scholarly journals Antibacterial Action of Polyphosphate onPorphyromonas gingivalis

2010 ◽  
Vol 55 (2) ◽  
pp. 806-812 ◽  
Author(s):  
Ji-Hoi Moon ◽  
Jae-Hong Park ◽  
Jin-Yong Lee
Keyword(s):  
Oxidative Stress ◽  
Inoculum Size ◽  
Dilution Method ◽  
Agar Dilution Method ◽  
Iron Storage ◽  
Gram Negative ◽  
Dense Granules ◽  
Genes Encoding ◽  
Atypical Cells ◽  
And Oxidative Stress

ABSTRACTPolyphosphate [poly(P)] has antibacterial activity against various Gram-positive bacteria. In contrast, Gram-negative bacteria are generally resistant to poly(P). Here, we describe the antibacterial characterization of poly(P) against a Gram-negative periodontopathogen,Porphyromonas gingivalis. The MICs of pyrophosphate (Na4P2O7) and all poly(P) (Nan+ 2PnO3n+ 1;n= 3 to 75) tested for the bacterium by the agar dilution method were 0.24% and 0.06%, respectively. Orthophosphate (Na2HPO4) failed to inhibit bacterial growth. Poly-P75 was chosen for further study. In liquid medium, 0.03% poly-P75 was bactericidal againstP. gingivalisirrespective of the growth phase and inoculum size, ranging from 105to109cells/ml. UV-visible spectra of the pigments fromP. gingivalisgrown on blood agar with or without poly-P75 showed that poly-P75 reduced the formation of μ-oxo bisheme by the bacterium. Poly-P75 increased hemin accumulation on theP. gingivalissurface and decreased energy-driven uptake of hemin by the bacterium. The expression of the genes encoding hemagglutinins, gingipains, hemin uptake loci, chromosome replication, and energy production was downregulated, while that of the genes related to iron storage and oxidative stress was upregulated by poly-P75. The transmission electron microscope showed morphologically atypical cells with electron-dense granules and condensed nucleoid in the cytoplasm. Collectively, poly(P) is bactericidal againstP. gingivalis, in which hemin/heme utilization is disturbed and oxidative stress is increased by poly(P).

scholarly journals Roles of FadRACB system in formaldehyde detoxification, oxidative stress alleviation and antibiotic susceptibility in Stenotrophomonas maltophilia

2020 ◽  
Author(s):  
Li-Hua Li ◽  
Cheng-Mu Wu ◽  
Yi-Tsung Lin ◽  
Sz-Yun Pan ◽  
Tsuey-Ching Yang
Keyword(s):  
Oxidative Stress ◽  
Antibiotic Susceptibility ◽  
Stenotrophomonas Maltophilia ◽  
Dilution Method ◽  
Agar Dilution Method ◽  
Rt Pcr ◽  
Stress Alleviation ◽  
Significant Difference ◽  
Formaldehyde Toxicity ◽  
And Oxidative Stress

Abstract Background Formaldehyde toxicity is invariably stressful for microbes. Stenotrophomonas maltophilia, a human opportunistic pathogen, is widely distributed in different environments and has evolved an array of systems to alleviate various stresses. Objectives To characterize the role of the formaldehyde detoxification system FadRACB of S. maltophilia in formaldehyde detoxification, oxidative stress alleviation and antibiotic susceptibility. Methods Presence of the fadRACB operon was verified by RT–PCR. Single or combined deletion mutants of the fadRACB operon were constructed for functional assays. Formaldehyde, menadione and quinolone susceptibilities were assessed by observing cell viability in formaldehyde-, menadione- and quinolone-containing media, respectively. Susceptibility to hydrogen peroxide was evaluated by disc diffusion assay. The agar dilution method was used to assess bacterial antibiotic susceptibilities. Expression of fadRACB was assessed by quantitative RT–PCR. Results The fadR, fadA, fadC and fadB genes were arranged in an operon. Mutants of fadA and/or fadB were more susceptible to formaldehyde and oxidative stress than the WT KJ strain of S. maltophilia. No significant difference was observed in the ability of a fadC single mutant to ameliorate formaldehyde and oxidative stress; however, simultaneous inactivation of fadA, fadB and fadC further enhanced susceptibility to formaldehyde and oxidative stress. In addition, compared with WT KJ, the triple mutant KJΔFadACB was more susceptible to quinolones and more resistant to aminoglycosides. FadR functions as a repressor for the fadRACB operon. The FadRACB operon has moderate expression in aerobically grown WT KJ and is further derepressed by formaldehyde challenge or oxidative stress, but not by antibiotics. Conclusions The FadACB system contributes to mitigation of formaldehyde toxicity and oxidative stress and cross-protects S. maltophilia from quinolones.

