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Li R, Zhu X, Zhang P, Wu X, Jin Q, Pan J. Ser/Thr protein kinase Stk1 phosphorylates the key transcriptional regulator AlgR to modulate virulence and resistance in Pseudomonas aeruginosa. Virulence 2024; 15:2367649. [PMID: 38898809 PMCID: PMC11197903 DOI: 10.1080/21505594.2024.2367649] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Accepted: 06/09/2024] [Indexed: 06/21/2024] Open
Abstract
Pseudomonas aeruginosa is one of the leading causes of nosocomial infections worldwide and has emerged as a serious public health threat, due in large part to its multiple virulence factors and remarkable resistance capabilities. Stk1, a eukaryotic-type Ser/Thr protein kinase, has been shown in our previous work to be involved in the regulation of several signalling pathways and biological processes. Here, we demonstrate that deletion of stk1 leads to alterations in several virulence- and resistance-related physiological functions, including reduced pyocyanin and pyoverdine production, attenuated twitching motility, and enhanced biofilm production, extracellular polysaccharide secretion, and antibiotic resistance. Moreover, we identified AlgR, an important transcriptional regulator, as a substrate for Stk1, with its phosphorylation at the Ser143 site catalysed by Stk1. Intriguingly, both the deletion of stk1 and the mutation of Ser143 of AlgR to Ala result in similar changes in the above-mentioned physiological functions. Furthermore, assays of algR expression in these strains suggest that changes in the phosphorylation state of AlgR, rather than its expression level, underlie changes in these physiological functions. These findings uncover Stk1-mediated phosphorylation of AlgR as an important mechanism for regulating virulence and resistance in P. aeruginosa.
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Affiliation(s)
- Rui Li
- Zhejiang Provincial Key Laboratory of Silkworm Bioreactor and Biomedicine, College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Hangzhou, China
| | - Xuan Zhu
- Zhejiang Provincial Key Laboratory of Silkworm Bioreactor and Biomedicine, College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Hangzhou, China
| | - Pengfei Zhang
- Zhejiang Provincial Key Laboratory of Silkworm Bioreactor and Biomedicine, College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Hangzhou, China
| | - Xuan Wu
- Zhejiang Provincial Key Laboratory of Silkworm Bioreactor and Biomedicine, College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Hangzhou, China
| | - Qian Jin
- Zhejiang Provincial Key Laboratory of Silkworm Bioreactor and Biomedicine, College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Hangzhou, China
| | - Jianyi Pan
- Zhejiang Provincial Key Laboratory of Silkworm Bioreactor and Biomedicine, College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Hangzhou, China
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2
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Zhu J, Zhao H, Yang Z. Genetic Analysis of the ts-Lethal Mutant Δpa0665/ pTS-pa0665 Reveals Its Role in Cell Morphology and Oxidative Phosphorylation in Pseudomonas aeruginosa. Genes (Basel) 2024; 15:590. [PMID: 38790219 PMCID: PMC11120684 DOI: 10.3390/genes15050590] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2024] [Revised: 05/01/2024] [Accepted: 05/03/2024] [Indexed: 05/26/2024] Open
Abstract
Pa0665 in Pseudomonas aeruginosa shares homologous sequences with that of the essential A-type iron-sulfur (Fe-S) cluster insertion protein ErpA in Escherichia coli. However, its essentiality in P. aeruginosa and its complementation with E. coli erpA has not been experimentally examined. To fulfill this task, we constructed plasmid-based ts-mutant Δpa0665/pTS-pa0665 using a three-step protocol. The mutant displayed growth defects at 42 °C, which were complemented by expressing ec.erpA. Microscopic observations indicated a petite cell phenotype for Δpa0665/pTS-pa0665 at 42 °C, correlated with the downregulation of the oprG gene. RNA sequencing revealed significant transcriptional changes in genes associated with the oxidative phosphorylation (OXPHOS) system, aligning with reduced ATP levels in Δpa0665/pTS-pa0665 under 42 °C. Additionally, the ts-mutant showed heightened sensitivity to H2O2 at 42 °C. Overall, our study demonstrates the essential role of pa0665 for OXPHOS function and is complemented by ec.erpA. We propose that the plasmid-based ts-allele is useful for genetic analysis of essential genes of interest in P. aeruginosa.
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Affiliation(s)
| | | | - Zhili Yang
- Systems Biology, School for Marine Science and Technology, Zhejiang Ocean University, Zhoushan 316022, China; (J.Z.); (H.Z.)
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3
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Sultan M, Arya R, Chaurasia AK, Kim KK. Sensor histidine kinases kdpD and aauS regulate biofilm and virulence in Pseudomonas aeruginosa PA14. Front Cell Infect Microbiol 2023; 13:1270667. [PMID: 37881370 PMCID: PMC10595159 DOI: 10.3389/fcimb.2023.1270667] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Accepted: 09/25/2023] [Indexed: 10/27/2023] Open
Abstract
Pseudomonas aeruginosa is a multidrug-resistant opportunistic human pathogen that utilizes two-component systems (TCSs) to sense pathophysiological signals and coordinate virulence. P. aeruginosa contains 64 sensor histidine kinases (HKs) and 72 response regulators (RRs) that play important roles in metabolism, bacterial physiology, and virulence. However, the role of some TCSs in virulence remains uncharacterized. In this study, we evaluated the virulence potential of some uncharacterized sensor HK and RR knockouts in P. aeruginosa using a Galleria mellonella infection model. Furthermore, we demonstrated that KdpD and AauS HKs regulate virulence by affecting P. aeruginosa biofilm formation and motility. Both ΔkdpD and ΔaauS showed reduced biofilm and motility which were confirmed by restored phenotypes upon complementation. Moreover, ΔkdpD and ΔaauS exhibited increased survival of HeLa cells and G. mellonella during in vivo infection. Altered expression of the transcriptional regulators anR and lasR, along with the virulence genes lasA, pelA, cupA, pqsA, pqsB, pqsC, and pqsD in the mutant strains elucidated the mechanism by which ΔkdpD and ΔaauS affect virulence. These findings confirm that kdpD and aauS play important roles in P. aeruginosa pathogenesis by regulating biofilm formation and motility.
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Affiliation(s)
- Maria Sultan
- Department of Precision Medicine, Graduate School of Basic Medical Science, Institute for Antimicrobial Resistance Research and Therapeutics, Sungkyunkwan University School of Medicine, Suwon, Republic of Korea
| | - Rekha Arya
- Department of Precision Medicine, Graduate School of Basic Medical Science, Institute for Antimicrobial Resistance Research and Therapeutics, Sungkyunkwan University School of Medicine, Suwon, Republic of Korea
- Department of Orthopedic Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
| | - Akhilesh Kumar Chaurasia
- Department of Precision Medicine, Graduate School of Basic Medical Science, Institute for Antimicrobial Resistance Research and Therapeutics, Sungkyunkwan University School of Medicine, Suwon, Republic of Korea
| | - Kyeong Kyu Kim
- Department of Precision Medicine, Graduate School of Basic Medical Science, Institute for Antimicrobial Resistance Research and Therapeutics, Sungkyunkwan University School of Medicine, Suwon, Republic of Korea
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4
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Coppola D, Buonocore C, Palisse M, Tedesco P, de Pascale D. Exploring Oceans for Curative Compounds: Potential New Antimicrobial and Anti-Virulence Molecules against Pseudomonas aeruginosa. Mar Drugs 2022; 21:md21010009. [PMID: 36662182 PMCID: PMC9865402 DOI: 10.3390/md21010009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Revised: 12/16/2022] [Accepted: 12/20/2022] [Indexed: 12/28/2022] Open
Abstract
Although several antibiotics are already widely used against a large number of pathogens, the discovery of new antimicrobial compounds with new mechanisms of action is critical today in order to overcome the spreading of antimicrobial resistance among pathogen bacteria. In this regard, marine organisms represent a potential source of a wide diversity of unique secondary metabolites produced as an adaptation strategy to survive in competitive and hostile environments. Among the multidrug-resistant Gram-negative bacteria, Pseudomonas aeruginosa is undoubtedly one of the most important species due to its high intrinsic resistance to different classes of antibiotics on the market and its ability to cause serious therapeutic problems. In the present review, we first discuss the general mechanisms involved in the antibiotic resistance of P. aeruginosa. Subsequently, we list the marine molecules identified up until now showing activity against P. aeruginosa, dividing them according to whether they act as antimicrobial or anti-virulence compounds.
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Affiliation(s)
- Daniela Coppola
- Department of Ecosustainable Marine Biotechnology, Stazione Zoologica Anton Dohrn, Via Ammiraglio Ferdinando Acton 55, 80133 Naples, Italy
- Correspondence: (D.C.); (D.d.P.)
| | - Carmine Buonocore
- Department of Ecosustainable Marine Biotechnology, Stazione Zoologica Anton Dohrn, Via Ammiraglio Ferdinando Acton 55, 80133 Naples, Italy
| | - Morgan Palisse
- Département des Sciences de la Vie et de la Terre, Université de Caen Normandie, Boulevard Maréchal Juin CS, CEDEX, 14032 Caen, France
| | - Pietro Tedesco
- Department of Ecosustainable Marine Biotechnology, Stazione Zoologica Anton Dohrn, Via Ammiraglio Ferdinando Acton 55, 80133 Naples, Italy
| | - Donatella de Pascale
- Department of Ecosustainable Marine Biotechnology, Stazione Zoologica Anton Dohrn, Via Ammiraglio Ferdinando Acton 55, 80133 Naples, Italy
- Correspondence: (D.C.); (D.d.P.)
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5
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Distinct Long- and Short-Term Adaptive Mechanisms in Pseudomonas aeruginosa. Microbiol Spectr 2022; 10:e0304322. [PMID: 36374016 PMCID: PMC9769816 DOI: 10.1128/spectrum.03043-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Heterogeneous environments such as the chronically infected cystic fibrosis lung drive the diversification of Pseudomonas aeruginosa populations into, e.g., mucoid, alginate-overproducing isolates or small-colony variants (SCVs). In this study, we performed extensive genome and transcriptome profiling on a clinical SCV isolate that exhibited high cyclic diguanylate (c-di-GMP) levels and a mucoid phenotype. We observed a delayed, stepwise decrease of the high levels of c-di-GMP as well as alginate gene expression upon passaging the SCV under noninducing, rich medium growth conditions over 7 days. Upon prolonged passaging, this lagging reduction of the high c-di-GMP levels under noninducing planktonic conditions (reminiscent of a hysteretic response) was followed by a phenotypic switch to a large-colony morphology, which could be linked to mutations in the Gac/Rsm signaling pathway. Complementation of the Gac/Rsm signaling-negative large-colony variants with a functional GacSA system restored the SCV colony morphotype but was not able to restore the high c-di-GMP levels of the SCV. Our data thus suggest that expression of the SCV colony morphotype and modulation of c-di-GMP levels are genetically separable and follow different evolutionary paths. The delayed switching of c-di-GMP levels in response to fluctuating environmental conditions might provide a unique opportunity to include a time dimension to close the gap between short-term phenotypic and long-term genetic adaptation to biofilm-associated growth conditions. IMPORTANCE Extreme environments, such as those encountered during an infection process in the human host, make effective bacterial adaptation inevitable. While bacteria adapt individually by activating stress responses, long-term adaptation of bacterial communities to challenging conditions can be achieved via genetic fixation of favorable traits. In this study, we describe a two-pronged bacterial stress resistance strategy in the opportunistic pathogen Pseudomonas aeruginosa. We show that the production of adjusted elevated c-di-GMP levels, which drive protected biofilm-associated phenotypes in vivo, resembles a stable hysteretic response which prevents unwanted frequent switching. Cellular hysteresis might provide a link between individual adaptability and evolutionary adaptation to ensure the evolutionary persistence of host-adapted stress response strategies.
