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Kumar P, Kandi SK, Mukhopadhyay K, Rawat DS. Synthesis of novel monocarbonyl curcuminoids, evaluation of their efficacy against MRSA, including ex vivo infection model and their mechanistic studies. Eur J Med Chem 2020; 195:112276. [PMID: 32279050 DOI: 10.1016/j.ejmech.2020.112276] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Revised: 02/27/2020] [Accepted: 03/24/2020] [Indexed: 02/06/2023]
Abstract
In continuation of our effort to improve the physiological stability and the antibacterial activity of curcuminoids against drug-resistant bacteria, a series of novel monocarbonyl curcuminoids were synthesized and screened for antibacterial activity against S. aureus and E. coli strains. These curcuminoids showed potent antibacterial activity against both methicillin-sensitive and methicillin-resistant strains of S. aureus with MIC values 2-8 and 4-16 μg/mL, respectively. They also exhibited moderate potency against E. coli strains. The four most active curcuminoids (7d, 7i, 7m, and 7p) were on further investigation found to be very stable under physiological conditions, non-hemolytic, and non-toxic toward mammalian cells up to 150 μg/mL concentration. Mechanistic studies revealed that these curcuminoids displayed potent bactericidal activity by targeting cell membranes. Further, in an ex vivo mammalian co-culture infection model study, remarkably, the curcuminoids 7i and 7p were able to clear the internalized bacteria in mammalian cells and the activity was found to be superior to conventional antibiotics such as vancomycin and linezolid. Therefore, the present study affords us water-soluble, stable, non-toxic curcuminoids that may serve as lead molecules for development as antibacterial agents against MRSA infections.
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Affiliation(s)
- Prince Kumar
- Antimicrobial Research Laboratory, School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, 110067, India
| | | | - Kasturi Mukhopadhyay
- Antimicrobial Research Laboratory, School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, 110067, India.
| | - Diwan S Rawat
- Department of Chemistry, University of Delhi, Delhi, 110007, India.
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2
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Evaluation of in vitro and in vivo antibiotic efficacy against a novel bioluminescent Shigella flexneri. Sci Rep 2019; 9:13567. [PMID: 31537849 PMCID: PMC6753072 DOI: 10.1038/s41598-019-49729-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Accepted: 08/30/2019] [Indexed: 12/13/2022] Open
Abstract
Shigella spp., the bacteria responsible for shigellosis, are one of the leading causes of diarrheal morbidity and mortality amongst children. There is a pressing need for the development of novel therapeutics, as resistance of Shigella to many currently used antibiotics is rapidly emerging. This paper describes the development of robust in vitro and in vivo tools to study antibiotic efficacy against Shigella flexneri. A novel bioluminescent S. flexneri strain (S. flexneri lux1) was generated, which can be used in a mammalian epithelial cell co-culture assay to evaluate antibiotic intracellular and extracellular efficacy. In addition, the S. flexneri lux1 strain was used with an intraperitoneal (IP) murine model of shigellosis to test the efficacy of ciprofloxacin and ampicillin. Both antibiotics significantly reduced the observed radiance from the gastrointestinal tissue of infected mice compared to vehicle control. Furthermore, plated gastrointestinal tissue homogenate confirmed antibiotic treatment significantly reduced the S. flexneri infection. However, in contrast to the results generated with tissue homogenate, the radiance data was not able to distinguish between the efficacy of ampicillin and ciprofloxacin. Compared to traditional methods, these models can be utilized for efficient screening of novel antibiotics aiding in the discovery of new treatments against shigellosis.
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VanCleave TT, Pulsifer AR, Connor MG, Warawa JM, Lawrenz MB. Impact of Gentamicin Concentration and Exposure Time on Intracellular Yersinia pestis. Front Cell Infect Microbiol 2017; 7:505. [PMID: 29312891 PMCID: PMC5732358 DOI: 10.3389/fcimb.2017.00505] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Accepted: 11/22/2017] [Indexed: 11/27/2022] Open
Abstract
The study of intracellular bacterial pathogens in cell culture hinges on inhibiting extracellular growth of the bacteria in cell culture media. Aminoglycosides, like gentamicin, were originally thought to poorly penetrate eukaryotic cells, and thus, while inhibiting extracellular bacteria, these antibiotics had limited effect on inhibiting the growth of intracellular bacteria. This property led to the development of the antibiotic protection assay to study intracellular pathogens in vitro. More recent studies have demonstrated that aminoglycosides slowly penetrate eukaryotic cells and can even reach intracellular concentrations that inhibit intracellular bacteria. Therefore, important considerations, such as antibiotic concentration, incubation time, and cell type need to be made when designing the antibiotic protection assay to avoid potential false positive/negative observations. Yersinia pestis, which causes the human disease known as the plague, is a facultative intracellular pathogen that can infect and replicate in macrophages. Y. pestis is sensitive to gentamicin and this antibiotic is often employed in the antibiotic protection assay to study the Y. pestis intracellular life cycle. However, a large variety of gentamicin concentrations and incubation periods have been reported in the Y. pestis literature without a clear characterization of the potential influences that variations in the gentamicin protection assay could have on intracellular growth of this pathogen. This raised concerns that variations in the gentamicin protection assay could influence phenotypes and reproducibility of data. To provide a better understanding of the potential consequences that variations in the gentamicin protection assay could have on Y. pestis, we systematically examined the impact of multiple variables of the gentamicin protection assay on Y. pestis intracellular survival in macrophages. We found that prolonged incubation periods with low concentrations of gentamicin, or short incubation periods with higher concentrations of the antibiotic, have a dramatic impact on intracellular growth. Furthermore, the degree of sensitivity of intracellular Y. pestis to gentamicin was also cell type dependent. These data highlight the importance to empirically establish cell type specific gentamicin protection assays to avoid potential artificial data in Y. pestis intracellular studies.