scholarly journals Detection of OXA-181/OXA-48 carbapenemase producing Enterobacteriaceae in Bangladesh

2016 ◽  
Vol 9 (2) ◽  
pp. 45-51 ◽  
Author(s):  
Rehana Khatun ◽  
SM Shamsuzzaman
Keyword(s):  
Health Concern ◽  
Dilution Method ◽  
Agar Dilution Method ◽  
College Hospital ◽  
Medical College ◽  
Epidemiological Monitoring ◽  
Diffusion Technique ◽  
Genes Encoding ◽  
High Level ◽  
Phenotypic Tests

Carbapenem resistant Enterobacteriaceae (CRE) is becoming a major public health concern globally. Detection of carbapenem hydrolyzing enzyme carbapenemase in Enterobacteriaceae is important to institute appropriate therapy and to initiate preventive measures. This study was designed to determine the presence of carbapenemase producers among the CRE isolated from patients at Dhaka Medical College Hospital, Bangladesh. Twenty-nine CRE strains detected by disk diffusion technique were included in the study. Minimum inhibitory concentration of imipenem and tigecycline was determined by agar dilution method. Carbapenemase production was phenotypically detected by Modified Hodge test while MBL producers were detected by combined disk and double disk synergy tests. Genes encoding blaNDM-1, blaOXA-181, blaOXA-48, blaKPC, blaCTX-M-15, blaOXA-1-group were identified by polymerase chain reaction (PCR). Out of 29 CRE, nineteen (65.6%) were positive for carbapenemase by any of the three phenotypic tests namely MHT, CD or DD tests. Those 19 isolates were also positive either for blaNDM-1 or blaOXA-181/blaOXA-48 by PCR. Of the 19 PCR positive isolates, the rate of positivity for blaNDM- 1, blaOXA-181/blaOXA-48 and blaNDM-1+ blaOXA-181/blaOXA-48 was 73.7% (14/19), 57.9% (11/19) and 31.6% (6/19) respectively. Both blaOXA-181 and blaOXA-48 co-existed. All the carbapenemase producing organisms harboured blaCTX-M-15 except one C. freundii strain. The rate of resistance to different classes of antibiotics ranged from 63.2% to 100% except colistin and tigecycline. Organisms positive for OXA-181/OXA-48 had a low level of resistance to carbapenem (MIC 1 - 4 ì g/ml) while with NDM-1 had high level resistance to imipenem (MICs 16 - ? 32 ì g/ ml). Out of 19 carbapenemase positive isolates, 12 (63.16%) were extensively drug-resistant (XDR) and were only sensitive to tigecycline and colistin. The result of this study showed the presence of blaOXA-181/ blaOXA-48, blaNDM-1 positive strains in Bangladesh and colistin and tigecycline were the most effective drugs against carbapenemase producing Enterobacteriaceae (CPE). Epidemiological monitoring of carbapenemase producing organisms in Bangladesh is important to prevent their dissemination.Ibrahim Med. Coll. J. 2015; 9(2): 45-51

scholarly journals Novel Antibiotic Susceptibility Tests by the ATP-Bioluminescence Method Using Filamentous Cell Treatment

