aeruginosa and A. baumannii isolates were susceptible to GaPP and GaMP, with MICs ranging from 0.5 to ∼32 μg/ml in iron-depleted medium. Significant intra- and extracellular growth inhibition was observed against P. aeruginosa cultured in macrophages at a gallium concentration of 3.3 μg/ml (5 μM) of all Ga(III) compounds, including nanoparticles. Nanoparticle formulations showed prolonged activity against both P. aeruginosa and A. baumannii in previously infected macrophages. When the macrophages were loaded with the nanoparticles 3 days prior to infection, there was a 5-fold decrease in growth of P. aeruginosa in the presence of single emulsion F127 copolymer nanoparticles encapsulating GaMP (eFGaMP). In addition, all Ga(III) porphyrins and nanoparticles showed significant intracellular and antibiofilm activity against both pathogens, with the nanoparticles exhibiting intracellular activity for 3 days. Ga nanoparticles also increased the survival rate of Caenorhabditis elegans nematodes infected by P. aeruginosa and A. baumannii. Our results demonstrate that Ga nanoparticles have prolonged in vitro and in vivo activities against both P. aeruginosa and A. baumannii, including disruption of their biofilms.

scholarly journals Antimicrobial and anti-biofilm potencies of dermcidin-derived peptide DCD-1L against Acinetobacter baumannii: an in vivo wound healing model

2022 ◽  
Vol 22 (1) ◽  
Author(s):  
Zahra Farshadzadeh ◽  
Maryam Pourhajibagher ◽  
Behrouz Taheri ◽  
Alireza Ekrami ◽  
Mohammad Hossein Modarressi ◽  
...  
Keyword(s):  
Wound Healing ◽  
Acinetobacter Baumannii ◽  
Biofilm Formation ◽  
Histopathological Examination ◽  
Inhibitory Effect ◽  
Bacterial Attachment ◽  
Burn Wound ◽  
Conventional Antibiotics

Abstract Background The global emergence of Acinetobacter baumannii resistance to most conventional antibiotics presents a major therapeutic challenge and necessitates the discovery of new antibacterial agents. The purpose of this study was to investigate in vitro and in vivo anti-biofilm potency of dermcidin-1L (DCD-1L) against extensively drug-resistant (XDR)-, pandrug-resistant (PDR)-, and ATCC19606-A. baumannii. Methods After determination of minimum inhibitory concentration (MIC) of DCD-1L, in vitro anti-adhesive and anti-biofilm activities of DCD-1L were evaluated. Cytotoxicity, hemolytic activity, and the effect of DCD-1L treatment on the expression of various biofilm-associated genes were determined. The inhibitory effect of DCD-1L on biofilm formation in the model of catheter-associated infection, as well as, histopathological examination of the burn wound sites of mice treated with DCD-1L were assessed. Results The bacterial adhesion and biofilm formation in all A. baumannii isolates were inhibited at 2 × , 4 × , and 8 × MIC of DCD-1L, while only 8 × MIC of DCD-1L was able to destroy the pre-formed biofilm in vitro. Also, reduce the expression of genes involved in biofilm formation was observed following DCD-1L treatment. DCD-1L without cytotoxic and hemolytic activities significantly reduced the biofilm formation in the model of catheter-associated infection. In vivo results showed that the count of A. baumannii in infected wounds was significantly decreased and the promotion in wound healing by the acceleration of skin re-epithelialization in mice was observed following treatment with 8 × MIC of DCD-1L. Conclusions Results of this study demonstrated that DCD-1L can inhibit bacterial attachment and biofilm formation and prevent the onset of infection. Taking these properties together, DCD-1L appears as a promising candidate for antimicrobial and anti-biofilm drug development.

scholarly journals Combined Stimulation of Toll-Like Receptor 5 and NOD1 Strongly Potentiates Activity of NF-κB, Resulting in Enhanced Innate Immune Reactions and Resistance to Salmonella enterica Serovar Typhimurium Infection

2013 ◽  
Vol 81 (10) ◽  
pp. 3855-3864 ◽  
Author(s):  
Amir I. Tukhvatulin ◽  
Ilya I. Gitlin ◽  
Dmitry V. Shcheblyakov ◽  
Natalia M. Artemicheva ◽  
Lyudmila G. Burdelya ◽  
...  
Keyword(s):  
Critical Role ◽  
Immune Defense ◽  
Innate Immune ◽  
Microbial Infection ◽  
Immune Reactions ◽  
Content Type ◽  
Essential Components ◽  
Stimulation Of

