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Influence of selected antimicrobials on the viability, endotoxicity and lipopolysaccharide composition of Pseudomonas aeruginosa in vitro. Int J Antimicrob Agents 2009; 34:419-23. [PMID: 19656661 DOI: 10.1016/j.ijantimicag.2009.06.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2009] [Revised: 06/01/2009] [Accepted: 06/04/2009] [Indexed: 11/21/2022]
Abstract
This research focused on the influence of selected antimicrobial agents (AMAs) on the lipopolysaccharide (LPS) composition of Pseudomonas aeruginosa, a common causative agent of nosocomial infections. As LPS has been shown to play a role in attachment and virulence, the research is primarily aimed at shedding light on the response of these organisms to cleaning regimens in healthcare settings using various disinfectants. The endotoxicity and viability of the organisms following disinfection were further investigated via propagation in sublethal concentrations of the selected AMAs. The AMAs included a CIP chlorinated disinfectant, a heavy-duty alkaline detergent and a phenolic handwash solution. The effects of the antimicrobials on LPS both from intact cells and from debris were assessed by gas chromatography-mass spectrometry (GC-MS) analysis and a chromogenic Limulus amoebocyte lysate assay. Results indicated significant changes in the supramolecular structure of the O-polysaccharide when exposed to the AMAs. Adaptations occurred in both the total assessed saccharide and the lipid fractions, especially in the case of the heavy-duty alkaline detergent. Endotoxicity was found to be influenced by changes in the O-chain rather than the lipid fraction. The phenolic handwash and chlorine-based AMA treatments resulted in a slight decrease in the total amount of fatty acids in the LPS compared with saccharides, whereas the heavy-duty alkaline detergent resulted in a notable reduction in total saccharides. Microbial adaptation of the supramolecular structure of LPS may cause a reduction in membrane solubility of these organisms in an aqueous environment, thus affecting the organism's susceptibility to water-soluble AMAs as well as its ability to adhere to charged surfaces.
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252
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El Solh AA, Alhajhusain A. Update on the treatment of Pseudomonas aeruginosa pneumonia. J Antimicrob Chemother 2009; 64:229-238. [DOI: 10.1093/jac/dkp201] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/30/2023] Open
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253
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Involvement of pmrAB and phoPQ in polymyxin B adaptation and inducible resistance in non-cystic fibrosis clinical isolates of Pseudomonas aeruginosa. Antimicrob Agents Chemother 2009; 53:4345-51. [PMID: 19635950 DOI: 10.1128/aac.01267-08] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
During investigation of susceptibility testing methods for polymyxins, 24 multidrug-resistant clinical isolates of Pseudomonas aeruginosa were observed to have a distinct, reproducible phenotype in which skipped wells were observed during broth microdilution testing for polymyxin B. Possible mechanisms underlying this phenotype were investigated. The effects of various concentrations of polymyxin B on growth, the expression of resistance genes, and outer-membrane permeability were observed. Real-time PCR was performed to compare the expression, in response to selected concentrations of polymyxin B, of genes related to the PhoP-PhoQ and PmrA-PmrB two-component regulatory systems in polymyxin B-susceptible isolate PAO1, polymyxin B-resistant isolate 9BR, and two isolates (19BR and 213BR) exhibiting the skipped-well phenotype. 19BR and 213BR appeared to have similar basal levels of expression compared to that of PAO1 for phoQ, arnB, and PA4773 (from the pmrAB operon), and in contrast, 9BR had 52- and 280-fold higher expression of arnB and PA4773, respectively. The expression of arnB and PA4773 increased in response to polymyxin B in a concentration-dependent manner for 9BR but not for 19BR and 213BR. For these isolates, expression was significantly increased for arnB and PA4773, as well as phoQ, only upon exposure to 2 mug/ml polymyxin B but not at a lower concentration of 0.125 microg/ml. The sequencing of the pmrAB and phoPQ operons for all three isolates revealed a number of unique mutations compared to that for PAO1. 1-N-phenylnaphthylamine (NPN) was used to study the effect of preincubation with polymyxin B on the self-promoted uptake of polymyxin B across the outer membrane. The preincubation of cells with 2 microg/ml polymyxin B affected baseline membrane permeability in 19BR and 213BR and also resulted in a reduced rate of NPN uptake in these isolates and in PAO1 but not in 9BR. The results presented here suggest that the skipped-well isolates have the ability to adapt to specific concentrations of polymyxin B, inducing known polymyxin B resistance genes involved in generating alterations in the outer membrane.
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254
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Karasova D, Sebkova A, Vrbas V, Havlickova H, Sisak F, Rychlik I. Comparative analysis of Salmonella enterica serovar Enteritidis mutants with a vaccine potential. Vaccine 2009; 27:5265-70. [PMID: 19577637 DOI: 10.1016/j.vaccine.2009.06.060] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2009] [Revised: 06/12/2009] [Accepted: 06/12/2009] [Indexed: 10/20/2022]
Abstract
If any new live Salmonella vaccine is introduced in the future, it is quite probable that detailed characterisation of its attenuation will be required. In this study we therefore compared 34 isogenic mutants of S. Enteritidis in aroA, aroD, galE, ssrA, sseA, phoP, rpoS, ompR, htrA, clpP, lon, rfaL, rfaG, rfaC, hfq, sodCI, hilA, sipA, avrA, sopB, sopA, sopE, sifA, shdA, fliC, fur, relA, spoT, rel-spoT, misL, rmbA, STM4258, STM4259 and spvBC genes for their resistance to stresses likely to be expected in the host and for their virulence and immunogenicity in Balb/C mice. We found that the cold and bile resistances essentially did not correlate with the resistances to other stress factors. Resistance to acid pH, heat, polymyxin and serum correlated with each other and also with the attenuation. When the residual virulence and immunogenicity were both considered, mutants in htrA, ompR, aroA, aroD and lon performed the best in mice. Furthermore, when a detailed comparison of polymyxin and serum sensitive mutants was performed, the serum sensitive mutants were more immunogenic.
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Affiliation(s)
- D Karasova
- Veterinary Research Institute, Hudcova 70, 621 00 Brno, Czech Republic
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255
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Resistance to colistin in Acinetobacter baumannii associated with mutations in the PmrAB two-component system. Antimicrob Agents Chemother 2009; 53:3628-34. [PMID: 19528270 DOI: 10.1128/aac.00284-09] [Citation(s) in RCA: 352] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The mechanism of colistin resistance (Col(r)) in Acinetobacter baumannii was studied by selecting in vitro Col(r) derivatives of the multidrug-resistant A. baumannii isolate AB0057 and the drug-susceptible strain ATCC 17978, using escalating concentrations of colistin in liquid culture. DNA sequencing identified mutations in genes encoding the two-component system proteins PmrA and/or PmrB in each strain and in a Col(r) clinical isolate. A colistin-susceptible revertant of one Col(r) mutant strain, obtained following serial passage in the absence of colistin selection, carried a partial deletion of pmrB. Growth of AB0057 and ATCC 17978 at pH 5.5 increased the colistin MIC and conferred protection from killing by colistin in a 1-hour survival assay. Growth in ferric chloride [Fe(III)] conferred a small protective effect. Expression of pmrA was increased in Col(r) mutants, but not at a low pH, suggesting that additional regulatory factors remain to be discovered.