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Affiliation(s)
- Tiva T VanCleave
- Department of Microbiology and Immunology and Center for Predictive Medicine for Biodefense and Emerging Infectious Diseases, University of Louisville School of Medicine, Louisville, KY, United States
| | - Amanda R Pulsifer
- Department of Microbiology and Immunology and Center for Predictive Medicine for Biodefense and Emerging Infectious Diseases, University of Louisville School of Medicine, Louisville, KY, United States
| | - Michael G Connor
- Department of Microbiology and Immunology and Center for Predictive Medicine for Biodefense and Emerging Infectious Diseases, University of Louisville School of Medicine, Louisville, KY, United States
| | - Jonathan M Warawa
- Department of Microbiology and Immunology and Center for Predictive Medicine for Biodefense and Emerging Infectious Diseases, University of Louisville School of Medicine, Louisville, KY, United States
| | - Matthew B Lawrenz
- Department of Microbiology and Immunology and Center for Predictive Medicine for Biodefense and Emerging Infectious Diseases, University of Louisville School of Medicine, Louisville, KY, United States
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4
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Horn J, Stelzner K, Rudel T, Fraunholz M. Inside job: Staphylococcus aureus host-pathogen interactions. Int J Med Microbiol 2017; 308:607-624. [PMID: 29217333 DOI: 10.1016/j.ijmm.2017.11.009] [Citation(s) in RCA: 129] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Revised: 11/17/2017] [Accepted: 11/21/2017] [Indexed: 12/21/2022] Open
Abstract
Staphylococcus aureus is a notorious opportunistic pathogen causing a plethora of diseases. Recent research established that once phagocytosed by neutrophils and macrophages, a certain percentage of S. aureus is able to survive within these phagocytes which thereby even may contribute to dissemination of the pathogen. S. aureus further induces its uptake by otherwise non-phagocytic cells and the ensuing intracellular cytotoxicity is suggested to lead to tissue destruction, whereas bacterial persistence within cells is thought to lead to immune evasion and chronicity of infections. We here review recent work on the S. aureus host pathogen interactions with a focus on the intracellular survival of the pathogen.
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Affiliation(s)
- Jessica Horn
- Chair of Microbiology, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Kathrin Stelzner
- Chair of Microbiology, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Thomas Rudel
- Chair of Microbiology, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Martin Fraunholz
- Chair of Microbiology, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany.
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5
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Chu J, Smelkinson MG, Dorward DW, Zarember KA, Gallin JI. Early Intracellular Trafficking of Granulibacter bethesdensis in Human Macrophages. Infect Immun 2017; 85:e00847-16. [PMID: 28320834 PMCID: PMC5442635 DOI: 10.1128/iai.00847-16] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Accepted: 03/12/2017] [Indexed: 01/30/2023] Open
Abstract
Granulibacter bethesdensis is a Gram-negative bacterium that infects patients with chronic granulomatous disease (CGD), a primary immunodeficiency marked by a defect in NOX2, the phagocyte NADPH oxidase. Previous studies have shown that NOX2 is essential for killing of G. bethesdensis by neutrophils and monocytes and that the bacteriostatic activity of monocyte-derived macrophages (MDM) requires NOX2 and gamma interferon (IFN-γ) pretreatment. To determine whether G. bethesdensis evades phagolysosomal killing, a host defense pathway intact in both normal and CGD MDM, or whether it occupies a distinct intracellular niche in CGD MDM, we assessed the trafficking patterns of this organism. We observed colocalization of G. bethesdensis with an early endosome antigen 1 (EEA1)-positive compartment, followed by colocalization with lysosome-associated membrane protein 1 (LAMP1)-positive and LysoTracker-positive late phagosomes; these characteristics were similar in both normal and CGD MDM. Despite localization to acidified late phagosomes, viable G. bethesdensis cells were recovered from viable MDM in numbers greater than in the initial input up to 6 days after infection. G. bethesdensis remains, and in some cases appears to divide, within a membrane-bound compartment for the entire 6-day time course. These findings indicate that this organism resists both oxygen-dependent and oxygen-independent phagolysosomal antimicrobial systems of human macrophages.
