scholarly journals Severe Acinetobacter baumannii Sepsis Is Associated with Elevation of Pentraxin 3

2014 ◽  
Vol 82 (9) ◽  
pp. 3910-3918 ◽  
Author(s):  
Patrick M. Ketter ◽  
M. Neal Guentzel ◽  
Beverly Schaffer ◽  
Maryanne Herzig ◽  
Xiaowu Wu ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Lethal Dose ◽  
Antimicrobial Properties ◽  
Bloodstream Infections ◽  
Multidrug Resistant ◽  
Mouse Serum ◽  
Myeloperoxidase Activity ◽  
Content Type

ABSTRACTMultidrug-resistantAcinetobacter baumanniiis among the most prevalent bacterial pathogens associated with trauma-related wound and bloodstream infections. Although septic shock and disseminated intravascular coagulation have been reported following fulminantA. baumanniisepsis, little is known about the protective host immune response to this pathogen. In this study, we examined the role of PTX3, a soluble pattern recognition receptor with reported antimicrobial properties and stored within neutrophil granules. PTX3 production by murine J774a.1 macrophages was assessed following challenge withA. baumanniistrains ATCC 19606 and clinical isolates (CI) 77, 78, 79, 80, and 86. Interestingly, only CI strains 79, 80, and 86 induced PTX3 synthesis in murine J774a.1 macrophages, with greatest production observed following CI 79 and 86 challenge. Subsequently, C57BL/6 mice were challenged intraperitoneally with CI 77 and 79 to assess the role of PTX3in vivo.A. baumanniistrain CI 79 exhibited significantly (P< 0.0005) increased mortality, with an approximate 50% lethal dose (LD50) of 105CFU, while an equivalent dose of CI 77 exhibited no mortality. Plasma leukocyte chemokines (KC, MCP-1, and RANTES) and myeloperoxidase activity were also significantly elevated following challenge with CI 79, indicating neutrophil recruitment/activation associated with significant elevation in serum PTX3 levels. Furthermore, 10-fold-greater PTX3 levels were observed in mouse serum 12 h postchallenge, comparing CI 79 to CI 77 (1,561 ng/ml versus 145 ng/ml), with concomitant severe pathology (liver and spleen) and coagulopathy. Together, these results suggest that elevation of PTX3 is associated with fulminant disease duringA. baumanniisepsis.

scholarly journals In VitroandIn VivoAntimicrobial Activities of Gallium Nitrate against Multidrug-Resistant Acinetobacter baumannii

2012 ◽  
Vol 56 (11) ◽  
pp. 5961-5970 ◽  
Author(s):  
Luísa C. S. Antunes ◽  
Francesco Imperi ◽  
Fabrizia Minandri ◽  
Paolo Visca
Keyword(s):  
Human Serum ◽  
Acinetobacter Baumannii ◽  
Galleria Mellonella ◽  
Therapeutic Potential ◽  
Survival Rates ◽  
Bloodstream Infections ◽  
Multidrug Resistant ◽  
Gallium Nitrate ◽  
Content Type ◽  
Bacterial Physiology

ABSTRACTMultidrug-resistantAcinetobacter baumanniiposes a tremendous challenge to traditional antibiotic therapy. Due to the crucial role of iron in bacterial physiology and pathogenicity, we investigated iron metabolism as a possible target for anti-A. baumanniichemotherapy using gallium as an iron mimetic. Due to chemical similarity, gallium competes with iron for binding to several redox enzymes, thereby interfering with a number of essential biological reactions. We found that Ga(NO3)3, the active component of an FDA-approved drug (Ganite), inhibits the growth of a collection of 58A. baumanniistrains in both chemically defined medium and human serum, at concentrations ranging from 2 to 80 μM and from 4 to 64 μM, respectively. Ga(NO3)3delayed the entry ofA. baumanniiinto the exponential phase and drastically reduced bacterial growth rates. Ga(NO3)3activity was strongly dependent on iron availability in the culture medium, though the mechanism of growth inhibition was independent of dysregulation of gene expression controlled by the ferric uptake regulator Fur. Ga(NO3)3also protectedGalleria mellonellalarvae from lethalA. baumanniiinfection, with survival rates of ≥75%. At therapeutic concentrations for humans (28 μM plasma levels), Ga(NO3)3inhibited the growth in human serum of 76% of the multidrug-resistantA. baumanniiisolates tested by ≥90%, raising expectations on the therapeutic potential of gallium for the treatment ofA. baumanniibloodstream infections. Ga(NO3)3also showed strong synergism with colistin, suggesting that a colistin-gallium combination holds promise as a last-resort therapy for infections caused by pan-resistantA. baumannii.

