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59 Cards in this Set
- Front
- Back
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staph aureus is part of normal flora of _______?
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upper respiratory tract, , especially in health care workers
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staph aureus is the major cause of which infection?
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nosocomial infection and community-acquired infection
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pathogenicity of staph aureus?
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suppurative cutaneous infections, toxic shock syndrome, food poisoning
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staph not aureus include all the staph species except___?
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staph aureus and staph saprophyticus
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most common staph not aureus is ___?
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staph epidermidis
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pathogenic characteristics of STN
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1)Slime layer (biofilm) allow adherence to medical devices
2) affinity to acquire resistance to common antibiotics |
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which key test is used to differeciate staph and strep?
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catalase test
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what is principle of catalase test?
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the enzyme catalase present in the organism breaks down Hydrogen peroxide to water and oxygen gas
positive reaction-Air bubbles |
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staph is catalase positive or negative?
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Positive = immediate vigorous bubble formation = staph
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strep is catalase positive or negative?
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Negative = no bubble/smooth suspension = Strep
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what is the principle of Oxidation Fermentation Media OF media?
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To differentiate between Staphylococcus and Micrococcus
Based on organism’s ability to either ferment, oxidize, or not utilize glucose at all |
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Indicator of Oxidation Fermentation Media OF media?
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Indicator : Bromthymol Blue
Acid = yellow Alkaline = blue-green |
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how does Oxidation Fermentation Media OF media differenciate staphylococcus and micrococcus?
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Staph = fermenter
Micrococcus = oxidizer or Asaccharolytic (non-utilizer) |
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procedure of Oxidation Fermentation Media OF media?
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1)Inoculate two tubes of media using a straight plastic needle
2)Overlay one tube with mineral oil (1/4 inch),Provides anaerobic environment 3)Incubate 18-24hrs May require longer incubation time |
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pricinciple of coagulase test?
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coagulase present in organism could convert fibrinogen to fibrin (forms clots or agglutination)
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principle of Staphaurex Latex test?
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Latex particles coated with IgG bind to staphaurex cell wall antigen (protein A and clumping factor)to form agglutination
agglutination--->staphaurex no agglutination----->STN |
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Principle of Dnase test and what's the indicator in the plates?
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organism like STA produces DNase which hydrolyzes DNA into nucleic acids
Indicator in plate: Toluidine blue |
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result of Dnase test?
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Positive = Pink halo around well = Staph aureus
Negative = Media remains blue = STN/CNS |
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principle of Mannitol Salt Agar (MSA)?
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STA is able to ferment mannitol in the presence of high salt (NaCl) content and Other Staph species cannot
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Novobiocin Disk presumptively identify which organsim in UTI’s?
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Staph saprophyticus
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is it true staph saprophyticus is resistent to Novobiocin disk when zone size < 16mm?
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true
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LAB ID of staph aureus?
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95% β hemolytic
Coagulase =positive DNase= positive Staphaurex latex test = positive Mannitol salt agar=yellow colonies surrounded by a yellow halo Novobiocin susc= sensitive |
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LAB ID of Staph saprophyticus?
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Coagulase=negative
DNase=negative Staphaurex latex test=negative Mannitol salt agar=red or clear colonies Novobiocin susceptibility= resistant |
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LAB ID of Staph species, not aureus?
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Coagulase=negative
Dnase= negative Staphaurex=negative Mannitol salt agar= red colonies ( color of media) Novobiocin =sensitive |
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ALWAYS perform Susceptibility Testing for Staph aureus, is it true?
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True
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why most Staph aureux resistent to penicillin and beta-lactam drugs?
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D/t altered Penicillin-binding protein (PBP 2a) site renders drug ineffective
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Drug of choice for MRSA?
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Vancomycin
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how Bacitracin susceptibility (Taxo A) differenciate micrococcus and staph?
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Zone of > or =10mm = S = Micrococcus
Zone of <10mm = R = Staph |
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Rothia also called_______?
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"sticky staph"
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what media does strep grow on?