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256
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Sun S, Negrea A, Rhen M, Andersson DI. Genetic analysis of colistin resistance in Salmonella enterica serovar Typhimurium. Antimicrob Agents Chemother 2009; 53:2298-305. [PMID: 19332669 PMCID: PMC2687247 DOI: 10.1128/aac.01016-08] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2008] [Revised: 09/29/2008] [Accepted: 03/23/2009] [Indexed: 11/20/2022] Open
Abstract
Colistin is a cyclic cationic peptide that kills gram-negative bacteria by interacting with and disrupting the outer membrane. We isolated 44 independent mutants in Salmonella enterica serovar Typhimurium with reduced susceptibility to colistin and identified 27 different missense mutations located in the pmrA and pmrB genes (encoding the regulator and sensor of a two-component regulatory system) that conferred increased resistance. By comparison of the two homologous sensor kinases, PmrB and EnvZ, the 22 missense mutations identified in pmrB were shown to be located in four different structural domains of the protein. All five pmrA mutations were located in the phosphate receiver domain of the regulator protein. The mutants appeared at a mutation rate of 0.6 x 10(-6) per cell per generation. The MICs of colistin for the mutants increased 2- to 35-fold, and the extent of killing was reduced several orders of magnitude compared to the susceptible strain. The growth rates of the mutants were slightly reduced in both rich medium and M9-glycerol minimal medium, whereas growth in mice appeared unaffected by the pmrA and pmrB mutations. The low fitness costs and the high mutation rate suggest that mutants with reduced susceptibility to colistin could emerge in clinical settings.
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Affiliation(s)
- Song Sun
- Department of Medical Biochemistry and Microbiology, Uppsala University, S-751 23 Uppsala, Sweden
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257
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Abstract
OBJECTIVE Although most reviews of Pseudomonas aeruginosa therapeutics focus on antibiotics currently in use or in the pipeline, we review evolving translational strategies aimed at using virulence factor antagonists as adjunctive therapies. DATA SOURCE Current literature regarding P. aeruginosa virulence determinants and approaches that target them, with an emphasis on type III secretion, quorum-sensing, biofilms, and flagella. DATA EXTRACTION AND SYNTHESIS P. aeruginosa remains one of the most important pathogens in nosocomial infections, with high associated morbidity and mortality. Its predilection to develop resistance to antibiotics and expression of multiple virulence factors contributes to the frequent ineffectiveness of current therapies. Among the many P. aeruginosa virulence determinants that impact infections, type III secretion, quorum sensing, biofilm formation, and flagella have been the focus on much recent investigation. Here we review how increased understanding of these important bacterial structures and processes has enabled the development of novel approaches to inhibit each. These promising translational strategies may lead to the development of adjunctive therapies capable of improving outcomes. CONCLUSIONS Adjuvant therapies directed against virulence factors have the potential to improve outcomes in P. aeruginosa infections.
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258
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The sensor kinase PhoQ mediates virulence in Pseudomonas aeruginosa. Microbiology (Reading) 2009; 155:699-711. [DOI: 10.1099/mic.0.024554-0] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Pseudomonas aeruginosa is a ubiquitous environmental Gram-negative bacterium that is also a major opportunistic human pathogen in nosocomial infections and cystic fibrosis chronic lung infections. PhoP-PhoQ is a two-component regulatory system that has been identified as essential for virulence and cationic antimicrobial peptide resistance in several other Gram-negative bacteria. This study demonstrated that mutation of phoQ caused reduced twitching motility, biofilm formation and rapid attachment to surfaces, 2.2-fold reduced cytotoxicity to human lung epithelial cells, substantially reduced lettuce leaf virulence, and a major, 10 000-fold reduction in competitiveness in chronic rat lung infections. Microarray analysis revealed that PhoQ controlled the expression of many genes consistent with these phenotypes and with its known role in polymyxin B resistance. It was also demonstrated that PhoQ controls the expression of many genes outside the known PhoP regulon.
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259
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Harvey DJ. Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2003-2004. MASS SPECTROMETRY REVIEWS 2009; 28:273-361. [PMID: 18825656 PMCID: PMC7168468 DOI: 10.1002/mas.20192] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2008] [Revised: 07/07/2008] [Accepted: 07/07/2008] [Indexed: 05/13/2023]
Abstract
This review is the third update of the original review, published in 1999, on the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings the topic to the end of 2004. Both fundamental studies and applications are covered. The main topics include methodological developments, matrices, fragmentation of carbohydrates and applications to large polymeric carbohydrates from plants, glycans from glycoproteins and those from various glycolipids. Other topics include the use of MALDI MS to study enzymes related to carbohydrate biosynthesis and degradation, its use in industrial processes, particularly biopharmaceuticals and its use to monitor products of chemical synthesis where glycodendrimers and carbohydrate-protein complexes are highlighted.
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Affiliation(s)
- David J Harvey
- Department of Biochemistry, Oxford Glycobiology Institute, University of Oxford, Oxford OX1 3QU, UK.
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260
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Gooderham WJ, Hancock REW. Regulation of virulence and antibiotic resistance by two-component regulatory systems inPseudomonas aeruginosa. FEMS Microbiol Rev 2009; 33:279-94. [DOI: 10.1111/j.1574-6976.2008.00135.x] [Citation(s) in RCA: 238] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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261
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Kalhorn TF, Kiavand A, Cohen IE, Nelson AK, Ernst RK. A sensitive liquid chromatography/mass spectrometry-based assay for quantitation of amino-containing moieties in lipid A. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2009; 23:433-42. [PMID: 19130491 PMCID: PMC2716696 DOI: 10.1002/rcm.3900] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A novel sensitive liquid chromatography/mass spectrometry-based assay was developed for the quantitation of aminosugars, including 2-amino-2-deoxyglucose (glucosamine, GlcN), 2-amino-2-deoxygalactose (galactosamine, GalN), and 4-amino-4-deoxyarabinose (aminoarabinose, AraN), and for ethanolamine (EtN), present in lipid A. This assay enables the identification and quantitation of all amino-containing moieties present in lipopolysaccharide or lipid A from a single sample. The method was applied to the analysis of lipid A (endotoxin) isolated from a variety of biosynthetic and regulatory mutants of Salmonella enterica serovar Typhimurium and Francisella tularensis subspecies novicida. Lipid A is treated with trifluoroacetic acid to liberate and deacetylate individual aminosugars and mass tagged with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate, which reacts with primary and secondary amines. The derivatives are separated using reversed-phase chromatography and analyzed using a single quadrupole mass spectrometer to detect quantities as small as 20 fmol. GalN was detected only in Francisella and AraN only in Salmonella, while GlcN was detected in lipid A samples from both species of bacteria. Additionally, we found an approximately 10-fold increase in the level of AraN in lipid A isolated from Salmonella grown in magnesium-limited versus magnesium-replete conditions. Salmonella with defined mutations in lipid A synthesis and regulatory genes were used to further validate the assay. Salmonella with null mutations in the phoP, pmrE, and prmF genes were unable to add AraN to their lipid A, while Salmonella with constitutively active phoP and pmrA exhibited AraN modification of lipid A even in the normally repressive magnesium-replete growth condition. The described assay produces excellent repeatability and reproducibility for the detection of amino-containing moieties in lipid A from a variety of bacterial sources.
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Affiliation(s)
- Thomas F. Kalhorn
- Department of Medicinal Chemistry, University of Washington, Seattle, WA 98195, USA
| | - Anahita Kiavand
- Department of Medicine, University of Washington, Seattle, WA 98195, USA
| | - Ilana E. Cohen
- Department of Medicine, University of Washington, Seattle, WA 98195, USA
| | - Amanda K. Nelson
- Department of Medicine, University of Washington, Seattle, WA 98195, USA
| | - Robert K. Ernst
- Department of Medicine, University of Washington, Seattle, WA 98195, USA
- Department of Microbial Pathogenesis, University of Maryland Dental School, Baltimore, MD 21201, USA
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262
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Llobet E, Tomás JM, Bengoechea JA. Capsule polysaccharide is a bacterial decoy for antimicrobial peptides. MICROBIOLOGY-SGM 2009; 154:3877-3886. [PMID: 19047754 DOI: 10.1099/mic.0.2008/022301-0] [Citation(s) in RCA: 208] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Antimicrobial peptides (APs) are important host weapons against infections. Nearly all APs are cationic and their microbicidal action is initiated through interactions with the anionic bacterial surface. It is known that pathogens have developed countermeasures to resist these agents by reducing the negative charge of membranes, by active efflux and by proteolytic degradation. Here we uncover a new strategy of resistance based on the neutralization of the bactericidal activity of APs by anionic bacterial capsule polysaccharide (CPS). Purified CPSs from Klebsiella pneumoniae K2, Streptococcus pneumoniae serotype 3 and Pseudomonas aeruginosa increased the resistance to polymyxin B of an unencapsulated K. pneumoniae mutant. Furthermore, these CPSs increased the MICs of polymyxin B and human neutrophil alpha-defensin 1 (HNP-1) for unencapsulated K. pneumoniae, Escherichia coli and P. aeruginosa PAO1. Polymyxin B or HNP-1 released CPS from capsulated K. pneumoniae, S. pneumoniae serotype 3 and P. aeruginosa overexpressing CPS. Moreover, this material also reduced the bactericidal activity of APs. We postulate that APs may trigger in vivo the release of CPS, which in turn will protect bacteria against APs. We found that anionic CPSs, but not cationic or uncharged ones, blocked the bactericidal activity of APs by binding them, thereby reducing the amount of peptides reaching the bacterial surface. Supporting this, polycations inhibited such interaction and the bactericidal activity was restored. We postulate that trapping of APs by anionic CPSs is an additional selective virulence trait of these molecules, which could be considered as bacterial decoys for APs.
