Effect of Serum Albumin, a Component of Human Pleural Fluid, on Transcriptional and Phenotypic Changes on Acinetobacter baumannii A118

Acinetobacter baumannii is a multidrug-resistant pathogen that causes numerous infections associated with high mortality rates. Exposure to human body fluids, such as human pleural fluid (HPF) and human serum, modulates gene expression in A. baumannii, leading to changes in its pathogenic behavior. Diverse degrees of effects at the transcriptional level were observed in susceptible and carbapenem-resistant strains. The transcriptional analysis of AB5075, a hyper-virulent and extensively drug-resistant strain showed changes in genes associated with quorum sensing, quorum quenching, fatty acids metabolism, and high-efficient iron uptake systems. In addition, the distinctive role of human serum albumin (HSA) as a critical component of HPF was evidenced. In the present work, we used model strain to analyze more deeply into the contribution of HSA in triggering A. baumannii’s response. By qRT-PCR analysis, changes in the expression level of genes associated with quorum sensing, biofilm formation, and phenylacetic acid pathway were observed. Phenotypic approaches confirmed the transcriptional response. HSA, a predominant component of HPF, can modulate the expression and behavior of genes not only in a hyper-virulent and extensively drug-resistant A. baumannii model, but also in other strains with a different degree of susceptibility and pathogenicity.Fil: Le, Casin. California State University; Estados UnidosFil: Pimentel, Camila. California State University; Estados UnidosFil: Tuttobene, Marisel Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; ArgentinaFil: Subils, Tomás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Procesos Biotecnológicos y Químicos Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Procesos Biotecnológicos y Químicos Rosario; ArgentinaFil: Papp Wallace, Krisztina M.. Case Western Reserve University School of Medicine; Estados UnidosFil: Bonomo, Robert A.. Case Western Reserve University School of Medicine; Estados UnidosFil: Actis, Luis A.. Miami University; Estados UnidosFil: Tolmasky, Marcelo E.. California State University; Estados UnidosFil: Ramirez, Maria Soledad. California State University; Estados Unido

Acinetobacter baumannii response to cefiderocol challenge in human urine

Cefiderocol (CFDC) is a novel chlorocatechol-substituted siderophore antibiotic approved to treatcomplicated urinary tract infections (cUTI) and hospital-acquired and ventilator-acquired pneumonia(HAP/VAP). Previous work determined that albumin-rich human fluids increase the minimuminhibitory concentration (MICs) of Acinetobacter baumannii against CFDC and reduce the expressionof genes related to iron uptake systems. This latter effect may contribute to the need for higherconcentrations of CFDC to inhibit growth. The presence of human urine (HU), which contains lowalbumin concentrations, did not modify MIC values of two carbapenem-resistant A. baumannii. Levelsof resistance to CFDC were not modified by HU in strain AMA40 but were reduced in strain AB5075.Expanding the studies to other carbapenem-resistant A. baumannii isolates showed that the presenceof HU resulted in unmodified or reduced MIC of CDFC values. The expression of piuA, pirA, bauA,and bfnH determined by qRT-PCR was enhanced in A. baumannii AMA40 and AB5075 by the presenceof HU in the culture medium. All four tested genes code for functions related to recognition andtransport of ferric-siderophore complexes. The effect of HU on expression of pbp1, pbp3, blaOXA-51-like, blaADC, and blaNDM-1, genes associated with resistance to β-lactams, as well as genes coding for efflux pumps and porins was variable, showing dependence with the strain analyzed. We conclude that the lack of significant concentrations of albumin and free iron in HU makes this fluid behave differently from others we tested. Unlike other albumin rich fluids, the presence of HU does not impact the antibacterial activity of CFDC when tested against A. baumannii.Fil: Nishimura, Brent. California State University. College Of Natural Science And Mathematics; Estados UnidosFil: Escalante, Jenny. California State University. College Of Natural Science And Mathematics; Estados UnidosFil: Tuttobene, Marisel Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Centro de Estudios Fotosintéticos y Bioquímicos. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Centro de Estudios Fotosintéticos y Bioquímicos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; ArgentinaFil: Subils, Tomás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Procesos Biotecnológicos y Químicos Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Procesos Biotecnológicos y Químicos Rosario; ArgentinaFil: Mezcord, Vyanka. California State University. College Of Natural Science And Mathematics; Estados UnidosFil: Pimentel, Camila. California State University. College Of Natural Science And Mathematics; Estados UnidosFil: Georgeos, Nardin. California State University. College Of Natural Science And Mathematics; Estados UnidosFil: Pasteran, Fernando. Dirección Nacional de Institutos de Investigación. Administración Nacional de Laboratorios e Institutos de Salud. Instituto Nacional de Enfermedades Infecciosas. Área de Antimicrobianos; ArgentinaFil: Rodriguez, Maria Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; ArgentinaFil: Sieira, Rodrigo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Actis, Luis A.. Miami University; Estados UnidosFil: Tolmasky, Marcelo E.. California State University. College Of Natural Science And Mathematics; Estados UnidosFil: Bonomo, Robert A.. Center for Antimicrobial Resistance and Epidemiology; Estados Unidos. Case Western Reserve University; Estados UnidosFil: Ramirez, Maria Soledad. California State University. College Of Natural Science And Mathematics; Estados Unido

