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152 Cards in this Set
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When classifying organisms, the genotypic class is based on genetic relatedness and is related to... And the phenotypic class is based on.... |
Genotypic: based on nucleic acid base composition and ratio Phenotypic: traditional microbiology, morphology, biochemical characteristics , antigenic relationships (observable) |
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The biological classification of organisms uses specific nomenclature, what is this pyramid of terms? |
Kingdom Phylum Class Order Family Genus Species |
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If a host is infected by a micro-organism, but not harmed it is called... If the host IS harmed it is referred to as... |
Not harmed: Colonization Harmed: Infectious disease |
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What is the word that describes a microorgnaism that is CAPABLE of causing an infectious disease? |
Pathogen |
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DEFINE: 1. True Pathogen 2. Opportunist Pathogen 3. Nosocomial infection |
1. True pathogenMicroorganism that causes disease in healthyimmunocompetent host 2. Opportunist pathogenNormally nonpathogenic microorganisms that are capable ofcausing infection in an immunocompromised host 3. Nosocomial infectionInfection acquired in the hospital or other health caresetting |
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The virulence of an organism is the relative ability of a microorganism to cause disease, or the degree of pathogenicity. It is based upon: |
Virulence is based on:
1. the number of organisms 2. virulence factors (organism characteristics (tools) thatprotect organism against host attack or mediate damagingeffects on host cells) |
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The most common way that microorganisms resists phagocytosis in the host is through this characteristic... |
Having a polysaccharide capsule enables microorganisms to resist phagocytosis because it masks the surface receptors. Organisms with capsules tend to be more virulent. |
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What are three ways that microorganisms can resist phagocytosis (other than having a polysaccharide capsule): |
1. release of potent materials such as hemolysin and leukocidin (toxic to WBC) 2. Inhibit WBC chemotaxis 3. Protein A (interferes with binding of host's antibodies) |
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What bacterial structures promote adhesion in the host?
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1. Adhesin - cell surface structure that mediates attachement 2. Pili - in gram negative 3. Fimbriae in both gram negative and gram postive |
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After attachment to the host cell, a microorganism must proliferate. This proliferation is done through two key tactics: |
1. IgA protease development (bacterial enzyme that degrades IgA found atmucosalsurfaces) 2. Shifting key cell surface antigens so cannot be recognized byhost’s immunoglobulins |
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Define: 1. Toxin: 2. Exotoxin 3. Endotoxin |
1. Toxin: Protein substance produced by some pathogenic bacteriathat is highly toxic for other living organisms (a poison) 2. Exotoxin: Gram-pos bacteria (some gram-neg), toxin that targets specific host cells, released by bacteria, heat labile (except Staph enterotoxin) 2. Endotoxin: part of the bacterial membrane |
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What is an example of an endotoxin of gram-negative bacteria? |
Lipid A portion of LPS (which is a portion of the outer membrane of the cell wall) Heat stable. Ex. Gram-neg septicemia |
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What is: A toxin produced by a microorganism that is specific for the intestinal mucosa? Can be either an endotoxin or an exotoxin. Example: Staphfood poisoning |
ENTEROTOXIN |
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What is: A toxin produced by a microorganism that is destructive tonerve tissue? Example: tetanus toxin. |
NEUROTOXIN |
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Which two extracellular enzymes are used by microorganisms to help them persist in the host and cause disease? |
Proteases Hyaluronidases These liquefy hyaluronic acid ofconnective tissue matrix and aid in spreading bacteria into tissues |
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ANTIMICROBIAL SUBSTANCES: How do hosts protect themselves against pathogens? |
Lysozymes-hydrolyzes peptidoglycan Antibodies-secretory IgA β-lysins-released from platelets, kill gram positivebacteria Interferons-bind to nonviral infected cells-inhibitviral replication |
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Normally Sterile Body SitesColonization of one of these sites generallyinvolves a defect or breach in the naturaldefenses that creates a portal of entry: |