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Affiliation(s)
- Enrique Llobet
- Centro de Investigación Biomédica en Red de Enfermedades Respiratorias (CIBERES), Bunyola, Spain.,Program Infection and Immunity, Fundació Caubet-CIMERA Illes Balears, Bunyola, Spain
| | - Juan M Tomás
- Departamento de Microbiología, Facultad de Biología, Universidad de Barcelona, Barcelona, Spain
| | - Jose A Bengoechea
- Área de Microbiología, Facultad Biología, Universitat Illes Balears, Palma Mallorca, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Respiratorias (CIBERES), Bunyola, Spain.,Program Infection and Immunity, Fundació Caubet-CIMERA Illes Balears, Bunyola, Spain
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263
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Lepsanovic Z, Libisch B, Tomanovic B, Nonkovici Z, Balogh B, Füzi M. Characterisation of the first VIM metallo-beta-lactamase-producing Pseudomonas aeruginosa clinical isolate in Serbia. Acta Microbiol Immunol Hung 2008; 55:447-54. [PMID: 19130752 DOI: 10.1556/amicr.55.2008.4.9] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
From the Central-East European region the first VIM metallo-beta-lactamase (MBL) producing Pseudomonas aeruginosa strains were published from Croatia, Poland and Hungary. The aim of this study was to assess the contribution of MBL-production to carbapenem-resistance among P. aeruginosa clinical isolates in the Military Medical Academy (MMA) in Belgrade, Serbia between August 2004 and September 2007. Only one P. aeruginosa isolate with strain number 722 proved MBL-positive that harboured a novel class 1 integron with a bla(VIM-2)-like cassette in the first position, followed by orfD, a putative gene with unknown function. Our data indicate that MBL-producing strains occur at a prevalence of less than 1% among imipenem-nonsusceptible P. aeruginosa clinical isolates in this Belgrade hospital. The newly identified VIM MBL-producing P. aeruginosa strain 722 could be assigned to serotype O11, and it was panresistant to all antimicrobials tested. The isolate displayed sequence type ST235 by multilocus sequence typing which is the founder sequence type of the previously identified international clonal complex CC11 that already contains bla(VIM)-positive isolates from Italy, Greece, Sweden, Hungary and Poland. In conclusion, this is the first report of VIM MBL-producing P. aeruginosa from Serbia and also of the occurrence of such isolates belonging to the international clonal complex CC11 in this country.
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Affiliation(s)
- Zorica Lepsanovic
- Institute of Epidemiology, Military Medical Academy, Cmotravska 17, S-11040 Belgrade, Serbia
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264
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Extracellular DNA chelates cations and induces antibiotic resistance in Pseudomonas aeruginosa biofilms. PLoS Pathog 2008; 4:e1000213. [PMID: 19023416 PMCID: PMC2581603 DOI: 10.1371/journal.ppat.1000213] [Citation(s) in RCA: 439] [Impact Index Per Article: 27.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2008] [Accepted: 10/21/2008] [Indexed: 01/18/2023] Open
Abstract
Biofilms are surface-adhered bacterial communities encased in an extracellular matrix composed of DNA, bacterial polysaccharides and proteins, which are up to 1000-fold more antibiotic resistant than planktonic cultures. To date, extracellular DNA has been shown to function as a structural support to maintain Pseudomonas aeruginosa biofilm architecture. Here we show that DNA is a multifaceted component of P. aeruginosa biofilms. At physiologically relevant concentrations, extracellular DNA has antimicrobial activity, causing cell lysis by chelating cations that stabilize lipopolysaccharide (LPS) and the outer membrane (OM). DNA-mediated killing occurred within minutes, as a result of perturbation of both the outer and inner membrane (IM) and the release of cytoplasmic contents, including genomic DNA. Sub-inhibitory concentrations of DNA created a cation-limited environment that resulted in induction of the PhoPQ- and PmrAB-regulated cationic antimicrobial peptide resistance operon PA3552–PA3559 in P. aeruginosa. Furthermore, DNA-induced expression of this operon resulted in up to 2560-fold increased resistance to cationic antimicrobial peptides and 640-fold increased resistance to aminoglycosides, but had no effect on β-lactam and fluoroquinolone resistance. Thus, the presence of extracellular DNA in the biofilm matrix contributes to cation gradients, genomic DNA release and inducible antibiotic resistance. DNA-rich environments, including biofilms and other infection sites like the CF lung, are likely the in vivo environments where extracellular pathogens such as P. aeruginosa encounter cation limitation. Pseudomonas aeruginosa is an opportunistic pathogen, which causes a variety of serious infections in immunocompromised patients and cystic fibrosis (CF) sufferers. The biofilm-forming ability of P. aeruginosa is thought to contribute to chronic P. aeruginosa infection of the CF lung. Biofilms are dense communities of bacteria, encased in an extracellular matrix, that are practically impossible to eradicate using available antimicrobial therapies. Understanding the mechanisms by which biofilm bacteria develop resistance to antibiotics is paramount to expanding the treatment options available to patients with chronic biofilm infections. In this study we have identified a novel mechanism of biofilm-specific antibiotic resistance. Extracellular DNA, a known component of biofilms, was found to induce antibiotic resistance. This previously unidentified function of DNA was due to its ability to bind and sequester cations, including magnesium, from the surrounding environment. This environmental cue was then detected by P. aeruginosa leading to induction of genes involved in modification of the cell surface component, lipopolysaccharide (LPS), resulting in physical alterations in the bacterial outer membrane (OM). These results demonstrate a novel function for DNA in biofilms and identify cation chelation by DNA as a previously unrecognized mechanism, which can explain the increased resistance of biofilms to antimicrobial agents.
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265
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Kwa AL, Tam VH, Falagas ME. Polymyxins: A Review of the Current Status Including Recent Developments. ANNALS OF THE ACADEMY OF MEDICINE, SINGAPORE 2008. [DOI: 10.47102/annals-acadmedsg.v37n10p870] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
Introduction: Polymyxins have become the drug of choice for treatment of multidrug-resistant gram-negative bacilli infections in Singapore, simply because these pathogens are only susceptible to either aminoglycosides and polymyxins, or polymyxins only. Furthermore, there is no new antibiotic in the pipeline that targets these difficult-to-treat infections.
Materials and Methods: All published literatures (up to end of February 2008) regarding polymyxins are included for review.
Results: This review serves to give a summary of polymyxins from the current available literature, highlighting relevant clinical studies and information that help to guide informed prescription of polymyxins, should the need arise.
Conclusions: However, there are substantial information gaps that needed to be filled urgently, to preserve the clinical utility of this very last line of antibiotic.
