DOCSLIB.ORG

Gram-Positive Cocci Enterobac.Pdf

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Gram-Positive Cocci Enterobac.Pdf General Considerations 530 different Bacterial Species or taxa reported by clinical laboratory 95% of Isolated reported are distributed among 27 different taxa More than 90% of Isolated reported are distributed among 16 different taxa CATAlASE-POSITIVE GRAM-POSITIVE COCCI Staphylococci Micrococcaceae Staphylococci have been traditionally differentiated from micrococci on the basis of oxidation-fermentation (O/F) reactions produced in O/F glucose medium Staphylococci ferment glucose, whereas micrococci fail to produce acid under anaerobic conditions. Bacitracin & Furazolidone Susceptible Bacitracin = or > 10 mm Furazolidone = or > 15 mm Differentiation Among Gram- Positive, Catalase-Positive Cocci Staphylococci Bacitracin = R ,some strains show opposite reaction Microccocus / 48-72 hrs. Some micrococci produce a yellow pigment CAP > BAP Microccocus Staphylococci Staphylococci is currently composed 35 species and 17 subspecies Gram positive Cocci Catalase Positive Nonmotile Spherical cells (0.5 to 1.5 Micron) that appear singly, in pairs, and in clusters Clusters of Staphylococci G + cocci in cluster After antimicrobial therapy & older cells easily decolorized Presumptive report: Gram-Positive Cocci resembling Staphylococci Staphylococci Colonies produced after 18 to 24 hours of incubation appear cream-colored, white or rarely light gold, and buttery-looking in 1 to 3 mm in diameter and 3 to 8 mm by 3 days Hold plates for 72 h can result in selection of more than one species or strain Some species are B-hemolytic on sheep blood agar at 18 to 24 hours Staphylococci Colonies should be allowed to developed on primary isolation medium for 3 to 4 days at 35 to 37°C and then for 2 days at room temperature for identify colonial morphology of strains in staphylococcal species Staphylococcus aureus B-hemolytic, creamy, buttery-looking colonies Catalase Test Catalase enzyme that hydrolyzes hydrogen peroxide into water and oxygen (bubbles) Hydrogen peroxide (3%, aqueous). Dilute 30% (v/v) hydrogen peroxide 1:10 in sterile distilled water • Store at 4 °C in a dark bottle Catalase Test 30% H2O2 can be used for catalase test but it is more hazardous 30% H2O2 is extremely caustic to skin If contact occurs ,wash immediately with 70% Ethyl Alcohol , NOT WATER Catalase Test / Procedure 1-Touch the center of well-isolated young colony (18-24 hrs.) with a wooden stick to transfer to a clean ,dry glass slide. • Older cultures may give false-negative result Place 1 drop of reagent and observe immediately bubbles • Do not reverse ; False Negative Results can occur. Catalase Test / Procedure Be careful to avoid picking up any of the agar medium RBCs contain catalase and Blood agar may produce false-positive reaction due to peroxidase • CHOC dose not interfere with the assay Catalase Test / Interpretation Positive reaction : immediate appearance of bubbles • QC : S. aureus ATCC 25923- Catalase Positive Negative reaction : No bubbles, or the slow elaboration of a few bubbles after 20 seconds • Some strain of Enterococcus faecalis growth on SBA may appear weakly Positive / Pseudocatalase test Catalase Test / Limitations False-positive : some metal bacteriological loop materials Platinum loops do not yield false-positive results Catalase Test / Precautions Rapid evolution of oxygen may generate droplet or aerosol formation The catalase reaction does not affect organism viability Coagulase Test / Clumping factor Formerly referred to as cell-bound coagulase, causes agglutination in human , rabbit plasma Clumping factor on the surface of the bacterial cells directly converts fibrinogen to fibrin, which precipitates onto the cell surface, causing