Brain: Central Nervous System Blood: Tissues; Organ systems Sinuses: Inner and Middle Ear Lower Respiratory Tract: Larynx; Trachea;Bronchioles(bronchi); Lungs; Alveoli Kidneys: Ureters; Urinary Bladder Uterus: Endometrium (Inner mucous membrane ofuterus ); Fallopian Tubes |
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Phagocytosis (non-specific response) involves: |
Chemotaxis - movement of phagocytic cells (PMNs andmono/macros)into tissues Attachment – opsonization enhances PMN attaching tomicroorganism Ingestion – degranulation (lysosomes release contents) Killing |
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_______ is a mixture of active or inactive neutrophils, otherinflammatory cells, bacterial cells, and extravascular fluid |
PUS |
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_________________/____________/__________________ reaction: inflammatory response toinfections resulting in theaccumulation of pus |
Suppurative/Pyogenic/Purulent reaction– inflammatory response toinfections resulting in theaccumulation of pus |
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The two specific immune system responses of the host include: |
Humoral immunity – antibody-mediated immunity Cellular immunity – cell-mediated immunity |
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What are the three clinically significant genera of all the GPC? |
Staphylococcus, Streptococcusand Enterococcus |
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Staphylococcus Coagulasepositive (CPS): ________ Coagulase negative (CNS): _________, ___________, ____________ |
Coagulase positive (CPS): S. aureus Coagulase negative (CNS): S. epidermidis •S. saprophyticus •S. lugdenensis •Other CNS |
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Most staph are facultative anaerobes |
can use either aerobic respiration and/orfermentationdependingon the availabilityof oxygen,doesnot solely depend on aerobic respirationfor growth |
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Staph: Grow on any nutrientmedia that contains _______ •Inhibitedby media that containscrystal violetdye orvery high conc.ofbile salts (aka ___________)•Abundantgrowthat ________ hr.•Motility? |
•Grow on any nutrientmedia that contains peptone•Inhibitedby media that containscrystal violetdye orvery high conc.ofbile salts (aka MacConkey)•Abundantgrowthat 18-24 hr.•Non-motile |
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Staphylococcus•Therearemany species (morethan 30). Thereare 4 major species: |
aureus epidermidis saprophyticus lugdunensis |
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•MacConkey Agar is selective for what |
selective for gram negative |
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Staphylococci on gram stain: |
Gram stain:GPC in singles, pairs,tetrads and/orclusters |
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Catalase test principle: Staph and micrococcus- strep and enterococcus- |
Catalase(enzyme)convertshydrogen peroxide(H2O2) into waterand oxygen. Staphylococcus and Micrococcus are typicallycatalase positive Streptococcus and Enterococcus speciesare typically negative. Enterococcus can be a weak positive, but is stillconsidered negative. |
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Tests to Identify Staph sp. |
Coagulase (slide, tube, latex), Mannitol Salt agar Novobiocin Susceptibility PYR hydrolysis Rapid Ornithine (decarboxylaseactivity) DNase |
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Identification methods used to differentiate the genus Micrococcus from the genus Staphylococcus: |
Modified Oxidase Oxidative-Fermatative Test Bacitracin (Taxo A) Lysostaphin susceptibility |
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Coagulase Test (Coagulase is an enzymethatconverts solublefibrinogen into insoluble fibrin) Slide measures... Tube measures... Latex measures... |
Slide – measures bound coagulase (clumpingfactor) which is attached to the cellwallsof the bacteria Tube – measures free coagulase (extracellular enzyme) Latex – measures protein A (and bound coagulase) |
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Negative slide coagulase reactions must be confirmed by what test? |
Negative slide reactions must be confirmed by the tube test. |
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What temp is the tube coat test incubated at? |
Incubate at 35-37C. Observe at 2 – 4 hours for the formationof a clot (positivereaction). |
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In the latex agglutination test, what are the latex particles coated with? |
Latex particlescoatedwithhuman fibrinogen fordetection ofclumping factorand coatedwithspecific IgG for detection of protein A. |
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Mannitolsalt agar (MSA)is a selectiveand differentialmedium used to isolate ______________. If it grows and can ferment what color is the media around the colonies? |
Mannitolsalt agar (MSA)is a selectiveand differentialmedium used to isolate Staphylococcusaureus. yellow |
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This test is used todifferentiate Staphylococcus saprophyticus (resistant)from other coagulase negativeStaphylococcus (susceptible)fromorganisms isolatedfrom urine specimens. what media is used? |