Key words: Acinetobacter baumannii, Colistin, Multidrug resistance, Polymyxin B, Pseudomonas aeruginosa
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266
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Johansen HK, Moskowitz SM, Ciofu O, Pressler T, Høiby N. Spread of colistin resistant non-mucoid Pseudomonas aeruginosa among chronically infected Danish cystic fibrosis patients. J Cyst Fibros 2008; 7:391-7. [DOI: 10.1016/j.jcf.2008.02.003] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2007] [Revised: 01/27/2008] [Accepted: 02/04/2008] [Indexed: 11/16/2022]
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267
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Moskowitz SM, Silva SJ, Mayer-Hamblett N, Pasta DJ, Mink DR, Mabie JA, Konstan MW, Wagener JS. Shifting patterns of inhaled antibiotic use in cystic fibrosis. Pediatr Pulmonol 2008; 43:874-81. [PMID: 18668689 DOI: 10.1002/ppul.20873] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
RATIONALE Antibiotic inhalation has become widely accepted as a standard treatment for cystic fibrosis (CF) airway infection. We assessed the prevalence and context of inhaled antibiotic use in the North American CF population. Our working hypothesis was that a shift from acute to chronic use of inhaled antibiotics has coincided with increased prevalence of use among CF patients. METHODS Descriptive statistics were collected for 30,833 patients enrolled in the Epidemiologic Study of CF (ESCF) during 1996 through 2005. A multivariate analysis was performed on data from a subgroup of 18,021 patients enrolled in ESCF during 2003 through 2005. RESULTS The prevalence of inhaled antibiotic use in the North American CF population increased during 1996 through 2005 due to increased chronic use, while acute use to treat pulmonary exacerbations decreased. In 2005, 50% of CF patients used inhaled tobramycin and 9% used inhaled colistin chronically; most of the latter used both agents concurrently. Airway obstruction severity and airway infection status were predictors of inhaled antibiotic use. CONCLUSIONS Increased chronic use and decreased acute use of inhaled antibiotics presumably reflect a shift toward more proactive management of airway infections in the North American CF population. The effects of these usage patterns on long-term clinical outcomes and emergence of antibiotic-resistant Pseudomonas aeruginosa strains warrant further study.
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Affiliation(s)
- Samuel M Moskowitz
- Department of Pediatrics, University of Washington School of Medicine, Seattle, Washington 98195-7740, USA.
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268
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Induction by cationic antimicrobial peptides and involvement in intrinsic polymyxin and antimicrobial peptide resistance, biofilm formation, and swarming motility of PsrA in Pseudomonas aeruginosa. J Bacteriol 2008; 190:5624-34. [PMID: 18556795 DOI: 10.1128/jb.00594-08] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas aeruginosa is an important opportunistic pathogen that causes infections that can be extremely difficult to treat due to its high intrinsic antibiotic resistance and broad repertoire of virulence factors, both of which are highly regulated. It is demonstrated here that the psrA gene, encoding a transcriptional regulator, was upregulated in response to subinhibitory concentrations of cationic antimicrobial peptides. Compared to the wild type and the complemented mutant, a P. aeruginosa PAO1 psrA::Tn5 mutant displayed intrinsic supersusceptibility to polymyxin B, a last-resort antimicrobial used against multidrug-resistant infections, and the bovine neutrophil antimicrobial peptide indolicidin; this supersusceptibility phenotype correlated with increased outer membrane permeabilization by these agents. The psrA mutant was also defective in simple biofilm formation, rapid attachment, and swarming motility, all of which could be complemented by the cloned psrA gene. The role of PsrA in global gene regulation was studied by comparing the psrA mutant to the wild type by microarray analysis, demonstrating that 178 genes were up- or downregulated >or=2-fold (P <or= 0.05). Dysregulated genes included those encoding certain known PsrA targets, those encoding the type III secretion apparatus and effectors, adhesion and motility genes, and a variety of metabolic, energy metabolism, and outer membrane permeability genes. This suggests that PsrA might be a key regulator of antimicrobial peptide resistance and virulence.
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269
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Gunn JS. The Salmonella PmrAB regulon: lipopolysaccharide modifications, antimicrobial peptide resistance and more. Trends Microbiol 2008; 16:284-90. [PMID: 18467098 DOI: 10.1016/j.tim.2008.03.007] [Citation(s) in RCA: 243] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2007] [Revised: 03/19/2008] [Accepted: 03/28/2008] [Indexed: 11/30/2022]
Abstract
Microbes are able to sense and respond to their environment primarily through the use of two-component regulatory systems. Many of these systems activate virulence-factor expression and are regulated by host-derived signals, having evolved to control gene expression at the key time and place for optimal establishment and maintenance of infection. Salmonella spp. are enteric pathogens that are able to survive both within host macrophages during systemic spread and killing by innate immune factors at intestinal mucosal surfaces. This review focuses on a key mechanism of pathogenesis that involves the PmrA-PmrB two-component system, which is activated in vivo by direct or indirect means and regulates genes that modify lipopolysaccharide, aiding survival in host (and non-host) environments.
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Affiliation(s)
- John S Gunn
- Center for Microbial Interface Biology, Department of Molecular Virology, Immunology and Medical Genetics, The Ohio State University, 460 W. 12th Avenue, Columbus, OH 43210-1214, USA.
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270
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Ryan RP, Fouhy Y, Garcia BF, Watt SA, Niehaus K, Yang L, Tolker-Nielsen T, Dow JM. Interspecies signalling via the Stenotrophomonas maltophilia diffusible signal factor influences biofilm formation and polymyxin tolerance in Pseudomonas aeruginosa. Mol Microbiol 2008; 68:75-86. [DOI: 10.1111/j.1365-2958.2008.06132.x] [Citation(s) in RCA: 173] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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271
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Pamp SJ, Gjermansen M, Johansen HK, Tolker-Nielsen T. Tolerance to the antimicrobial peptide colistin in Pseudomonas aeruginosa biofilms is linked to metabolically active cells, and depends on the pmr and mexAB-oprM genes. Mol Microbiol 2008; 68:223-40. [DOI: 10.1111/j.1365-2958.2008.06152.x] [Citation(s) in RCA: 355] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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272
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Role of RppA in the regulation of polymyxin b susceptibility, swarming, and virulence factor expression in Proteus mirabilis. Infect Immun 2008; 76:2051-62. [PMID: 18316383 DOI: 10.1128/iai.01557-07] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Proteus mirabilis, a human pathogen that frequently causes urinary tract infections, is intrinsically highly resistant to cationic antimicrobial peptides, such as polymyxin B (PB). To explore the mechanisms underlying P. mirabilis resistance to PB, a mutant which displayed increased (> 160-fold) sensitivity to PB was identified by transposon mutagenesis. This mutant was found to have Tn5 inserted into a novel gene, rppA. Sequence analysis indicated that rppA may encode a response regulator of the two-component system and is located upstream of the rppB gene, which may encode a membrane sensor kinase. An rppA knockout mutant of P. mirabilis had an altered lipopolysaccharide (LPS) profile. The LPS purified from the rppA knockout mutant could bind more PB than the LPS purified from the wild type. These properties of the rppA knockout mutant may contribute to its PB-sensitive phenotype. The rppA knockout mutant exhibited greater swarming motility and cytotoxic activity and expressed higher levels of flagellin and hemolysin than the wild type, suggesting that RppA negatively regulates swarming, hemolysin expression, and cytotoxic activity in P. mirabilis. PB could modulate LPS synthesis and modification, swarming, hemolysin expression, and cytotoxic activity in P. mirabilis through an RppA-dependent pathway, suggesting that PB could serve as a signal to regulate RppA activity. Finally, we demonstrated that the expression of rppA was up-regulated by a low concentration of PB and down-regulated by a high concentration of Mg2+. Together, these data highlight the essential role of RppA in regulating PB susceptibility and virulence functions in P. mirabilis.
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273
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Risk factors associated with the isolation of colistin-resistant Gram-negative bacteria: A matched case-control study. Crit Care Med 2008; 36:807-11. [DOI: 10.1097/ccm.0b013e3181652fae] [Citation(s) in RCA: 124] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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274
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Abstract
Lipopeptide daptomycin is one of the few recently approved antibiotics based on the novel mechanism of action. Recent advances in synthetic lipopeptides, driven by the biochemical and biophysical research, expanded their spectrum of antimicrobial activity and reduced their size to achieve economically viable production. Lipopeptides, consisting of a short peptide chain conjugated with an acyl chain, form a structurally defined conformation, which inserts into the bacterial membrane and dissipates its transmembrane potential. In addition to antimicrobial activity, synthetic lipopeptides also suppress inflammation through the neutralization of bacterial agonists of the innate immune response, synergize with conventional antibiotics and have improved proteolytic stability. Activities in animal models indicate that synthetic lipopeptides may surpass the natural lipopeptides as the perspective class of anti-infective agents.