Contribution of the a-baumannii A1S_0114 gene to the interaction with eukaryotic cells and virulence

Genetic and functional studies showed that some components of the Acinetobacter baumannii ATCC 17978 A1S_0112-A1S_0119 gene cluster are critical for biofilm biogenesis and surface motility. Recently, our group has shown that the A1S_0114 gene was involved in biofilm formation, a process related with pathogenesis. Confirming our previous results, microscopy images revealed that the ATCC 17978 10114 derivative lacking this gene was unable to form a mature biofilm structure. Therefore, other bacterial phenotypes were analyzed to determine the role of this gene in the pathogenicity of A. baumannii ATCC 17978. The interaction of the ATCC 17978 parental strain and the 10114 mutant with A549 human alveolar epithelial cells was quantified revealing that the A1S_0114 gene was necessary for proper attachment to A549 cells. This dependency correlates with the negative effect of the A1S_0114 deletion on the expression of genes coding for surface proteins and pili-assembly systems, which are known to play a role in adhesion. Three different experimental animal models, including vertebrate and invertebrate hosts, confirmed the role of the A1S_0114 gene in virulence. All of the experimental infection assays indicated that the virulence of the ATCC 17978 was significantly reduced when this gene was inactivated. Finally, we discovered that the A1S_0114 gene was involved in the production of a small lipopeptide-like compound herein referred to as acinetin 505 (Ac-505). Ac-505 was isolated from ATCC 17978 spent media and its chemical structure was interpreted by mass spectrometry. Overall, our observations provide novel information on the role of the A1S_0114 gene in A. baumannii’s pathobiology and lay the foundation for future work to determine the mechanisms by which Ac-505, or possibly an Ac-505 precursor, could execute critical functions as a secondary metaboliteS

First catalogue of stars with photoelectric astrolabe in San Juan

On the basis of data observed in San Juan of Argentina with the photoelectric astrolabe mark II (PA II) of Beijing Astronomical Observatory from Feb. 23, 1992 to Feb. 28, 1995, residuals of 7200 stars are reduced from about 230000 observations of stars. The mean precision of the residuals is ± 0:046. Using the data, the first catalogue of stars (CPASJ1) has been compiled. There are 2980 stars in this catalogue, including 989 FK5/FK4 Supp stars, 658 FK5 Ext stars, 387 SRS stars, 687 CAMC4 stars, 192 GC stars, and 72 Hipparcos stars. The mean precisions are ±3.2 ms and ± 0:061 in right ascension and declination, respectively. The magnitudes of stars are from 2.0 to 11.3. The declinations are from to -3° to -60°. The mean epoch is 1993.6. Finally, systematic corrections of (CPASJ1-FK5) are given.Facultad de Ciencias Astronómicas y Geofísica

Klebsiella pneumoniae Multiresistance Plasmid pMET1: Similarity with the Yersinia pestis Plasmid pCRY and Integrative Conjugative Elements