NovobiocinSusceptibility done on BA |
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PYR test CAN BE used to differentiate S.aureus from S.lugdenensis What are the results of this test?? |
S. aureus = negative S. lugdenensis = positive (pink to cherry-red color) |
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Rapid Ornithine (decarboxylaseactivity) is used to detect which organism? |
Used to identify Staphylococcus lugdunensis Staphylococcus lugdunensisis rapid ornithine positive• Other Staphylococcus species are negative (except rare strains of S. epidermidis) |
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The DNase test is used to identify which Staph species |
Staphylococcus aureusgivesa positive DNasereaction (show by clearinga dye in the medium.TheDNase producedby Staphylococcusaureus isalso thermostable. |
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What is the modified oxidase test "looking for"? |
Used todifferentiate Micrococcus from Staphylococcus. Test is lookingfor thepresence of cytochrome c enzymes Test uses Microdase Disks. (Micrococcus: Pos=dark blue... Staph=negative) |
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Oxidative-FermentativeTest Results for Staph and Micrococcus |
Staphylococcus ferments glucose Micrococcus oxidizes glucose/nonsaccharolytic Fermentative– acid productionin both tubes.Oxidative– acid productionin the aerobictube, no acid productionin the anaerobictube. Nonsaccharolyticor Asaccharolytic– no acid productionin either tube. |
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Bacitracin (Taxo A) Results for Micrococcus and Staph |
Susceptible– zone of inhibition ≥10mm.(Micrococcus) Resistant– no zone of inhibition.(Staphylococcus) |
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Results from Lysostaphin susceptibility testing |
Staph=lysed Micrococcus= not lysed |
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Which staph may cause a double zone of hemolysis |
Staph aureus Most strains are beta hemolytic (not all strains)and may show a double zone of hemolysis. |
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Pseudomembranous enterocolitis |
Staph aureus entertotoxin |
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Exfoliative toxin (or epidermolytic toxin) Cause the epidermal layer of skin to slough off |
staphylococcal scalded skin syndrome |
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Toxic Shock Syndrome Toxin 1 (TSST-1) |
Staph aureus exotoxin |
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Panton-Valentine leukocidin (PVL) |
Staph aureus Cytolytic toxin lethal to WBCs– Contributes to the spread of infection by suppressingphagocytosis– Causes severe cutaneous infections and necrotizingpneumonia |
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Organisms that produce _________________ can form protective barriers of fibrin around themselves,making themselves highly resistant to phagocytosis, other immune responses, and some otherantimicrobial agents |
coagulase |
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Responsible for clotbreakdown in the tube coagulase test |
Staph aureus enzyme: Fibrinolysin (staphylokinase) |
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This staph aureus extracellular enzyme hydrolyzes acid in connective tissue allowing spread of infection |
• Hyaluronidase |
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This staph aureus extracellular enzyme confers resistance against penicillin |
Beta-lactamse |
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this staph aureus enzyme Allows colonization by acting on fass present on the surface of the skin. |
Lipase |
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Which staph aureus virulence factor is found in the cell wall, binds to Fc part of IgG and blocks phagocytosis |
Protein A |
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Whats up with pus? |
Accumulationof pus-mix of active and inactive neutrophils,bacterial cells and extravascular fluid |
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Staph aureus skin infections: |
Folliculitis, Boils (furuncles) and carbuncles (mass of furuncles) |
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The pustules of staph are different from the pustules of strep in what way? |
Staph = larger with redness |
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Scalded skin syndrome is caused by which organism? Toxin? Another name? |
S. aureus Exfoliative/epidermolytic toxin Ritter Disease |
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Food poisoning from Staph aureus is most commonly caused by which toxins |
enterotoxin A and D Heat stable toxins that are not destroyed byreheating foods |
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Common food culprits of Staph aureus poisonin' Symptoms |
potato salad, processed meats,custards, bakery goods Cause vomiting and diarrhea 2-8 hrs. after ingestion– Lack fever and symptoms usually resolve within 24to 48 hrs |