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Affiliation(s)
- Roman Jerala
- National Institute of Chemistry, Department of Biotechnology, Hajdrihova 19, Ljubljana, Slovenia.
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275
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Ernst RK, Moskowitz SM, Emerson JC, Kraig GM, Adams KN, Harvey MD, Ramsey B, Speert DP, Burns JL, Miller SI. Unique lipid a modifications in Pseudomonas aeruginosa isolated from the airways of patients with cystic fibrosis. J Infect Dis 2007; 196:1088-92. [PMID: 17763333 PMCID: PMC2723782 DOI: 10.1086/521367] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2007] [Accepted: 05/08/2007] [Indexed: 12/17/2022] Open
Abstract
Three structural features of lipid A (addition of palmitate [C16 fatty acid], addition of aminoarabinose [positively charged amino sugar residue], and retention of 3-hydroxydecanoate [3-OH C10 fatty acid]) were determined for Pseudomonas aeruginosa isolates from patients with cystic fibrosis (CF; n=86), from the environment (n=13), and from patients with other conditions (n=14). Among P. aeruginosa CF isolates, 100% had lipid A with palmitate, 24.6% with aminoarabinose, and 33.3% retained 3-hydroxydecanoate. None of the isolates from the environment or from patients with other conditions displayed these modifications. These results indicate that unique lipid A modifications occur in clinical P. aeruginosa CF isolates.
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Affiliation(s)
- Robert K Ernst
- Department of Medicine, University of Washington, Seattle, WA 98195, USA.
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276
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Mentzelopoulos SD, Pratikaki M, Platsouka E, Kraniotaki H, Zervakis D, Koutsoukou A, Nanas S, Paniara O, Roussos C, Giamarellos-Bourboulis E, Routsi C, Zakynthinos SG. Prolonged use of carbapenems and colistin predisposes to ventilator-associated pneumonia by pandrug-resistant Pseudomonas aeruginosa. Intensive Care Med 2007; 33:1524-32. [PMID: 17549457 DOI: 10.1007/s00134-007-0683-2] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2006] [Accepted: 04/02/2007] [Indexed: 01/05/2023]
Abstract
OBJECTIVE We present our experience with five cases of pandrug-resistant Pseudomonas aeruginosa ventilator-associated pneumonia (VAP) and analysis of risk factors. DESIGN AND SETTING Case-control study in a 15-bed intensive care unit (ICU). PATIENTS AND PARTICIPANTS The study included 5 cases and 20 controls. Each case patient was matched to four contemporary controls according to gender, prior hospital admissions, hospitalization duration, ICU admission cause, Acute Physiology and Chronic Health Evaluation (APACHE) II and Sequential Organ Function Assessment (SOFA) scores on ICU admission, and length of ICU stay, and mechanical ventilation duration until first VAP episode by a multidrug-resistant bacterium. MEASUREMENTS AND RESULTS Recorded variables included age, gender, daily APACHE II and SOFA scores, patient medication, treatment interventions, positive cultures and corresponding antibiograms, occurrence of infection, sepsis, and septic shock, other ICU-associated morbidity, length of ICU stay and mechanical ventilation, and patient outcome. Healthcare worker and environmental cultures, and a hand-disinfection survey were performed. Pandrug-resistant P. aeruginosa isolates belonged to the same genotype and were bla (VIM-1)-like gene positive. The outbreak resolved following reinforcement of infection-control measures (September 27). The sole independent predictor for pandrug-resistant P. aeruginosa VAP was combined use of carbapenem for more than 20 days and colistin use for and more than 13 days (odds ratio 76.0; 95% confidence interval 3.7-1487.6). An additional risk factor was more than 78 open suctioning procedures during 6-26 September (odds ratio 16.0; 95% confidence interval 1.4-185.4). CONCLUSIONS Prolonged carbapenem-colistin use predisposes to VAP by pandrug-resistant P. aeruginosa. Cross-transmission may be facilitated by open suctioning.
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Affiliation(s)
- Spyros D Mentzelopoulos
- University of Athens Medical School, First Department of Critical Care, 45-47 Ipsilandou Street, GR-10675 Athens, Greece.
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277
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Clements A, Tull D, Jenney AW, Farn JL, Kim SH, Bishop RE, McPhee JB, Hancock REW, Hartland EL, Pearse MJ, Wijburg OLC, Jackson DC, McConville MJ, Strugnell RA. Secondary acylation of Klebsiella pneumoniae lipopolysaccharide contributes to sensitivity to antibacterial peptides. J Biol Chem 2007; 282:15569-77. [PMID: 17371870 PMCID: PMC5007121 DOI: 10.1074/jbc.m701454200] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Klebsiella pneumoniae is an important cause of nosocomial Gram-negative sepsis. Lipopolysaccharide (LPS) is considered to be a major virulence determinant of this encapsulated bacterium and most mutations to the lipid A anchor of LPS are conditionally lethal to the bacterium. We studied the role of LPS acylation in K. pneumoniae disease pathogenesis by using a mutation of lpxM (msbB/waaN), which encodes the enzyme responsible for late secondary acylation of immature lipid A molecules. A K. pneumoniae B5055 (K2:O1) lpxM mutant was found to be attenuated for growth in the lungs in a mouse pneumonia model leading to reduced lethality of the bacterium. B5055DeltalpxM exhibited similar sensitivity to phagocytosis or complement-mediated lysis than B5055, unlike the non-encapsulated mutant B5055nm. In vitro, B5055DeltalpxM showed increased permeability of the outer membrane and an increased susceptibility to certain antibacterial peptides suggesting that in vivo attenuation may be due in part to sensitivity to antibacterial peptides present in the lungs of BALB/c mice. These data support the view that lipopolysaccharide acylation plays a important role in providing Gram-negative bacteria some resistance to structural and innate defenses and especially the antibacterial properties of detergents (e.g. bile) and cationic defensins.