scholarly journals Characterization of RelA in Acinetobacter baumannii

2020 ◽  
Vol 202 (12) ◽  
Author(s):  
María Pérez-Varela ◽  
Aimee R. P. Tierney ◽  
Ju-Sim Kim ◽  
Andrés Vázquez-Torres ◽  
Philip Rather
Keyword(s):  
Acinetobacter Baumannii ◽  
Galleria Mellonella ◽  
Multidrug Resistant ◽  
Cell Physiology ◽  
Content Type ◽  
Content Model ◽  
Transposon Insertion ◽  
Downstream Effectors

ABSTRACT In response to nutrient depletion, the RelA and SpoT proteins generate the signaling molecule (p)ppGpp, which then controls a number of downstream effectors to modulate cell physiology. In Acinetobacter baumannii strain AB5075, a relA ortholog (ABUW_3302) was identified by a transposon insertion that conferred an unusual colony phenotype. An in-frame deletion in relA (ΔrelA) failed to produce detectable levels of ppGpp when amino acid starvation was induced with serine hydroxamate. The ΔrelA mutant was blocked from switching from the virulent opaque colony variant (VIR-O) to the avirulent translucent colony variant (AV-T), but the rate of AV-T to VIR-O switching was unchanged. In addition, the ΔrelA mutation resulted in a pronounced hypermotile phenotype on 0.35% agar plates. This hypermotility was dependent on the activation of a LysR regulator ABUW_1132, which was required for expression of AbaR, a LuxR family quorum-sensing regulator. In the ΔrelA mutant, ABUW_1132 was also required for the increased expression of an operon composed of the ABUW_3766-ABUW_3773 genes required for production of the surfactant-like lipopeptide acinetin 505. Additional phenotypes identified in the ΔrelA mutant included (i) cell elongation at high density, (ii) reduced formation of persister cells tolerant to colistin and rifampin, and (iii) decreased virulence in a Galleria mellonella model. IMPORTANCE Acinetobacter baumannii is a pathogen of worldwide importance. Due to the increasing prevalence of antibiotic resistance, these infections are becoming increasingly difficult to treat. New therapies are required to combat multidrug-resistant isolates. The role of RelA in A. baumannii is largely unknown. This study demonstrates that like in other bacteria, RelA controls a variety of functions, including virulence. Strategies to inhibit the activity of RelA and the resulting production of ppGpp could inhibit virulence and may represent a new therapeutic approach.

scholarly journals In VitroandIn VivoActivities of E-101 Solution against Acinetobacter baumannii Isolates from U.S. Military Personnel

2011 ◽  
Vol 55 (7) ◽  
pp. 3603-3608 ◽  
Author(s):  
G. A. Denys ◽  
J. C. Davis ◽  
P. D. O'Hanley ◽  
J. T. Stephens
Keyword(s):  
Acinetobacter Baumannii ◽  
Bactericidal Activity ◽  
Military Personnel ◽  
Multidrug Resistant ◽  
Full Thickness ◽  
Content Type ◽  
Full Thickness Excision ◽  
Time Kill

ABSTRACTWe evaluated thein vitroandin vivoactivity of a novel topical myeloperoxidase-mediated antimicrobial, E-101 solution, against 5 multidrug-resistantAcinetobacter baumanniiisolates recovered from wounded American soldiers. Time-kill studies demonstrated rapid bactericidal activity against allA. baumanniistrains tested in the presence of 3% blood. Thein vitrobactericidal activity of E-101 solution againstA. baumanniistrains was confirmed in a full-thickness excision rat model. Additionalin vivostudies appear warranted.

scholarly journals Critical Roles of Clostridium difficile Toxin B Enzymatic Activities in Pathogenesis