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antibiotic-associated colitis and occurswhen the normal flora of the large bowel is altered |
Staph aureusPseudomembranous enterocolitis |
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Common Antibiotics prescribed for Staph aureus |
methicillin, oxacillin, nafcillin (resistant to enzyme penicillinase) |
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gene responsible for altering penicillin binding proteins |
MecA |
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drug of choice for MRSA |
Vancomycin |
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Resistant strains of MRSA grow: more slowly/fasterly? |
Resistant strains grow more slowly |
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When performing antimicrobial testing optimaldetection of MRSA is obtained by: |
direct inoculation 24H cooler incubation (30-35C) Neutral pH (7.0-7.4) media with 2% NaCl |
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Gold Standard for MRSA detection |
Nucleic acid probes or PCR amplification fordetection of mecA gene |
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Other Methods to Detect MRSA : A _________________ disk has been proven to be a good inducerof the mecA gene which is responsible for methicillinresistance |
– Cefoxitin Disk (30 ug) Due to heterotypic resistance phenotype some MRSAmay not be detected by MIC microdilution methods |
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VRSA= VISA= |
VRSA= vancomycin resistant Staphylococcus aureus VISA= vancomycin intermediate Saphylococcus aureus |
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Differential and Screening media used forMRSA: |
CHROMagar or Spectra MRSA agar– Selective media with specificchromogenic substrates– Cefoxitin is incorporated in the CHROMagar to induce the mecA gene andallow for increased detection Mueller-Hinton agar with 4% NaCl and 6 ug Oxacillin(Oxacillin Screen agar) |
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Infections with these organisms are predominantly hospital acquired,associated with instrumentation procedures, immunosuppressivetherapy and immunocompromised patients. |
Coagulase Negative Staphylococci |
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Most frequently isolated Coagulase Negative Staphylococcus inclinical lab is |
Staph. epidermidis. |
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Colony morphology of Staph epidermidis. |
Opaque, smooth, raised, entire (smooth orregular border), gray-white, non-hemolytic |
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Strains of staph epidermidis are able to inhibit immune functions including theaction of lymphocytes and neutrophils (opsonization and phagocytosis) because of this: |
Extracellular Slime substance |
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Staphylococcus epidermidisInfections: |
Subacute bacterial endocarditis (SBE) Meningitis Bacteremia/septicemia Wound infections Urinary tract infections Post-operative surgical infections |
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______________________ is generally more resistant than Staphylococcus aureus treatment: |
Staphylococcus epidermidis Methicillin (oxacillin)Vancomycin for methicillin resistant strains |
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Staphylococcus saprophyticus colony morph |
Opaque, smooth, raised,entire,glossy white-yellow, non-hemolytic.Some strains look bright white. |
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A coagulase negative Staphylococcus that is resistant to Novobiocinis indictative of _______________________________ in urinary tract cultures and nofurther identification is usually necessary. |
S. saprophyticus |
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2nd to Escherichiacoli as the cause of UTI in young girls |
Staphylococcus saprophyticus treatment: nitrofurantoin,trimethoprim/sulfa, fluoroquinolones |
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Staphylococcus lugdunensis colony morph |
Usually opaque, very white, non-hemolytic,canbe beta hemolytic but developslater |
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Which staph/micrococcus organism is positive for rapid ornithine? |
Staphylococcus lugdunensis |
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Besides the coagulase test, what test could you do to differentiate S. aureus from S. lugdunensis? |
PYR S. lug = positive s. aureus = negative |
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Staphylococcus lugdunensis Clinical significance: |
Endocarditis, septicemia, meningitis, skin and soft tissueinfections, urinary tract infections, and septic shock May possess mecA gene |
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D test |
Measures induceable resistance to clindamycin – Use erythromycin and clindamycin disks• Growth between disks but not on side of clindamycindisk– Inducible resistance |
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Micrococcus oxygen requirements: |
Obligate aerobe, usually will not grow anaerobically Remember: staph are facultative anaerobes |
