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 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 Candida guilliermondii Complex Is Characterized by High Antifungal Resistance but Low Mortality in 22 Cases of Candidemia

2017 ◽  
Vol 61 (7) ◽  
Author(s):  
Laura Judith Marcos-Zambrano ◽  
Mireia Puig-Asensio ◽  
Felipe Pérez-García ◽  
Pilar Escribano ◽  
Carlos Sánchez-Carrillo ◽  
...  
Keyword(s):  
Metabolic Activity ◽  
Biofilm Formation ◽  
Galleria Mellonella ◽  
Sensu Stricto ◽  
Candida Guilliermondii ◽  
Molecular Techniques ◽  
Content Type ◽  
Content Model ◽  
Crystal Violet Assay

ABSTRACT The objectives of our study were to describe the characteristics of patients with Candida guilliermondii candidemia and to perform an in-depth microbiological characterization of isolates and compare them with those of patients with C. albicans candidemia. We described the risk factors and outcomes of 22 patients with candidemia caused by the C. guilliermondii complex. Incident isolates were identified using molecular techniques, and susceptibility to fluconazole, anidulafungin, and micafungin was studied. Biofilm formation was measured using the crystal violet assay (biomass production) and the XTT reduction assay (metabolic activity), and virulence was studied using the Galleria mellonella model. Biofilm formation was compared with that observed for C. albicans. The main conditions predisposing to infection were malignancy (68%), immunosuppressive therapy (59%), and neutropenia (18%). Clinical presentation of candidemia was less severe in patients infected by the C. guilliermondii complex than in patients infected by C. albicans, and 30-day mortality was lower in C. guilliermondii patients (13.6% versus 33.9%, respectively; P = 0.049). Isolates were identified as C. guilliermondii sensu stricto (n = 17) and Candida fermentati (n = 5). The isolates produced biofilms with low metabolic activity and moderate biomass. The G. mellonella model showed that C. guilliermondii was less virulent than C. albicans (mean of 6 days versus 1 day of survival, respectively; P < 0.001). Patients with candidemia caused by the C. guilliermondii complex had severe and debilitating underlying conditions. Overall, the isolates showed diminished susceptibility to fluconazole and echinocandins, although poor biofilm formation and the low virulence were associated with a favorable outcome.

scholarly journals Functional Characterization of AbaQ, a Novel Efflux Pump Mediating Quinolone Resistance inAcinetobacter baumannii

2018 ◽  
Vol 62 (9) ◽  
Author(s):  
María Pérez-Varela ◽  
Jordi Corral ◽  
Jesús Aranda ◽  
Jordi Barbé
Keyword(s):  
Acinetobacter Baumannii ◽  
Antimicrobial Agents ◽  
Efflux Pump ◽  
Functional Characterization ◽  
Multidrug Resistant ◽  
Quinolone Resistance ◽  
Nosocomial Pathogen ◽  
Content Type ◽  
Mfs Transporter

ABSTRACTAcinetobacter baumanniihas emerged as an important multidrug-resistant nosocomial pathogen. In previous work, we identified a putative MFS transporter, AU097_RS17040, involved in the pathogenicity ofA. baumannii(M. Pérez-Varela, J. Corral, J. A. Vallejo, S. Rumbo-Feal, G. Bou, J. Aranda, and J. Barbé, Infect Immun 85:e00327-17, 2017,https://doi.org/10.1128/IAI.00327-17). In this study, we analyzed the susceptibility to diverse antimicrobial agents ofA. baumanniicells defective in this transporter, referred to as AbaQ. Our results showed that AbaQ is mainly involved in the extrusion of quinolone-type drugs inA. baumannii.

scholarly journals Globally Expanding Carbapenemase Finally Appears in Spain: Nosocomial Outbreak of Acinetobacter baumannii Producing Plasmid-Encoded OXA-23 in Barcelona, Spain

2013 ◽  
Vol 57 (10) ◽  
pp. 5155-5157 ◽  
Author(s):  
Noraida Mosqueda ◽  
Paula Espinal ◽  
Clara Cosgaya ◽  
Sergio Viota ◽  
Virginia Plasensia ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Molecular Characterization ◽  
Multidrug Resistant ◽  
Sequence Type ◽  
Clinical Isolates ◽  
Nosocomial Outbreak ◽  
Content Type ◽  
Hospital Outbreak

ABSTRACTResistance ofAcinetobacter baumanniiclinical isolates to carbapenems is on the rise worldwide mainly in association with the production of OXA-23. Until recently, however, OXA-23 was absent in Spain. In this work, we report the molecular characterization of a hospital outbreak of OXA-23-producingA. baumanniiin Barcelona caused by a multidrug-resistant (MDR) clone belonging to international clone IC-II/sequence type ST85 between October 2010 and May 2011.blaOXA-23was carried in a plasmid of 90 kb and located within the composite transposon Tn2006.

scholarly journals Effect of Incubation Temperature on Antibiotic Resistance and Virulence Factors of Acinetobacter baumannii ATCC 17978