1998 ◽  
Vol 42 (6) ◽  
pp. 1406-1411 ◽  
Author(s):  
Noriaki Hattori ◽  
Moto-O Nakajima ◽  
Koji O’Hara ◽  
Tetsuo Sawai
Keyword(s):  
Antimicrobial Agents ◽  
Susceptibility Testing ◽  
Dilution Method ◽  
Agar Dilution Method ◽  
Test Model ◽  
The Novel ◽  
Gram Negative ◽  
Atp Bioluminescence ◽  
Filamentous Cell ◽  
Bioluminescence Method

ABSTRACT Antimicrobial susceptibility testing by the ATP-bioluminescence method has been noted for its speed; it provides susceptibility results within 2 to 5 h. However, several disagreements between the ATP method and standard methodology have been reported. The present paper describes a novel ATP method in a 3.5-h test which overcomes these deficiencies through the elimination of false-resistance discrepancies in tests on gram-negative bacteria with β-lactam agents. In our test model using Pseudomonas aeruginosa and piperacillin, it was shown that ATP in filamentous cells accounted for the false resistance. We found that 0.5% 2-amino-2-methyl-1,3-propanediol (AMPD) extracted ATP from the filamentous cells without affecting normal cells and that 0.3 U of adenosine phosphate deaminase (APDase)/ml simultaneously digested the extracted ATP. We used the mixture of these reagents for the pretreatment of cells in a procedure we named filamentous cell treatment, prior to ATP measurements. This novel ATP method with the filamentous cell treatment eliminated false-resistance discrepancies in tests on P. aeruginosa with β-lactam agents, including piperacillin, cefoperazone, aztreonam, imipenem-cilastatin, ceftazidime, and cefsulodin. Furthermore, this novel methodology produced results which agreed with those of the standard microdilution method in other tests on gram-negative and gram-positive bacteria, including P. aeruginosa, Escherichia coli,Staphylococcus aureus, and Enterococcus faecalis, for non-β-lactam agents, such as fosfomycin, ofloxacin, minocycline, and aminoglycosides. MICs obtained by the novel ATP method were also in agreement with those obtained by the agar dilution method of susceptibility testing. From these results, it was shown that the novel ATP method could be used successfully to test the activities of antimicrobial agents with the elimination of the previously reported discrepancies.

scholarly journals Oxidative Stress Sensor Keap1 Functions as an Adaptor for Cul3-Based E3 Ligase To Regulate Proteasomal Degradation of Nrf2

2004 ◽  
Vol 24 (16) ◽  
pp. 7130-7139 ◽  
Author(s):  
Akira Kobayashi ◽  
Moon-Il Kang ◽  
Hiromi Okawa ◽  
Makiko Ohtsuji ◽  
Yukari Zenke ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Stress Proteins ◽  
E3 Ligase ◽  
Genes Encoding ◽  
Cullin 3 ◽  
Ubiquitin Proteasome ◽  
A Subunit ◽  
Antioxidant Stress ◽  
And Oxidative Stress

ABSTRACT Transcription factor Nrf2 is a major regulator of genes encoding phase 2 detoxifying enzymes and antioxidant stress proteins in response to electrophilic agents and oxidative stress. In the absence of such stimuli, Nrf2 is inactive owing to its cytoplasmic retention by Keap1 and rapid degradation through the proteasome system. We examined the contribution of Keap1 to the rapid turnover of Nrf2 (half-life of less than 20 min) and found that a direct association between Keap1 and Nrf2 is required for Nrf2 degradation. In a series of domain function analyses of Keap1, we found that both the BTB and intervening-region (IVR) domains are crucial for Nrf2 degradation, implying that these two domains act to recruit ubiquitin-proteasome factors. Indeed, Cullin 3 (Cul3), a subunit of the E3 ligase complex, was found to interact specifically with Keap1 in vivo. Keap1 associates with the N-terminal region of Cul3 through the IVR domain and promotes the ubiquitination of Nrf2 in cooperation with the Cul3-Roc1 complex. These results thus provide solid evidence that Keap1 functions as an adaptor of Cul3-based E3 ligase. To our knowledge, Nrf2 and Keap1 are the first reported mammalian substrate and adaptor, respectively, of the Cul3-based E3 ligase system.