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Affiliation(s)
- Jessica Chu
- Laboratory of Host Defenses, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Margery G Smelkinson
- Biological Imaging Section, Research Technologies Branch, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - David W Dorward
- Electron Microscopy Unit, Research Technologies Branch, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
| | - Kol A Zarember
- Laboratory of Host Defenses, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - John I Gallin
- Laboratory of Host Defenses, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
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Greenlee-Wacker MC, Nauseef WM. IFN-γ targets macrophage-mediated immune responses toward Staphylococcus aureus. J Leukoc Biol 2016; 101:751-758. [PMID: 27707882 DOI: 10.1189/jlb.4a1215-565rr] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Revised: 09/01/2016] [Accepted: 09/08/2016] [Indexed: 12/20/2022] Open
Abstract
Infections, especially with Staphylococcus aureus (SA), commonly cause morbidity and mortality in patients with chronic granulomatous disease (CGD), a condition characterized by a defective phagocyte oxidase. IFN-γ reduces the frequency and consequences of infection in CGD by mechanisms that remain unknown. As IFN-γ promotes bacterial killing, efferocytosis of effete polymorphonuclear neutrophils (PMN), and cytokine production in macrophages-the same macrophage effector functions that are impaired in response to SA-we hypothesized that IFN-γ may reverse these defects and thereby, augment macrophage control of SA during infection. IFN-γ primed activation of the NADPH oxidase in a time-dependent manner, enhanced killing of ingested SA independent of any effects on phagocytosis, and increased binding of SA-laden neutrophils (PMN-SA) to macrophages. However, IFN-γ did not increase the percentage of apoptotic PMN or PMN-SA internalized by macrophages. Under conditions in which viable SA were eliminated, PMN-SA primed the inflammasome for subsequent activation by silica but did not induce IL-1β production by macrophages. IFN-γ enhanced IL-6 production in response to SA or PMN-SA but did not increase inflammasome activation in response to either agonist. In summary, IFN-γ augmented direct killing of SA by macrophages, promoted engagement of PMN-SA, and enhanced macrophage-mediated cytokine responses that could collectively augment control of SA infection. Together, these findings support the hypothesis that IFN-γ improves responsiveness of macrophages to SA and provides insights into the mechanism of the clinical benefits of IFN-γ.
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Affiliation(s)
| | - William M Nauseef
- Inflammation Program and Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, and Veterans Affairs Medical Center, Iowa City, Iowa, USA
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Ravasi T, Mavromatis CH, Bokil NJ, Schembri MA, Sweet MJ. Co-transcriptomic Analysis by RNA Sequencing to Simultaneously Measure Regulated Gene Expression in Host and Bacterial Pathogen. Methods Mol Biol 2016; 1390:145-158. [PMID: 26803628 DOI: 10.1007/978-1-4939-3335-8_10] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Intramacrophage pathogens subvert antimicrobial defence pathways using various mechanisms, including the targeting of host TLR-mediated transcriptional responses. Conversely, TLR-inducible host defence mechanisms subject intramacrophage pathogens to stress, thus altering pathogen gene expression programs. Important biological insights can thus be gained through the analysis of gene expression changes in both the host and the pathogen during an infection. Traditionally, research methods have involved the use of qPCR, microarrays and/or RNA sequencing to identify transcriptional changes in either the host or the pathogen. Here we describe the application of RNA sequencing using samples obtained from in vitro infection assays to simultaneously quantify both host and bacterial pathogen gene expression changes, as well as general approaches that can be undertaken to interpret the RNA sequencing data that is generated. These methods can be used to provide insights into host TLR-regulated transcriptional responses to microbial challenge, as well as pathogen subversion mechanisms against such responses.
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Affiliation(s)
- Timothy Ravasi
- Integrative Systems Biology Laboratory, Division of Biological and Environmental Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal, Kingdom of Saudi Arabia.
- Division of Computer, Electricaland Mathematical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal, Kingdom of Saudi Arabia.
- Division of Medical Genetics, Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA.
| | - Charalampos Harris Mavromatis
- Integrative Systems Biology Laboratory, Division of Biological and Environmental Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal, Kingdom of Saudi Arabia
- Division of Computer, Electricaland Mathematical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal, Kingdom of Saudi Arabia
- Division of Medical Genetics, Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA
| | - Nilesh J Bokil
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, Brisbane, QLD, 4072, Australia
- Australian Infectious Diseases Research Centre, The University of Queensland, St Lucia, Brisbane, QLD, 4072, Australia
| | - Mark A Schembri
- Australian Infectious Diseases Research Centre, The University of Queensland, St Lucia, Brisbane, QLD, 4072, Australia
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Matthew J Sweet
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, Brisbane, QLD, 4072, Australia.
- Australian Infectious Diseases Research Centre, The University of Queensland, St Lucia, Brisbane, QLD, 4072, Australia.
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8
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Mulye M, Bechill MP, Grose W, Ferreira VP, Lafontaine ER, Wooten RM. Delineating the importance of serum opsonins and the bacterial capsule in affecting the uptake and killing of Burkholderia pseudomallei by murine neutrophils and macrophages. PLoS Negl Trop Dis 2014; 8:e2988. [PMID: 25144195 PMCID: PMC4140662 DOI: 10.1371/journal.pntd.0002988] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2014] [Accepted: 05/18/2014] [Indexed: 12/30/2022] Open
Abstract
Infection of susceptible hosts by the encapsulated Gram-negative bacterium Burkholderia pseudomallei (Bp) causes melioidosis, with septic patients attaining mortality rates ≥ 40%. Due to its high infectivity through inhalation and limited effective therapies, Bp is considered a potential bioweapon. Thus, there is great interest in identifying immune effectors that effectively kill Bp. Our goal is to compare the relative abilities of murine macrophages and neutrophils to clear Bp, as well as determine the importance of serum opsonins and bacterial capsule. Our findings indicate that murine macrophages and neutrophils are inherently unable to clear either unopsonized Bp or the relatively-avirulent acapsular bacterium B. thailandensis (Bt). Opsonization of Bp and Bt with complement or pathogen-specific antibodies increases macrophage-uptake, but does not promote clearance, although antibody-binding enhances complement deposition. In contrast, complement opsonization of Bp and Bt causes enhanced uptake and killing by neutrophils, which is linked with rapid ROS induction against bacteria exhibiting a threshold level of complement deposition. Addition of bacteria-specific antibodies enhances complement deposition, but antibody-binding alone cannot elicit neutrophil clearance. Bp capsule provides some resistance to complement deposition, but is not anti-phagocytic or protective against reactive oxygen species (ROS)-killing. Macrophages were observed to efficiently clear Bp only after pre-activation with IFNγ, which is independent of serum- and/or antibody-opsonization. These studies indicate that antibody-enhanced complement activation is sufficient for neutrophil-clearance of Bp, whereas macrophages are ineffective at clearing serum-opsonized Bp unless pre-activated with IFNγ. This suggests that effective immune therapies would need to elicit both antibodies and Th1-adaptive responses for successful prevention/eradication of melioidosis.