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Hedayati Ch M, Mehmandoost Du E, Golshekan M, Mojtahedi A, Mobayen M. Synthesis of MCM‐41@SO
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H‐Polymixin B Nanocomposite for Extraction and Determination of Lipopolysaccharide from Aqueous Solutions using Taguchi Fractional Factorial Design. ChemistrySelect 2022. [DOI: 10.1002/slct.202203401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Affiliation(s)
- Mojtaba Hedayati Ch
- Virology and Microbial Toxins Department School of Medicine Guilan University of Medical Sciences Rasht Iran 4199613769
| | - Edris Mehmandoost Du
- Virology and Microbial Toxins Department School of Medicine Guilan University of Medical Sciences Rasht Iran 4199613769
| | - Mostafa Golshekan
- Guilan Road Trauma Research Center Guilan University of Medical Sciences Rasht Iran 4193713194
| | - Ali Mojtahedi
- Virology and Microbial Toxins Department School of Medicine Guilan University of Medical Sciences Rasht Iran 4199613769
| | - Mohammadreza Mobayen
- Burn and Regenerative Medicine Research Center Guilan University of Medical Sciences Rasht Iran 4193713194
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Adhikari BR, Sinha S, Gordon KC, Das SC. Amino Acids Improve Aerosolization and Chemical Stability of Potential Inhalable Amorphous Spray-dried Ceftazidime for Pseudomonas aeruginosa Lung Infection. Int J Pharm 2022; 621:121799. [PMID: 35525472 DOI: 10.1016/j.ijpharm.2022.121799] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Revised: 04/26/2022] [Accepted: 04/30/2022] [Indexed: 11/30/2022]
Abstract
Pseudomonas aeruginosa infection is common in cystic fibrosis as well non-cystic fibrosis bronchiectasis. The pathogen presents challenges for treatment due to its adaptive antibiotic-resistance, mainly pertaining to its biofilm-forming ability, as well as limitations associated with conventional drug delivery in achieving desired therapeutic concentration in the infection site. Hence, therapeutic approach has shifted towards the inhalation of antibiotics. Ceftazidime is a potent antibiotic against the pathogen; however, it is currently only available as a parenteral formulation. Here, spray-dryer was employed to generate inhalable high dose ceftazidime microparticles. In addition, the use of amino acids (valine, leucine, methionine, phenylalanine, and tryptophan) to improve aerosolization as well as chemical stability of amorphous ceftazidime was explored. The particles were characterized using X ray diffraction, infrared (IR) spectroscopy, calorimetry, electron microscopy, particle size analyzer, and next generation impactor. The chemical stability at 25 °C/<15% was assessed using chromatography. All co-spray dried formulations were confirmed as monophasic amorphous systems using calorimetry. In addition, principal component analysis of the IR spectra suggested potential interaction between tryptophan and ceftazidime in the co-amorphous matrix. Inclusion of amino acids improved aerosolization and chemical stability in all cases. Increase in surface asperity was clear with the use of amino acids which likely contributed to the improved aerosol performance, and potential interaction between amino acids and ceftazidime was plausibly the reason for improved chemical stability. Leucine offered the best aerosolization enhancement with a fine particle fraction of 78% and tryptophan showed stabilizing superiority by reducing chemical degradation by 51% over 10 weeks in 1:1 molar ratio. The protection against ceftazidime degradation varied with the nature of amino acids. Additionally, there was a linear relationship between degradation protection and molar mass of amino acids or percentage weight of amino acids in the formulations. None of the amino acids were successful in completely inhibiting degradation of ceftazidime in amorphous spray-dried powder to prepare a commercially viable product with desired shelf-life. All the amino acids and ceftazidime were non-toxic to A549 alveolar cell line.
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Affiliation(s)
| | - Shubhra Sinha
- School of Pharmacy, University of Otago, Dunedin 9054, New Zealand
| | - Keith C Gordon
- The Dodd-Walls Centre for Photonic and Quantum Technologies, Department of Chemistry, University of Otago, Dunedin 9016, New Zealand
| | - Shyamal C Das
- School of Pharmacy, University of Otago, Dunedin 9054, New Zealand.
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8
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Enespa, Chandra P, Singh DP. Sources, purification, immobilization and industrial applications of microbial lipases: An overview. Crit Rev Food Sci Nutr 2022; 63:6653-6686. [PMID: 35179093 DOI: 10.1080/10408398.2022.2038076] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Microbial lipase is looking for better attention with the fast growth of enzyme proficiency and other benefits like easy, cost-effective, and reliable manufacturing. Immobilized enzymes can be used repetitively and are incapable to catalyze the reactions in the system continuously. Hydrophobic supports are utilized to immobilize enzymes when the ionic strength is low. This approach allows for the immobilization, purification, stability, and hyperactivation of lipases in a single step. The diffusion of the substrate is more advantageous on hydrophobic supports than on hydrophilic supports in the carrier. These approaches are critical to the immobilization performance of the enzyme. For enzyme immobilization, synthesis provides a higher pH value as well as greater heat stability. Using a mixture of immobilization methods, the binding force between enzymes and the support rises, reducing enzyme leakage. Lipase adsorption produces interfacial activation when it is immobilized on hydrophobic support. As a result, in the immobilization process, this procedure is primarily used for a variety of industrial applications. Microbial sources, immobilization techniques, and industrial applications in the fields of food, flavor, detergent, paper and pulp, pharmaceuticals, biodiesel, derivatives of esters and amino groups, agrochemicals, biosensor applications, cosmetics, perfumery, and bioremediation are all discussed in this review.
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Affiliation(s)
- Enespa
- School for Agriculture, Sri Mahesh Prasad Post Graduate College, University of Lucknow, Lucknow, Uttar Pradesh, India
| | - Prem Chandra
- Food Microbiology & Toxicology Laboratory, Department of Microbiology, School for Environmental Sciences, Babasaheb Bhimrao Ambedkar University (A Central) University, Lucknow, Uttar Pradesh, India
| | - Devendra Pratap Singh
- Department of Environmental Science, School for Environmental Sciences, Babasaheb Bhimrao Ambedkar University (A Central) University, Lucknow, Uttar Pradesh, India
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9
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Stone JR. Diseases of small and medium-sized blood vessels. Cardiovasc Pathol 2022. [DOI: 10.1016/b978-0-12-822224-9.00020-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/17/2022] Open
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Denman S, Tellam R, Vuocolo T, Ingham A, Wijffels G, James P, Colditz I. Fleece rot and dermatophilosis (lumpy wool) in sheep: opportunities and challenges for new vaccines. ANIMAL PRODUCTION SCIENCE 2021. [DOI: 10.1071/an21120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
During prolonged wetting of the fleece, proliferation of bacterial flora often dominated by Pseudomonas aeruginosa or Dermatophilus congolensis can induce dermatitis and fleece damage termed fleece rot and dermatophilosis respectively, which predispose sheep to blowfly strike. A large research effort in the 1980s and 1990s on vaccines to control fleece rot and dermatophilosis met with limited success. This review examines theoretical and technological advances in microbial ecology, pathogenesis, immunology, vaccine development and the characterisation of microbial virulence factors that create new opportunities for development of vaccines against these diseases. Genomic technologies have now created new opportunities for examining microbial dynamics and pathogen virulence in dermatitis. An effective vaccine requires the combination of appropriate antigens with an adjuvant that elicits a protective immune response that ideally provides long-lasting protection in the field. A clinical goal informed by epidemiological, economic and animal welfare values is needed as a measure of vaccine efficacy. Due to dependence of fleece rot and dermatophilosis on sporadic wet conditions for their expression, vaccine development would be expedited by in vitro correlates of immune protection. The efficacy of vaccines is influenced by genetic and phenotypic characteristics of the animal. Advances in understanding vaccine responsiveness, immune defence in skin and immune competence in sheep should also inform any renewed efforts to develop new fleece rot and dermatophilosis vaccines. The commercial imperatives for new vaccines are likely to continue to increase as the animal welfare expectations of society intensify and reliance on pharmacotherapeutics decrease due to chemical resistance, market pressures and societal influences. Vaccines should be considered part of an integrated disease control strategy, in combination with genetic selection for general immune competence and resistance to specific diseases, as well as management practices that minimise stress and opportunities for disease transmission. The strategy could help preserve the efficacy of pharmacotherapeutics as tactical interventions to alleviate compromised welfare when adverse environmental conditions lead to a break down in integrated strategic disease control. P. aeruginosa and D. congolensis are formidable pathogens and development of effective vaccines remains a substantial challenge.
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Sultan M, Arya R, Kim KK. Roles of Two-Component Systems in Pseudomonas aeruginosa Virulence. Int J Mol Sci 2021; 22:12152. [PMID: 34830033 PMCID: PMC8623646 DOI: 10.3390/ijms222212152] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Revised: 11/01/2021] [Accepted: 11/02/2021] [Indexed: 12/28/2022] Open
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen that synthesizes and secretes a wide range of virulence factors. P. aeruginosa poses a potential threat to human health worldwide due to its omnipresent nature, robust host accumulation, high virulence, and significant resistance to multiple antibiotics. The pathogenicity of P. aeruginosa, which is associated with acute and chronic infections, is linked with multiple virulence factors and associated secretion systems, such as the ability to form and utilize a biofilm, pili, flagella, alginate, pyocyanin, proteases, and toxins. Two-component systems (TCSs) of P. aeruginosa perform an essential role in controlling virulence factors in response to internal and external stimuli. Therefore, understanding the mechanism of TCSs to perceive and respond to signals from the environment and control the production of virulence factors during infection is essential to understanding the diseases caused by P. aeruginosa infection and further develop new antibiotics to treat this pathogen. This review discusses the important virulence factors of P. aeruginosa and the understanding of their regulation through TCSs by focusing on biofilm, motility, pyocyanin, and cytotoxins.