agglutination. Coagulase Test / Clumping factor A heavy suspension of the suspected organism is prepared on a glass slide in water to give a milky suspension and spread over 10mm area of the circle Colonies that are less than 24h old Hemolytic Colonies on fresh BAP at 18h Coagulase Test / Clumping factor Stirring the mixture to a homogeneous so as not to confuse clumping with autoagglutination Autoagglutination / Sticky organism ; Perform Tube Coaglulase Coagulase Test / Clumping factor Adding 1 drop of plasma, and observing for clumping within 10 sec. False-positive result may appear with reaction times longer than 10 sec. Coagulase Test / Clumping factor Coagulase Test / Clumping factor False-positive ; Autoagglutination ,colonies from media containing high concentrations of salt e.g., Mannitol Salt Agar Coagulase Test / Clumping factor Isolates can also be occasionally confused as coagulase-positive staphylococci because of the presence of clumping factor • S. lugdunensis • S. schleiferi subsp. Schleiferi Reaction is more efficient if human plasma is used rather than rabbit plasma Coagulase Test / Clumping factor Because about 10-15% (previously 5% )of S. aureus ,especially MRSA, do not produce clumping factor MRSA : low level Bound Coagulase & Protein A & mask the cell wall with capsular polysacchaides Coagulase Test / Clumping factor Negative slide coagulase test result, must be confirmed with the tube method, which detects free coagulase • Especially if it is from normally sterile body site , blood joint isolates • Methicillin Resistant Staphylococci Coagulase Test / Clumping factor +Protein A Some strains of ; S. saprophyticus ( Protein A) / nonhemolytic colonies S.warneri ( Protein A) S.capitis ( Protein A ) S. lugdunensis (Clumping factor ) / PYR + S. schleiferi (Clumping factor ) / PYR + • may produce positive tests with this method, but they would be tube coagulase negative Tube Coagulase Test Free Coagulase Staphylocoagulase reacts with a thermostable, thrombinlike molecule called coagulase-reacting factor (CRF) to form coagulase-CRF complex. The complex resembles thrombin and indirectly converts fibrinogen to fibrin Tube Coagulase Test Staphylocoagulase producing (coagulase positive) staphylococci are S. aureus in human & animal • VP + & hemolytic at 18hrs S. intermedius in Dog & very rarely found in human ( Dog bite) / VP - & nonhemolytic at 18hrs Some strains of S. hyicus in Pig &very rarely found in human / VP - & nonhemolytic at 18hrs Frequency of Isolation of Staphylococcus intermedius from Humans We collected 3,397 consecutive isolates of coagulase- positive staphylococci from various specimens of hospitalized patients. All were retrospectively classified as Staphylococcus aureus, except two which were identified as S. intermedius = 0.06 % or 6 / 10000 coagulase-positive staphylococci One isolated from the nasal flora of a healthy carrier and the other isolated from pleural fluid, probably as a sample contaminant Tube Coagulase Test Sterile rabbit Plasma containing EDTA most satisfactory • Rehydrated reagent expires after 1 month if stored at -20°C or 5 days if stored at 2 to 8°C • Do not use citrated plasma ,a false –positive result can occur Emulsify several colonies in 0.5 ml of rabbit plasma with EDTA Tube Coagulase Test Incubate at 37° C Look for clot formation hourly up to 4 hours by slowly tilting it 90° from vertical If no clot appears the tube should be left at room temperature to incubate overnight and checked the following day • Rare S. aureus strains require >4 hours to clot the tube coagulase reagent Tube Coagulase Test Tube Coagulase Test Some strains of S. aureus produce a staphylokinase , a plasmid –carried enzyme ,that dissolves the clot, giving a false-negative result Staphylokinase is less active at 25°C Tube Coagulase