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Gram stain/morphology of Micrococcus: |
LargeGPC in pairs, tetrads,or masses |
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Colony morphology of Micrococcus |
Smooth, raised,opaquewhite, bright yellow, pink |
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Some animal isolates (S. intermedius, S. hyicus, and S.delphini) may be tube coagulase_____________ and should beconsidered in wounds involving animal bites. |
POSITIVE |
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Coagulase negative species S. lugdunensis and S.schleiferi produce clumping factor so: Coagulase test: Latex agglutinationtests: Tubecoagulase test: |
Coagulase test: POSITIVE Latex agglutination tests: POSITIVE Tube coagulase test: NEGATIVE |
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THIS organism shows strong adherence to the agar surface when you try to pick up thecolony due to the presence of a capsule (colony will stand up like eggwhites if teased with a stick) |
Stomatococcus (Rothia)mucilanginosus Encapsulated GPC that is part of normal human respiratory flora |
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The modified oxidase/bacitracin susceptibility testing is typically only done when... |
the colonies look yellow. This is b/c you may suspect Micrococcus which are: Mod. Oxidase: positive Bacitracin: Susceptible |
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This is most likely which organism(s)? |
STREPTOCOCCUS, ENTEROCOCCUS,AND RELATED ORGANISMS GPC in pairs and chains (can be encapsulated) |
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General Characteristics ofStreptococcus and Enterococcus: O2/CO2 requirements: Media: |
Most behave as facultative anaerobes May need increased CO2 togrow Typically required enriched media (BA) for growth. |
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Brown's classification is based on... Lancefield is based on... |
Browns: Hemolytic pattern Lancefield: based on specific cell wall polysaccharide antigens |
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Lancefield classification is used for which group of organisms? |
Strep |
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Hemolytic patterns: alpha- beta- gamma- |
alpha: incomplete or partial lysis (greening) beta: complete lysis(colorless, clearzone) gamma: non-hemolytic |
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Hemolytic Patterns of Strep: Group A: Group B: Group C: Group D: Group F: Group G: |
Hemolytic Patterns of Strep: Group A: large zone, strong Group B: narrow zone, weakGroup C: large zone, strong Group D: variable (may be alpha, beta, or gamma) Group F: narrow zone, weak Group G: large zone, strong |
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Which organisms belong to these groups? Group A: Group B: Group C: Group D: |
Group A: S. pyogenes Group B: S. agalactiae Group C: S. equisimilis, S. equi, S. zooepidemicus Group D: Enterococcus sp., Strep bovis, Strep equinus: Strep pneumoniae: none |
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Bacitracin (Taxo A) susceptibilityUsed to identify group __ streptococci |
Group A S. pyogenes (SUSCEPTIBLE) |
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Which test is often used wtih Taxo A to identify group A and group B strep?
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Sulfamethoxazole-Trimethoprim (SXT)Susceptibilty
Group A: resistant Group B: resistant Group C, D, F, G: susceptible (any zone) |
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CAMP test principle: identifies: |
CAMP factor is a diffusible compound that produces a characteristic “arrowhead” pattern when streakedperpendicular to beta hemolytic Staph aureus. Group B organism |
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Bile Esculin Agar is used to identify |
group D streptococci (and Enterococcus.) Positive: growth and medium turns black(minimum of 50% of medium) |
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6.5% NaCl BrothUsed to differentiate |
Used to differentiate group D enterococci from group D nonenterococci POSITIVE= Group D Enterococcus sp. NEGATIVE=Group D not Enterococcus sp. |
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PYRase test can be used to differentiate Enterococcus and Group AStreptococcus from other organisms |
(Tests for the ability to hydrolyze the substrate L-pyrrolidonyl-alphanapthylamide(PYR) Enterococcus or Group A Strep: positive Other GPC, catalase negative organisms: negative |
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Another name for the Optochin test is: What differentiation is it used for? Incubation: |
Taxo P: Used to differentiate Streptococcus pneumoniae from other alpha hemolyticStreptococcus. S. pneumoniae=SUSCEPTIBLE Incubated in CO2 |
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Bile Solubility is also used to differentiate Streptococcus pneumoniae from Streptococcus viridans Results: |
Strep pneumoniae: dissolves (positive) viridans Strep: doesnt dissolve (neg) |