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Affiliation(s)
| | - Rekha Arya
- Department of Precision Medicine, Graduate School of Basic Medical Science (GSBMS), Institute for Antimicrobial Resistance Research and Therapeutics, Sungkyunkwan University School of Medicine, Suwon 16419, Korea;
| | - Kyeong Kyu Kim
- Department of Precision Medicine, Graduate School of Basic Medical Science (GSBMS), Institute for Antimicrobial Resistance Research and Therapeutics, Sungkyunkwan University School of Medicine, Suwon 16419, Korea;
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12
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A pilot metagenomic study reveals that community derived mobile phones are reservoirs of viable pathogenic microbes. Sci Rep 2021; 11:14102. [PMID: 34239006 PMCID: PMC8266881 DOI: 10.1038/s41598-021-93622-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Accepted: 06/28/2021] [Indexed: 11/28/2022] Open
Abstract
There is increasing attention focussed on the risks associated with mobile phones possibly serving as ‘Trojan Horse’ fomites for microbial transmission in healthcare settings. However, little is reported on the presence of microbes on community derived mobile phones which in 2021, numbered in the billions in circulation with majority being used on a daily basis. Identify viable microbial organisms swabbed from smartphones on a university campus. Entire surfaces of 5 mobile phones were swabbed and examined for their microbial content using pre-agar-based growths followed by downstream DNA metagenomic next-generation sequencing analysis. All phones were contaminated with viable microbes. 173 bacteria, 8 fungi, 8 protists, 53 bacteriophages, 317 virulence factor genes and 41 distinct antibiotic resistant genes were identified. While this research represents a pilot study, the snapshot metagenomic analysis of samples collected from the surface of mobile phones has revealed the presence of a large population of viable microbes and an array of antimicrobial resistant factors. With billions of phones in circulation, these devices might be responsible for the rise of community acquired infections. These pilot results highlight the importance of public health authorities considering mobile phones as ‘Trojan Horse’ devices for microbial transmission and ensure appropriate decontamination campaigns are implemented.
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Gupte A, Jyot J, Ravi M, Ramphal R. High pyocyanin production and non-motility of Pseudomonas aeruginosa isolates are correlated with septic shock or death in bacteremic patients. PLoS One 2021; 16:e0253259. [PMID: 34115807 PMCID: PMC8195364 DOI: 10.1371/journal.pone.0253259] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Accepted: 06/01/2021] [Indexed: 12/26/2022] Open
Abstract
Studies of the outcome of Pseudomonas aeruginosa bacteremia (Pab) have focused mainly on antibiotic appropriateness. However, P. aeruginosa possesses many virulence factors whose roles in outcomes have not been examined in humans, except for the type III secretion system (T3SS) toxins. The purpose of this study was to examine the role of virulence factors other than the T3SS toxins. Bacterial isolates were collected from 75 patients who suffered from Pa blood stream infections. Host factors such as neutropenia, immunosuppression, comorbidities, time to effective antibiotics, source of bacteremia, and presence of multidrug resistant (MDR) isolate were studied. The isolates were analyzed for the presence of toxin genes, proteolytic activity, swimming and twitching motility, and pyocyanin production. The data were analyzed to ascertain which virulence factors correlated with poor outcomes defined as septic shock or death (SS) within 7 days. Septic shock or death occurred in 25/75 patients. Univariate analysis identified age as a host factor that exerted a significant effect on these outcomes. Ineffective antibiotics administered during the first 24 hours of treatment or MDR P. aeruginosa did not influence the frequency of SS, nor did the presence of lasB, exoA, exoS exoU, plcH genes and proteolytic activity. However, 6/8 patients infected with non-motile isolates, developed SS, p = 0.014 and 5/6 isolates that produced large amounts of pyocyanin (>18ug/ml), were associated with SS, p = 0.014. Multivariate analysis indicated that the odds ratio (OR) for development of SS with a non-motile isolate was 6.8, with a 95% confidence interval (CI) (1.37, 51.5), p = 0.030 and with high pyocyanin producing isolates, an OR of 16.9, 95% CI = (2.27, 360), p = .017. This study evaluating the role of microbial factors that significantly effect outcomes following Pa bloodstream infection suggests that P. aeruginosa strains showing high pyocyanin production and the lack of motility independently increase the risk of SS.
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Affiliation(s)
- Asmita Gupte
- Division of Infectious Diseases and Global Medicine, Department of Medicine, University of Florida, Gainesville, Florida, United States of America
- * E-mail: (AG); (RR)
| | - Jeevan Jyot
- Division of Infectious Diseases and Global Medicine, Department of Medicine, University of Florida, Gainesville, Florida, United States of America
- Department of Pharmaceutical Outcomes & Policy, College of Pharmacy, University of Florida, Gainesville, Florida, United States of America
| | - Malleswari Ravi
- Division of Infectious Diseases and Global Medicine, Department of Medicine, University of Florida, Gainesville, Florida, United States of America
| | - Reuben Ramphal
- Division of Infectious Diseases and Global Medicine, Department of Medicine, University of Florida, Gainesville, Florida, United States of America
- * E-mail: (AG); (RR)
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14
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Terra ACG, Salvador EA. In silico integrative analysis predicts relevant properties of exotoxin-derived peptides for the design of vaccines against Pseudomonas aeruginosa. INFECTION GENETICS AND EVOLUTION 2020; 85:104424. [PMID: 32561294 DOI: 10.1016/j.meegid.2020.104424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Revised: 05/25/2020] [Accepted: 06/12/2020] [Indexed: 11/18/2022]
Abstract
Pseudomonas aeruginosa (PA) is an opportunistic human pathogen responsible for causing serious infections in patients with cystic fibrosis. Infections caused by PA are difficult to treat and eradicate due to intrinsic and added resistance to antibiotic therapy. Therefore, it is necessary to establish effective prevention strategies against this infectious agent. In this study, a combination of immunoinformatic tools was applied to predict immunogenic and immunodominant regions in the structure of exotoxins commonly secreted as virulence factors in PA infection (ExoA, ExoS, ExoT, ExoU and ExoY). The peptides derived from exotoxins were evaluated for the potential affinity for human leukocyte antigen (HLA) I and HLA-II molecules, antigenicity score and toxicity profile. From an initial screening of 941 peptides, 13 (1.38%) were successful in all analyzes. The peptides with relevant immunogenic properties were mainly those derived from Exo A (10 / 76.9%). All peptides selected in the last analysis present a high population coverage rate based on the interaction of HLA alleles (95.36 ± 7.83%). Therefore, the peptides characterized in this study are recommended for in vitro and in vivo studies and can provide the basis for the rational design of a vaccine against PA.
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Asif M, Imran M. Effect of Quorum Sensing Inhibitor Agents against Pseudomonas aeruginosa. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2020. [DOI: 10.1134/s1068162020020041] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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Malhotra S, Hayes D, Wozniak DJ. Cystic Fibrosis and Pseudomonas aeruginosa: the Host-Microbe Interface. Clin Microbiol Rev 2019; 32:e00138-18. [PMID: 31142499 PMCID: PMC6589863 DOI: 10.1128/cmr.00138-18] [Citation(s) in RCA: 231] [Impact Index Per Article: 46.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
In human pathophysiology, the clash between microbial infection and host immunity contributes to multiple diseases. Cystic fibrosis (CF) is a classical example of this phenomenon, wherein a dysfunctional, hyperinflammatory immune response combined with chronic pulmonary infections wreak havoc upon the airway, leading to a disease course of substantial morbidity and shortened life span. Pseudomonas aeruginosa is an opportunistic pathogen that commonly infects the CF lung, promoting an accelerated decline of pulmonary function. Importantly, P. aeruginosa exhibits significant resistance to innate immune effectors and to antibiotics, in part, by expressing specific virulence factors (e.g., antioxidants and exopolysaccharides) and by acquiring adaptive mutations during chronic infection. In an effort to review our current understanding of the host-pathogen interface driving CF pulmonary disease, we discuss (i) the progression of disease within the primitive CF lung, specifically focusing on the role of host versus bacterial factors; (ii) critical, neutrophil-derived innate immune effectors that are implicated in CF pulmonary disease, including reactive oxygen species (ROS) and antimicrobial peptides (e.g., LL-37); (iii) P. aeruginosa virulence factors and adaptive mutations that enable evasion of the host response; and (iv) ongoing work examining the distribution and colocalization of host and bacterial factors within distinct anatomical niches of the CF lung.
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Affiliation(s)
- Sankalp Malhotra
- Department of Microbial Infection and Immunity, The Ohio State University, Columbus, Ohio, USA
- The Ohio State University College of Medicine, Columbus, Ohio, USA
| | - Don Hayes
- The Ohio State University College of Medicine, Columbus, Ohio, USA
- Department of Pediatrics, The Ohio State University, Columbus, Ohio, USA
- Section of Pulmonary Medicine, Nationwide Children's Hospital, Columbus, Ohio, USA
| | - Daniel J Wozniak
- The Ohio State University College of Medicine, Columbus, Ohio, USA
- Section of Pulmonary Medicine, Nationwide Children's Hospital, Columbus, Ohio, USA
- Department of Microbiology, The Ohio State University, Columbus, Ohio, USA
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Caskey S, Stirling J, Moore J, Rendall J. Occurrence ofPseudomonas aeruginosain waters: implications for patients with cystic fibrosis (CF). Lett Appl Microbiol 2018. [DOI: 10.1111/lam.12876] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- S. Caskey
- Regional Adult Cystic Fibrosis Centre; Level 8; Belfast City Hospital; Belfast UK
| | - J. Stirling
- Northern Ireland Public Health Laboratory; Department of Bacteriology; Belfast City Hospital; Belfast UK
| | - J.E. Moore
- Regional Adult Cystic Fibrosis Centre; Level 8; Belfast City Hospital; Belfast UK
- Northern Ireland Public Health Laboratory; Department of Bacteriology; Belfast City Hospital; Belfast UK
| | - J.C. Rendall
- Regional Adult Cystic Fibrosis Centre; Level 8; Belfast City Hospital; Belfast UK
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Lo YL, Chen CL, Shen L, Chen YC, Wang YH, Lee CC, Wang LC, Chuang CH, Janapatla RP, Chiu CH, Chang HY. Characterization of the role of global regulator FliA in the pathophysiology of Pseudomonas aeruginosa infection. Res Microbiol 2018; 169:135-144. [PMID: 29432810 DOI: 10.1016/j.resmic.2018.02.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2017] [Revised: 01/31/2018] [Accepted: 02/02/2018] [Indexed: 12/29/2022]
Abstract
FliA is known to be a sigma factor that regulates bacterial flagella gene expression. Accumulating evidence suggests that FliA is involved in bacterial behavior other than motility. To elucidate the contribution of FliA to Pseudomonas aeruginosa pathophysiology, we analyzed the biological properties and gene expression profiles of a ΔfliA mutant. Transcriptome analysis results demonstrated that the expression levels of flagella biogenesis genes decreased dramatically in the mutant; consequently, the ΔfliA mutant failed to synthesize flagella and exhibited reduced motility. The ΔfliA mutant displayed stronger hemolytic and caseinolytic activities, as well as pyocyanin production. The expression of type 6 secretion system-II genes and interbacterial competition activity was decreased in the ΔfliA mutant. Direct evidence of fliA participation in virulence was obtained from analysis of hypervirulent strain B136-33. Adhesion to and cytotoxicity toward mammalian cells and penetration through cell layers were noted; furthermore, the colonization ability of the fliA::Tn5 mutant in the intestines of laboratory mice was compromised. Notably, the fliA-overexpressing strain displayed phenotypes similar to that of the fliA-defective strain, indicating that optimal FliA levels are critical to bacterial physiology. Our findings indicate that FliA plays diverse roles in P. aeruginosa, not only in flagella biosynthesis, but also in pathophysiology.