scholarly journals Toll-Like Receptor 4 Promotes NO Synthesis by Upregulating GCHI Expression under Oxidative Stress Conditions in Sheep Monocytes/Macrophages

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Shoulong Deng ◽  
Kun Yu ◽  
Baolu Zhang ◽  
Yuchang Yao ◽  
Zhixian Wang ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Nitric Oxide ◽  
Inflammatory Responses ◽  
Gram Negative Bacteria ◽  
Toll Like Receptor ◽  
Toll Like Receptor 4 ◽  
Gram Negative ◽  
Transgenic Sheep ◽  
And Oxidative Stress

Many groups of Gram-negative bacteria cause diseases that are harmful to sheep. Toll-like receptor 4 (TLR4), which is critical for detecting Gram-negative bacteria by the innate immune system, is activated by lipopolysaccharide (LPS) to initiate inflammatory responses and oxidative stress. Oxidation intermediates are essential activators of oxidative stress, as low levels of free radicals form a stressful oxidative environment that can clear invading pathogens. NO is an oxidation intermediate and its generation is regulated by nitric oxide synthase (iNOS). Guanosine triphosphate cyclohydrolase (GCHI) is the rate-limiting enzyme for tetrahydrobiopterin (BH4) synthesis, which is essential for the production of inducible iNOS. Previously, we made vectors to overexpress the sheepTLR4gene. Herein, first generation (G1) of transgenic sheep was stimulated with LPSin vivoandin vitro, and oxidative stress and GCHI expression were investigated. Oxidative injury caused by TLR4 overexpression was tightly regulated in tissues. However, the transgenic (Tg) group still secreted nitric oxide (NO) when an iNOS inhibitor was added. Furthermore, GCHI expression remained upregulated in both serum and monocytes/macrophages. Thus, overexpression of TLR4 in transgenic sheep might accelerate the clearance of invading microbes through NO generation following LPS stimulation. Additionally, TLR4 overexpression also enhances GCHI activation.

scholarly journals Stringent Response Governs the Virulence and Oxidative Stress Resistance of Francisella tularensis

2019 ◽  
Author(s):  
Zhuo Ma ◽  
Kayla King ◽  
Maha Alqahtani ◽  
Madeline Worden ◽  
Parthasarthy Muthuraman ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Stress Response ◽  
Francisella Tularensis ◽  
Stress Resistance ◽  
Stringent Response ◽  
Oxidative Stress Response ◽  
Stress Conditions ◽  
Gram Negative ◽  
And Oxidative Stress ◽  
Starvation Conditions

AbstractFrancisella tularensis is a Gram-negative bacterium responsible for causing tularemia in the northern hemisphere. F. tularensis has long been developed as a biological weapon due to its ability to cause severe illness upon inhalation of as few as ten organisms and based on its potential to be used as a bioterror agent is now classified as a Tier 1 Category A select agent by the CDC. The stringent response facilitates bacterial survival under nutritionally challenging starvation conditions. The hallmark of stringent response is the accumulation of the effector molecules ppGpp and (p)ppGpp known as stress alarmones. The relA and spoT gene products generate alarmones in several Gram-negative bacterial pathogens. RelA is a ribosome-associated ppGpp synthetase that gets activated under amino acid starvation conditions whereas, SpoT is a bifunctional enzyme with both ppGpp synthetase and ppGpp hydrolase activities. Francisella encodes a monofunctional RelA and a bifunctional SpoT enzyme. Previous studies have demonstrated that stringent response under nutritional stresses increases expression of virulence-associated genes encoded on Francisella Pathogenicity Island. This study investigated how stringent response governs the oxidative stress response of F. tularensis. We demonstrate that RelA/SpoT-mediated ppGpp production alters global gene transcriptional profile of F. tularensis in the presence of oxidative stress. The lack of stringent response in relA/spoT gene deletion mutants of F. tularensis makes bacteria more susceptible to oxidants, attenuates survival in macrophages, and virulence in mice. Mechanistically, we provide evidence that the stringent response in Francisella contributes to oxidative stress resistance by enhancing the production of antioxidant enzymes.ImportanceThe unique intracellular life cycle of Francisella in addition to nutritional stress also exposes the bacteria to oxidative stress conditions upon its brief residence in the phagosomes, and escape into the cytosol where replication takes place. However, the contribution of the stringent response in gene regulation and management of the oxidative stress response when Francisella is experiencing oxidative stress conditions is not known. Our results provide a link between the stringent and oxidative stress responses. This study further improves our understanding of the intracellular survival mechanisms of F. tularensis.