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The HippurateTest is used to differentiate which streps from other groups? |
Group B! Group B Streptococcus: positive Group A, C, D, F, and G: negative |
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What does the LAP test help in differentiating....? |
Helps differentiate Aerococcus viridans (negative) and Leuconostoc(negative) from other Streps and Strep-like organismsUsed in combination with PYR and EsculinTest for leucine aminopeptidase which is able to hydrolyze peptidebonds adjacent to a free amino acid group |
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The Latex Agglutination (Streptex) is used for whhhhhhat |
Used to differentiate Streptococcus into Group A, B, C, D, F, or G.• Test is based on looking for the particular carbohydrate group that isunique to each group.• Test uses latex particles coated with antibodies to the particlecarbohydrate group. Typically, the organism is placed in a solution ofan extract (acid) to expose the carbohydrate |
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Beta hemolytic Streptococci: |
Group A Strep (Streptococcus pyogenes) Group B Strep (Streptococcus agalactiae) Groups C, F, and G Strep.. |
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Alpha hemolytic Strep: |
Streptococcus pneumoniae(pneumococci) Viridans group (S. salivarius, S. mitis, S.anginosus, S. sanguinus, S. mutans, S.bovis) |
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Gamma hemolytic Streptococci: |
Group D Strep |
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Group D Streptococcus NOT Enterococcus: |
S. bovis |
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Group A Strep colony morph: |
Small, glossy, transparent, smooth, large zone beta hemolysis |
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Hey girl - you got this. |
XOXO, Ryan |
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Group A Strep Identification: – Immunologic tests to detect previous infection |
PYR = POSTIVE BAcitracin = Sensitive SXT = resisitant Anti-Streptolysin O (ASO), DNase B (most specific), Antistreptokinase,and anti- hyaluronidase titers |
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Group A Streptococcus(Streptococcus pyogenes)Major virulence factor, found in organism’s cell wall: |
M Protein |
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Which toxin causes the rash in scarlet fever? |
Streptococcal pyrogenic exotoxins (Spes)• previously called Erythrogenic toxin |
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Group A Streptococcus(Streptococcus pyogenes) hemolysins: |
Streptolysin S:Non-antigenic, oxygen stable, responsible for surface hemolysis. Streptolysin O:Antigenic, oxygen labile, produced mainly by group A streptococci (also C andG), responsible for hemolysis in reduced O2 environments. |
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The oval-shaped areas of clearing around the stab marks in the picture are caused by which toxin? |
Streptolysin O |
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Streptococcal pharyngitis (sore throat): Most common infection caused by__________ |
Group A Strep Diagnosed by antigen testing and/or culture (sheep blood agarshould be stabbed to check for SLO) |
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Erysipelas: what is that? |
Skin and lymphatics under skin infected by Group AStrep Swollen, red, tender area Infection through scratch on skin surface Culture watery blisters oradvanced edge of spreadinginfection |
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Impetigo Localized blisters of superficialskin Contagious over own body andperson-to-person (Strep pyogenes) |
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Cellulitis• Develop following deeper invasionby Group A Strep• Serious, life-threatening infection,can be accompanied by bacteremiaorsepsis• Skin infection involving deep tissues |
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Describe this suppurative (pus-producing) disease: |
Scarlet feverIf infecting Group A Strep produces pyrogenic exotoxinsSpes (erythrogenic toxin), rash occurs unless patienthas antitoxic immunity Rash not caused by organism directly |
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____________ is considered the most common cause of necrotizing fasciitis. |
Group A strep |
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Non-suppurativeGroup A Strepto0coccus(Streptococcus pyogenes) diseases: |
Post-streptococcalsequelae: Rheumatic feveror Acute glomerulonephritis |
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Strep Group A:The most serious “delayed sequelae” type disease as it results indamage to the heart muscle and its valves |
Rheumatic feverOccurs 2-3 weeks after a throat Group A Strep infection• Patient has high ASO titer (also anti-hyaluronidase and/or anti-DNase)• Symptoms include fever, malaise, polyarthritis and inflammation of allparts of the heart leading to thick, deformed valves and perivasculargranulomas in the heartmuscle• Exact mechanism not known (thought to be a cross-reaction betweenstrep antibodies and heart tissue) |