Test Flocculent or fibrous precipitate is not a true clot and should be recorded as negative result Some strains of S. intermedius and most coagulase-producing strains of S. hyicus require more than 4 h (12 to 24 hours) for positive Coagulase Test Staphylococcus aureus Gram-positive cocci in clusters Catalase-positive Staphylococcus aureus Cultural Characteristics Round, smooth, white, creamy colonies on SBA after 18 to 24 hours of incubation at 35° to 37° C May produce hemolytic zones around the colonies May exhibit pigment production (yellow) with extended incubation Staphylococcus aureus Small –Colony Variants ( SCVs) Small –Colony Variants ( SCVs) of S.aureus with large capsule & grows slowly and produce small , glistening, wet , convex colonies . SCVs are most common in patient with unusually persistent infections, such as chronic osteomylitis and who are chronically exposed to aminoglycosides and CO-timoxazole Mannitol Salt Agar (MSA) NaCl ; 7.5% Incubation for at least 48 to 72 hours S.saprophyticus resemble S.aureus Odor ? Staphylococcus aureus Rapid thermonuclease test Positive result in the rapid (four-hour) thermonuclease test accurately identifies S.aureus • S. Schleiferi & S.intermedius : positive Several colonies in to broth Boiling for 15 min Punch a hole in TBO DANase agar Fill well with 2 drops of cooled broth Incubate at 35 for 3 h, and observe for color change Coagulase-negative Staphylococci (CoNS) CoNS Coagulase-negative Staphylococci (CoNS) 35 recognized species of coagulase- negative staphylococci The most clinically significant species in this group are • S. epidermidis • S. saprophyticus Staphylococci Staphylococcus epidermidis Infections caused by S. epidermidis are predominantly hospital acquired Biofilm production is a key component in bacterial pathogenesis S. epidermidis has been linked to important nosocomial infections, often associated with foreign body implants Staphylococcus epidermidis Small to medium , most colonies nonhemolytic , slime-producing strains are extremely
Load more

Recommended publications
  • Elevated Hydrogen Peroxide and Decreased Catalase and Glutathione
    Sullivan-Gunn and Lewandowski BMC Geriatrics 2013, 13:104 http://www.biomedcentral.com/1471-2318/13/104 RESEARCH ARTICLE Open Access Elevated hydrogen peroxide and decreased catalase and glutathione peroxidase protection are associated with aging sarcopenia Melanie J Sullivan-Gunn1 and Paul A Lewandowski2* Abstract Background: Sarcopenia is the progressive loss of skeletal muscle that contributes to the decline in physical function during aging. A higher level of oxidative stress has been implicated in aging sarcopenia. The current study aims to determine if the higher level of oxidative stress is a result of increased superoxide (O2‾ ) production by the NADPH oxidase (NOX) enzyme or decrease in endogenous antioxidant enzyme protection. Methods: Female Balb/c mice were assigned to 4 age groups; 6, 12, 18 and 24 months. Body weight and animal survival rates were recorded over the course of the study. Skeletal muscle tissues were collected and used to measure NOX subunit mRNA, O2‾ levels and antioxidant enzymes. Results: Key subunit components of NOX expression were elevated in skeletal muscle at 18 months, when sarcopenia was first evident. Increased superoxide dismutase 1 (SOD1) activity suggests an increase in O2‾ dismutation and this was further supported by elevated levels of hydrogen peroxide (H2O2) and decline in catalase and glutathione peroxidase (GPx) antioxidant protection in skeletal muscle at this time. NOX expression was also higher in skeletal muscle at 24 months, however this was coupled with elevated levels of O2‾ and a decline in SOD1 activity, compared to 6 and 12 months but was not associated with further loss of muscle mass.