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Affiliation(s)
- Minal Mulye
- Department of Medical Microbiology and Immunology, University of Toledo College of Medicine, Toledo, Ohio, United States of America
| | - Michael P. Bechill
- Department of Medical Microbiology and Immunology, University of Toledo College of Medicine, Toledo, Ohio, United States of America
| | - William Grose
- Department of Medical Microbiology and Immunology, University of Toledo College of Medicine, Toledo, Ohio, United States of America
- Department of Infectious Diseases, University of Georgia, Athens, Georgia, United States of America
| | - Viviana P. Ferreira
- Department of Medical Microbiology and Immunology, University of Toledo College of Medicine, Toledo, Ohio, United States of America
| | - Eric R. Lafontaine
- Department of Infectious Diseases, University of Georgia, Athens, Georgia, United States of America
| | - R. Mark Wooten
- Department of Medical Microbiology and Immunology, University of Toledo College of Medicine, Toledo, Ohio, United States of America
- * E-mail:
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Pávková I, Brychta M, Strašková A, Schmidt M, Macela A, Stulík J. Comparative proteome profiling of host–pathogen interactions: insights into the adaptation mechanisms of Francisella tularensis in the host cell environment. Appl Microbiol Biotechnol 2013; 97:10103-15. [DOI: 10.1007/s00253-013-5321-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Revised: 09/30/2013] [Accepted: 10/09/2013] [Indexed: 11/30/2022]
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10
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Larsen AK, Nymo IH, Boysen P, Tryland M, Godfroid J. Entry and elimination of marine mammal Brucella spp. by hooded seal (Cystophora cristata) alveolar macrophages in vitro. PLoS One 2013; 8:e70186. [PMID: 23936159 PMCID: PMC3723690 DOI: 10.1371/journal.pone.0070186] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Accepted: 06/16/2013] [Indexed: 11/26/2022] Open
Abstract
A high prevalence of Brucellapinnipedialis serology and bacteriology positive animals has been found in the Northeast Atlantic stock of hooded seal (Cystophoracristata); however no associated gross pathological changes have been identified. Marine mammal brucellae have previously displayed different infection patterns in human and murine macrophages. To investigate if marine mammal Brucella spp. are able to invade and multiply in cells originating from a presumed host species, we infected alveolar macrophages from hooded seal with a B. pinnipedialis hooded seal isolate. Hooded seal alveolar macrophages were also challenged with B. pinnipedialis reference strain (NCTC 12890) from harbor seal (Phocavitulina), B. ceti reference strain (NCTC 12891) from harbor porpoise (Phocoenaphocoena) and a B. ceti Atlantic white-sided dolphin (Lagenorhynchusacutus) isolate (M83/07/1), to evaluate possible species-specific differences. Brucella suis 1330 was included as a positive control. Alveolar macrophages were obtained by post mortem bronchoalveolar lavage of euthanized hooded seals. Phenotyping of cells in the lavage fluid was executed by flow cytometry using the surface markers CD14 and CD18. Cultured lavage cells were identified as alveolar macrophages based on morphology, expression of surface markers and phagocytic ability. Alveolar macrophages were challenged with Brucella spp. in a gentamicin protection assay. Following infection, cell lysates from different time points were plated and evaluated quantitatively for colony forming units. Intracellular presence of B. pinnipedialis hooded seal isolate was verified by immunocytochemistry. Our results show that the marine mammal brucellae were able to enter hooded seal alveolar macrophages; however, they did not multiply intracellularly and were eliminated within 48 hours, to the contrary of B. suis that showed the classical pattern of a pathogenic strain. In conclusion, none of the four marine mammal strains tested were able to establish a persistent infection in primary alveolar macrophages from hooded seal.
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Affiliation(s)
- Anett K Larsen
- Section for Arctic Veterinary Medicine, Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, Tromsø, Norway.
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Hamza T, Dietz M, Pham D, Clovis N, Danley S, Li B, Li B. Intra-cellular Staphylococcus aureus alone causes infection in vivo. Eur Cell Mater 2013; 25:341-50; discussion 350. [PMID: 23832687 PMCID: PMC3830899 DOI: 10.22203/ecm.v025a24] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Chronic and recurrent bone infections occur frequently but have not been explained. Staphylococcus aureus (S. aureus) is often found among chronic and recurrent infections and may be responsible for such infections. One possible reason is that S. aureus can internalize and survive within host cells and by doing so, S. aureus can evade both host defense mechanisms and most conventional antibiotic treatments. In this study, we hypothesized that intra-cellular S. aureus could induce infections in vivo. Osteoblasts were infected with S. aureus and, after eliminating extra-cellular S. aureus, inoculated into an open fracture rat model. Bacterial cultures and radiographic observations at post-operative day 21 confirmed local bone infections in animals inoculated with intra-cellular S. aureus within osteoblasts alone. We present direct in vivo evidence that intra-cellular S. aureus could be sufficient to induce bone infection in animals; we found that intra-cellular S. aureus inoculation of as low as 102 colony forming units could induce severe bone infections. Our data may suggest that intra-cellular S. aureus can "hide" in host cells during symptom-free periods and, under certain conditions, they may escape and lead to infection recurrence. Intra-cellular S. aureus therefore could play an important role in the pathogenesis of S. aureus infections, especially those chronic and recurrent infections in which disease episodes may be separated by weeks, months, or even years.