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Affiliation(s)
- Yi-Ling Lo
- Institute of Molecular Medicine, National Tsing Hua University, Hsinchu, Taiwan
| | - Chyi-Liang Chen
- Molecular Infectious Disease Research Center, Division of Pediatric Infectious Diseases, Department of Pediatrics, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Taoyuan, Taiwan
| | - Lunda Shen
- Institute of Molecular Medicine, National Tsing Hua University, Hsinchu, Taiwan
| | - Ying-Ching Chen
- Molecular Infectious Disease Research Center, Division of Pediatric Infectious Diseases, Department of Pediatrics, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Taoyuan, Taiwan
| | - Yi-Hsin Wang
- Molecular Infectious Disease Research Center, Division of Pediatric Infectious Diseases, Department of Pediatrics, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Taoyuan, Taiwan
| | - Chung-Chan Lee
- Molecular Infectious Disease Research Center, Division of Pediatric Infectious Diseases, Department of Pediatrics, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Taoyuan, Taiwan
| | - Lian-Chen Wang
- Division of Parasitology, Chang Gung University, Taoyuan, Taiwan
| | | | - Rajendra Prasad Janapatla
- Molecular Infectious Disease Research Center, Division of Pediatric Infectious Diseases, Department of Pediatrics, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Taoyuan, Taiwan
| | - Cheng-Hsun Chiu
- Molecular Infectious Disease Research Center, Division of Pediatric Infectious Diseases, Department of Pediatrics, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Taoyuan, Taiwan.
| | - Hwan-You Chang
- Institute of Molecular Medicine, National Tsing Hua University, Hsinchu, Taiwan.
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Interactions between Neutrophils and Pseudomonas aeruginosa in Cystic Fibrosis. Pathogens 2017; 6:pathogens6010010. [PMID: 28282951 PMCID: PMC5371898 DOI: 10.3390/pathogens6010010] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Accepted: 03/03/2017] [Indexed: 12/23/2022] Open
Abstract
Cystic fibrosis (CF) affects 70,000 patients worldwide. Morbidity and mortality in CF is largely caused by lung complications due to the triad of impaired mucociliary clearance, microbial infections and chronic inflammation. Cystic fibrosis airway inflammation is mediated by robust infiltration of polymorphonuclear neutrophil granulocytes (PMNs, neutrophils). Neutrophils are not capable of clearing lung infections and contribute to tissue damage by releasing their dangerous cargo. Pseudomonas aeruginosa is an opportunistic pathogen causing infections in immunocompromised individuals. P. aeruginosa is a main respiratory pathogen in CF infecting most patients. Although PMNs are key to attack and clear P. aeruginosa in immunocompetent individuals, PMNs fail to do so in CF. Understanding why neutrophils cannot clear P. aeruginosa in CF is essential to design novel therapies. This review provides an overview of the antimicrobial mechanisms by which PMNs attack and eliminate P. aeruginosa. It also summarizes current advances in our understanding of why PMNs are incapable of clearing P. aeruginosa and how this bacterium adapts to and resists PMN-mediated killing in the airways of CF patients chronically infected with P. aeruginosa.
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Reinhart AA, Oglesby-Sherrouse AG. Regulation of Pseudomonas aeruginosa Virulence by Distinct Iron Sources. Genes (Basel) 2016; 7:genes7120126. [PMID: 27983658 PMCID: PMC5192502 DOI: 10.3390/genes7120126] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Revised: 12/02/2016] [Accepted: 12/05/2016] [Indexed: 02/06/2023] Open
Abstract
Pseudomonas aeruginosa is a ubiquitous environmental bacterium and versatile opportunistic pathogen. Like most other organisms, P. aeruginosa requires iron for survival, yet iron rapidly reacts with oxygen and water to form stable ferric (FeIII) oxides and hydroxides, limiting its availability to living organisms. During infection, iron is also sequestered by the host innate immune system, further limiting its availability. P. aeruginosa’s capacity to cause disease in diverse host environments is due to its ability to scavenge iron from a variety of host iron sources. Work over the past two decades has further shown that different iron sources can affect the expression of distinct virulence traits. This review discusses how the individual components of P. aeruginosa’s iron regulatory network allow this opportunist to adapt to a multitude of host environments during infection.
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Affiliation(s)
- Alexandria A Reinhart
- Wound Infections Department, Bacterial Diseases Branch, Walter Reed Army Institute of Research, Silver Spring, MD 20910, USA.
| | - Amanda G Oglesby-Sherrouse
- Department of Pharmaceutical Sciences, School of Pharmacy, and Department of Microbiology and Immunology, School of Medicine, University of Maryland, Baltimore, MD 21201, USA.
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Colmer-Hamood JA, Dzvova N, Kruczek C, Hamood AN. In Vitro Analysis of Pseudomonas aeruginosa Virulence Using Conditions That Mimic the Environment at Specific Infection Sites. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2016; 142:151-91. [PMID: 27571695 DOI: 10.1016/bs.pmbts.2016.05.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen that causes chronic lung infection in patients with cystic fibrosis (CF) and acute systemic infections in severely burned patients and immunocompromised patients including cancer patients undergoing chemotherapy and HIV infected individuals. In response to the environmental conditions at specific infection sites, P. aeruginosa expresses certain sets of cell-associated and extracellular virulence factors that produce tissue damage. Analyzing the mechanisms that govern the production of these virulence factors in vitro requires media that closely mimic the environmental conditions within the infection sites. In this chapter, we review studies based on media that closely resemble three in vivo conditions, the thick mucus accumulated within the lung alveoli of CF patients, the serum-rich wound bed and the bloodstream. Media resembling the CF alveolar mucus include standard laboratory media supplemented with sputum obtained from CF patients as well as prepared synthetic mucus media formulated to contain the individual components of CF sputum. Media supplemented with serum or individual serum components have served as surrogates for the soluble host components of wound infections, while whole blood has been used to investigate the adaptation of pathogens to the bloodstream. Studies using these media have provided valuable information regarding P. aeruginosa gene expression in different host environments as varying sets of genes were differentially regulated during growth in each medium. The unique effects observed indicate the essential role of these in vitro media that closely mimic the in vivo conditions in providing accurate information regarding the pathogenesis of P. aeruginosa infections.
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Affiliation(s)
- J A Colmer-Hamood
- Department of Immunology and Molecular Microbiology, Texas Tech University Health Sciences Center, Lubbock, TX, United States; Department of Medical Education, Texas Tech University Health Sciences Center, Lubbock, TX, United States.
| | - N Dzvova
- Department of Immunology and Molecular Microbiology, Texas Tech University Health Sciences Center, Lubbock, TX, United States
| | - C Kruczek
- Honors College, Texas Tech University, Lubbock, TX, United States
| | - A N Hamood
- Department of Immunology and Molecular Microbiology, Texas Tech University Health Sciences Center, Lubbock, TX, United States; Department of Surgery, Texas Tech University Health Sciences Center, Lubbock, TX, United States
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Grøftehauge MK, Truan D, Vasil A, Denny PW, Vasil ML, Pohl E. Crystal Structure of a Hidden Protein, YcaC, a Putative Cysteine Hydrolase from Pseudomonas aeruginosa, with and without an Acrylamide Adduct. Int J Mol Sci 2015; 16:15971-84. [PMID: 26184183 PMCID: PMC4519933 DOI: 10.3390/ijms160715971] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2015] [Revised: 06/04/2015] [Accepted: 06/15/2015] [Indexed: 11/26/2022] Open
Abstract
As part of the ongoing effort to functionally and structurally characterize virulence factors in the opportunistic pathogen Pseudomonas aeruginosa, we determined the crystal structure of YcaC co-purified with the target protein at resolutions of 2.34 and 2.56 Å without a priori knowledge of the protein identity or experimental phases. The three-dimensional structure of YcaC adopts a well-known cysteine hydrolase fold with the putative active site residues conserved. The active site cysteine is covalently bound to propionamide in one crystal form, whereas the second form contains an S-mercaptocysteine. The precise biological function of YcaC is unknown; however, related prokaryotic proteins have functions in antibacterial resistance, siderophore production and NADH biosynthesis. Here, we show that YcaC is exceptionally well conserved across both bacterial and fungal species despite being non-ubiquitous. This suggests that whilst YcaC may not be part of an integral pathway, the function could confer a significant evolutionary advantage to microbial life.
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Affiliation(s)
- Morten K Grøftehauge
- School of Biological and Biomedical Sciences, Durham University, Durham DH1 3LE, UK.
| | - Daphne Truan
- Swiss Light Source, Paul Scherrer Institute, Villigen CH-5232, Switzerland.
| | - Adriana Vasil
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO 80045, USA.
| | - Paul W Denny
- School of Biological and Biomedical Sciences, Durham University, Durham DH1 3LE, UK.
- School of Medicine, Pharmacy and Health, Durham University, Stockton-on-Tees TS17 6BH, UK.
| | - Michael L Vasil
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO 80045, USA.
| | - Ehmke Pohl
- School of Biological and Biomedical Sciences, Durham University, Durham DH1 3LE, UK.
- Department of Chemistry, Durham University, Durham DH1 3LE, UK.
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Spoils of war: iron at the crux of clinical and ecological fitness of Pseudomonas aeruginosa. Biometals 2015; 28:433-43. [DOI: 10.1007/s10534-015-9848-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 03/13/2015] [Indexed: 01/07/2023]
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Yoon SS, Hassett DJ. Chronic Pseudomonas aeruginosa infection in cystic fibrosis airway disease: metabolic changes that unravel novel drug targets. Expert Rev Anti Infect Ther 2014; 2:611-23. [PMID: 15482224 DOI: 10.1586/14787210.2.4.611] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The cystic fibrosis (CF) airways have an incompletely characterized defect in innate defense that eventually leads to bacterial infection and airway inflammation. Persistent Pseudomonas aerugionsa infection resulting from defective innate immunity and a bacterial phenotypic switch to a more intractable mucoid form inside the airway are now well established as important components of CF pathogenesis. Broad-based factors leading to chronic infection will be discussed with respect to: bacterial virulence in the context of biofilm formation, quorum sensing machinery and alginate overproduction, and failure of innate lung immunity in CF airways. In addition, a controversial question as to whether inflammation or infection comes first during CF airway disease will be addressed. Finally, a new hypothesis, that P. aeruginosa thrives as biofilms within the thickened anaerobic mucus layers, will be developed.
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Affiliation(s)
- Sang Sun Yoon
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, OH 45267-0524, USA.