    [Show full text]
  • Tryptose Blood Agar Base
    Tryptose Blood Agar Base Intended Use Principles of the Procedure Tryptose Blood Agar Base is used with blood in isolating, Tryptose is the source of nitrogen, carbon and amino acids in cultivating and determining the hemolytic reactions of fastidi- Tryptose Blood Agar Base. Beef extract provides additional ous microorganisms. nitrogen. Sodium chloride maintains osmotic balance. Agar is the solidifying agent. Summary and Explanation Investigations of the nutritive properties of tryptose demon- Supplementation with 5-10% blood provides additional growth strated that culture media prepared with this peptone were factors for fastidious microorganisms and is used to determine superior to the meat infusion peptone media previously used hemolytic patterns of bacteria. for the cultivation of Brucella, streptococci, pneumococci, me- Formula ningococci and other fastidious bacteria. Casman1,2 reported Difco™ Tryptose Blood Agar Base that a medium consisting of 2% tryptose, 0.3% beef extract, Approximate Formula* Per Liter 0.5% NaCl, 1.5% agar and 0.03% dextrose equaled fresh beef Tryptose .................................................................... 10.0 g infusion base with respect to growth of organisms. The small Beef Extract ................................................................. 3.0 g amount of carbohydrate was noted to interfere with hemolytic Sodium Chloride ......................................................... 5.0 g Agar ......................................................................... 15.0 g reactions, unless the medium was incubated in an atmosphere *Adjusted and/or supplemented as required to meet performance criteria. of carbon dioxide. Tryptose Blood Agar Base is a nutritious infusion-free basal Directions for Preparation from medium typically supplemented with 5-10% sheep, rabbit or Dehydrated Product horse blood for use in isolating, cultivating and determining 1. Suspend 33 g of the powder in 1 L of purified water.
    [Show full text]
  • Catalase and Oxidase Test
    CATALASE TEST Catalase is the enzyme that breaks hydrogen peroxide (H 2O2) into H 2O and O 2. Hydrogen peroxide is often used as a topical disinfectant in wounds, and the bubbling that is seen is due to the evolution of O 2 gas. H 2O2 is a potent oxidizing agent that can wreak havoc in a cell; because of this, any cell that uses O 2 or can live in the presence of O 2 must have a way to get rid of the peroxide. One of those ways is to make catalase. PROCEDURE a. Place a small amount of growth from your culture onto a clean microscope slide. If using colonies from a blood agar plate, be very careful not to scrape up any of the blood agar— blood cells are catalase positive and any contaminating agar could give a false positive. b. Add a few drops of H 2O2 onto the smear. If needed, mix with a toothpick. DO NOT use a metal loop or needle with H 2O2; it will give a false positive and degrade the metal. c. A positive result is the rapid evolution of O 2 as evidenced by bubbling. d. A negative result is no bubbles or only a few scattered bubbles. e. Dispose of your slide in the biohazard glass disposal container. Dispose of any toothpicks in the Pipet Keeper. OXIDASE TEST Basically, this is a test to see if an organism is an aerobe. It is a check for the presence of the electron transport chain that is the final phase of aerobic respiration.
    [Show full text]
  • Myeloperoxidase Mediates Cell Adhesion Via the Αmβ2 Integrin (Mac-1, Cd11b/CD18)
    Journal of Cell Science 110, 1133-1139 (1997) 1133 Printed in Great Britain © The Company of Biologists Limited 1997 JCS4390 Myeloperoxidase mediates cell adhesion via the αMβ2 integrin (Mac-1, CD11b/CD18) Mats W. Johansson1,*, Manuel Patarroyo2, Fredrik Öberg3, Agneta Siegbahn4 and Kenneth Nilsson3 1Department of Physiological Botany, University of Uppsala, Villavägen 6, S-75236 Uppsala, Sweden 2Microbiology and Tumour Biology Centre, Karolinska Institute, PO Box 280, S-17177 Stockholm, Sweden 3Department of Pathology, University of Uppsala, University Hospital, S-75185 Uppsala, Sweden 4Department of Clinical Chemistry, University of Uppsala, University Hospital, S-75185 Uppsala, Sweden *Author for correspondence (e-mail: [email protected]) SUMMARY Myeloperoxidase is a leukocyte component able to to αM (CD11b) or to β2 (CD18) integrin subunits, but not generate potent microbicidal substances. A homologous by antibodies to αL (CD11a), αX (CD11c), or to other invertebrate blood cell protein, peroxinectin, is not only integrins. Native myeloperoxidase mediated dose- a peroxidase but also a cell adhesion ligand. We demon- dependent cell adhesion down to relatively low concen- strate in this study that human myeloperoxidase also trations, and denaturation abolished the adhesion mediates cell adhesion. Both the human myeloid cell line activity. It is evident that myeloperoxidase supports cell HL-60, when differentiated by treatment with 12-O- adhesion, a function which may be of considerable tetradecanoyl-phorbol-13-acetate (TPA) or retinoic acid, importance for leukocyte migration and infiltration in and human blood leukocytes, adhered to myeloperoxi- inflammatory reactions, that αMβ2 integrin (Mac-1 or dase; however, undifferentiated HL-60 cells showed only CD11b/CD18) mediates this adhesion, and that the αMβ2 minimal adhesion.
