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Microbiology
Exam 3
| Question | Answer |
|---|---|
| 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
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