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Microbiology

Exam 3

QuestionAnswer
MacConkey selective for gram negative organism differential based on fermentation of lactose pink=lactose fermenter (E.coli) clear=non-lactose fermenter (P.aeruginosa)
BAP (blood agar plate)5% sheep blood supportive media for most organisms except fstidious differential based on type of hemolysis
Beta Hemolysis clear = complete hemolysis
Alpha hemolysis partial clearing, greenish zone
Gamma Hemolysis no hemolysis no clearing
EMB Eosin Methylene Blue selective for gram negative organisms differential based on lactose fermentation metallic green= lactose fermenter
Mannitol Salt Agar Selective for halophilic differential based on mannitol fermentation yellow= mannitol ferementation
Staph aureus avoid host defenses by hiding their antigens kill phagocytes resistance to antibiotics release toxin
S. aureus produce this protein to increase virulence Protein A
Skin and wound infections caused by S. aureus Folliculitis Impetigo
Extensions of folliculitis Furuncles Carbuncles
Toxin mediated syndromes of S. aureus toxic shock syndrome scalded skin syndrome food poisoning
Leads to endocarditis in IV drug users Staphlococcal bacteremial= blood infection
Common post-operative infection and important nosocomial agent S.aureus
most common Staphylococcus coagulase negative S.epidermidis
Step 1 for isolation and identification Direct smear from specimen
Step 2 for isolation and identification Streaking culture plates
Step 3 for isolation and identification Colonies Gram stained
Step 4 for isolation and identification isolated bacteria are speciated
Step 5 for isolation and identifiction antibiotic susceptibility testing
Stapylococcus and Micrococcus are gram... positive cocci
Staphylococcus and Micrococcus grow on what type of media BAP
Staphylococcus and Micrococcus incubate in... 35 degrees C in CO2 or ambient air
Colony appearance of S. aureus B-hemolyic, creamy
Colony appearance of Micrococcus Yellow pigment
Colony appearance of S.epidermidis flat, white
Presumptive ID of An organism that is Gram Positive Catalase- Positive Coagulase- positive S.auerus
One enzyme that can catalyze the conversion of hydrogen peroxide back to water and oxygen catalase
What you will see in a positive catalase test bubbles
If bacteria in question produce catalase they will convert the hydrogen peroxide and what will be evolved? oxygen gas
What is the most significant way to identify gram positive cocci? catalase test
If catalase test is positive what is the next test that you do? coagulase
coagulase on the surface of the bacterial cell directly converts fibrinogen to what? fibrin
the precipitation of fibrin onto the cell surface causes what? agglutination
any negative coagulase slide test can be confirmed with what test? the tube method which detects free coagulase
staphylocoagulase is an extracellular molecule that causes what to form? and when? a clot to form when cells are incubated with serum
Staph coagulase negative are positve or negative on the modified oxidase test? Negative
Micrococcus are positve or negative on the modified oxidase test? positive
Staph coag. negative are susceptible or resistant to bacitracin? Resistant
Micrococcus are susceptible or resistant to bacitracin? Susceptible
S. saprophyticus are susceptible or resistant to novobiocin? Resistant
When is S. saprophyticus usually found? urine cultures
Oxidase test is used for Gram positive cocci or gram negative rods? Gram negative rods
The presence of cytochrome oxidase can be detected when colonies are exposed to what? methylphenylenediamine (an electron donor to cytochrome enzyme)
The bacteria does what to the disk or reagent of the oxidase test? oxidizes it. (removes electrons)
A positive oxidase test will change to what color? Purple or blue
Bacitracin "A" disk contains how much bacitracin? 0.04 units
Bacitracin is an antibiotic that was originally isolated from? Bacillus species organism
Bacitracin belong to a class of antibiotic that do what to the cell? Inhibit cell wall synthsis
How long does a plate with bacitracin "A" disc on it have to be incubated for and at what temp? overnight at 35-37 degrees C
what size zone around the bacitracin disk indicates susceptibility? ANY clear zone
Novobiocin is used for? coag negative Staphylococci in a urine specimen
What size does the zone have to be around Novobiocin to indicate resistance? a zone of less than 16mm is resistant
In addition to Gram stain, catalase, and coagulase what other tests can be done to identify S. aureus? Mannitol Plate, DNAse enzyme test, VP test, and Rapid kit testing
Mannitol salt agar is selective for? Halophilic organisms
Mannitol salt agar is differential for? mannitol fermenters
DNAse agar has what on it? DNA
DNAse is what kind of enzyme? what does it do? exoenzyme. it will break down DNA into smaller molecules
Around the area of growth what will you see on a DNAse Agar? A clear zone
What will the rest of the DNAse agar look like when there is growth? Opaque white
what can be added to the DNAse plate to better indicate a zone? methyl green
VP Voges-Prosakuer test detects organisms that utilize what? butylene glycol pathway
The reagents for a VP test are? Barritt's A (alpha-napthol) and Barritta's B (potassium hydroxide)
The presence of what gives a positive VP test? acetoin
What color is a positive VP test? RED
Columbia CNA with sheep blood supress the growth of what type of organisms? Gram negative
PEA- Phenylethyl Alcohol Agar inhibit growth of what type of organisms? Gram negative
General Characteristics of Sterptococcus and Enterococcus -Gram positive cocci -catalase negative -facultative anaeobes -some are capnophilic
Streptococci tend to be more what when compared to other cocci? Elongated
Chaining tends to occur more when? Isolate is from broth media
Lansfield classification does what? grouping of cell wall carbohydrates to classify Streptococci
S. pyogenes is Group? A
S. agalactiae is Group? B
S. equi is Group? C
S. bovis and Enterococcus is Group? D
What has S. bovis been renamed to? S. gallolyticus
Major Strep pathogens that are Beta hemolytic? S. pyogenes and S. agalactiae
Major Strep pathogens that are Alpha hemolytic? S. pneumoniae and Viridans Streptococci
Major Enterococcus pathogens that are Gamma hemolytic? E. faecium
What pathogen can show as either alpha or beta hemolytic? E. faecalis
Many organisms of the Strep and Enterococci group are found as normal flora. Especially where in the body? Respiratory tract
What is the "big bad bug" of the Strep group? S. pyogenes
What protein causes Strep cell to resist phagocytosis and plays a role in adherence to mucosal cells? M protein
What do Strep cells have that allow them to mask their antigens? Capsules
What do Streps contain that can cause scarlet fever? Streptococcal pyogenic exotoxins
What is S. pyogenes most known for causing? Strep throat
When does necrotizing fasciitis usually occur? In patients with underlying illness that experience trauma to the skin.