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Wolf P, Elsässer-Beile U. Pseudomonas exotoxin A: from virulence factor to anti-cancer agent. Int J Med Microbiol 2009; 299:161-76. [PMID: 18948059 DOI: 10.1016/j.ijmm.2008.08.003] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2008] [Revised: 07/07/2008] [Accepted: 08/13/2008] [Indexed: 11/24/2022] Open
Abstract
The pathogenic bacterium Pseudomonas aeruginosa has the ability to cause severe acute and chronic infections in humans. Pseudomonas exotoxin A (PE) is the most toxic virulence factor of this bacterium. It has ADP-ribosylation activity and decisively affects the protein synthesis of the host cells. The cytotoxic pathways of PE have been elucidated, and it could be shown that PE uses several molecular strategies developed under evolutionary pressure for effective killing. Interestingly, a medical benefit from this molecule has also been ascertained in recent years and several PE-based immunotoxins have been constructed and tested in preclinical and clinical trials against different cancers. In these molecules, the enzymatic active domain of PE is specifically targeted to tumor-related antigens. This review describes the current knowledge about the cytotoxic pathways of PE. Additionally, it summarizes preclinical and clinical trials of PE-based immunotoxins and furthermore discusses current problems and answers with these agents.
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Affiliation(s)
- Philipp Wolf
- Department of Urology, University of Freiburg, Germany.
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27
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Dötsch A, Pommerenke C, Bredenbruch F, Geffers R, Häussler S. Evaluation of a microarray-hybridization based method applicable for discovery of single nucleotide polymorphisms (SNPs) in the Pseudomonas aeruginosa genome. BMC Genomics 2009; 10:29. [PMID: 19152677 PMCID: PMC2658670 DOI: 10.1186/1471-2164-10-29] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2008] [Accepted: 01/19/2009] [Indexed: 01/09/2023] Open
Abstract
Background Whole genome sequencing techniques have added a new dimension to studies on bacterial adaptation, evolution and diversity in chronic infections. By using this powerful approach it was demonstrated that Pseudomonas aeruginosa undergoes intense genetic adaptation processes, crucial in the development of persistent disease. The challenge ahead is to identify universal infection relevant adaptive bacterial traits as potential targets for the development of alternative treatment strategies. Results We developed a microarray-based method applicable for discovery of single nucleotide polymorphisms (SNPs) in P. aeruginosa as an easy and economical alternative to whole genome sequencing. About 50% of all SNPs theoretically covered by the array could be detected in a comparative hybridization of PAO1 and PA14 genomes at high specificity (> 0.996). Variations larger than SNPs were detected at much higher sensitivities, reaching nearly 100% for genetic differences affecting multiple consecutive probe oligonucleotides. The detailed comparison of the in silico alignment with experimental hybridization data lead to the identification of various factors influencing sensitivity and specificity in SNP detection and to the identification of strain specific features such as a large deletion within the PA4684 and PA4685 genes in the Washington Genome Center PAO1. Conclusion The application of the genome array as a tool to identify adaptive mutations, to depict genome organizations, and to identify global regulons by the "ChIP-on-chip" technique will expand our knowledge on P. aeruginosa adaptation, evolution and regulatory mechanisms of persistence on a global scale and thus advance the development of effective therapies to overcome persistent disease.
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Affiliation(s)
- Andreas Dötsch
- Helmholtz Centre for Infection Research, Braunschweig, Germany.
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Synergy between polyethylenimine and different families of antibiotics against a resistant clinical isolate of Pseudomonas aeruginosa. Antimicrob Agents Chemother 2008; 52:1635-41. [PMID: 18285485 DOI: 10.1128/aac.01071-07] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The in vitro activities of 10 families of antimicrobial agents alone and in combination with a synthetic polycationic polymer, polyethylenimine (PEI), against a resistant clinical isolate of Pseudomonas aeruginosa were investigated by MIC assays, checkerboard testing, and killing curve studies. At a concentration of 250 nM, PEI (10 kDa) was not directly bactericidal or bacteriostatic; but when it was used in combination with novobiocin, ceftazidime, ampicillin, ticarcillin, carbenicillin, piperacillin, cefotaxime, chloramphenicol, rifampin, or norfloxacin, it significantly reduced the MICs of these antibiotics by 1.5- to 56-fold. However, the MICs of aminoglycosides, polymyxins, and vancomycins were increased by 1.2- to 5-fold when these drugs were combined with PEI; and the MICs of tetracycline, erythromycin, ciprofloxacin, and ofloxacin were not affected when these drugs were combined with PEI. In the killing curve studies, combinations of PEI with novobiocin, ceftazidime, chloramphenicol, or rifampin resulted in 5- to 8-log(10) CFU/ml reductions in bacterial counts when 25% of the MIC of each antibiotic was used. These results indicate that infections due to resistant Pseudomonas strains could be treated by the use of a synergistic combination of PEI and antimicrobial drugs.
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Okino N, Ito M. Ceramidase enhances phospholipase C-induced hemolysis by Pseudomonas aeruginosa. J Biol Chem 2007; 282:6021-30. [PMID: 17202150 DOI: 10.1074/jbc.m603088200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We previously reported the purification, molecular cloning, and characterization of a neutral ceramidase from Pseudomonas aeruginosa strain AN17 (Okino, N., Tani, M., Imayama, S., and Ito, M. (1998) J. Biol. Chem. 273, 14368-14373; Okino, N., Ichinose, S., Omori, A., Imayama, S., Nakamura, T., and Ito, M. (1999) J. Biol. Chem. 274, 36616-36622). Interestingly, the gene encoding the enzyme is adjacent to that encoding hemolytic phospholipase C (plcH) in the genome of Pseudomonas aeruginosa, which is a well known pathogen for opportunistic infections. We report here that simultaneous production of PlcH and ceramidase was induced by several lipids and PlcH-induced hemolysis was significantly enhanced by the action of the ceramidase. When the strain was cultured with sphingomyelin or phosphatidylcholine, production of both enzymes drastically increased, causing the increase of hemolytic activity in the cell-free culture supernatant. Ceramide and sphingosine were also effective in promoting the production of ceramidase but not that of PlcH. Furthermore, we found that the hemolytic activity of a Bacillus cereus sphingomyelinase was significantly enhanced by addition of a recombinant Pseudomonas ceramidase. TLC analysis of the erythrocytes showed that ceramide produced from sphingomyelin by the sphingomyelinase was partly converted to sphingosine by the ceramidase. A ceramidase-null mutant strain caused much less hemolysis of sheep erythrocytes than did the wild-type strain. Sphingosine was detected in the erythrocytes co-cultured with the wild-type strain but not the mutant strain. Finally, we found that the enhancement of PlcH-induced hemolysis by the ceramidase occurred in not only sheep but also human erythrocytes. These results may indicate that the ceramidase enhances the PlcH-induced cytotoxicity and provide new insights into the role of sphingolipid-degrading enzymes in the pathogenicity of P. aeruginosa.
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Affiliation(s)
- Nozomu Okino
- Department of Bioscience and Biotechnology, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, 6-10-1, Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.
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Tart AH, Blanks MJ, Wozniak DJ. The AlgT-dependent transcriptional regulator AmrZ (AlgZ) inhibits flagellum biosynthesis in mucoid, nonmotile Pseudomonas aeruginosa cystic fibrosis isolates. J Bacteriol 2006; 188:6483-9. [PMID: 16952938 PMCID: PMC1595476 DOI: 10.1128/jb.00636-06] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas aeruginosa is a microorganism associated with the disease cystic fibrosis. While environmental P. aeruginosa strains are generally nonmucoid and motile, isolates recovered from the cystic fibrosis lung frequently display a mucoid, nonmotile phenotype. This phenotypic conversion is mediated by the alternative sigma factor AlgT. Previous work has shown that repression of fleQ by AlgT accounts for the loss of flagellum biosynthesis in these strains. Here, we elucidate the mechanism involved in the AlgT-mediated control of fleQ. Electrophoretic mobility shift assays using purified AlgT and extracts derived from isogenic AlgT(+) and AlgT(-) strains revealed that AlgT inhibits fleQ indirectly. We observed that the AlgT-dependent transcriptional regulator AmrZ interacts directly with the fleQ promoter. To determine whether AmrZ functions as a repressor of fleQ, we mutated amrZ in the mucoid, nonmotile P. aeruginosa strain FRD1. Unlike the parental strain, the amrZ mutant was nonmucoid and motile. Complementation of the mutant with amrZ restored the mucoid, nonmotile phenotype. Thus, our data show that AlgT inhibits flagellum biosynthesis in mucoid, nonmotile P. aeruginosa cystic fibrosis isolates by promoting expression of AmrZ, which subsequently represses fleQ. Since fleQ directly or indirectly controls the expression of almost all flagellar genes, its repression ultimately leads to the loss of flagellum biosynthesis.
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Affiliation(s)
- Anne H Tart
- Department of Microbiology and Immunology, Wake Forest University School of Medicine, Medical Center Blvd., Winston-Salem, NC 27157-1064, USA
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Tart AH, Wolfgang MC, Wozniak DJ. The alternative sigma factor AlgT represses Pseudomonas aeruginosa flagellum biosynthesis by inhibiting expression of fleQ. J Bacteriol 2005; 187:7955-62. [PMID: 16291668 PMCID: PMC1291279 DOI: 10.1128/jb.187.23.7955-7962.2005] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas aeruginosa poses a serious risk in individuals suffering from cystic fibrosis (CF). Strains colonizing the CF lung are generally motile but frequently convert to a nonmotile phenotype as the disease progresses. In many cases, this is coordinately regulated with the overproduction of the exopolysaccharide alginate. Both the expression of alginate (mucoidy) and the loss of flagellum synthesis may provide the bacterium with a selective advantage in the CF lung. Previously published data showed that the regulation of alginate production and flagellum biosynthesis in the CF isolate FRD1 is inversely controlled by the alternative sigma factor AlgT. In this study, we observed that in CF isolates, the mucoid and the nonmotile phenotypes occur predominantly together. Using microarrays, we compared the transcriptomes of isogenic AlgT(+) and AlgT(-) P. aeruginosa and discovered that AlgT significantly downregulated the majority of flagellar genes. A pronounced inhibitory effect was observed in several genes essential for proper flagellum expression, including fleQ, which encodes an essential flagellar regulator. The microarray data were confirmed by reverse transcriptase PCR analysis and promoter fusion assays in isogenic AlgT(+) and AlgT(-) strains. Transmission electron microscopy, motility assays, and Western blots showed that ectopic expression of FleQ in mucoid, nonmotile CF isolates restored flagellum biosynthesis and motility. Together, these data show that AlgT mediates the negative control of flagellum expression by inhibiting the expression of the flagellar regulator fleQ.