2014 ◽  
Vol 83 (2) ◽  
pp. 502-513 ◽  
Author(s):  
Shan Li ◽  
Lianfa Shi ◽  
Zhiyong Yang ◽  
Yongrong Zhang ◽  
Gregorio Perez-Cordon ◽  
...  
Keyword(s):  
Clostridium Difficile ◽  
Cysteine Protease ◽  
Lethal Dose ◽  
Enzymatic Activities ◽  
Target Cells ◽  
Content Type ◽  
Cytopathic Effects

TcdB is one of the key virulence factors ofClostridium difficilethat is responsible for causing serious and potentially fatal colitis. The toxin contains at least two enzymatic domains: an effector glucosyltransferase domain for inactivating host Rho GTPases and a cysteine protease domain for the delivery of the effector domain into host cytosol. Here, we describe a novel intrabody approach to examine the role of these enzymes of TcdB in cellular intoxication. By screening a single-domain heavy chain (VHH) library raised against TcdB, we identified two VHH antibodies, 7F and E3, that specifically inhibit TcdB cysteine protease and glucosyltransferase activities, respectively. Cytoplasmic expression of 7F intrabody in Vero cells inhibited TcdB autoprocessing and delayed cellular intoxication, whereas E3 intrabody completely blocked the cytopathic effects of TcdB holotoxin. These data also demonstrate for the first time that toxin autoprocessing occurs after cysteine protease and glucosyltransferase domains translocate into the cytosol of target cells. We further determined the role of the enzymatic activities of TcdB inin vivotoxicity using a sensitive systemic challenge model in mice. Consistent with thesein vitroresults, a cysteine protease noncleavable mutant, TcdB-L543A, delayed toxicity in mice, whereas glycosyltransferase-deficient TcdB demonstrated no toxicity up to 500-fold of the 50% lethal dose (LD50) when it was injected systemically. Thus, glucosyltransferase but not cysteine protease activity is critical for TcdB-mediated cytopathic effects and TcdB systemic toxicity, highlighting the importance of targeting toxin glucosyltransferase activity for future therapy.

scholarly journals Epinecidin-1 Has Immunomodulatory Effects, Facilitating Its Therapeutic Use in a Mouse Model of Pseudomonas aeruginosa Sepsis

2014 ◽  
Vol 58 (8) ◽  
pp. 4264-4274 ◽  
Author(s):  
Chieh-Yu Pan ◽  
Jian-Chyi Chen ◽  
Jenn-Feng Sheen ◽  
Tai-Lang Lin ◽  
Jyh-Yih Chen
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Mouse Model ◽  
Antimicrobial Properties ◽  
Bacterial Pathogen ◽  
Multidrug Resistant ◽  
Behavioral Effects ◽  
Immunomodulatory Effects ◽  
Kidney Toxicity ◽  
Content Type

ABSTRACTAntimicrobial peptides (AMPs) are garnering attention as possible alternatives to antibiotics. Here, we describe the antimicrobial properties of epinecidin-1 against a multidrug-resistant clinical isolate ofP. aeruginosa(P. aeruginosaR) and aP. aeruginosastrain from ATCC (P. aeruginosaATCC 19660)in vivo. The MICs of epinecidin-1 againstP. aeruginosaR andP. aeruginosaATCC 19660 were determined and compared with those of imipenem. Epinecidin-1 was found to be highly effective at combating peritonitis infection caused byP. aeruginosaR orP. aeruginosaATCC 19660 in mouse models, without inducing adverse behavioral effects or liver or kidney toxicity. Taken together, our results indicate that epinecidin-1 enhances the rate of survival of mice infected with the bacterial pathogenP. aeruginosathrough both antimicrobial and immunomodulatory effects.

scholarly journals Dual Role of gnaA in Antibiotic Resistance and Virulence in Acinetobacter baumannii

2019 ◽  
Vol 63 (10) ◽  
Author(s):  
Qingye Xu ◽  
Tao Chen ◽  
Biyong Yan ◽  
Linyue Zhang ◽  
Borui Pi ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Capsular Polysaccharide ◽  
Treatment Options ◽  
Drug Susceptibility ◽  
Multidrug Resistant ◽  
Bacterial Virulence ◽  
Content Type ◽  
Evolution Experiment