scholarly journals PerR Controls Oxidative Stress Resistance and Iron Storage Proteins and Is Required for Virulence in Staphylococcus aureus

2001 ◽  
Vol 69 (6) ◽  
pp. 3744-3754 ◽  
Author(s):  
Malcolm J. Horsburgh ◽  
Mark O. Clements ◽  
Howard Crossley ◽  
Eileen Ingham ◽  
Simon J. Foster
Keyword(s):  
Oxidative Stress ◽  
Staphylococcus Aureus ◽  
Stress Resistance ◽  
Iron Homeostasis ◽  
Storage Proteins ◽  
Iron Storage ◽  
Oxidative Stress Resistance ◽  
Genes Encoding ◽  
Starvation Survival ◽  
Iron Storage Proteins

ABSTRACT The Staphylococcus aureus genome encodes three ferric uptake regulator (Fur) homologues: Fur, PerR, and Zur. To determine the exact role of PerR, we inactivated the gene by allelic replacement using a kanamycin cassette, creating strain MJH001 (perR). PerR was found to control transcription of the genes encoding the oxidative stress resistance proteins catalase (KatA), alkyl hydroperoxide reductase (AhpCF), bacterioferritin comigratory protein (Bcp), and thioredoxin reductase (TrxB). Furthermore, PerR regulates transcription of the genes encoding the iron storage proteins ferritin (Ftn) and the ferritin-like Dps homologue, MrgA. Transcription of perR was autoregulated, and PerR repressed transcription of the iron homeostasis regulator Fur, which is a positive regulator of catalase expression. PerR functions as a manganese-dependent, transcriptional repressor of the identified regulon. Elevated iron concentrations produced induction of the PerR regulon. PerR may act as a peroxide sensor, since addition of external hydrogen peroxide to 8325-4 (wild type) resulted in increased transcription of most of the PerR regulon, except forfur and perR itself. The PerR-regulatedkatA gene encodes the sole catalase of S. aureus, which is an important starvation survival determinant but is surprisingly not required for pathogenicity in a murine skin abscess model of infection. In contrast, PerR is not necessary for starvation survival but is required for full virulence (P < 0.005) in this model of infection. PerR ofS. aureus may act as a redox sentinel protein during infection, analogous to the in vitro activities of OxyR and PerR ofEscherichia coli and Bacillus subtilis, respectively. However, it differs in its response to the metal balance within the cell and has the added capability of regulating iron uptake and storage.

scholarly journals Synthesis andIn VitroAntibacterial Activity of New 2-(1-Methyl-4-nitro-1H-imidazol-5-ylsulfonyl)-1,3,4-thiadiazoles

2011 ◽  
Vol 8 (3) ◽  
pp. 1120-1123 ◽  
Author(s):  
Bahram Letafat ◽  
Negar Mohammadhosseini ◽  
Ali Asadipour ◽  
Alireza Foroumadi
Keyword(s):  
Staphylococcus Aureus ◽  
Staphylococcus Epidermidis ◽  
Antibacterial Activities ◽  
Dilution Method ◽  
Agar Dilution Method ◽  
Gram Positive ◽  
Gram Negative ◽  
Gram Positive Bacteria ◽  
Agar Dilution

In the present study we report the synthesis and antibacterial activity of a new series 2-(1-methyl-4-nitro-1H-imidazol-5-ylsulfonyl)-1,3,4-thiadiazoles (6a-c). Compounds6a-cwere testedin vitroby the conventional agar dilution method against a panel of microorganisms including gram-negative and gram-positive bacteria. Compound6bwith 5-(5-nitrofuran-2-yl)-residue on 1,3,4-thiadiazole scaffold have shown promising antibacterial activities against gram-positive bacteria includingStaphylococcus aureus, Staphylococcus epidermidisandBacillus subtilis.