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Affiliation(s)
- Abigail Clements
- CRC for Vaccine Technology in the Department of Microbiology & Immunology, University of Melbourne, Parkville, Victoria 3010, Australia
- Australian Bacterial Pathogenesis Program in the Department of Microbiology and Immunology, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Dedreia Tull
- Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Adam W. Jenney
- CRC for Vaccine Technology in the Department of Microbiology & Immunology, University of Melbourne, Parkville, Victoria 3010, Australia
- Australian Bacterial Pathogenesis Program in the Department of Microbiology and Immunology, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Jacinta L. Farn
- CRC for Vaccine Technology in the Department of Microbiology & Immunology, University of Melbourne, Parkville, Victoria 3010, Australia
- Australian Bacterial Pathogenesis Program in the Department of Microbiology and Immunology, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Sang-Hyun Kim
- Department of Biochemistry, University of Toronto, Ontario M5S1A8, Canada
| | - Russell E. Bishop
- Department of Biochemistry, University of Toronto, Ontario M5S1A8, Canada
| | - Joseph B. McPhee
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia V6T1Z4, Canada
| | - Robert E. W. Hancock
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia V6T1Z4, Canada
| | - Elizabeth L. Hartland
- CRC for Vaccine Technology in the Department of Microbiology, Monash University, Clayton, Victoria 3800, Australia
- Australian Bacterial Pathogenesis Program in the Department of Microbiology and Immunology, University of Melbourne, Parkville, Victoria 3010, Australia
| | | | - Odilia L. C. Wijburg
- CRC for Vaccine Technology in the Department of Microbiology & Immunology, University of Melbourne, Parkville, Victoria 3010, Australia
- Australian Bacterial Pathogenesis Program in the Department of Microbiology and Immunology, University of Melbourne, Parkville, Victoria 3010, Australia
| | - David C. Jackson
- CRC for Vaccine Technology in the Department of Microbiology & Immunology, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Malcolm J. McConville
- Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Richard A. Strugnell
- CRC for Vaccine Technology in the Department of Microbiology & Immunology, University of Melbourne, Parkville, Victoria 3010, Australia
- Australian Bacterial Pathogenesis Program in the Department of Microbiology and Immunology, University of Melbourne, Parkville, Victoria 3010, Australia
- To whom correspondence should be addressed: Dept. of Microbiology & Immunology, University of Melbourne, Parkville VIC 3010, Australia. Tel.: 61-3-8344-5712; Fax: 61-3-9347-1540;
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278
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Li J, Nation RL, Turnidge JD, Milne RW, Coulthard K, Rayner CR, Paterson DL. Colistin: the re-emerging antibiotic for multidrug-resistant Gram-negative bacterial infections. THE LANCET. INFECTIOUS DISEASES 2006; 6:589-601. [PMID: 16931410 DOI: 10.1016/s1473-3099(06)70580-1] [Citation(s) in RCA: 999] [Impact Index Per Article: 55.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Increasing multidrug resistance in Gram-negative bacteria, in particular Pseudomonas aeruginosa, Acinetobacter baumannii, and Klebsiella pneumoniae, presents a critical problem. Limited therapeutic options have forced infectious disease clinicians and microbiologists to reappraise the clinical application of colistin, a polymyxin antibiotic discovered more than 50 years ago. We summarise recent progress in understanding the complex chemistry, pharmacokinetics, and pharmacodynamics of colistin, the interplay between these three aspects, and their effect on the clinical use of this important antibiotic. Recent clinical findings are reviewed, focusing on evaluation of efficacy, emerging resistance, potential toxicities, and combination therapy. In the battle against rapidly emerging bacterial resistance we can no longer rely entirely on the discovery of new antibiotics; we must also pursue rational approaches to the use of older antibiotics such as colistin.
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Affiliation(s)
- Jian Li
- Facility for Anti-infective Drug Development and Innovation, Victorian College of Pharmacy, Monash University, Parkville, Victoria, Australia.
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279
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McPhee JB, Bains M, Winsor G, Lewenza S, Kwasnicka A, Brazas MD, Brinkman FSL, Hancock REW. Contribution of the PhoP-PhoQ and PmrA-PmrB two-component regulatory systems to Mg2+-induced gene regulation in Pseudomonas aeruginosa. J Bacteriol 2006; 188:3995-4006. [PMID: 16707691 PMCID: PMC1482896 DOI: 10.1128/jb.00053-06] [Citation(s) in RCA: 154] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
When grown in divalent cation-limited medium, Pseudomonas aeruginosa becomes resistant to cationic antimicrobial peptides and polymyxin B. This resistance is regulated by the PhoP-PhoQ and PmrA-PmrB two-component regulatory systems. To further characterize Mg(2+) regulation in P. aeruginosa, microarray transcriptional profiling was conducted to compare wild-type P. aeruginosa grown under Mg(2+)-limited and Mg(2+)-replete conditions to isogenic phoP and pmrA mutants grown under Mg(2+)-limited conditions. Under Mg(2+)-limited conditions (0.02 mM Mg(2+)), approximately 3% of the P. aeruginosa genes were differentially expressed compared to the expression in bacteria grown under Mg(2+)-replete conditions (2 mM Mg(2+)). Only a modest subset of the Mg(2+)-regulated genes were regulated through either PhoP or PmrA. To determine which genes were directly regulated, a bioinformatic search for conserved binding motifs was combined with confirmatory reverse transcriptase PCR and gel shift promoter binding assays, and the results indicated that very few genes were directly regulated by these response regulators. It was found that in addition to the previously known oprH-phoP-phoQ operon and the pmrHFIJKLM-ugd operon, the PA0921 and PA1343 genes, encoding small basic proteins, were regulated by Mg(2+) in a PhoP-dependent manner. The number of known PmrA-regulated genes was expanded to include the PA1559-PA1560, PA4782-PA4781, and feoAB operons, in addition to the previously known PA4773-PA4775-pmrAB and pmrHFIJKLM-ugd operons.
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Affiliation(s)
- Joseph B McPhee
- Department of Microbiology and Immunology and Centre for Microbial Diseases and Immunity Research, University of British Columbia, 232-2259 Lower Mall, Vancouver, BC, Canada V6T 1Z4
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280
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Saugar JM, Rodríguez-Hernández MJ, de la Torre BG, Pachón-Ibañez ME, Fernández-Reyes M, Andreu D, Pachón J, Rivas L. Activity of cecropin A-melittin hybrid peptides against colistin-resistant clinical strains of Acinetobacter baumannii: molecular basis for the differential mechanisms of action. Antimicrob Agents Chemother 2006; 50:1251-6. [PMID: 16569836 PMCID: PMC1426946 DOI: 10.1128/aac.50.4.1251-1256.2006] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Acinetobacter baumannii has successfully developed resistance against all common antibiotics, including colistin (polymyxin E), the last universally active drug against this pathogen. The possible widespread distribution of colistin-resistant A. baumannii strains may create an alarming clinical situation. In a previous work, we reported differences in lethal mechanisms between polymyxin B (PXB) and the cecropin A-melittin (CA-M) hybrid peptide CA(1-8)M(1-18) (KWKLFKKIGIGAVLKVLTTGLPALIS-NH2) on colistin-susceptible strains (J. M. Saugar, T. Alarcón, S. López-Hernández, M. López-Brea, D. Andreu, and L. Rivas, Antimicrob. Agents Chemother. 46:875-878, 2002). We now demonstrate that CA(1-8)M(1-18) and three short analogues, namely CA(1-7)M(2-9) (KWKLFKKIGAVLKVL-NH2), its Nalpha-octanoyl derivative (Oct-KWKLFKKIGAVLKVL-NH2), and CA(1-7)M(5-9) (KWKLLKKIGAVLKVL-NH2) are active against two colistin-resistant clinical strains. In vitro, resistance to colistin sulfate was targeted to the outer membrane, as spheroplasts were equally lysed by a given peptide, regardless of their respective level of colistin resistance. The CA-M hybrids were more efficient than colistin in displacing lipopolysaccharide-bound dansyl-polymyxin B from colistin-resistant but not from colistin-susceptible strains. Similar improved performance of the CA-M hybrids in permeation of the inner membrane was observed, regardless of the resistance pattern of the strain. These results argue in favor of a possible use of CA-M peptides, and by extension other antimicrobial peptides with similar features, as alternative chemotherapy in colistin-resistant Acinetobacter infections.
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Affiliation(s)
- José María Saugar
- Centro de Investigaciones Biológicas (CSIC), Madrid, and Hospitales Universitarios Virgen del Rocío, Sevilla, Spain
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281
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Ernst RK, Adams KN, Moskowitz SM, Kraig GM, Kawasaki K, Stead CM, Trent MS, Miller SI. The Pseudomonas aeruginosa lipid A deacylase: selection for expression and loss within the cystic fibrosis airway. J Bacteriol 2006; 188:191-201. [PMID: 16352835 PMCID: PMC1317579 DOI: 10.1128/jb.188.1.191-201.2006] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Lipopolysaccharide (LPS) is the major surface component of gram-negative bacteria, and a component of LPS, lipid A, is recognized by the innate immune system through the Toll-like receptor 4/MD-2 complex. Pseudomonas aeruginosa, an environmental gram-negative bacterium that opportunistically infects the respiratory tracts of patients with cystic fibrosis (CF), can synthesize various structures of lipid A. Lipid A from P. aeruginosa strains isolated from infants with CF has a specific structure that includes the removal of the 3 position 3-OH C10 fatty acid. Here we demonstrate increased expression of the P. aeruginosa lipid A 3-O-deacylase (PagL) in isolates from CF infants compared to that in environmental isolates. PagL activity was increased in environmental isolates by growth in medium limited for magnesium and decreased by growth at low temperature in laboratory-adapted strains of P. aeruginosa. P. aeruginosa PagL was shown to be an outer membrane protein by isopycnic density gradient centrifugation. Heterologous expression of P. aeruginosa pagL in Salmonella enterica serovar Typhimurium and Escherichia coli resulted in removal of the 3-OH C14 fatty acid from lipid A, indicating that P. aeruginosa PagL recognizes either 3-OH C10 or 3-OH C14. Finally, deacylated lipid A species were not observed in some clinical P. aeruginosa isolates from patients with severe pulmonary disease, suggesting that loss of PagL function can occur during long-term adaptation to the CF airway.