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BAP, CHOC, PEA, CNA
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Morphology of strep?
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Small, pinpoint colonies which are translucent or grayish
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what is Lancefield grouping?
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Isolate different type of strep Based on cell wall polysaccharide carbohydrates or cell wall antigens, but Not all strep fit into this classification system
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The name of group A strep?
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Strep pyogenes
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the name of group B strep?
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Strep agalactiae
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Virulence Factors Streptokinase?
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Causes lysis of fibrin clots which aids in the spread of infection
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which organism has Polysaccharide capsule
organism resistant to phagocytosis? |
Strep pneumoniae
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which test is used for presumptive identification of Group A strep?
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Bacitracin susceptibility (Taxo A)Any size zone = sensitive = group A strep
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what color is PYR positive?
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pink is positive, colorless is negative
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PYR could ID could two organisms?
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Group A and Enterococcus sp.
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which organism has positive result for CAMP test (show arrowhead on the plate)
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Group B strep forms “arrowhead”
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which organism has hippuricase enzyme, which hydrolyzes hippuric acid to its components, glycine and benzoic acid?
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Group B strep
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what test is used for the presumptive ID Enterococcus and Group D strep?
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Bile Esculin test
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result of bile esculin test?
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positive is black, negative is no color change
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Strep pneumoniae is sensitive to _______ disk?
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strep pneumoniae is sensitive to Optochin (Taxo P) disk, Viridans strep is resistent to P disk.
Positive=sensitive ≥ 14mm Negative =resistant <14mm |
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what could lysis strep pneumoniae?
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Bile salts
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which organism has the LAB RESULT as below?
100% are beta hemolytic Colonies are tiny or small with a very large zone of β hemolysis** Susceptible to bacitracin NOTE: the A disk ids Grp A strep PYR= positive Latex agglutination=group A positive |
Streptococcus pyogenes, Group A strep
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why is so important to screen all pregnant women for Group B strep?
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GBS is the normal flora in the genitourinary tract (esp vagina and rectum) AND it's the most common cause of neonatal meningitis and sepsis
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Streptococcus agalactiae, Group B strep should plant in _____?
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Planted in LIM, Todd-Hewitt or Carrot broth
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what is the characteristic of Streptococcus (Group B strep) agalactiae on BAP?
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95% are β hemolytic with large colonies and small zone of hemolysis
5% are non-hemolytic |
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Group B strep has:
CAMP test= Hippurate hydrolysis = Latex agglutination = |
CAMP test=positive- arrowhead hemolysis
Hippurate hydrolysis = positive Latex agglutination = Group B positive |
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what are lab tests to ID Group D strep, Group D non-enterococcal Streptococcus bovis?
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5% are α hemolytic
5% are β hemolytic 90% are γ hemolytic Bile esculin = positive Salt tolerance test = negative Latex agglutination= Group D positive |
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Strep pneumoniae has 100% _____ hemolytic?
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alpha
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vaccine for Strep pneumoniae is available but not effective on patients less than _____years old
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two
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ID Strep pneumoniae?
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Optochin test- “P” disc sensitive (zone size ≥14mm)
Note: P disc for Pneumo Bile solubility = positive Pneumoslide = positive Quellung reaction = positive |
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which organism is the number 1 cause of endocarditis?
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Viridans Streptococci
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Viridans Streptococci Identification?
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Optochin test=resistant (zone size<14mm)
Bile solubility = negative Bile esculin = negative Salt tolerance test = negative PYR = negative |
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which organism Contain group D cell wall carbohydrate
Highly resistant to penicillin, and many resistant to vancomycin? |
Enterococcus
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Enterococcus:
___% are non-hemolytic ___% are α hemolytic ___% are β hemolytic |
90% are non-hemolytic
5% are α hemolytic 5% are β hemolytic |
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ID Enterococcus?
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Bile esculin = positive
Salt tolerance test = positive PYR= positive Catalase= negative BUT possibility of pseudocatalase activity= weak pos rxn |