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Affiliation(s)
- Therwa Hamza
- Department of Orthopaedics, School of Medicine, West Virginia University, Morgantown, WV 26506,Department of Basic Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, WV 26506
| | - Matthew Dietz
- Department of Orthopaedics, School of Medicine, West Virginia University, Morgantown, WV 26506
| | - Danh Pham
- Department of Orthopaedics, School of Medicine, West Virginia University, Morgantown, WV 26506
| | - Nina Clovis
- Department of Orthopaedics, School of Medicine, West Virginia University, Morgantown, WV 26506
| | - Suzanne Danley
- Department of Orthopaedics, School of Medicine, West Virginia University, Morgantown, WV 26506
| | - Bingyun Li
- Department of Orthopaedics, School of Medicine, West Virginia University, Morgantown, WV 26506,Department of Basic Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, WV 26506,WVNano Initiative, Morgantown, WV 26506,Mary Babb Randolph Cancer Center, Morgantown, WV 26506,Correspondence to: Bingyun Li, PhD, Associate Professor, Director, Nanomedicine Laboratory, Department of Orthopaedics, School of Medicine, West Virginia University, Morgantown, WV 26506-9196, USA, Tel: 1-304-293-1075, Fax: 1-304-293-7070,
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12
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Bokil NJ, Totsika M, Carey AJ, Stacey KJ, Hancock V, Saunders BM, Ravasi T, Ulett GC, Schembri MA, Sweet MJ. Intramacrophage survival of uropathogenic Escherichia coli: Differences between diverse clinical isolates and between mouse and human macrophages. Immunobiology 2011; 216:1164-71. [DOI: 10.1016/j.imbio.2011.05.011] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Accepted: 05/16/2011] [Indexed: 10/18/2022]
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Medina E, Goldmann O. In vivo and ex vivo protocols for measuring the killing of extracellular pathogens by macrophages. ACTA ACUST UNITED AC 2011; Chapter 14:Unit 14.19.1-17. [PMID: 21400679 DOI: 10.1002/0471142735.im1419s92] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
This unit describes a series of in vivo/ex vivo combined protocols for investigating the interactions (adhesion, phagocytosis, and killing) of extracellular bacteria with peritoneal murine macrophages. It includes steps needed for in vivo infection of murine peritoneal macrophages after intraperitoneal inoculation with the pathogen of interest, as well as the measurement of bacteria associated with or truly internalized by these phagocytic cells. Several protocols for the ex vivo measurement of the ability of peritoneal macrophages to kill the microorganisms that have been ingested during the in vivo infection assay are included.
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Affiliation(s)
- Eva Medina
- Infection Immunology Research Group, Helmholtz Centre for Infection Research, Braunschweig, Germany
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14
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Nitric oxide protects bacteria from aminoglycosides by blocking the energy-dependent phases of drug uptake. Antimicrob Agents Chemother 2011; 55:2189-96. [PMID: 21343448 DOI: 10.1128/aac.01203-10] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Our investigations have identified a mechanism by which exogenous production of nitric oxide (NO) induces resistance of Gram-positive and -negative bacteria to aminoglycosides. An NO donor was found to protect Salmonella spp. against structurally diverse classes of aminoglycosides of the 4,6-disubstituted 2-deoxystreptamine group. Likewise, NO generated enzymatically by inducible NO synthase of gamma interferon-primed macrophages protected intracellular Salmonella against the cytotoxicity of gentamicin. NO levels that elicited protection against aminoglycosides repressed Salmonella respiratory activity. NO nitrosylated terminal quinol cytochrome oxidases, without exerting long-lasting inhibition of NADH dehydrogenases of the electron transport chain. The NO-mediated repression of respiratory activity blocked both energy-dependent phases I and II of aminoglycoside uptake but not the initial electrostatic interaction of the drug with the bacterial cell envelope. As seen in Salmonella, the NO-dependent inhibition of the electron transport chain also afforded aminoglycoside resistance to the clinically important pathogens Pseudomonas aeruginosa and Staphylococcus aureus. Together, these findings provide evidence for a model in which repression of aerobic respiration by NO fluxes associated with host inflammatory responses can reduce drug uptake, thus promoting resistance to several members of the aminoglycoside family in phylogenetically diverse bacteria.
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15
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Vincenti JE. The influence of cell-free Lactobacillus rhamnosus GG supernatant on the phagocytic activity of macrophages. ACTA ACUST UNITED AC 2010. [DOI: 10.1093/biohorizons/hzq014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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16
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Paterson GK, Cone DB, Peters SE, Maskell DJ. The enzyme phosphoglucomutase (Pgm) is required by Salmonella enterica serovar Typhimurium for O-antigen production, resistance to antimicrobial peptides and in vivo fitness. MICROBIOLOGY-SGM 2009; 155:3403-3410. [PMID: 19589833 DOI: 10.1099/mic.0.029553-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The enzyme phosphoglucomutase (Pgm) catalyses the interconversion of glucose 1-phosphate and glucose 6-phosphate and contributes to glycolysis and the generation of sugar nucleotides for biosynthesis. To assess the role of this enzyme in the biology of the pathogen Salmonella enterica serovar Typhimurium we have characterized a pgm deletion mutant in strain SL1344. Compared to SL1344, SL1344 pgm had impaired growth in vitro, was deficient in the ability to utilize galactose as a carbon source and displayed reduced O-antigen polymer length. The mutant was also more susceptible to antimicrobial peptides and showed decreased fitness in the mouse typhoid model. The in vivo phenotype of SL1344 pgm indicated a role for pgm in the early stages of infection, most likely through deficient O-antigen production. Although pgm mutants in other pathogens have potential as live attenuated vaccine strains, SL1344 pgm was not sufficiently attenuated for such use.