    [Show full text]
  • Laboratory Exercises in Microbiology: Discovering the Unseen World Through Hands-On Investigation
    City University of New York (CUNY) CUNY Academic Works Open Educational Resources Queensborough Community College 2016 Laboratory Exercises in Microbiology: Discovering the Unseen World Through Hands-On Investigation Joan Petersen CUNY Queensborough Community College Susan McLaughlin CUNY Queensborough Community College How does access to this work benefit ou?y Let us know! More information about this work at: https://academicworks.cuny.edu/qb_oers/16 Discover additional works at: https://academicworks.cuny.edu This work is made publicly available by the City University of New York (CUNY). Contact: [email protected] Laboratory Exercises in Microbiology: Discovering the Unseen World through Hands-On Investigation By Dr. Susan McLaughlin & Dr. Joan Petersen Queensborough Community College Laboratory Exercises in Microbiology: Discovering the Unseen World through Hands-On Investigation Table of Contents Preface………………………………………………………………………………………i Acknowledgments…………………………………………………………………………..ii Microbiology Lab Safety Instructions…………………………………………………...... iii Lab 1. Introduction to Microscopy and Diversity of Cell Types……………………......... 1 Lab 2. Introduction to Aseptic Techniques and Growth Media………………………...... 19 Lab 3. Preparation of Bacterial Smears and Introduction to Staining…………………...... 37 Lab 4. Acid fast and Endospore Staining……………………………………………......... 49 Lab 5. Metabolic Activities of Bacteria…………………………………………….…....... 59 Lab 6. Dichotomous Keys……………………………………………………………......... 77 Lab 7. The Effect of Physical Factors on Microbial Growth……………………………... 85 Lab 8. Chemical Control of Microbial Growth—Disinfectants and Antibiotics…………. 99 Lab 9. The Microbiology of Milk and Food………………………………………………. 111 Lab 10. The Eukaryotes………………………………………………………………........ 123 Lab 11. Clinical Microbiology I; Anaerobic pathogens; Vectors of Infectious Disease….. 141 Lab 12. Clinical Microbiology II—Immunology and the Biolog System………………… 153 Lab 13. Putting it all Together: Case Studies in Microbiology…………………………… 163 Appendix I.