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Affiliation(s)
- Anne H Tart
- Department of Microbiology and Immunology, Wake Forest University School of Medicine, Winston-Salem, NC 27157-1064, USA
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Horii T, Muramatsu H, Monji A, Miyagishima D. Release of exotoxin A, peptidoglycan and endotoxin after exposure of clinical Pseudomonas aeruginosa isolates to carbapenems in vitro. Chemotherapy 2005; 51:324-31. [PMID: 16224183 DOI: 10.1159/000088955] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2004] [Accepted: 03/12/2005] [Indexed: 11/19/2022]
Abstract
BACKGROUND Production of several cell-associated components and extracellular enzymes can play important roles in the pathogenesis of Pseudomonas aeruginosa infections. METHODS We characterized the time course of morphological changes, production of exotoxin A (ETA) and release of peptidoglycan (PG) and endotoxin (ET) in clinical P. aeruginosa isolates after exposure to carbapenems including imipenem, panipenem, meropenem and biapenem at 0.5, 2, 8 and 32 microg/ml. RESULTS The amount of ETA in the supernatant of bacterial cultures exposed to carbapenems correlated with the number of viable cells, independently of morphological changes. Formation of ovoid cells and rapid cell lysis induced by carbapenems above the minimal inhibitory concentrations (MICs) decreased ETA production and ET release, while filamentation and prolonged cell lysis increased ETA production and/or ET release. Neither the number of viable cells nor bacterial morphology was related to the amount of PG released throughout the 6-hour observation period. CONCLUSION Exposure to concentrations of carbapenems above the MIC resulted in rapid cell lysis of P. aeruginosa and decreased ETA levels and ET release, while filamentation and prolonged cell lysis induced by exposure to sub-MICs of carbapenems were associated with increased ETA production and/or greater ET release.
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Affiliation(s)
- Toshinobu Horii
- Department of Laboratory Medicine, Hamamatsu University School of Medicine, Japan.
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Bredenbruch F, Nimtz M, Wray V, Morr M, Müller R, Häussler S. Biosynthetic pathway of Pseudomonas aeruginosa 4-hydroxy-2-alkylquinolines. J Bacteriol 2005; 187:3630-5. [PMID: 15901684 PMCID: PMC1112037 DOI: 10.1128/jb.187.11.3630-3635.2005] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The role of intercellular communication in the regulation of bacterial multicellular behavior has received widespread attention, and a variety of signal molecules involved in bacterial communication have been discovered. In addition to the N-acyl-homoserine lactones, 4-hydroxy-2-alkylquinolines (HAQs), including the Pseudomonas quinolone signal, have been shown to function as signal molecules in Pseudomonas aeruginosa. In this study we unraveled the biosynthetic pathway of HAQs using feeding experiments with isotope-labeled precursors and analysis of extracted HAQs by gas chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy. Our results show that the biosynthesis of various HAQ metabolites is directed via a common metabolic pathway involving a "head-to-head" condensation of anthranilic acid and beta-keto fatty acids. Moreover, we provide evidence that the beta-keto-(do)decanoic acids, crucial for the biosynthesis of the heptyl and nonyl derivatives of the 4-hydroxyquinolines in P. aeruginosa, are at least in part derived from a common pool of beta-hydroxy(do)decanoic acids involved in rhamnolipid biosynthesis.
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Affiliation(s)
- Florian Bredenbruch
- Department of Cell Biology, Gesellschaft für Biotechnologische Forschung (GBF), Mascheroder Weg 1, D-38124 Braunschweig, Germany
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Wenderoth DF, Ferslev B, Macarri G, Molinari G, Lünsdorf H, Timmis KN. Leitbakteria of microbial biofilm communities causing occlusion of biliary stents. Environ Microbiol 2004; 5:859-66. [PMID: 14510839 DOI: 10.1046/j.1462-2920.2003.00513.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Biliary stents inserted to relieve obstructive jaundice caused by biliary or pancreatic malignancies inevitably become occluded by microbial growth in the form of diverse microbial community biofilms. The scarce information available on these communities is based on cultivation methods, but such methods usually provide distorted overviews of community composition, so commonalities and differences in biliary stent communities are uncertain. We extracted DNA and RNA from the microbial communities of 11 biliary stents explanted from nine patients in hospitals from two different countries, amplified 16S rRNA and rDNA sequences, analysed the amplicons by the single-strand conformation polymorphism (SSCP) method, and sequenced and deduced phylogenetic assignments of the major amplicons representing the major biofilm community members. We used a Modified Robbins Device (MRD) to study de novo development of a stent biofilm from a patient stent microbial community. Single-strand conformation polymorphism fingerprinting revealed the same six abundant bacterial species, here designated Leitbakteria, namely Klebsiella pneumoniae, Enterococcus faecalis, Pseudomonas aeruginosa, Enterobacter aerogenes, and two unculturable bacteria distantly related to E. coli and Shigella sonnei, in all of the stent biofilm communities. In the experimental biliary stent system, a sequential colonization of the stent surface was observed, with P. aeruginosa being the pioneer colonizer, followed by K. pneumoniae and one of the unculturable Leitbakteria, followed by the remainder of the community. The overview of microbial biofilm communities of biliary stents gained by the use of culture-independent methods revealed new unculturable bacteria as major members of biliary stent biofilms, and the diversity of the abundant members of the stent biofilms is considerably lower than suggested from earlier studies based on cultivation methods, and that communities from different stents from different patients in different countries are remarkably similar and have similar major members, the stent Leitbakteria.
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Affiliation(s)
- Dirk F Wenderoth
- Division of Microbiology, GBF-German Research Centre for Biotechnology, 38124 Braunschweig, Germany.
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35
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State of the art: why do the lungs of patients with cystic fibrosis become infected and why can't they clear the infection? Respir Res 2003; 4:8. [PMID: 14511398 PMCID: PMC203156 DOI: 10.1186/1465-9921-4-8] [Citation(s) in RCA: 158] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2003] [Accepted: 08/27/2003] [Indexed: 12/19/2022] Open
Abstract
Cystic Fibrosis (CF) lung disease, which is characterized by airway obstruction, chronic bacterial infection, and an excessive inflammatory response, is responsible for most of the morbidity and mortality. Early in life, CF patients become infected with a limited spectrum of bacteria, especially P. aeruginosa. New data now indicate that decreased depth of periciliary fluid and abnormal hydration of mucus, which impede mucociliary clearance, contribute to initial infection. Diminished production of the antibacterial molecule nitric oxide, increased bacterial binding sites (e.g., asialo GM-1) on CF airway epithelial cells, and adaptations made by the bacteria to the airway microenvironment, including the production of virulence factors and the ability to organize into a biofilm, contribute to susceptibility to initial bacterial infection. Once the patient is infected, an overzealous inflammatory response in the CF lung likely contributes to the host's inability to eradicate infection. In response to increased IL-8 and leukotriene B4 production, neutrophils infiltrate the lung where they release mediators, such as elastase, that further inhibit host defenses, cripple opsonophagocytosis, impair mucociliary clearance, and damage airway wall architecture. The combination of these events favors the persistence of bacteria in the airway. Until a cure is discovered, further investigations into therapies that relieve obstruction, control infection, and attenuate inflammation offer the best hope of limiting damage to host tissues and prolonging survival.
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Carty NL, Rumbaugh KP, Hamood AN. Regulation of toxA by PtxR in Pseudomonas aeruginosa PA103. Can J Microbiol 2003; 49:450-64. [PMID: 14569286 DOI: 10.1139/w03-058] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Exotoxin A (ETA) production in Pseudomonas aeruginosa requires the regulatory locus regAB. Pseudomonas aeruginosa PA103 produces significantly higher levels of ETA than the prototypic strain PAO1 does, partly because of differences in the regAB locus. Other factors that contribute to this variation are not known. We previously described the P. aeruginosa gene ptxR that positively regulates production of ETA through regAB. ETA production was enhanced but still iron regulated in the PAO1 strain PAO1-XR that carries two copies of ptxR on its chromosome. Here we determine whether ptxR regulation of ETA is different in PA103. In contrast to PAO1-XR, ETA activity produced by PA103-2R, a PA103 strain carrying two copies of ptxR, is enhanced tenfold and partially deregulated in the presence of iron. Real-time PCR transcriptional analysis showed that the copy number of toxA mRNA in PA103-2R is significantly higher than in PA103 in both the presence and absence of iron, yet no similar increase in either regAB or ptxR mRNA copy number was detected. The integrated plasmid together with adjoining DNA was retrieved from the PA103-2R chromosome to determine whether integration-induced DNA changes played a role in this phenotype. Introduction of the retrieved plasmid in PA103 produced a phenotype similar to that of PA103-2R. Sequence analysis of the plasmid revealed the loss of 322 bp within the region 3' of ptxR. A plasmid construct carrying a 4-bp insertion in this same region produced in PA103 a phenotype similar to that of PA103-2R. Our results suggest that the effect of ptxR on toxA expression is different in PA103 than in PAO1 and that this variation in PA103-2R does not occur solely through regAB. Changes within the region 3' of ptxR are critical for the production of the unique PA103-2R phenotype, which occurs in trans and requires intact ptxR, but is not caused by ptxR overexpression.
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Affiliation(s)
- Nancy L Carty
- Department of Microbiology and Immunology, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
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Jendrossek V, Fillon S, Belka C, Müller I, Puttkammer B, Lang F. Apoptotic response of Chang cells to infection with Pseudomonas aeruginosa strains PAK and PAO-I: molecular ordering of the apoptosis signaling cascade and role of type IV pili. Infect Immun 2003; 71:2665-73. [PMID: 12704141 PMCID: PMC153227 DOI: 10.1128/iai.71.5.2665-2673.2003] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Pseudomonas aeruginosa is a gram-negative facultative opportunistic pathogen associated with severe infections in immunocompromised hosts and in patients with cystic fibrosis. P. aeruginosa strains show divergent pathogenicity in vivo and trigger apoptosis of and/or are internalized into human host cells. In the present study, we studied the molecular ordering of apoptosis signaling upon infection of human conjunctiva epithelial Chang cells with P. aeruginosa PAK as well as the role of bacterial pili in the response to the infection. Our results show that CD95 up-regulation is followed by early activation of caspase-8 and -3 and cleavage of the caspase-3 substrate poly(ADP-ribose) polymerase. The data also demonstrate release of apoptosis inducing factor into the cytosol of infected cells. Induction of mitochondrial alterations, i.e., mitochondrial depolarization and release of cytochrome c, as well as cleavage of caspase-9, -7, and -1 occurred only at later time points. In addition, our results demonstrate that pili are required for P. aeruginosa-induced apoptosis of human epithelial cells. While the two piliated P. aeruginosa strains, PAO-I and PAK, induced apoptosis of Chang cells within 3 h of infection, the pilus-deficient P. aeruginosa mutants PAK Delta pilA and PAK Delta pilA Delta all were without effect. The pilus-deficient mutants failed to induce a significant up-regulation of CD95 on the cell surface and to trigger mitochondrial alterations or activation of caspase-8, -3, and -7. In addition, only the piliated wild-type strains induced caspase-1-mediated activation of interleukin-1 beta. Thus, pili are necessary for distinct infection-induced cellular responses of human epithelial cells.
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Affiliation(s)
- Verena Jendrossek
- Department of Physiology, University of Tübingen, 72076 Tübingen, Germany.