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Affiliation(s)
- G K Paterson
- Department of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB3 0ES, UK
| | - D B Cone
- Department of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB3 0ES, UK
| | - S E Peters
- Department of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB3 0ES, UK
| | - D J Maskell
- Department of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB3 0ES, UK
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17
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King P, Ngui J, Oppedisano F, Robins-Browne R, Holmes P, Holdsworth S. Effect of interferon gamma and CD40 ligation on intracellular monocyte survival of nontypeable Haemophilus influenzae. APMIS 2009; 116:1043-9. [PMID: 19133006 DOI: 10.1111/j.1600-0463.2008.01078.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Nontypeable Haemophilus influenzae (NTHi) is a mucosal pathogen that is a major cause of respiratory infection, including sinusitis, otitis media and bronchitis. This bacterium has evolved a number of mechanisms to facilitate its survival in the human host. Recently it has been recognized that it is capable of intracellular survival in monocytes/macrophages and epithelial cells. Previous work by the authors has demonstrated that the protective response to NTHi is Th1 predominant. This information led to the hypothesis that the intracellular survival of NTHi in human monocytes may be reduced by two key effector mechanisms of Th1-mediated immunity: interferon gamma and ligation of CD40. This study assessed the effect of interferon gamma and ligation of CD40 on the intracellular survival of NTHi in human monocytes. Responses were studied in monocytes from subjects with bronchiectasis and persistent airway infection with NTHi and compared with control subjects. The results demonstrated that different isolates of NTHi were able to survive inside monocytes. Killing of one strain of NTHi could be enhanced by the addition of interferon gamma and CD40 ligation in both control and bronchiectasis subjects. Other strains were more resistant.
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Affiliation(s)
- Paul King
- Monash University Department of Medicine, Monash Medical Centre, Melbourne, Australia.
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18
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TLR9-independent effects of inhibitory oligonucleotides on macrophage responses to S. typhimurium. Immunol Cell Biol 2008; 87:218-25. [PMID: 19048019 DOI: 10.1038/icb.2008.95] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Detection of bacterial CpG-containing DNA (CpG DNA) by innate immune cells is dependent on toll-like receptor 9 (TLR9). Here we show that the expression of tlr9 mRNA was induced in mouse bone marrow-derived macrophages (BMMs) upon infection with the facultative Gram-negative intracellular bacterium Salmonella enterica serovar Typhimurium (S. typhimurium). Treatment of BMM with the inhibitory oligonucleotide (ODN) 2114, an antagonist of TLR9 signalling, enhanced intracellular S. typhimurium numbers approximately fivefold, whereas a control ODN (2310) had no significant effect. Surprisingly, 2114 also amplified S. typhimurium bacterial loads in TLR9-deficient BMM. Indeed, 2114 suppressed responses (nuclear factor-kappaB-dependent reporter gene expression and interleukin-12p40 secretion) to not only CpG DNA, but also the TLR2 ligand Pam(3)Cys, in BMM and RAW264 cells in a sequence-specific manner. Inhibitory ODNs, which have been proposed as therapeutic agents for the treatment of systemic lupus erythematosus because of their inhibitory effects on TLR9 signalling, may thus compromise the host response to bacterial pathogens through TLR9-independent mechanisms.
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19
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High-throughput, single-cell analysis of macrophage interactions with fluorescently labeled Bacillus anthracis spores. Appl Environ Microbiol 2008; 74:5201-10. [PMID: 18552183 DOI: 10.1128/aem.02890-07] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The engulfment of Bacillus anthracis spores by macrophages is an important step in the pathogenesis of inhalational anthrax. However, from a quantitative standpoint, the magnitude to which macrophages interact with and engulf spores remains poorly understood, in part due to inherent limitations associated with commonly used assays. To analyze phagocytosis of spores by RAW264.7 macrophage-like cells in a high-throughput, nonsubjective manner, we labeled B. anthracis Sterne 7702 spores prior to infection with an Alexa Fluor 488 amine-reactive dye in a manner that did not alter their germination, growth kinetics, and heat resistance. Using flow cytometry, large numbers of cells exposed to labeled spores were screened to concurrently discriminate infected from uninfected cells and surface-associated from internalized spores. These experiments revealed that spore uptake was not uniform, but instead, highly heterogeneous and characterized by subpopulations of infected and uninfected cells, as well as considerable variation in the number of spores associated with individual cells. Flow cytometry analysis of infections demonstrated that spore uptake was independent of the presence or absence of fetal bovine serum, a germinant that, while routinely used in vitro, complicates the interpretation of the outcome of infections. Two commonly used macrophage cell lines, RAW264.7 and J774A.1 cells, were compared, revealing significant disparity between these two models in the rates of phagocytosis of labeled spores. These studies provide the experimental framework for investigating mechanisms of spore phagocytosis, as well as quantitatively evaluating strategies for interfering with macrophage binding and uptake of spores.