    [Show full text]
  • Francisella Tularensis 6/06 Tularemia Is a Commonly Acquired Laboratory Colony Morphology Infection; All Work on Suspect F
    Francisella tularensis 6/06 Tularemia is a commonly acquired laboratory Colony Morphology infection; all work on suspect F. tularensis cultures .Aerobic, fastidious, requires cysteine for growth should be performed at minimum under BSL2 .Grows poorly on Blood Agar (BA) conditions with BSL3 practices. .Chocolate Agar (CA): tiny, grey-white, opaque A colonies, 1-2 mm ≥48hr B .Cysteine Heart Agar (CHA): greenish-blue colonies, 2-4 mm ≥48h .Colonies are butyrous and smooth Gram Stain .Tiny, 0.2–0.7 μm pleomorphic, poorly stained gram-negative coccobacilli .Mostly single cells Growth on BA (A) 48 h, (B) 72 h Biochemical/Test Reactions .Oxidase: Negative A B .Catalase: Weak positive .Urease: Negative Additional Information .Can be misidentified as: Haemophilus influenzae, Actinobacillus spp. by automated ID systems .Infective Dose: 10 colony forming units Biosafety Level 3 agent (once Francisella tularensis is . Growth on CA (A) 48 h, (B) 72 h suspected, work should only be done in a certified Class II Biosafety Cabinet) .Transmission: Inhalation, insect bite, contact with tissues or bodily fluids of infected animals .Contagious: No Acceptable Specimen Types .Tissue biopsy .Whole blood: 5-10 ml blood in EDTA, and/or Inoculated blood culture bottle Swab of lesion in transport media . Gram stain Sentinel Laboratory Rule-Out of Francisella tularensis Oxidase Little to no growth on BA >48 h Small, grey-white opaque colonies on CA after ≥48 h at 35/37ºC Positive Weak Negative Positive Catalase Tiny, pleomorphic, faintly stained, gram-negative coccobacilli (red, round, and random) Perform all additional work in a certified Class II Positive Biosafety Cabinet Weak Negative Positive *Oxidase: Negative Urease *Catalase: Weak positive *Urease: Negative *Oxidase, Catalase, and Urease: Appearances of test results are not agent-specific.
    [Show full text]
  • Peroxisomal Disorders and Their Mouse Models Point to Essential Roles of Peroxisomes for Retinal Integrity
    International Journal of Molecular Sciences Review Peroxisomal Disorders and Their Mouse Models Point to Essential Roles of Peroxisomes for Retinal Integrity Yannick Das, Daniëlle Swinkels and Myriam Baes * Lab of Cell Metabolism, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, 3000 Leuven, Belgium; [email protected] (Y.D.); [email protected] (D.S.) * Correspondence: [email protected] Abstract: Peroxisomes are multifunctional organelles, well known for their role in cellular lipid homeostasis. Their importance is highlighted by the life-threatening diseases caused by peroxisomal dysfunction. Importantly, most patients suffering from peroxisomal biogenesis disorders, even those with a milder disease course, present with a number of ocular symptoms, including retinopathy. Patients with a selective defect in either peroxisomal α- or β-oxidation or ether lipid synthesis also suffer from vision problems. In this review, we thoroughly discuss the ophthalmological pathology in peroxisomal disorder patients and, where possible, the corresponding animal models, with a special emphasis on the retina. In addition, we attempt to link the observed retinal phenotype to the underlying biochemical alterations. It appears that the retinal pathology is highly variable and the lack of histopathological descriptions in patients hampers the translation of the findings in the mouse models. Furthermore, it becomes clear that there are still large gaps in the current knowledge on the contribution of the different metabolic disturbances to the retinopathy, but branched chain fatty acid accumulation and impaired retinal PUFA homeostasis are likely important factors. Citation: Das, Y.; Swinkels, D.; Baes, Keywords: peroxisome; Zellweger; metabolism; fatty acid; retina M. Peroxisomal Disorders and Their Mouse Models Point to Essential Roles of Peroxisomes for Retinal Integrity.
    [Show full text]
  • SHEEP BLOOD AGAR - for in Vitro Use Only - Catalogue No
    SHEEP BLOOD AGAR - For in vitro use only - Catalogue No. PS58 Our Sheep Blood Agar is a highly nutritious Interpretation of Results medium used for the cultivation and isolation of a variety of microorganisms. Sheep Blood Agar can be used as a primary- Our Sheep Blood Agar is based on the Oxoid plating medium. Primary isolation is performed to formulation; the prepared medium is said to offer separate and isolate organisms present in a sample. improved nutritional value resulting in better growth This separation allows for characterization of and larger colony size as well giving more colony types and may indicate the presence of consistent hemolytic reactions especially among the clinically significant bacteria. When examining streptococci. The base is specifically designed for plates a hand lens or stereoscopic microscope use with sheep blood as horse blood has shown to should be available for examining very small give different and conflicting hemolytic reactions colonies. The different types of colonial when incorporated into other blood agars. morphology appearing on the agar plate should be The nutritional components include pancreatic noted as well as the number of each morphotype digest of casein, neutralized peptone, and yeast present. Hemolysis is also a very useful differential extract, and the addition of sodium chloride characteristic that is best viewed when a bright light provides an osmotically balanced medium for is transmitted from behind the plate. Four different bacterial cells. The addition of 5% defibrinated types of hemolysis can be described: sheep blood allows for the determination of hemolytic reactions, an important differential 1. Alpha-hemolysis ( α) – Partial hemolysis that characteristic.