Necrotizing fasciitis is also known as what? Flesh eating bacteria
Scarlet fever is characterized by what? rash and "strawberry tongue"
Streptococcal Toxic shock syndrome is caused by what? virulent strains of exotoxin producing streptococcus
Rheumatic fever is a complication that is usually followed by what? S. pyogenes pharyngitis
Rheumatic fever is characterized by? inflammation of the heart, joints, blood vessels, and subcutaneous tissue
What happens with Rheumatic fever that causes damage to the heart? Antibodies produced to fight Strep infections cross react and begin to attack the heart tissue
Poststreptoccal ________ causes damage to the kidneys. Glomerulonephritis
S. agalactiae is usually associated with what in humans? neonates
When during the birthing process can S. agalactaiae be acquired? before and during
What precentage of pregnant women is colonization of S. agalactiae found? 10-30%
What drug is S. agalactiae usually treated with? Penicillin
What is the primary pathogen of the alpha hemolytic group? S. pneumoniae
When does S. pneumoniae become pathogenic? When it gains access to the lungs by aspiration
When S. pneumoniae gains access to the lungs it becomes what? bacterial pneumoniae
S. pneumonia can become pathogenic when it gains access to the blood or meninges and causes? Bacterial meningitis
Otitis media and sinusitis are caused by? S. pneumoniae
The term viridans means what? green
Some species in the viridans group include? S. intermedius, S. sanguis, S. mitis, S. mutans, and S. salivarius
Group D viridans include? S. gallolyticus, and S. infantarius
S. gallolyticus is found in? endocarditis and association with colon cancer
S. infantarius is associated with what? neonatal meningitis
What is the virulence of Enterococci? Able to grow in extreme condititons
Enterococci can grow in a high concentration of what? Salt
The presence of what enzyme in Enetococci help it to adhere to heart valves and renal epithelial cells? Gelantinase
What two species of Enterococci are usually identified? E. faecalis and E. faecium
What are the most common infections associated with Enterococci? UTI
Two rare Streptococcal like organisms Gemalla and Pediococcus
Lim broth is also known as what? Todd-Hewitt
Lim broth is most commonly used for what? to support the growth of S. agalactiae and diminish growth of normal vaginal flora
What Strep is susceptible to Bacitracin? S. pyogenes
If bacitracin is resistant what other tests can be done? CAMP test and Hippurate Hydrolysis
Positive CAMP test results in what? an arrow shaped area of beta hemolysis
What color indicates a positve Hippurate Hydrolysis test? Purple
What is the reagent is Hippurate Hydrolysis that gives the color change? Ninhydrin
Optichin disc test is used when determining what type of hemolytic Streptococci? Alpha hemolytic
What Strep is sensitive to Optichin? S. pneumoniae
A zone of how many mm indicate S. pneumoniae on an otichin disk test? >14mm
No zone on an optichin disk test indicate what? Viridans Streptococci or Enterococcus
Bile solubility test distinguish between S. pneumoniae from other alpha hemolytic Strep
The quelling reaction consists of what? Mixing a loopful of colony with equal quantity of specimen antiserum and examining microscopically at 1000X for capsular swelling
What tests can be done for Enterococcus identification? Bile esculin, PYR, 6.5% NaCl
What result will Viridans Streptococcus give on Bile Esculin and Otptichin? Negative
What does bile esculin test? the ability of an oranism to hydrolyze glucoside esculin
Bile esculin contains what? bile salt
Bile esculin inhibits most____ type organisms Gram positive
If a bile esculin test is positive what color will be seen? Black
Turbidity indicates what result in 6.5% NaCl? positive
The PYR test is what kind of procedure? qualitative
What plus what equals a positive PYR test? amine + aldehyde
What percent of Group A Strep. hydrolyze PYR? 98%
What percent of Enetococci hydrolyze PYR? 96%
Created by: aestalker2013