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38
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Marier JF, Lavigne J, Ducharme MP. Pharmacokinetics and efficacies of liposomal and conventional formulations of tobramycin after intratracheal administration in rats with pulmonary Burkholderia cepacia infection. Antimicrob Agents Chemother 2002; 46:3776-81. [PMID: 12435676 PMCID: PMC132795 DOI: 10.1128/aac.46.12.3776-3781.2002] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The objective of the present study was to determine the pharmacokinetics and efficacies of liposomal and conventional formulations of tobramycin against Burkholderia cepacia in a model of chronic lung infection. Male Sprague-Dawley rats were inoculated intratracheally with 10(6) CFU of a very resistant strain of B. cepacia (strain BC 1368; MIC, 128 micro g/ml) to establish lung infection. A 1,200- micro g dose of tobramycin was administered intratracheally as a liposomal formulation and as a conventional formulation. Rats were anesthetized and exsanguinated by cardiac puncture at different times over 24 h to assess pulmonary tobramycin concentrations and the number of residual CFU. Pharmacokinetic parameters were calculated by using a two-compartment model with NONMEM. The mean half-life at the beta phase (t(1/2beta)) and the pulmonary exposure (the area under the concentration-time curve [AUC]) of liposomal tobramycin were 19.7 h (coefficient of variation [CV], 24.2%) and 6,811 micro g. h/lungs (CV, 19.7%), respectively. The pharmacokinetics of conventional tobramycin were statistically different, with a t(1/2beta) and AUC of 12.9 h (CV, 31.4%) and 821 micro g. h/lungs (CV, 15.0%), respectively. Pearson chi-square analyses were performed on residual CFU data distributed in the following categories: <10(3), 10(3) to 10(5), and >10(5). Differences in CFU data between formulations showed a statistical trend (P < 0.10) when data from all time points were used, and statistically significant differences were found after 12 h (P < 0.05), with greater eradication achieved with the liposomal formulation. In conclusion, intratracheal administration of tobramycin in liposomes was associated with marked changes in the pharmacokinetics of the drug in the lung and an apparent trend for a prolonged efficacy against B. cepacia. These results support the hypothesis that inhalation of liposomal tobramycin may improve the management of chronic pulmonary infections caused by resistant bacteria in patients with cystic fibrosis.
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Armstrong S, Yates SP, Merrill AR. Insight into the catalytic mechanism of Pseudomonas aeruginosa exotoxin A. Studies of toxin interaction with eukaryotic elongation factor-2. J Biol Chem 2002; 277:46669-75. [PMID: 12270928 DOI: 10.1074/jbc.m206916200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The molecular nature of the protein-protein interactions between the catalytic domain from Pseudomonas aeruginosa exotoxin A (PE24H) and its protein substrate, eukaryotic elongation factor-2 (eEF-2) were probed using a fluorescence resonance energy transfer method. Single cysteine mutant proteins of PE24H were prepared and site-specifically labeled with the donor fluorophore IAEDANS (5-(2-iodoacetylaminoethylamino)-1-napthalenesulfonic acid), whereas eEF-2 was labeled with the acceptor fluorophore fluorescein. The association was found to be independent of ionic strength and of the co-substrate, NAD(+) but dependent upon pH. The lack of requirement for NAD(+) to produce the toxin-eEF-2 complex demonstrates that the catalytic process is a random order mechanism, thereby disputing the current model. The previously observed pH dependence for catalytic function can be assigned to the toxin-eEF-2 binding event, as the pH dependence of binding observed in this study showed a strong correlation with enzymatic activity. The ability of the toxin to bind eEF-2 with bound GTP/GDP was assessed using nonhydrolyzable analogues. The results from the substrate binding and catalytic activity experiments indicate that PE24H is able to interact and bind with eEF-2 in all of its guanyl nucleotide-induced conformational states. Thus, the toxin ribosylates eEF-2 regardless of the nucleotide-charged state of eEF-2. These results represent the first detailed characterization of the molecular details and physiological conditions governing this protein-protein interaction.
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Affiliation(s)
- Souzan Armstrong
- Guelph-Waterloo Centre for Graduate Work in Chemistry and Biochemistry, Department of Chemistry and Biochemistry, University of Guelph, Ontario N1G 2W1, Canada
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40
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Zafar AB, Sylvester LK, Beidas SO. Pseudomonas aeruginosa infections in a neonatal intensive care unit. Am J Infect Control 2002; 30:425-9. [PMID: 12410220 DOI: 10.1067/mic.2002.121153] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This report describes a cluster of nosocomial infections with Pseudomonas aeruginosa in a neonatal intensive care nursery. All 5 cases of P aeruginosa infection were clustered in September 1999. Aggressive infection control measures were instituted, including installation of a user-friendly handwashing soap and environmental cleaning. On the basis of the finding of persistent dirty equipment, a new full-time position was created that was dedicated to equipment cleaning. These measures were effective in eliminating the cluster. The nursery has remained free of P aeruginosa infection for more than 2 years, attesting to the success of our program.
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Affiliation(s)
- Abdul B Zafar
- Prince George's Hospital Center, Cheverly, MD 20785, USA
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41
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Burns JL, Saiman L, Whittier S, Larone D, Krzewinski J, Liu Z, Marshall SA, Jones RN. Comparison of agar diffusion methodologies for antimicrobial susceptibility testing of Pseudomonas aeruginosa isolates from cystic fibrosis patients. J Clin Microbiol 2000; 38:1818-22. [PMID: 10790106 PMCID: PMC86597 DOI: 10.1128/jcm.38.5.1818-1822.2000] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas aeruginosa is the most common pathogen infecting the lungs of patients with cystic fibrosis (CF). Improved antimicrobial chemotherapy has significantly increased the life expectancy of these patients. However, accurate susceptibility testing of P. aeruginosa isolates from CF sputum may be difficult because the organisms are often mucoid and slow growing. This study of 597 CF isolates of P. aeruginosa examined the correlation of disk diffusion and Etest (AB BIODISK, Solna, Sweden) results with a reference broth microdilution method. The rates of interpretive errors for 12 commonly used antipseudomonal antimicrobials were determined. The disk diffusion method correlated well (zone diameter versus MIC) for all of the agents tested. However, for mucoid isolates, correlation coefficients (r values) for piperacillin, piperacillin-tazobactam, and meropenem were <0.80. The Etest correlation with reference broth microdilution results (MIC versus MIC) was acceptable for all of the agents tested, for both mucoid and nonmucoid isolates. Category interpretation errors were similar for the disk diffusion and Etest methods with 0.4 and 0.1%, respectively, very major errors (false susceptibility) and 1.1 and 2.2% major errors (false resistance). Overall, both agar diffusion methods appear to be broadly acceptable for routine clinical use in susceptibility testing of CF isolates of P. aeruginosa.
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Affiliation(s)
- J L Burns
- Department of Pediatrics, Division of Infectious Disease, University of Washington, Seattle, Washington, USA.
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42
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Beaulac C, Sachetelli S, Lagacé J. Aerosolization of low phase transition temperature liposomal tobramycin as a dry powder in an animal model of chronic pulmonary infection caused by Pseudomonas aeruginosa. J Drug Target 1999; 7:33-41. [PMID: 10614813 DOI: 10.3109/10611869909085490] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Eradication of mucoid Pseudomonas aeruginosa in an animal model of chronic pulmonary infection has been previously demonstrated following the intratracheal administration of Fluidosomes, a low phase transition temperature (low T(C)) liposomal tobramycin preparation administered in liquid form (Beaulac et al., Antimicrob. Agents Chemother., 40, 665-669, 1996). In the present work, the same liposomal formulation was administered as a dry powder aerosol to an animal model of chronic pulmonary infection in view of a possible clinical development in cystic fibrosis patients. Chronic infection was established by intratracheal administration of 10(5) cfu of a mucoid variant of P. aeruginosa, PA 508, prepared in agar beads. Sixteen hours after one aerosol treatment, the cfu counts performed on lungs (pair) treated with liposomal tobramycin were of 4.31x10(5) cfu/lungs comparatively to 1.32x10(8) and 3.02x10(8) cfu/lungs respectively in untreated and in lungs treated with free antibiotic. Considering the quantity of liposome-tobramycin that has reached the lungs, the results suggest that aerosolization of low T(C) liposomal tobramycin used as a dry powder preparation could be an effective way of treating chronic pulmonary infection caused by Pseudomonas.
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Affiliation(s)
- C Beaulac
- Department of Microbiology and Immunology, Faculty of Medicine, Université de Montréal, Québec, Canada
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43
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Colmer JA, Hamood AN. Expression ofptxRand its effect ontoxAandregAexpression during the growth cycle ofPseudomonas aeruginosastrain PAO1. Can J Microbiol 1999. [DOI: 10.1139/w99-103] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The expression of the toxA and regA genes in Pseudomonas aeruginosa is negatively regulated by iron at the transcriptional level. We have previously described ptxR, an exotoxin A regulatory gene which appears to enhance toxA expression through regA. In this study, we have tried to determine if ptxR expression correlates with its effect on toxA and regA expression throughout the growth cycle of P. aeruginosa strain PAO1. This was done using Northern blot hybridization experiments (with toxA, regA, and ptxR probes), and ptxR transcriptional fusion studies. To avoid problems related to the presence of multiple copies of ptxR in PAO1, we have constructed a PAO1 strain (PAO1-XR) that carries only two ptxR genes in its chromosome. Our results showed that when PAO1-XR was grown in iron-limited conditions, the increase in exotoxin A activity and the accumulation of toxA mRNA appeared at about mid- to late-exponential phase. A similar increase in the accumulation of regA mRNA was detected. Both regA transcripts, T1 and T2, were enhanced in PAO1-XR. In iron-sufficient medium, neither toxA nor regA mRNA was detected at any time point in the growth cycle of PAO1-XR. In contrast, the accumulation of ptxR mRNA was detected throughout the growth cycle of PAO1-XR under both iron-deficient and iron-sufficient conditions. The presence of iron in the growth medium also had no effect on the level of β-galactosidase activity produced by a ptxR-lacZ fusion in PAO1. These results suggest that (i) the enhancement in toxA expression by ptxR correlates with the enhancement in regA expression; (ii) ptxR affects the expression of the regA P1 and P2 promoters; (iii) ptxR expression precedes its effect on toxA and regA expression; and (iv) unlike toxA and regA, the overall expression of ptxR throughout the growth cycle of PAO1 is not negatively regulated by iron.Key words: ptxR, differential expression, transcriptional regulation, regA, toxA.