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Affiliation(s)
- Robert K Ernst
- Department of Medicine, University of Washington, HSB T-293, Box 357710, 1959 Pacific Street N.E., Seattle, WA 98195, USA.
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282
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Abstract
Signal transduction pathways provide mechanisms for adaptation to stress conditions. One of the most studied of these pathways is the HOG1 MAP kinase pathway that in Saccharomyces cerevisiae is used to adapt cells to osmostress. The HOG1 MAPK has also been studied in Candida albicans, and more recently observations on the Hog1p functions have been described in two other human pathogens, Aspergillus fumigatus and Cryptococcus neoformans. The important, but not surprising, concept is that this pathway is used for different yet similar functions in each of these fungi, given their need to adapt to different environmental signals. Current studies of C. albicans focus upon the identification of two-component signal proteins that, in both C. albicans and S. cerevisiae, regulate the HOG1 MAPK. In C. albicans, these proteins regulate cell wall biosynthesis (and, therefore, adherence to host cells), osmotic and oxidant adaptation, white-opaque switching, morphogenesis, and virulence of the organism.
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Affiliation(s)
- Michael Kruppa
- Department of Microbiology & Immunology, Georgetown University Medical Center, Washington DC 20057, USA
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283
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Nuding S, Fellermann K, Wehkamp J, Mueller HAG, Stange EF. A flow cytometric assay to monitor antimicrobial activity of defensins and cationic tissue extracts. J Microbiol Methods 2005; 65:335-45. [PMID: 16182394 DOI: 10.1016/j.mimet.2005.08.004] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2005] [Revised: 08/09/2005] [Accepted: 08/16/2005] [Indexed: 10/25/2022]
Abstract
To determine the antibacterial activity of defensins and other antimicrobial peptides in biopsy extracts, we evaluated a flow cytometric method with the membrane potential sensitive dye bis-(1,3-dibutylbarbituric acid) trimethine oxonol [DiBAC4(3)]. This assay enables us to discriminate intact non-fluorescent and depolarized fluorescent bacteria after exposure to antimicrobial peptides by measurement at the direct target, the cytoplasmic membrane and the membrane potential. The feasibility of the flow cytometric assay was evaluated with recombinant human beta-defensin 3 (HBD-3) against 25 bacterial strains representing 12 species. HBD-3 showed a broad-spectrum dose dependent activity and the minimal dose to cause depolarization ranged from 1.25 to >15 microg/ml HBD-3, depending on the species tested. The antibacterial effect was diminished with sodium chloride or dithiothreitol and could be abrogated with a HBD-3 antibody. Additionally, isolated cationic extracts from human intestinal biopsies showed a strong bactericidal effect against Escherichia coli K12, E. coli ATCC 25922 and Staphylococcus aureus ATCC 25923, which was diminished towards E. coli at 150 mM NaCl, whereas the activity towards S. aureus ATCC 25923 remained unaffected at physiological salt concentrations. DTT blocked the bactericidal effect of biopsy extracts completely.
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Affiliation(s)
- Sabine Nuding
- Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology, Robert Bosch Hospital, Auerbachstr. 110, 73061 Stuttgart, Germany.
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284
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Tzeng YL, Ambrose KD, Zughaier S, Zhou X, Miller YK, Shafer WM, Stephens DS. Cationic antimicrobial peptide resistance in Neisseria meningitidis. J Bacteriol 2005; 187:5387-96. [PMID: 16030233 PMCID: PMC1196002 DOI: 10.1128/jb.187.15.5387-5396.2005] [Citation(s) in RCA: 175] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2005] [Accepted: 05/04/2005] [Indexed: 11/20/2022] Open
Abstract
Cationic antimicrobial peptides (CAMPs) are important components of the innate host defense system against microbial infections and microbial products. However, the human pathogen Neisseria meningitidis is intrinsically highly resistant to CAMPs, such as polymyxin B (PxB) (MIC > or = 512 microg/ml). To ascertain the mechanisms by which meningococci resist PxB, mutants that displayed increased sensitivity (> or =4-fold) to PxB were identified from a library of mariner transposon mutants generated in a meningococcal strain, NMB. Surprisingly, more than half of the initial PxB-sensitive mutants had insertions within the mtrCDE operon, which encodes proteins forming a multidrug efflux pump. Additional PxB-sensitive mariner mutants were identified from a second round of transposon mutagenesis performed in an mtr efflux pump-deficient background. Further, a mutation in lptA, the phosphoethanolamine (PEA) transferase responsible for modification of the lipid A head groups, was identified to cause the highest sensitivity to PxB. Mutations within the mtrD or lptA genes also increased meningococcal susceptibility to two structurally unrelated CAMPs, human LL-37 and protegrin-1. Consistently, PxB neutralized inflammatory responses elicited by the lptA mutant lipooligosaccharide more efficiently than those induced by wild-type lipooligosaccharide. mariner mutants with increased resistance to PxB were also identified in NMB background and found to contain insertions within the pilMNOPQ operon involved in pilin biogenesis. Taken together, these data indicated that meningococci utilize multiple mechanisms including the action of the MtrC-MtrD-MtrE efflux pump and lipid A modification as well as the type IV pilin secretion system to modulate levels of CAMP resistance. The modification of meningococcal lipid A head groups with PEA also prevents neutralization of the biological effects of endotoxin by CAMP.
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Affiliation(s)
- Yih-Ling Tzeng
- Department of Veterans Affairs Medical Center, Research 151, Room 5A188, 1670 Clairmont Road, Decatur, GA 30033, USA
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285
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Stead C, Tran A, Ferguson D, McGrath S, Cotter R, Trent S. A novel 3-deoxy-D-manno-octulosonic acid (Kdo) hydrolase that removes the outer Kdo sugar of Helicobacter pylori lipopolysaccharide. J Bacteriol 2005; 187:3374-83. [PMID: 15866922 PMCID: PMC1111988 DOI: 10.1128/jb.187.10.3374-3383.2005] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The lipid A domain anchors lipopolysaccharide (LPS) to the outer membrane and is typically a disaccharide of glucosamine that is both acylated and phosphorylated. The core and O-antigen carbohydrate domains are linked to the lipid A moiety through the eight-carbon sugar 3-deoxy-D-manno-octulosonic acid known as Kdo. Helicobacter pylori LPS has been characterized as having a single Kdo residue attached to lipid A, predicting in vivo a monofunctional Kdo transferase (WaaA). However, using an in vitro assay system we demonstrate that H. pylori WaaA is a bifunctional enzyme transferring two Kdo sugars to the tetra-acylated lipid A precursor lipid IV(A). In the present work we report the discovery of a Kdo hydrolase in membranes of H. pylori capable of removing the outer Kdo sugar from Kdo2-lipid A. Enzymatic removal of the Kdo group was dependent upon prior removal of the 1-phosphate group from the lipid A domain, and mass spectrometric analysis of the reaction product confirmed the enzymatic removal of a single Kdo residue by the Kdo-trimming enzyme. This is the first characterization of a Kdo hydrolase involved in the modification of gram-negative bacterial LPS.