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20
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Al-Mariri A. Survival and replication of Escherichia coli O157:H7 inside the mice peritoneal macrophages. Braz J Microbiol 2008; 39:5-9. [PMID: 24031167 PMCID: PMC3768364 DOI: 10.1590/s1517-83822008000100002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2007] [Revised: 10/17/2007] [Accepted: 01/20/2008] [Indexed: 12/02/2022] Open
Abstract
The replication of Escherichia coli O157:H7 on the resident peritoneal macrophages of four mice strains (BALB/c, CD1, C57BL, and Swiss) has been investigated. Macrophagial bactericidal killing activity was estimated via studying their ability to internalize (gentamicin-protected) E. coli during 2, 4, 24, and 48 h assays. Host genetic background has been found to show no significant effect on the ability of resident peritoneal macrophages to kill E. coli O157:H7.
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Affiliation(s)
- Ayman Al-Mariri
- Department of Molecular Biology and Biotechnology , Atomic Energy Commission , Damascus Syria
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21
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Adkins I, Köberle M, Gröbner S, Bohn E, Autenrieth IB, Borgmann S. Yersinia outer proteins E, H, P, and T differentially target the cytoskeleton and inhibit phagocytic capacity of dendritic cells. Int J Med Microbiol 2007; 297:235-44. [PMID: 17462949 DOI: 10.1016/j.ijmm.2007.02.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2006] [Revised: 01/19/2007] [Accepted: 02/21/2007] [Indexed: 12/16/2022] Open
Abstract
Through Yersinia outer proteins (Yops) Yersinia disrupt the actin cytoskeleton of epithelial cells and macrophages, and this leads to a decreased capability of these cells to internalize bacteria. We examined the effects of different Yops of Y. enterocolitica serotype O8 on the cytoskeleton and phagocytic capacity of murine dendritic cells (DCs). DCs were infected with several Yersinia mutant strains deficient in one Yop or translocating only a single Yop. Analyses of infected DCs by microscopy showed that YopE, YopH and YopT cooperate to rapidly damage the actin cytoskeleton of DCs. Furthermore, microscopic analyses and gentamicin killing assays revealed that the maximum reduction of bacterial uptake was achieved by Yersinia mutant strains translocating only a single Yop (YopE or YopH) indicating that these Yops enable Yersinia to inhibit the phagocytic function of DCs.
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Affiliation(s)
- Irena Adkins
- Institute of Medical Microbiology and Hygiene, Eberhard-Karls-University of Tübingen, Tübingen, Germany.
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22
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Hu H, Sa Q, Koehler TM, Aronson AI, Zhou D. Inactivation of Bacillus anthracis spores in murine primary macrophages. Cell Microbiol 2006; 8:1634-42. [PMID: 16984418 DOI: 10.1111/j.1462-5822.2006.00738.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The current model for pathogenesis of inhalation anthrax indicates that the uptake and fate of Bacillus anthracis spores in alveolar macrophages are critical to the infection process. We have employed primary macrophages, which are more efficient for spore uptake than the macrophage-like cell line RAW264.7, to investigate spore uptake and survival. We found that at a multiplicity of infection (moi) of 5, greater than 80% of the spores of the Sterne strain containing only the pXO1 plasmid were internalized within 1 h. Within 4 h post infection, viability of internalized Sterne spores decreased to approximately 40%. Intracellular vegetative bacteria represented less than 1% of the total spore inoculum throughout the course of infection suggesting effective killing of germinated spores and/or vegetative bacteria. The Sterne spores trafficked quickly to phagolysosomes as indicated by colocalization with lysosome-associated membrane protein 1 (LAMP1). Expression of a dominant-negative Rab7 that blocked lysosome fusion enhanced Sterne spore survival. Addition of d-alanine to the infection resulted in 75% inhibition of spore germination and increased survival of internalized spores of the Sterne strain and a pathogenic strain containing both the pXO1 and pXO2 plasmids. Inhibition was reversed by the addition of l-alanine, which resumed spore germination and subsequent spore killing. Our data indicate that B. anthracis spores germinate in and are subsequently killed by primary macrophages.
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Affiliation(s)
- Haijing Hu
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
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23
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Leuzzi R, Serino L, Scarselli M, Savino S, Fontana MR, Monaci E, Taddei A, Fischer G, Rappuoli R, Pizza M. Ng-MIP, a surface-exposed lipoprotein of Neisseria gonorrhoeae, has a peptidyl-prolyl cis/trans isomerase (PPIase) activity and is involved in persistence in macrophages. Mol Microbiol 2006; 58:669-81. [PMID: 16238618 DOI: 10.1111/j.1365-2958.2005.04859.x] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Macrophage infectivity potentiators (MIPs) are a family of surface-exposed virulence factors of intracellular microorganisms such as Legionella, Chlamydia and Trypanosoma. These proteins display peptidyl-prolyl cis/trans isomerase (PPIase) activity that is inhibited by immunosuppressants FK506 and rapamycin. Here we describe the identification and characterization in Neisseria gonorrhoeae of Ng-MIP, a surface-exposed lipoprotein with high homology to MIPs. The protein is an homodimer with rapamycin-inhibited PPIase activity confirming that it is a functional member of the MIP family. A knock-out strain, generated by deletion of the mip gene in N. gonorrhoeae F62 strain, was evaluated for its role in infection of mouse and human macrophages. We show that Ng-MIP promotes the intracellular survival of N. gonorrhoeae in macrophages, highlighting a possible role of this protein in promoting the persistence of gonococcal infection.
