Flashcards
Practical 1
Cards in this deck (37)
- 1Why is mannitol salt agar used to select for normal skin flora?Because the high salt agar inhibits bacterial growth.
- 2What is mannitol salt agar used for? Which microbe.Staphylococci aureus
- 3After you have observed a Gram-positive coccus, you need additional information before performing a coagulase test. What is this additional information?Before performing a coagulase test you must perform a catalase. If positive you would do a coagulase test.
- 4If a bacteria is gram positive, catalase positive and co-agulase positive. What is it?S. aureus
- 5If a bacteria is gram positive, catalase positive and produces acid from mannose. What is it?S. epidemidis
- 6If a bacteria is gram positive, catalase positive and produces no acid from frutose. What is it?S. saprophyticus
- 7List three identifying characteristics of S. aureus.1. Gram positive
2. Catalase positive
3 Coagulase positive
4. Cocci shaped - 8List 4 factors that protect the skin from infection.1. Keratinised layer repels water and promotes skin dryness
2. Salt production from sweat glands inhibits microbial growth
3. sebum produced by sebaceous glands
4. Normal Microflora - 9What is coagulase? How is it related to pathogenicity of Staphylococci?Coagulase is a type of protein enzmye that acts as a mechanism for clotting within the blood by activating prothrombin. Staphylococci aureus uses coagulase within the blood to produce fibrinogen/coagulase clots that protect the bacteria from phagocytosis as they hide within these clots. Macropharges cannot reach the bacteria.
- 10When doing a skin culture, why is the swab first moistened with saline?Helps bacteria from sample to adhere to swab.
- 11What test can differentiate the three major species of Staphylococcus? List 4.1. Colony Pigment
3. Coagulase
4. Microbact Staph 12s
5. DNase test - 12How could you distinguish S. epidermidis from S. saprophyticus in the Micrococcaceae identification Key?S. epidemidis produces acid from mannose
S. saprophyticus does not produce acid from mannose, mannitol or fructose. - 13Why are staphylococcal infections frequent among hospital patients? 3 reasons.1. Staphylococci are commonly found on the skin of nurses, doctors and visitors and easily introduced into patients. 2. Hospitalised patients are more prone to infections as they are immunocompromised.
3. Intravenous therapy dramatically increases as microbes can colonise venous line in the vein resulting in infection. - 14What is Vogel Johnson Agar and what is it used for? Species Example Samples CompositionPathogenic Staphylococci
S. aureus
Samples: Food wounds and skin
Composed of: tellurite - 15What is the catalase test?Test that decides if the microorganism produces the enzyme catalse. Catalse breaks down hydrogen peroxide in to molecular O2 and H2O. Oxygen bubbles indicate a positive result.
- 16What is the coagulase test for? What microbe tests positive?Identifies coagulase positive microbes.
S. aureus is differentiated by this test. - 17List 5 identifying characteristics of S. epidermidis1. Coagulase negative
2. Catalase positive
3. Cocci shaped
4. Mannitol negative
5. Mannose positive (produces acid) - 18List 6 identify characteristics of S. saprophyticus1. Gram positive
2. Catalase positive
3. Coagulase negative
4. Cocci shaped
5. Manitol Negative
6. Fructose Negitive - 19List 4 tests that distinguish major species of Staphylococci1.Microbact 12s
2. DNase test
3. Colony Pigment test
4. Coagulase test - 20What is the DNase test and what is a positive result.It is the Deoxyribonuclease test. Indicates if a microbe uses Dnase as it's carbon source. A positive result displays clearing around the growth/colony sites.
- 21What is the colony pigment test? How does it work?It's purpose is to identify a microbial colony by colour and morphology. Carotenoid pigments are orange to yellow. Beta-galactosidase has a colour change from green to plum after the addition of fast blue reagent.
- 22What is the Staphlyococci Staph 12s kit do? How does it do it?Works by identifying the 22 clinically significant species of Staph. Works by sugar utilisation and and colormetric enzyme detection. Contains 12 tests that undergo colour metric change indicating a positive result. These changes occur via pH indicators and enzyme detection substrates.
- 23Why is blood agar a differential media for Streptococci?Because Steptococci undergoes RBC haemolysis on blood agar plates. Haemolysis types can be used for identification.
- 24Is gram staining results of significant importance for identification of microorganisms from the throat.Yes, although streptoccoci is common other bacteria such as Neisseria can also be found. Gram stain allows for separation of these species. Gram staining also allows the morphology of bacteria to be observed and there for identified.
- 25A gram-positive cocci has been found that cannot be identified as Staph or Strep. What enzyme test will quickly differentiate between these two bacteria?Catalase test. Staphylococci = positive and Streptococci= negative
- 26What type of haemolysis is produced by S. pneumoniae?Alpha
- 27What type of haemolysis is produced by S. pyogenes?Beta
- 28How do you determine is a sore throat is caused by S. pyogenes or S. pneumoniae?1. Complete a haemolysis test on blood agar (pnuemoniae = alpha; pyogenes = beta)
2. Bacitracin test
3. Optchin test (positive = S. pnuemoniae) - 29List the names of 4 types of diseases caused by S. pyrogenes.1. Scarlet fever
2. Acute pharyngitis
3. Strepticoccal toxic shock syndrome
4. Impetigo - 30How would you differentiate between alpha and beta haemolysis?Alpha haemolysis is caused by S. progenes and is complete haemolysis with a claen colony edge.
Beta haemolysis is caused by S. pneumoniae and is partial haemolysis. Methmoglobin is produced resulting in a cloudy green zone surrounding the colony. - 31What does the Optichin test illustrate?Alpha Haemolysis to differentiate S. pneumoniae and S. pyogenes. A positive result for S. pnuemoniae is considered when the zone of inhibition exceeds 14mm (6mm disk).
- 32What are the 3 types of haemolysis and what are their patterns?1. Alpha = partial haemolysis (methmoglobin production = green colony edge)
2. Beta = complete haemolysis
3. Gamma = no haemolysis - 33Which streptococci are considered most commonly pathogenic?Beta haemolysis= S. pyogenes
- 34What are the 4 main microflora in the throat/upper respiratory tract?1. Staphylococci
2. Streptococci
3. Neisseria
3. Haemaphilus - 35Why is infection rare in the upper respiratory tract?Because of microbial antagonism.
- 36What species causes acute pharyngitis?Streptococci species (specifically S. pyogenes)
- 37What is the bacitracin Test?Used to identify beta-haemolytic streptococci, S. pyogenes from other Strep. Any zone of inhibition is regarded positive for beta-haemolyitic Strep.
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- University Medical Microbiology Flashcards on Practical 1, created by Leah MacDonald on 13/10/2014.
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- Leah MacDonald
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