ABSTRACTPathogen recognition receptors (PRRs) are essential components of host innate immune systems that detect specific conserved pathogen-associated molecular patterns (PAMPs) presented by microorganisms. Members of two families of PRRs, transmembrane Toll-like receptors (TLRs 1, 2, 4, 5, and 6) and cytosolic NOD receptors (NOD1 and NOD2), are stimulated upon recognition of various bacterial PAMPs. Such stimulation leads to induction of a number of immune defense reactions, mainly triggered via activation of the transcription factor NF-κB. While coordination of responses initiated via different PRRs sensing multiple PAMPS present during an infection makes clear biological sense for the host, such interactions have not been fully characterized. Here, we demonstrate that combined stimulation of NOD1 and TLR5 (as well as other NOD and TLR family members) strongly potentiates activity of NF-κB and induces enhanced levels of innate immune reactions (e.g., cytokine production) bothin vitroandin vivo. Moreover, we show that an increased level of NF-κB activity plays a critical role in formation of downstream responses. In live mice, synergy between these receptors resulting in potentiation of NF-κB activity was organ specific, being most prominent in the gastrointestinal tract. Coordinated activity of NOD1 and TLR5 significantly increased protection of mice against enteroinvasiveSalmonellainfection. Obtained results suggest that cooperation of NOD and TLR receptors is important for effective responses to microbial infectionin vivo.

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.

scholarly journals Rifabutin Is Bactericidal against Intracellular and Extracellular Forms of Mycobacterium abscessus

2020 ◽  
Vol 64 (11) ◽  
Author(s):  
Matt D. Johansen ◽  
Wassim Daher ◽  
Françoise Roquet-Banères ◽  
Clément Raynaud ◽  
Matthéo Alcaraz ◽  
...  
Keyword(s):  
Opportunistic Pathogen ◽  
Mycobacterium Abscessus ◽  
Zebrafish Model ◽  
Content Type ◽  
Attractive Option ◽  
Conventional Antibiotics ◽  
Susceptibility Profiles ◽  
Combination Regimens

ABSTRACT Mycobacterium abscessus is increasingly recognized as an emerging opportunistic pathogen causing severe lung diseases. As it is intrinsically resistant to most conventional antibiotics, there is an unmet medical need for effective treatments. Repurposing of clinically validated pharmaceuticals represents an attractive option for the development of chemotherapeutic alternatives against M. abscessus infections. In this context, rifabutin (RFB) has been shown to be active against M. abscessus and has raised renewed interest in using rifamycins for the treatment of M. abscessus pulmonary diseases. Here, we compared the in vitro and in vivo activity of RFB against the smooth and rough variants of M. abscessus, differing in their susceptibility profiles to several drugs and physiopathologial characteristics. While the activity of RFB is greater against rough strains than in smooth strains in vitro, suggesting a role of the glycopeptidolipid layer in susceptibility to RFB, both variants were equally susceptible to RFB inside human macrophages. RFB treatment also led to a reduction in the number and size of intracellular and extracellular mycobacterial cords. Furthermore, RFB was highly effective in a zebrafish model of infection and protected the infected larvae from M. abscessus-induced killing. This was corroborated by a significant reduction in the overall bacterial burden, as well as decreased numbers of abscesses and cords, two major pathophysiological traits in infected zebrafish. This study indicates that RFB is active against M. abscessus both in vitro and in vivo, further supporting its potential usefulness as part of combination regimens targeting this difficult-to-treat mycobacterium.

scholarly journals Dopamine Is a Siderophore-Like Iron Chelator That PromotesSalmonella entericaSerovar Typhimurium Virulence in Mice

mBio ◽  
2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Stefanie Dichtl ◽  
Egon Demetz ◽  
David Haschka ◽  
Piotr Tymoszuk ◽  
Verena Petzer ◽  
...  
Keyword(s):  
Bacterial Growth ◽  
Iron Uptake ◽  
Iron Homeostasis ◽  
Iron Acquisition ◽  
Lipocalin 2 ◽  
Intracellular Iron ◽  
Content Type ◽  
Hepcidin Expression

ABSTRACTWe have recently shown that the catecholamine dopamine regulates cellular iron homeostasis in macrophages. As iron is an essential nutrient for microbes, and intracellular iron availability affects the growth of intracellular bacteria, we studied whether dopamine administration impacts the course ofSalmonellainfections. Dopamine was found to promote the growth ofSalmonellaboth in culture and within bone marrow-derived macrophages, which was dependent on increased bacterial iron acquisition. Dopamine administration to mice infected withSalmonella entericaserovar Typhimurium resulted in significantly increased bacterial burdens in liver and spleen, as well as reduced survival. The promotion of bacterial growth by dopamine was independent of the siderophore-binding host peptide lipocalin-2. Rather, dopamine enhancement of iron uptake requires both the histidine sensor kinase QseC and bacterial iron transporters, in particular SitABCD, and may also involve the increased expression of bacterial iron uptake genes. Deletion or pharmacological blockade of QseC reduced but did not abolish the growth-promoting effects of dopamine. Dopamine also modulated systemic iron homeostasis by increasing hepcidin expression and depleting macrophages of the iron exporter ferroportin, which enhanced intracellular bacterial growth.Salmonellalacking all central iron uptake pathways failed to benefit from dopamine treatment. These observations are potentially relevant to critically ill patients, in whom the pharmacological administration of catecholamines to improve circulatory performance may exacerbate the course of infection with siderophilic bacteria.IMPORTANCEHere we show that dopamine increases bacterial iron incorporation and promotesSalmonellaTyphimurium growth bothin vitroandin vivo. These observations suggest the potential hazards of pharmacological catecholamine administration in patients with bacterial sepsis but also suggest that the inhibition of bacterial iron acquisition might provide a useful approach to antimicrobial therapy.