Dissemination of antimicrobial resistance genes has become an important public health and biodefense threat. Plasmids are important contributors to the rapid acquisition of antibiotic resistance by pathogenic bacteria.The nucleotide sequence of the Klebsiella pneumoniae multiresistance plasmid pMET1 comprises 41,723 bp and includes Tn1331.2, a transposon that carries the bla(TEM-1) gene and a perfect duplication of a 3-kbp region including the aac(6')-Ib, aadA1, and bla(OXA-9) genes. The replication region of pMET1 has been identified. Replication is independent of DNA polymerase I, and the replication region is highly related to that of the cryptic Yersinia pestis 91001 plasmid pCRY. The potential partition region has the general organization known as the parFG locus. The self-transmissible pMET1 plasmid includes a type IV secretion system consisting of proteins that make up the mating pair formation complex (Mpf) and the DNA transfer (Dtr) system. The Mpf is highly related to those in the plasmid pCRY, the mobilizable high-pathogenicity island from E. coli ECOR31 (HPI(ECOR31)), which has been proposed to be an integrative conjugative element (ICE) progenitor of high-pathogenicity islands in other Enterobacteriaceae including Yersinia species, and ICE(Kp1), an ICE found in a K. pneumoniae strain causing primary liver abscess. The Dtr MobB and MobC proteins are highly related to those of pCRY, but the endonuclease is related to that of plasmid pK245 and has no significant homology with the protein of similar function in pCRY. The region upstream of mobB includes the putative oriT and shares 90% identity with the same region in the HPI(ECOR31).The comparative analyses of pMET1 with pCRY, HPI(ECOR31), and ICE(Kp1 )show a very active rate of genetic exchanges between Enterobacteriaceae including Yersinia species, which represents a high public health and biodefense threat due to transfer of multiple resistance genes to pathogenic Yersinia strains

Genetic and Phenotypic Analysis of Acinetobacter baumannii Insertion Derivatives Generated with a Transposome System

Acinetobacter baumannii is a metabolically versatile pathogen that causes severe infections in compromised patients. However, little is known about the genes and factors involved in its basic physiology and virulence properties. Insertion mutagenesis was used to initiate the identification and characterization of some of these factors and genes in the prototype strain 19606. The utilization of the pLOFKm suicide delivery vector, which harbors a suicide mini-Tn10 derivative, proved to be unsuccessful for this purpose. The EZ::TN 〈R6Kγori/KAN-2〉 Tnp transposome system available from Epicentre was then used in conjunction with electroporation to generate isogenic insertional derivatives of A. baumannii 19606. Replica plating showed that 2% of the colonies that grew after electroporation on agar plates without antibiotics also grew in the presence of 40 μg of kanamycin per ml. DNA hybridization proved that all of the kanamycin-resistant derivatives contained the EZ::TN 〈R6Kγori/KAN-2〉 insertion element, which was mapped to different genomic locations. Replica plating on Simmons citrate agar and microtiter plate-plastic tube assays identified growth- and biofilm-defective derivatives, respectively. The location of the insertion in several of these derivatives was determined by self-ligation of NdeI- or EcoRI-digested genomic DNA and electroporation of Escherichia coli TransforMax EC100D (pir(+)). Sequence analysis of the recovered plasmids showed that some of the A. baumannii 19606 growth-defective derivatives contain insertions within genes encoding activities required for the generation of energy and cell wall components and for the biosynthesis of amino acids and purines. A gene encoding a protein similar to the GacS sensor kinase was interrupted in four derivatives, while another had an insertion in a gene coding for a hypothetical sensor kinase. A. baumannii 19606 derivatives with defective attachment or biofilm phenotypes had insertions within genes that appear to be part of a chaperone-usher transport system described for other bacteria. DNA hybridization experiments showed that the presence of strain 19606 genes encoding regulatory and attachment or biofilm functions is widespread among other A. baumannii clinical isolates

The Acinetobacter baumannii 19606 OmpA Protein Plays a Role in Biofilm Formation on Abiotic Surfaces and in the Interaction of This Pathogen with Eukaryotic Cells▿

The ability of Acinetobacter baumannii to adhere to and persist on surfaces as biofilms could be central to its pathogenicity. The production of pili and a biofilm-associated protein and the expression of antibiotic resistance are needed for robust biofilm formation on abiotic and biotic surfaces. This multistep process also depends on the expression of transcriptional regulatory functions, some of which could sense nutrients available to cells. This report extends previous observations by showing that although outer membrane protein A (OmpA) of A. baumannii 19606 plays a partial role in the development of robust biofilms on plastic, it is essential for bacterial attachment to Candida albicans filaments and A549 human alveolar epithelial cells. In contrast to abiotic surfaces, the interaction with biotic surfaces is independent of the CsuA/BABCDE-mediated pili. The interaction of A. baumannii 19606 with fungal and epithelial cells also results in their apoptotic death, a response that depends on the direct contact of bacteria with these two types of eukaryotic cells. Furthermore, the bacterial adhesion phenotype correlates with the ability of bacteria to invade A549 epithelial cells. Interestingly, the killing activity of cell-free culture supernatants proved to be protease and temperature sensitive, suggesting that its cytotoxic activity is due to secreted proteins, some of which are different from OmpA