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Rumbaugh KP, Griswold JA, Hamood AN. Pseudomonas aeruginosa strains obtained from patients with tracheal, urinary tract and wound infection: variations in virulence factors and virulence genes. J Hosp Infect 1999; 43:211-8. [PMID: 10582188 DOI: 10.1053/jhin.1999.0252] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Pseudomonas aeruginosa produces several virulence factors including exotoxin A, exoenzyme S and elastase. In previous reports we have analysed several clinical isolates for the production of these three virulence factors and for possible heterogeneity within the genes that code for these factors (toxA, lasB and the exoS genes). The isolates were obtained from three specific sites (trachea, urinary tract and wounds). Although the isolates produced variable levels of these factors, isolates that were obtained specifically from urinary tract and wound infections produced increased levels of exotoxin A and exoenzyme S. In addition, a prolonged infection with P. aeruginosa appears to enhance exoenzyme S production. Restriction site polymorphism was very limited within the toxA, lasB, and exoS structural genes; however, the upstream region of toxA showed restriction site polymorphisms between the different isolates. The observed polymorphisms did not correlate with any variations in the levels of the virulence factors. In this article, we provide a short review of these studies.
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Affiliation(s)
- K P Rumbaugh
- Department of Microbiology and Immunology, University Health Sciences Center, Lubbock, Texas 79430, USA
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45
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Saiman L, Burns JL, Whittier S, Krzewinski J, Marshall SA, Jones RN. Evaluation of reference dilution test methods for antimicrobial susceptibility testing of Pseudomonas aeruginosa strains isolated from patients with cystic fibrosis. J Clin Microbiol 1999; 37:2987-91. [PMID: 10449487 PMCID: PMC85429 DOI: 10.1128/jcm.37.9.2987-2991.1999] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The development of multidrug-resistant Pseudomonas aeruginosa in patients with cystic fibrosis (CF) is most likely a consequence of increasing life expectancy and more prolonged exposure to antibiotics. The optimal method for antibiotic susceptibility testing of CF strains, particularly mucoid P. aeruginosa strains, is unknown. Antimicrobial susceptibilities of 48 CF strains (25 mucoid) and 50 non-CF strains to 12 anti-Pseudomonas agents were tested by both agar dilution and commercially custom-prepared broth microdilution plates (PML Microbiologicals, Portland, Oreg.) in three laboratories simultaneously to determine if broth microdilution could substitute for agar dilution as the reference method in subsequent studies. Comparison of MICs generated by agar dilution and broth microdilution demonstrated correlation coefficients (r) exceeding 0.85 for all agents tested; correlation was excellent for aminoglycosides (r >/= 0.92) and very good for beta-lactam agents including agents paired with a beta-lactamase inhibitor (r >/= 0.87) and for ciprofloxacin (r = 0.86). Correlation was not improved by 48-h readings, but correlation between 24- and 48-h readings ranged between 0.91 and 0.98 for both methods. Interlaboratory variations were minimal, as the percentage of acceptable variations was 94% for both methods, and serious discords were infrequent (<2% of comparisons). However, CF strains were more likely to have serious discords than were non-CF strains (P < 0. 0001), although mucoid strains were not more likely to have serious discords than were nonmucoid strains. In this study, MICs determined by custom-prepared broth microdilution compared favorably with MICs determined by agar dilution. Thus, this broth microdilution assay can serve as a reference method and facilitate future studies to determine the optimal method for antibiotic susceptibility testing of CF strains.
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Affiliation(s)
- L Saiman
- Department of Pediatrics and Clinical Microbiology, Columbia University, New York, New York 10032, USA.
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46
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Freud E, Farkash U, Prieto F, Janowski E, Zer M. Perineal reconstruction for severe sequela of ecthyma gangrenosum: report of a case. Dis Colon Rectum 1999; 42:961-3. [PMID: 10411447 DOI: 10.1007/bf02237111] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Ecthyma gangrenosum is a cutaneous gangrenous disorder which usually follows Pseudomona aeruginosa infection and is found mainly in immunosuppressed children. We describe a case of a five-year-old female with leukemia with a severe perineal ecthyma gangrenosum resulting in a cloaca-like deformity. One year later a perineoplasty with puborectalis interposition and overlapping external anal sphincteroplasty was successfully performed, achieving satisfactory continence.
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Affiliation(s)
- E Freud
- Department of Pediatric Surgery, Schneider Children's Medical Center of Israel, Petah Tiqva
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47
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Walsh AG, Burrows LL, Lam JS. Genetic and biochemical characterization of an operon involved in the biosynthesis of 3-deoxy-D-manno-octulosonic acid in Pseudomonas aeruginosa. FEMS Microbiol Lett 1999; 173:27-33. [PMID: 10220877 DOI: 10.1111/j.1574-6968.1999.tb13480.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
A Pseudomonas aeruginosa serotype O5 (PAO1) genomic DNA fragment that was able to complement a temperature-sensitive mutation in the 3-deoxy-D-manno-octulosonic acid (Kdo) 8-P synthase gene (kdsA) of Salmonella enterica serovar typhimurium was cloned. Nucleotide sequence analysis revealed the presence of a potential operon with the gene order pyrG, kdsA, eno. PyrG catalyzes the synthesis of the nucleotide cytidine triphosphate, while Eno catalyzes the formation of phosphoenolpyruvate from phosphoglycerate during glycolysis. Phosphoenolpyruvate is one of the substrates for Kdo-8-P biosynthesis by KdsA and cytidine triphosphate is the nucleotide used to activate Kdo prior to its transfer to lipid A. pyrG and eno are important for many metabolic pathways and it is interesting to find them linked to kdsA. A sigma 70-like promoter was found upstream of pyrG and evidence was provided to show that this promoter was responsible for the initiation of transcription of the genes in this operon. These genes mapped to 28.2-29.9 min on the 75-min PAO1 chromosome, unlinked to other lipopolysaccharide biosynthetic gene clusters.
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Affiliation(s)
- A G Walsh
- Canadian Bacterial Diseases Network, Department of Microbiology, University of Guelph, Ont., Canada
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Gupta SK, Masinick S, Garrett M, Hazlett LD. Pseudomonas aeruginosa lipopolysaccharide binds galectin-3 and other human corneal epithelial proteins. Infect Immun 1997; 65:2747-53. [PMID: 9199445 PMCID: PMC175387 DOI: 10.1128/iai.65.7.2747-2753.1997] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The aim of this study was to test whether galectin-3 is present in human corneal epithelium and whether lipopolysaccharide (LPS) purified from Pseudomonas aeruginosa ATCC 19660 binds to this animal lectin and/or to another human corneal epithelial protein(s) (HCEP) and to confirm which component of LPS (inner or outer core or lipid A) is important in bacterial binding by using the eye in organ culture. LPS isolated and purified from P. aeruginosa ATCC 19660 and a commercial LPS (serotype 10) differed in polyacrylamide gel analysis but bound similarly to blotted HCEP. Binding was determined to be a receptor-ligand type of interaction by the solid-phase assay, because it was both specific and saturable. Several LPS binding proteins in HCEP were identified by an overlay method. Western blotting with antibody against galectin-3 revealed the presence of this protein in both freshly isolated and cultured transformed human corneal epithelium. Binding inhibition assays showed that antibody specific for the outer core region of LPS and an anti-galectin antibody significantly inhibited bacterial binding in vitro. These data provide further evidence that LPS is an important adhesin of P. aeruginosa, that it binds to protein receptor molecules in HCEP, that one of the LPS binding proteins is galectin-3, and that the outer core portion of the molecule appears to be critical for LPS binding to the eye.
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Affiliation(s)
- S K Gupta
- Department of Anatomy/Cell Biology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA
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Niall DM, Murphy PG, Fogarty EE, Dowling FE, Moore DP. Puncture wound related pseudomonas infections of the foot in children. Ir J Med Sci 1997; 166:98-101. [PMID: 9159992 DOI: 10.1007/bf02944197] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Eleven children with Pseudomonas aeruginosa infection complicating foot puncture wounds were reviewed. Delay in presentation (mean 2 days) and diagnosis (mean 9 days) due to a paucity of clinical signs of deep infection was characteristic of this condition. Septic arthritis (5 patients) and osteomyelitis (3 patients) were frequent complications. Treatment involved multiple surgical debridements and prolonged intravenous antibiotic therapy. The clinical outcome was good although long-term radiographic changes were common.
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Affiliation(s)
- D M Niall
- Our Lady's Hospital for Sick Children, Crumlin, Dublin
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50
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Hoang TT, Williams S, Schweizer HP, Lam JS. Molecular genetic analysis of the region containing the essential Pseudomonas aeruginosa asd gene encoding aspartate-beta-semialdehyde dehydrogenase. MICROBIOLOGY (READING, ENGLAND) 1997; 143 ( Pt 3):899-907. [PMID: 9084174 DOI: 10.1099/00221287-143-3-899] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
asd mutants of Gram-negative and some Gram-positive bacteria have an obligate requirement for diaminopimelic acid (DAP), an essential constituent of the cell wall of these organisms. In environments deprived of DAP, for example mammalian tissues, they will undergo lysis. This was previously exploited to develop vaccine strains of Salmonella typhimurium and cloning vectors containing asd as an in vivo selectable marker. As a first step for development of such systems for Pseudomonas aeruginosa, the asd gene from wild-type strain PAO1 was cloned by a combined approach of PCR amplification from chromosomal DNA, construction of mini-libraries and by complementation of an Escherichia coli delta asd mutant. The nucleotide sequence of a 2433 bp Smal-Nsil fragment was determined. This fragment contained the C-terminal 47 nucleotides of leuB, encoding 3-isopropylmalate dehydrogenase; asd, encoding aspartate-beta-semialdehyde dehydrogenase (Asd); and orfA, whose product showed similarity to the Asd proteins from Vibrio spp. By subcloning, asd was localized to a 1.24 kb DNA fragment which in an E. coli T7 expression system strongly expressed a 40,000 Da protein. The amino acid sequence was deduced from the DNA sequence. A comparison of the Asd proteins from P. aeruginosa, E. coli and Haemophilus influenzae revealed greater than 63% identity, demonstrating the conserved nature of Asd in Gram-negative bacteria, and defined the active-site-containing consensus sequence GGNCTVXMLMXXXLGLF as a possible signature motif. Chromosomal delta asd mutants were isolated. They were auxotrophic for DAP, lysine, methionine and threonine, and lysed in the absence of DAP. Genetic analyses indicated that orfA probably is naturally frame-shifted and does not contribute to the Asd phenotype. By PFGE, the asd gene was mapped to between coordinates 1.89 and 2.15 Mbp, or 37-40 min, on the 5.9 Mbp P. aeruginosa chromosome.
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Affiliation(s)
- Tung T Hoang
- Department of Microbiology & Infectious Diseases, University of Calgary Health Sciences Center,Calgary, Alberta,Canada T2N 4N1
- Department of Microbiology, Colorado State University,Fort Collins, CO 80523,USA
| | - Scott Williams
- Department of Microbiology & Infectious Diseases, University of Calgary Health Sciences Center,Calgary, Alberta,Canada T2N 4N1
| | - Herbert P Schweizer
- Canadian Bacterial Diseases Network, University of Guelph,Guelph, Ontario,Canada N1G 2W1
- Department of Microbiology, Colorado State University,Fort Collins, CO 80523,USA
| | - Joseph S Lam
- Department of Microbiology, University of Guelph,Guelph, Ontario,Canada N1G 2W1
- Canadian Bacterial Diseases Network, University of Guelph,Guelph, Ontario,Canada N1G 2W1
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