scholarly journals In Vivo Fitness Adaptations of Colistin-Resistant Acinetobacter baumannii Isolates to Oxidative Stress

2016 ◽  
Vol 61 (3) ◽  
Author(s):  
Crystal L. Jones ◽  
Shweta S. Singh ◽  
Yonas Alamneh ◽  
Leila G. Casella ◽  
Robert K. Ernst ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Hydrogen Peroxide ◽  
Acinetobacter Baumannii ◽  
Catalase Activity ◽  
Content Type ◽  
Increased Susceptibility

ABSTRACT The loss of fitness in colistin-resistant (CR) Acinetobacter baumannii was investigated using longitudinal isolates from the same patient. Early CR isolates were outcompeted by late CR isolates for growth in broth and survival in the lungs of mice. Fitness loss was associated with an increased susceptibility to oxidative stress since early CR strains had reduced in vitro survival in the presence of hydrogen peroxide and decreased catalase activity compared to that of late CR and colistin-susceptible (CS) strains.

scholarly journals Pharmacokinetic andIn VivoEfficacy Studies of the Mycobactin Biosynthesis Inhibitor Salicyl-AMS in Mice

2013 ◽  
Vol 57 (10) ◽  
pp. 5138-5140 ◽  
Author(s):  
Shichun Lun ◽  
Haidan Guo ◽  
John Adamson ◽  
Justin S. Cisar ◽  
Tony D. Davis ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Single Dose ◽  
Iron Acquisition ◽  
Mouse Lung ◽  
Proof Of Concept ◽  
Content Type ◽  
Biosynthesis Inhibitor ◽  
Parameter Values

ABSTRACTMycobactin biosynthesis inMycobacterium tuberculosisfacilitates iron acquisition, which is required for growth and virulence. The mycobactin biosynthesis inhibitor salicyl-AMS [5′-O-(N-salicylsulfamoyl)adenosine] inhibitsM. tuberculosisgrowthin vitrounder iron-limited conditions. Here, we conducted a single-dose pharmacokinetic study and a monotherapy study of salicyl-AMS with mice. Intraperitoneal injection yielded much better pharmacokinetic parameter values than oral administration did. Monotherapy of salicyl-AMS at 5.6 or 16.7 mg/kg significantly inhibitedM. tuberculosisgrowth in the mouse lung, providing the firstin vivoproof of concept for this novel antibacterial strategy.

scholarly journals Role of Acinetobactin-Mediated Iron Acquisition Functions in the Interaction of Acinetobacter baumannii Strain ATCC 19606Twith Human Lung Epithelial Cells, Galleria mellonella Caterpillars, and Mice

2012 ◽  
Vol 80 (3) ◽  
pp. 1015-1024 ◽  
Author(s):  
Jennifer A. Gaddy ◽  
Brock A. Arivett ◽  
Michael J. McConnell ◽  
Rafael López-Rojas ◽  
Jerónimo Pachón ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Acinetobacter Baumannii ◽  
Galleria Mellonella ◽  
Ex Vivo ◽  
Iron Acquisition ◽  
Alveolar Epithelial Cells ◽  
Lung Epithelial Cells ◽  
Content Type ◽  
Alveolar Epithelial

Acinetobacter baumannii, which causes serious infections in immunocompromised patients, expresses high-affinity iron acquisition functions needed for growth under iron-limiting laboratory conditions. In this study, we determined that the initial interaction of the ATCC 19606Ttype strain with A549 human alveolar epithelial cells is independent of the production of BasD and BauA, proteins needed for acinetobactin biosynthesis and transport, respectively. In contrast, these proteins are required for this strain to persist within epithelial cells and cause their apoptotic death. Infection assays usingGalleria mellonellalarvae showed that impairment of acinetobactin biosynthesis and transport functions significantly reduces the ability of ATCC 19606Tcells to persist and kill this host, a defect that was corrected by adding inorganic iron to the inocula. The results obtained with theseex vivoandin vivoapproaches were validated using a mouse sepsis model, which showed that expression of the acinetobactin-mediated iron acquisition system is critical for ATCC 19606Tto establish an infection and kill this vertebrate host. These observations demonstrate that the virulence of the ATCC 19606Tstrain depends on the expression of a fully active acinetobactin-mediated system. Interestingly, the three models also showed that impairment of BasD production results in an intermediate virulence phenotype compared to those of the parental strain and the BauA mutant. This observation suggests that acinetobactin intermediates or precursors play a virulence role, although their contribution to iron acquisition is less relevant than that of mature acinetobactin.

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