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Affiliation(s)
- Christopher Stead
- Department of Microbiology, J. H. Quillen College of Medicine, Johnson City, Tennessee 37614, USA
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286
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Lewenza S, Falsafi RK, Winsor G, Gooderham WJ, McPhee JB, Brinkman FSL, Hancock REW. Construction of a mini-Tn5-luxCDABE mutant library in Pseudomonas aeruginosa PAO1: a tool for identifying differentially regulated genes. Genome Res 2005; 15:583-9. [PMID: 15805499 PMCID: PMC1074373 DOI: 10.1101/gr.3513905] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Pseudomonas aeruginosa is a major cause of nosocomial (hospital-derived) infections, is the predominant pathogen in chronic cystic fibrosis lung infections, and remains difficult to treat due to its high intrinsic antibiotic resistance. The completion of the P. aeruginosa PAO1 genome sequence provides the opportunity for genome-wide studies to increase our understanding of the pathogenesis and biology of this important pathogen. In this report, we describe the construction of a mini-Tn5-luxCDABE mutant library and a high-throughput inverse PCR method to amplify DNA flanking the site of insertion for sequencing and insertion site mapping. In addition to producing polar knockout mutations in nonessential genes, the promoterless luxCDABE reporter present in the transposon serves as a real-time reporter of gene expression for the inactivated gene. A total of 2519 transposon insertion sites were mapped, 77% of which were nonredundant insertions. Of the insertions within an ORF, -55% of total and unique insertion sites were transcriptional luxCDABE fusions. A bias toward low insertion-site density in the genome region that surrounds the predicted terminus of replication was observed. To demonstrate the utility of chromosomal lux fusions, we performed extensive regulatory screens to identify genes that were differentially regulated under magnesium or phosphate limitation. This approach led to the discovery of many known and novel genes necessary for these environmental adaptations, including genes involved in resistance to cationic antimicrobial peptides. This dual-purpose mutant library allows for functional and regulation studies and will serve as a resource for the research community to further our understanding of P. aeruginosa biology.
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Affiliation(s)
- Shawn Lewenza
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
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287
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Affiliation(s)
- Keith Poole
- Department of Microbiology & Immunology, Rm. 737 Botterell Hall, Queen's University, Kingston, ON K7L 3N6, Canada.
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288
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Winfield MD, Latifi T, Groisman EA. Transcriptional regulation of the 4-amino-4-deoxy-L-arabinose biosynthetic genes in Yersinia pestis. J Biol Chem 2005; 280:14765-72. [PMID: 15710615 DOI: 10.1074/jbc.m413900200] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Inducible membrane remodeling is an adaptive mechanism that enables Gram-negative bacteria to resist killing by cationic antimicrobial peptides and to avoid eliciting an immune response. Addition of 4-amino-4-deoxy-l -arabinose (4-aminoarabinose) moieties to the phosphate residues of the lipid A portion of the lipopolysaccharide decreases the net negative charge of the bacterial membrane resulting in protection from the cationic antimicrobial peptide polymyxin B. In Salmonella enterica serovar Typhimurium, the PmrA/PmrB two-component regulatory system governs resistance to polymyxin B by controlling transcription of the 4-aminoarabinose biosynthetic genes. Transcription of PmrA-activated genes is induced by Fe(3+), which is sensed by PmrA cognate sensor PmrB, and by low Mg(2+), in a mechanism that requires not only the PmrA and PmrB proteins but also the Mg(2+)-responding PhoP/PhoQ system and the PhoP-activated PmrD protein, a post-translational activator of the PmrA protein. Surprisingly, Yersinia pestis can promote PhoP-dependent modification of its lipid A with 4-aminoarabinose despite lacking a PmrD protein. Here we report that Yersinia uses different promoters to transcribe the 4-aminoarabinose biosynthetic genes pbgP and ugd depending on the inducing signal. This is accomplished by the presence of distinct binding sites for the PmrA and PhoP proteins in the promoters of the pbgP and ugd genes. Our results demonstrate that closely related bacterial species may use disparate regulatory pathways to control genes encoding conserved proteins.
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Affiliation(s)
- Mollie D Winfield
- Department of Molecular Microbiology, Howard Hughes Medical Institute, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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289
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Abstract
Toll-like receptors (TLRs) are key components of effective innate immunity. As such, pathogenic microorganisms must evade recognition by TLRs, manipulate the consequences of TLR activation, or contend with the inflammatory consequences of TLR activation. Recent studies have improved our understanding of the various mechanisms by which pathogenic organisms manipulate the TLR recognition system.
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Affiliation(s)
- David M Underhill
- Institute for Systems Biology, 1441 N. 34th St, Seattle, Washington 98103, USA.
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290
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Lee H, Hsu FF, Turk J, Groisman EA. The PmrA-regulated pmrC gene mediates phosphoethanolamine modification of lipid A and polymyxin resistance in Salmonella enterica. J Bacteriol 2004; 186:4124-33. [PMID: 15205413 PMCID: PMC421605 DOI: 10.1128/jb.186.13.4124-4133.2004] [Citation(s) in RCA: 252] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The PmrA/PmrB regulatory system of Salmonella enterica controls the modification of lipid A with aminoarabinose and phosphoethanolamine. The aminoarabinose modification is required for resistance to the antibiotic polymyxin B, as mutations of the PmrA-activated pbg operon or ugd gene result in strains that lack aminoarabinose in their lipid A molecules and are more susceptible to polymyxin B. Additional PmrA-regulated genes appear to participate in polymyxin B resistance, as pbgP and ugd mutants are not as sensitive to polymyxin B as a pmrA mutant. Moreover, the role that the phosphoethanolamine modification of lipid A plays in the resistance to polymyxin B has remained unknown. Here we address both of these questions by establishing that the PmrA-activated pmrC gene encodes an inner membrane protein that is required for the incorporation of phosphoethanolamine into lipid A and for polymyxin B resistance. The PmrC protein consists of an N-terminal region with five transmembrane domains followed by a large periplasmic region harboring the putative enzymatic domain. A pbgP pmrC double mutant resembled a pmrA mutant both in its lipid A profile and in its susceptibility to polymyxin B, indicating that the PmrA-dependent modification of lipid A with aminoarabinose and phosphoethanolamine is responsible for PmrA-regulated polymyxin B resistance.
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Affiliation(s)
- Hyunwoo Lee
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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291
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Tzeng YL, Datta A, Ambrose K, Lo M, Davies JK, Carlson RW, Stephens DS, Kahler CM. The MisR/MisS two-component regulatory system influences inner core structure and immunotype of lipooligosaccharide in Neisseria meningitidis. J Biol Chem 2004; 279:35053-62. [PMID: 15173178 DOI: 10.1074/jbc.m401433200] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Lipooligosaccharide (LOS) of Neisseria meningitidis is the major inflammatory mediator that contributes to meningococcal pathogenesis. Variable attachments to the HepII residue of the LOS inner core together with the alpha-chain heterogeneity result in immunologically distinct LOS structures, which may be selected for during human infection. Lpt-3, a phosphoethanolamine (PEA) transferase, and LgtG, a glucosyltransferase, mediate the substitution of PEA or glucose at the O-3 position of HepII in L3 or L2 LOS immunotypes, respectively. Inactivation of a two-component response regulator, encoded by NMB0595, in N. meningitidis strain NMB resulted in the loss of all PEA decorations on the LOS inner core expressed by the NMB0595 mutant. When compared with the parental strain NMB that predominantly expresses L2 immunotype LOS and other minor LOS structures, the NMB0595 mutant expresses a pure population of a novel LOS structure completely substituted at the HepII O-3 position with glucose, but lacking other PEA decorations on the inner core. Quantitative real time PCR experiments showed increased transcription of lgtG in the NMB0595 mutant, and no significant change in lpt-3 transcription. Inactivation of lgtG resulted in LOS inner cores without glucose, but these structures, even though the lpt-3 transcription was unaffected, also lacked the O-3-linked PEA. Consistently, a double mutation of lgtG and misR in strain NMB yielded a LOS structure without PEA or Glc substitution of HepII. These data indicated a new pathway for the regulation of LOS inner core structure in N. meningitidis through an environmental sensing two-component regulatory system, named misR(NMB0595)/misS(NMB0594) for regulator and sensor of the meningococcal inner core structure.
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Affiliation(s)
- Yih-Ling Tzeng
- Department of Medicine, Emory University School of Medicine, 1639 Pierce Drive, Atlanta, GA 30322, USA.
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