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Group B Streptococcus(Streptococcus agalactiae) Colony morph: |
Flat, glossy, grayish-white, small zone beta hemolysis (can be gamma) |
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Group B Streptococcus (Streptococcus agalactiae) "identification": |
• PYR = negative • Sodium hippurate = positive CAMP = positive |
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Group B Streptococcus(Streptococcus agalactiae)• Invasive disease in the newborn |
Early-onset (less than 7 days old): most common, caused byvertical transmission from the mother.» Infection often presents as a pneumonia or meningitiswith bacteremia» Recommend all pregnant women be screened for group Bstreptococci at 35-37 weeks gestation– Late-onset (at least 7 days old): usually presents as meningitis |
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GBS screening for pregnant women |
Todd-Hewitt and LIM broth Strep B Carrot broth is available |
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Group B Streptococcus(Streptococcus agalactiae)Disease states |
Adults– Vaginitis, postpartum fever and sepsis, endocarditis, urinarytract infections, upper respiratory disease, osteomyelitis, andwound infections |
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Groups C, F, and G StreptococcusDisease states |
Occasionally implicated in bacteremia, endocarditis, woundinfections, meningitis, pneumonia, genitourinary tractinfections, post-partum sepsis and severe pharyngitis (especiallyGroup C Strep) |
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Streptococcus pneumoniae(pneumococci) Colonial morphology |
Alpha hemolytic(checker or mucoid colonies)• Enzyme causes autolysis of cells, producedupon prolonged incubation which causes the sunken center |
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Which strep is susceptible to optochin? |
s. pneumoniae |
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Streptococcus pneumoniae(pneumococci) Lancet shaped cocci in pairs– seen best in clinical and broth specimens |
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Most common cause of community acquiredbacterial pneumonia |
Streptococcus pneumoniae (pneumococci) |
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Whcih strep organism is showing increased resistance to Penicillin G? |
Streptococcus pneumoniae(pneumococci) *Key point *: A disk diffusion susceptibility testmust be performed using an oxacillin (1 ug) KBdisk to check for penicillin susceptibility. Theisolate is tested on Mueller-Hinton agar with 5%sheep’s blood and incubated in CO2. |
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Viridans group (S. salivarius group, S. mitis group, S.anginosus group, S. sanguinus, S. mutans group, S.bovis group) Colonial morphology : |
Tiny, gray, domed, alpha hemolysis (can vary in morphologies)– Basically, any alpha Strep that is not S. pneumoniae or Enterococcus is a SVG |
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Viridans group (S. salivarius group, S. mitis group, S.anginosus group, S. sanguinus, S. mutans group, S.bovis group) IDENTIFICATION |
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Most common cause of subacute bacterialendocarditis |
Viridans group (S. salivarius group, S. mitis group, S.anginosus group, S. mutans group, S. bovis group) |
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Which strep Will grow in 40% bile and hydrolyzes esculin. |
Group D Streptococcus |
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Group D Streptococcus is divided into two subgroups: |
Enterococcus sp. non-Enterococcus |
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S. bovis belongs to which group(s) |
Strep bovis is a Group D non-Enterococcus Some people think they should be in the Viridans group (which is pretty much a group that is the catch-all for all strep that AREN'T beta-hemolytic streptococci, enterococci, or pneumococci) |
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endocarditis from which organism is highly correlatedwith gastrointestinal carcinoma |
Group D Strep NOT Enterococcus (S.bovis) |
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Important to distinguish Group D non-enterococcus from Enterococcus because... Group Dis sensitive to what? |
penicillin |
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Enterococcus consists of 2 major species: |
faecalis (most common; 80% – 85%) faecium (10%) |
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Which of the following is more resistant to antibiotics: Enterococcus Group D Strep |
Enterococcus!
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Other Strep-like bacteria: Just know that these exist... and that you can do tests to differentiate |
Aerococcus: opportunistic Gamella:Normal flora of upper respiratory tract and GI tract Lactococcus: dairy processing Leuconostoc: sauerkrautPediococcus: Group D antigen, grows @45C Abiotrophia: Requires Vitamin B6 or pyridoxal to grow, satellite growth aroundStaphylococcus aureus |
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