ABSTRACT Acinetobacter baumannii is an important Gram-negative pathogen in hospital-related infections. However, treatment options for A. baumannii infections have become limited due to multidrug resistance. Bacterial virulence is often associated with capsule genes found in the K locus, many of which are essential for biosynthesis of the bacterial envelope. However, the roles of other genes in the K locus remain largely unknown. From an in vitro evolution experiment, we obtained an isolate of the virulent and multidrug-resistant A. baumannii strain MDR-ZJ06, called MDR-ZJ06M, which has an insertion by the ISAba16 transposon in gnaA (encoding UDP-N-acetylglucosamine C-6 dehydrogenase), a gene found in the K locus. The isolate showed an increased resistance toward tigecycline, whereas the MIC decreased in the case of carbapenems, cephalosporins, colistin, and minocycline. By using knockout and complementation experiments, we demonstrated that gnaA is important for the synthesis of lipooligosaccharide and capsular polysaccharide and that disruption of the gene affects the morphology, drug susceptibility, and virulence of the pathogen.

scholarly journals Cefiderocol Resistance in Acinetobacter baumannii: Roles of β-Lactamases, Siderophore Receptors, and Penicillin Binding Protein 3

2020 ◽  
Vol 64 (11) ◽  
Author(s):  
Saquib Malik ◽  
Monica Kaminski ◽  
David Landman ◽  
John Quale
Keyword(s):  
Acinetobacter Baumannii ◽  
Binding Protein ◽  
Receptor Gene ◽  
Multidrug Resistant ◽  
Resistance Mechanisms ◽  
Penicillin Binding Protein ◽  
Gram Negative ◽  
Content Type ◽  
Siderophore Receptors

ABSTRACT Cefiderocol is a siderophore cephalosporin active against many multidrug-resistant (MDR) Gram-negative pathogens. We examined the resistance mechanisms in 12 Acinetobacter baumannii strains with cefiderocol MICs ranging from ≤0.03 to >32 μg/ml. Cefiderocol resistance could not be explained by β-lactamase activity. Cefiderocol resistance was associated with reduced expression of the siderophore receptor gene pirA. Mutations involving PBP3 may have contributed to resistance in one strain. Additional studies are needed to assess the role of other siderophore receptors.

scholarly journals Pharmacokinetics and Pharmacodynamics of Minocycline against Acinetobacter baumannii in a Neutropenic Murine Pneumonia Model

2017 ◽  
Vol 61 (5) ◽  
Author(s):  
Jian Zhou ◽  
Kimberly R. Ledesma ◽  
Kai-Tai Chang ◽  
Henrietta Abodakpi ◽  
Song Gao ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Multidrug Resistant ◽  
Time Curve ◽  
Content Type ◽  
Concentration Time ◽  
Dose Linearity ◽  
Unit Reduction ◽  
The Relationship

ABSTRACT Multidrug-resistant (MDR) Acinetobacter baumannii is increasingly more prevalent in nosocomial infections. Although in vitro susceptibility of A. baumannii to minocycline is promising, the in vivo efficacy of minocycline has not been well established. In this study, the in vivo activity of minocycline was evaluated in a neutropenic murine pneumonia model. Specifically, we investigated the relationship between minocycline exposure and bactericidal activity using five A. baumannii isolates with a broad range of susceptibility (MIC ranged from 0.25 mg/liter to 16 mg/liter). The pharmacokinetics of minocycline (single dose of 25 mg/kg of body weight, 50 mg/kg, 100 mg/kg, and a humanized regimen, given intraperitoneally) in serum and epithelial lining fluid (ELF) were characterized. Dose linearity was observed for doses up to 50 mg/kg and pulmonary penetration ratios (area under the concentration-time curve in ELF from 0 to 24 h [AUCELF,0–24]/area under the concentration time curve in serum from 0 to 24 h [AUCserum,0–24]) ranged from 2.5 to 2.8. Pharmacokinetic-pharmacodynamics (PK-PD) index values in ELF for various dose regimens against different A. baumannii isolates were calculated. The maximum efficacy at 24 h was approximately 1.5-log-unit reduction of pulmonary bacterial burdens from baseline. The AUC/MIC ratio was the PK-PD index most closely correlating to the bacterial burden (r 2 = 0.81). The required AUCELF,0–24/MIC for maintaining stasis and achieving 1-log-unit reduction were 140 and 410, respectively. These findings could guide the treatment of infections caused by A. baumannii using minocycline in the future. Additional studies to examine resistance development during therapy are warranted.