    [Show full text]
  • Kinetic Approaches to Measuring Peroxiredoxin Reactivity
    Mol. Cells 2016; 39(1): 26-30 http://dx.doi.org/10.14348/molcells.2016.2325 Molecules and Cells http://molcells.org Established in 1990 Kinetic Approaches to Measuring Peroxiredoxin Reactivity Christine C. Winterbourn*, and Alexander V. Peskin Peroxiredoxins are ubiquitous thiol proteins that catalyse demonstrated surprisingly low reactivity with thiol reagents such the breakdown of peroxides and regulate redox activity in as iodoacetamide and other oxidants such as chloramines the cell. Kinetic analysis of their reactions is required in (Peskin et al., 2007) and it is clear that the low pKa of the active order to identify substrate preferences, to understand how site thiol is insufficient to confer the high peroxide reactivity. In molecular structure affects activity and to establish their fact, typical low molecular weight and protein thiolates react -1 -1 physiological functions. Various approaches can be taken, with H2O2 with a rate constant of 20 M s whereas values of including the measurement of rates of individual steps in Prxs are 105-106 fold higher (Winterbourn and Hampton, 2008). the reaction pathway by stopped flow or competitive kinet- An elegant series of structural and mutational studies (Hall et al., ics, classical enzymatic analysis and measurement of pe- 2010; Nakamura et al., 2010; Nagy et al., 2011) have shown roxidase activity. Each methodology has its strengths and that to get sufficient rate enhancement, it is necessary to acti- they can often give complementary information. However, vate the peroxide. As discussed in detail elsewhere (Hall et al., it is important to understand the experimental conditions 2010; 2011), this involves formation of a transition state in of the assay so as to interpret correctly what parameter is which hydrogen bonding of the peroxide to conserved Arg and being measured.
    [Show full text]
  • Understanding the Structure and Function of Catalases: Clues from Molecular Evolution and in Vitro Mutagenesis
    PERGAMON Progress in Biophysics & Molecular Biology 72 (1999) 19±66 Understanding the structure and function of catalases: clues from molecular evolution and in vitro mutagenesis Marcel Za mocky *, Franz Koller Institut fuÈr Biochemie and Molekulare Zellbiologie and Ludwig Boltzmann Forschungsstelle fuÈr Biochemie, Vienna Biocenter, Dr. Bohr-Gasse 9, A-1030 Wien, Austria Abstract This review gives an overview about the structural organisation of dierent evolutionary lines of all enzymes capable of ecient dismutation of hydrogen peroxide. Major potential applications in biotechnology and clinical medicine justify further investigations. According to structural and functional similarities catalases can be divided in three subgroups. Typical catalases are homotetrameric haem proteins. The three-dimensional structure of six representatives has been resolved to atomic resolution. The central core of each subunit reveals a chracteristic ``catalase fold'', extremely well conserved among this group. In the native tetramer structure pairs of subunits tightly interact via exchange of their N- terminal arms. This pseudo-knot structures implies a highly ordered assembly pathway. A minor subgroup (``large catalases'') possesses an extra ¯avodoxin-like C-terminal domain. A r25AÊ long channel leads from the enzyme surface to the deeply buried active site. It enables rapid and selective diusion of the substrates to the active center. In several catalases NADPH is tightly bound close to the surface. This cofactor may prevent and reverse the formation of compound II, an inactive reaction intermediate. Bifunctional catalase-peroxidases are haem proteins which probably arose via gene duplication of an ancestral peroxidase gene. No detailed structural information is currently available. Even less is know about manganese catalases.