2017 ◽  
Vol 62 (1) ◽  
Author(s):  
P. Malaka De Silva ◽  
Patrick Chong ◽  
Dinesh M. Fernando ◽  
Garrett Westmacott ◽  
Ayush Kumar
Keyword(s):  
Acinetobacter Baumannii ◽  
Galleria Mellonella ◽  
Incubation Temperature ◽  
Opportunistic Pathogen ◽  
Effect Of Temperature ◽  
Content Type ◽  
Content Model ◽  
Key Factor ◽  
Plastic Surfaces ◽  
Increased Susceptibility

ABSTRACT Acinetobacter baumannii is a notorious opportunistic pathogen that is prevalent mainly in hospital settings. The ability of A. baumannii to adapt and to survive in a range of environments has been a key factor for its persistence and success as an opportunistic pathogen. In this study, we investigated the effect of temperature on the clinically relevant phenotypes displayed by A. baumannii at 37°C and 28°C. Surface-associated motility was significantly reduced at 28°C, while biofilm formation on plastic surfaces was increased at 28°C. Decreased susceptibility to aztreonam and increased susceptibility to trimethoprim-sulfamethoxazole were observed at 28°C. No differences in virulence, as assayed in a Galleria mellonella model, were observed. Proteomic analysis showed differential expression of 629 proteins, of which 366 were upregulated and 263 were downregulated at 28°C. Upregulation of the Csu and iron uptake proteins at 28°C was a key finding for understanding some of the phenotypes displayed by A. baumannii at 28°C.

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 GigC, a LysR Family Transcription Regulator, Is Required for Cysteine Metabolism and Virulence in Acinetobacter baumannii

2020 ◽  
Vol 89 (1) ◽  
pp. e00180-20
Author(s):  
Michael J. Gebhardt ◽  
Daniel M. Czyz ◽  
Shweta Singh ◽  
Daniel V. Zurawski ◽  
Lev Becker ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Galleria Mellonella ◽  
Multidrug Resistant ◽  
Resistant Isolate ◽  
Infection Model ◽  
Content Type ◽  
Transcription Regulator ◽  
Nutritional Immunity ◽  
Metabolic Products ◽  
Lysr Family

ABSTRACTA critical facet of mammalian innate immunity involves the hosts’ attempts to sequester and/or limit the availability of key metabolic products from pathogens. For example, nutritional immunity encompasses host approaches to limit the availability of key heavy metal ions such as zinc and iron. Previously, we identified several hundred genes in a multidrug-resistant isolate of Acinetobacter baumannii that are required for growth and/or survival in the Galleria mellonella infection model. In the present study, we further characterize one of these genes, a LysR family transcription regulator that we previously named GigC. We show that mutant strains lacking gigC have impaired growth in the absence of the amino acid cysteine and that gigC regulates the expression of several genes involved in the sulfur assimilation and cysteine biosynthetic pathways. We further show that cells harboring a deletion of the gigC gene are attenuated in two murine infection models, suggesting that the GigC protein, likely through its regulation of the cysteine biosynthetic pathway, plays a key role in the virulence of A. baumannii.

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 CsrA Supports both Environmental Persistence and Host-Associated Growth of Acinetobacter baumannii

2020 ◽  
Vol 88 (12) ◽  
Author(s):  
John M. Farrow ◽  
Greg Wells ◽  
Samantha Palethorpe ◽  
Mark D. Adams ◽  
Everett C. Pesci
Keyword(s):  
Acinetobacter Baumannii ◽  
Galleria Mellonella ◽  
Bacterial Pathogen ◽  
Multidrug Resistant ◽  
Growth Defect ◽  
Gene Encoding ◽  
Content Type ◽  
Indirect Transmission ◽  
Mutant Strains ◽  
Carbon Storage Regulator

ABSTRACT Acinetobacter baumannii is an opportunistic and frequently multidrug-resistant Gram-negative bacterial pathogen that primarily infects critically ill individuals. Indirect transmission from patient to patient in hospitals can drive infections, supported by this organism’s abilities to persist on dry surfaces and rapidly colonize susceptible individuals. To investigate how A. baumannii survives on surfaces, we cultured A. baumannii in liquid media for several days and then analyzed isolates that lost the ability to survive drying. One of these isolates carried a mutation that affected the gene encoding the carbon storage regulator CsrA. As we began to examine the role of CsrA in A. baumannii, we observed that the growth of ΔcsrA mutant strains was inhibited in the presence of amino acids. The ΔcsrA mutant strains had a reduced ability to survive drying and to form biofilms but an improved ability to tolerate increased osmolarity compared with the wild type. We also examined the importance of CsrA for A. baumannii virulence. The ΔcsrA mutant strains had a greatly reduced ability to kill Galleria mellonella larvae, could not replicate in G. mellonella hemolymph, and also had a growth defect in human serum. Together, these results show that CsrA is essential for the growth of A. baumannii on host-derived substrates and is involved in desiccation tolerance, implying that CsrA controls key functions involved in the transmission of A. baumannii in hospitals.

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.

Sign in / Sign up

Export Citation Format

Share Document