scholarly journals Validation of a Novel Murine Wound Model of Acinetobacter baumannii Infection

2013 ◽  
Vol 58 (3) ◽  
pp. 1332-1342 ◽  
Author(s):  
Mitchell G. Thompson ◽  
Chad C. Black ◽  
Rebecca L. Pavlicek ◽  
Cary L. Honnold ◽  
Matthew C. Wise ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Surgical Site Infections ◽  
Multidrug Resistant ◽  
Content Type ◽  
Wound Model ◽  
Community Profiling ◽  
Specific Pathogen ◽  
Uninoculated Control ◽  
Eskape Pathogens

ABSTRACTPatients recovering from traumatic injuries or surgery often require weeks to months of hospitalization, increasing the risk for wound and surgical site infections caused by ESKAPE pathogens, which includeA. baumannii(the ESKAPE pathogens areEnterococcus faecium,Staphylococcus aureus,Klebsiella pneumoniae,Acinetobacter baumannii,Pseudomonas aeruginosa, andEnterobacterspecies). As new therapies are being developed to counterA. baumanniiinfections, animal models are also needed to evaluate potential treatments. Here, we present an excisional, murine wound model in which a diminutive inoculum of a clinically relevant, multidrug-resistantA. baumanniiisolate can proliferate, form biofilms, and be effectively treated with antibiotics. The model requires a temporary, cyclophosphamide-induced neutropenia to establish an infection that can persist. A 6-mm-diameter, full-thickness wound was created in the skin overlying the thoracic spine, and after the wound bed was inoculated, it was covered with a dressing for 7 days. Uninoculated control wounds healed within 13 days, whereas infected, placebo-treated wounds remained unclosed beyond 21 days. Treated and untreated wounds were assessed with multiple quantitative and qualitative techniques that included gross pathology, weight loss and recovery, wound closure, bacterial burden, 16S rRNA community profiling, histopathology, peptide nucleic acid-fluorescencein situhybridization, and scanning electron microscopy assessment of biofilms. The range of differences that we are able to identify with these measures in antibiotic- versus placebo-treated animals provides a clear window within which novel antimicrobial therapies can be assessed. The model can be used to evaluate antimicrobials for their ability to reduce specific pathogen loads in wounded tissues and clear biofilms. Ultimately, the mouse model approach allows for highly powered studies and serves as an initial multifacetedin vivoassessment prior to testing in larger animals.

scholarly journals Immunomodulatory Role of Clarithromycin in Acinetobacter baumannii Infection via Formation of Neutrophil Extracellular Traps

2015 ◽  
Vol 60 (2) ◽  
pp. 1040-1048 ◽  
Author(s):  
Theocharis Konstantinidis ◽  
Konstantinos Kambas ◽  
Alexandros Mitsios ◽  
Maria Panopoulou ◽  
Victoria Tsironidou ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Ex Vivo ◽  
Neutrophil Extracellular Traps ◽  
Macrolide Antibiotics ◽  
Dependent Manner ◽  
Biofilm Inhibition ◽  
Content Type ◽  
Extracellular Traps

ABSTRACTMacrolide antibiotics have been shown to act as immunomodulatory molecules in various immune cells. However, their effect on neutrophils has not been extensively investigated. In this study, we investigated the role of macrolide antibiotics in the generation of neutrophil extracellular traps (NETs). By assessingex vivoandin vivoNET formation, we demonstrated that clarithromycin is able to induce NET generation bothin vitroandin vivo. Clarithromycin utilizes autophagy in order to form NETs, and these NETs are decorated with antimicrobial peptide LL-37. Clarithromycin-induced NETs are able to inhibitAcinetobacter baumanniigrowth and biofilm formation in an LL-37-dependent manner. Additionally, LL-37 antimicrobial function depends on NET scaffold integrity. Collectively, these data expand the knowledge on the immunomodulatory role of macrolide antibiotics via the generation of LL-37-bearing NETs, which demonstrate LL-37-dependent antimicrobial activity and biofilm inhibition againstA. baumannii.

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