    [Show full text]
  • Screening for Asymptomatic Bacteriuria in Adults: an Updated Systematic Review for the U.S
    Evidence Synthesis Number 183 Screening for Asymptomatic Bacteriuria in Adults: An Updated Systematic Review for the U.S. Preventive Services Task Force Prepared for: Agency for Healthcare Research and Quality U.S. Department of Health and Human Services 5600 Fishers Lane Rockville, MD 20857 www.ahrq.gov Contract No. HHSA-290-2015-00007-I, Task Order No. 3 Prepared by: Kaiser Permanente Research Affiliates Evidence-based Practice Center Kaiser Permanente Center for Health Research Portland, OR Investigators: Jillian T. Henderson, PhD, MPH Elizabeth M. Webber, MS Sarah I. Bean, MPH AHRQ Publication No. 19-05252-EF-1 September 2019 This report is based on research conducted by the Kaiser Permanente Research Affiliates Evidence-based Practice Center (EPC) under contract to the Agency for Healthcare Research and Quality (AHRQ), Rockville, MD (HHSA-290-2015-00007-I, Task Order No. 3). The findings and conclusions in this document are those of the authors, who are responsible for its contents, and do not necessarily represent the views of AHRQ. Therefore, no statement in this report should be construed as an official position of AHRQ or of the U.S. Department of Health and Human Services. The information in this report is intended to help health care decision makers—patients and clinicians, health system leaders, and policymakers, among others—make well-informed decisions and thereby improve the quality of health care services. This report is not intended to be a substitute for the application of clinical judgment. Anyone who makes decisions concerning the provision of clinical care should consider this report in the same way as any medical reference and in conjunction with all other pertinent information (i.e., in the context of available resources and circumstances presented by individual patients).
    [Show full text]
  • Special Microbiology Practical Week 3. – STREPTOCOCCI Streptococci
    Special Microbiology practical week 3. – STREPTOCOCCI Streptococci are Gram-positive, nonmotile, nonsporeforming, catalase-negative cocci that occur in pairs or chains. Older cultures may lose their Gram-positive character. Most streptococci are facultative anaerobes, and some are obligate (strict) anaerobes.Most require enriched media (blood agar). Streptococci are subdivided into groups by antibodies that recognize surface antigens These groups may include one or more species.Serologic grouping is based on antigenic differences in cell wall carbohydrates (groups A to V), in cell wall pili-associated protein, and in the polysaccharide capsule in group B streptococci.Rebecca Lancefield developed the serologic classification scheme in 1933. β-hemolyticstrains possess group- specific cell wall antigens, most of which are carbohydrates. These antigens can be detected by immunologic assays and have been useful for the rapid identification of some important streptococcal pathogens.The most important groupable streptococci are A, B and D. Among the groupable streptococci, infectious disease (particularly pharyngitis) is caused by group A. Group A streptococci have a hyaluronic acid capsule.Streptococcus pneumoniae(a major cause of human pneumonia) and Streptococcus mutansand other so-called viridans streptococci (among the causes of dental caries) do not possess group antigen.Streptococcus pneumoniaehas a polysaccharide capsulethat acts as a virulence factor for the organism,more than 90 different serotypesare known, and these types differ in virulence. Beta Hemolysis Streptococcus pyogenes, or Group A beta-hemolytic Streptococci (GAS), and Streptococcus agalactiae, or Group B beta-hemolytic Streptococci (GBS) blood agar cultures display beta hemolysis. Beta hemolysis (β-hemolysis), called complete hemolysis, is a complete lysisof red blood cells in the media around and under the colonies: the area appears lightened (yellow) and transparent.
    [Show full text]