scholarly journals Enterococcus faecalis zinc-responsive proteins mediate bacterial defence against zinc overload, lysozyme and oxidative stress

Microbiology ◽  
2014 ◽  
Vol 160 (12) ◽  
pp. 2755-2762 ◽  
Author(s):  
Marta C. Abrantes ◽  
Jan Kok ◽  
Maria de Fátima Silva Lopes
Keyword(s):  
Oxidative Stress ◽  
Enterococcus Faecalis ◽  
Zinc Homeostasis ◽  
Binding Motif ◽  
Defence Mechanisms ◽  
Promoter Regions ◽  
Genes Encoding ◽  
High Concentrations ◽  
P Type ◽  
And Oxidative Stress

Two Enterococcus faecalis genes encoding the P-type ATPase EF1400 and the putative SapB protein EF0759 were previously shown to be strongly upregulated in the presence of high concentrations of zinc. In the present work, we showed that a Zn2+-responsive DNA-binding motif (zim) is present in the promoter regions of these genes. Both proteins were further studied with respect to their involvement in zinc homeostasis and invasion of the host. EF0759 contributed to intramacrophage survival by an as-yet unknown mechanism(s). EF1400, here renamed ZntAEf, is an ATPase with specificity for zinc and plays a role in dealing with several host defences, i.e. zinc overload, oxidative stress and lysozyme; it provides E. faecalis cells with the ability to survive inside macrophages. As these three host defence mechanisms are important at several sites in the host, i.e. inside macrophages and in saliva, this work suggested that ZntAEf constitutes a crucial E. faecalis defence mechanism that is likely to contribute to the ability of this bacterium to endure life inside its host.

scholarly journals The Intracellular Siderophore Ferricrocin Is Involved in Iron Storage, Oxidative-Stress Resistance, Germination, and Sexual Development in Aspergillus nidulans

2006 ◽  
Vol 5 (10) ◽  
pp. 1596-1603 ◽  
Author(s):  
Martin Eisendle ◽  
Markus Schrettl ◽  
Claudia Kragl ◽  
Daniela Müller ◽  
Paul Illmer ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Iron Uptake ◽  
Iron Starvation ◽  
Efficient Utilization ◽  
Intracellular Iron ◽  
Iron Storage ◽  
Peptide Synthetase ◽  
Increased Sensitivity ◽  
Intracellular Storage ◽  
And Oxidative Stress

ABSTRACT Iron is required by most organisms, but an excess of this metal is potentially toxic. Consequently, uptake and intracellular storage of iron are tightly controlled. The filamentous fungus A. nidulans lacks the iron storage compound ferritin but possesses an intracellular siderophore, which is accumulated in a highly regulated manner as iron-free desferri-ferricrocin or iron-containing ferricrocin via transcriptional regulation of the nonribosomal peptide synthetase SidC. Biosynthesis of desferri-ferricrocin was low during iron-replete conditions but up-regulated by both iron starvation and intracellular iron excess, the latter caused by either a shift from iron-depleted to high-iron conditions or deregulation of iron uptake. Consequently, ferricrocin constituted only about 5% of the total iron content under iron-replete conditions but up to 64% during conditions of intracellular excess. In contrast, during iron starvation, desferri-ferricrocin was accumulated, which appears to represent a proactive strategy to prevent iron toxicity. Accumulation of the intracellular siderophore was also up-regulated by oxidative stress, which underscores the intertwining of iron metabolism and oxidative stress. Lack of the intracellular siderophore causes pleiotropic effects, as SidC deficiency results in (i) less-efficient utilization of iron, indicated by reduced growth under iron-depleted conditions and a higher iron demand under iron-replete conditions, (ii) delayed germination under iron-depleted conditions, (iii) increased sensitivity of conidia to oxidative stress, and (iv) elimination of cleistothecia formation in homothallic conditions.

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