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Affiliation(s)
- Rosanna Leuzzi
- IRIS, Chiron S.r.l., Via Fiorentina, 1, 53100 Siena, Italy
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24
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Kim HJ, Kim EY, Hong Y, Rhee JH, Choy HE. Alternative methods to limit extracellular bacterial activity for enumeration of intracellular bacteria. J Microbiol Methods 2006; 64:17-26. [PMID: 15927288 DOI: 10.1016/j.mimet.2005.04.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2004] [Revised: 04/01/2005] [Accepted: 04/06/2005] [Indexed: 11/15/2022]
Abstract
The gentamicin survival assay, a method routinely used to estimate bacterial infection of eukaryotic host cells, depends on the presumed limited penetration of gentamicin across the eukaryotic cell membrane. However, some studies have suggested that gentamicin may in fact enter eukaryotic cells and kill intracellular bacteria. In this study we devised alternative methods to enumerate intracellular Salmonellae using a lytic bacteriophage, SP6, and an amino acid auxotroph, Pro- mutant, which replicates selectively within host cells in the presence of its uptake inhibitor, 3,4-dehydro-L-proline. The conventional gentamicin survival assay was systematically compared with the alternative methods for the enumeration of intracellular Salmonellae. We found that gentamicin decreases the survival of intracellular Salmonellae when added to extracellular media at concentrations above 20 microg/ml. The alternative methods do not suffer from this disadvantage, suggesting that they should be used to replace the gentamicin survival assay. In addition, the proline auxotroph method could be applied to detect bacterial release from host cells.
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Affiliation(s)
- Hyun-Ju Kim
- Genome Research Center for Enteropathogenic Bacteria and Research Institute of Vibrio Infection, South Korea
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25
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Simons MP, Nauseef WM, Apicella MA. Interactions of Neisseria gonorrhoeae with adherent polymorphonuclear leukocytes. Infect Immun 2005; 73:1971-7. [PMID: 15784537 PMCID: PMC1087443 DOI: 10.1128/iai.73.4.1971-1977.2005] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Neisseria gonorrhoeae causes severe exudative urethritis. The exudates from infected individuals contain large numbers of polymorphonuclear leukocytes (PMN) with ingested gonococci. The fate of N. gonorrhoeae within PMN has been a topic of debate for years. In this study, we examined the interactions of N. gonorrhoeae with PMN adherent to surfaces as a system that better models events during clinical disease. Using chemiluminescence to measure reactive oxygen species (ROS), we found that N. gonorrhoeae stimulated PMN to produce a respiratory burst. Different kinetics were seen when PMN were stimulated with opsonized zymosan particles. In addition, ROS were produced predominantly inside the PMN in response to gonococci. Laser scanning confocal microscopy and transmission electron microscopy showed that N. gonorrhoeae rapidly associated with PMN under these experimental conditions and was internalized. Some gonococci were cleared in the first 30 to 60 min after phagocytosis, but a majority of the population persisted for 6 h after phagocytosis. Quantification of viable organisms showed that a significant portion of the population resisted killing. The viability of this subpopulation remained unchanged for 2 h after phagocytosis. A significant increase of viable gonococci from 1 to 6 h was also observed, suggesting intracellular replication. Four different N. gonorrhoeae strains demonstrated the same capacity to resist PMN-mediated killing, whereas Escherichia coli was rapidly killed by PMN under the same conditions. Taken together, these findings suggest that a subpopulation of N. gonorrhoeae resists killing and replicates within PMN phagosomes in spite of NADPH oxidase activation.
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Affiliation(s)
- Mark P Simons
- Department of Microbiology, 3-403 Bowen Science Building, University of Iowa, 51 Newton Rd., Iowa City, IA 52242, USA
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26
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Qazi SNA, Harrison SE, Self T, Williams P, Hill PJ. Real-time monitoring of intracellular Staphylococcus aureus replication. J Bacteriol 2004; 186:1065-77. [PMID: 14762001 PMCID: PMC344210 DOI: 10.1128/jb.186.4.1065-1077.2004] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A high-throughput system to rapidly assess the intracellular replication of Staphylococcus aureus has been developed utilizing S. aureus transformed with a dual gfp-luxABCDE reporter operon under the control of a growth-dependent promoter. Replication of tagged bacteria internalized into bovine mammary epithelial cells (MAC-T) could be measured by monitoring fluorescence and bioluminescence from the reporter operon following removal of extracellular bacteria from the plates. Bacterial replication inside cells was confirmed by a novel ex vivo time-lapse confocal microscopic method. This assay of bacterial replication was used to evaluate the efficacy of antibiotics which are commonly used to treat staphylococcal infections. Not all antibiotics tested were able to prevent intracellular replication of S. aureus and some were ineffective at preventing replication of intracellular bacteria at concentrations above the MIC determined for bacteria in broth culture. Comparison of the fluorescence and bioluminescence signals from the bacteria enabled effects on protein synthesis and metabolism to be discriminated and gave information on the entry of compounds into the eukaryotic cell, even if bacterial replication was not prevented. Elevated resistance of S. aureus to antibiotics inside host cells increases the likelihood of selecting S. aureus strains which are resistant to commonly used antimicrobial agents within the intracellular niche. The approach presented directly assesses intracellular efficacy of antibiotics and provides an evidence-based approach to antibiotic selection for prescribing physicians and medical microbiologists.
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Affiliation(s)
- S N A Qazi
- Institute of Infection, Immunity, and Inflammation. Institute of Cell Signalling, Queens Medical Centre, University of Nottingham, Nottingham NG7 2UH, United Kingdom
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