Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

2.2 Microbiology > Staphylococcus Species > Flashcards

Staphylococcus Species Flashcards

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards
1
Q

Give the preliminary ID Tests for staphylococci
(3)

A

Gram positive

Cocci

Catalase +

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How do you speciate staphylococci?
(3)

A

Coagulase test

+ = S. aureus

  • = S. epidermidis or saprophyticus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the three clinically significant species of staphylococci

A

S.aureus

S. epidermidis

S. saprophyticus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is a gram positive cocci but catalase negative species

A

Micrococcaceae

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How many genera of staphyloccaceae are there

A

6

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the most clinically significant micrococcaceae

A

Micrococcus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How are staphylococci arranged?

A

Grape like clusters

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How many species of staphylococci are there?

A

40+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Why are there only a few species of staphylococci that are considered clinically significant

A

Most species only exist as commensals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Name four species of commensal staphylococci that have some varying pathogenic potential

A

S. aureus

S. epidermidis

S. saprophyticus

S. haemolyticus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What clinical specimens can staphylococcus be found in?
(6)

A

Skin wab
Pus specimen
Wound swab
Blood - blood cultures for BSI
Sputum
Urine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What must be done with specimens potentially containing staph
(2)

A

MRSA surveillance to detect carriage

Screening swabs can be taken from the nasal, axilla groin or carriage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

In general what are the growth characteristics of staph?

A

Facultative aerobe
Halophilic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What does halophilic mean?

A

Can grow in NaCl as high as 15%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is query staph put up on on day 1 of investigation
(4)

A

General purpose: Blood agar

Selective agar
- Mannitol salt agar
- Chromogenic media e.g. S. aureus ID or CHROMagar MRSA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How should you incubate staphylococcus on blood agar?

A

Incubate at 37 degrees for 24 hours

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How should you incubate the selective and differential medias for Staphylococci?

A

Incubate for 24-48 hours at 37 degrees Celsius

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are the selective agents of Mannitol Salt agar and how do they work?

A

7.5% salt

High salt favours growth of salt-tolerant Staphylococcus species

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the differential agents of mannitol salt agar and how do they work?
(3)

A

Mannitol is the differential agent

S. aureus can ferment mannitol producing yellow colonies

S. epidermidis cannot ferment mannitol and will grow as pink or white colonies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

List the Chromogenic Mediums that can be used for Staphylococci
(3)

A

Oxoid Chromogenic MRSA Agar

BioMérieux Chrome ID

ChromID MRSA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How does Oxoid Chromogenic MRSA Agar work?
(3)

A

Chromogens detect phosphatase activity in S. aureus -> this will produce denim-blue colonies

Cefoxitin (methicillin) will inhibit MSSA colonies

This allows for the accurate detection of MRSA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How does the BioMérieux- Chrome ID work?
(3)

A

SAID -> S. aureus ID

Chromogens detect alpha glucuronidase in S. aureus

This forms green colonies i.e. S, aureus = green colonies

23
Q

How does the ChromID MRSA agar work?

A

MRSA stains indicated by green colonies

Results from alpha-glucuronidase producing colonies in the presence of cefoxitin

24
Q

How does the ChromID MRSA agar work?
(2)

A

MRSA stains indicated by green colonies

Results from alpha-glucuronidase producing colonies in the presence of cefoxitin

25
Q

What tests are carried out on Day 2 to identify Staphylococcus?
(9)

A

Colonial morphology
Gram stain -> GPC, grape-like clusters
Catalase positive

Coagulase
Protein A
DN’ase

Biochemical profile - Vitek/Phoenix
Protein profile - MALDI

Molecular ID systems - Real Time PCR

26
Q

What are the four classifications of tests carried out on day 2 for the identification of an organism

A

Basic characterisation tests

Manual Conventional confirmatory tests

Automated conventional confirmatory tests

Molecular confirmatory tests

27
Q

What manual conventional confirmatory tests are carried out for Staphylococcus
(3)

A

Coagulase
Protein A
DN’ase

28
Q

What automated conventional confirmatory tests are carried out for staphylococcus?

A

Biochemical profile on the Vitek/Phoenix
Protein profile on the MALDI

29
Q

What molecular confirmatory tests are carried out for Staphylococcus?

A

Molecular ID systems - Real Time PCR

30
Q

What is the definitive test to identify S. aureus?

A

Coagulase test

Test for the detection of coagulase enzyme

31
Q

What are the two ways of carrying out coagulase test?

A

Slide coagulase/clumping factor test

Tube method

32
Q

What is the slide coagulase/clumping factor test and how do you carry it out?

A

Detects bound coagulase only

Mix bacterial saline suspension with rabbit plasma (source of fibrinogen), observe agglutination

33
Q

What is the slide coagulase/clumping factor test and how do you carry it out?

A

Detects bound coagulase only

Mix bacterial saline suspension with rabbit plasma (source of fibrinogen), observe agglutination

34
Q

What is the tube method of coagulase test and how is it carried out?

A

Detects free and bound coagulase

Mix 9 drops of 3hr incubated test suspension with 1 drop rabbit plasma -> incubate over night -> observe clot

35
Q

What does a positive coagulase test mean?

A

This is sufficient to identify S. aureus

36
Q

What does a negative coagulase mean?

A

Coagulase negative staphylococcus species

These are collectively called CNS

37
Q

What is the most common way of detecting coagulase

A

Staphaurex Plus

38
Q

What is Staphaurex Plus

A

Rapid latex agglutination test for the identification of S. aureus

39
Q

Why should Staphaurex be used instead of methods of testing for coagulase?
(3)

A

In addition to coagulase, protein A is also found on the surface of 95% of human strains of S. aureus

Certain MRSA possess a capsule that masks both protein A and the coagulase

With Staphaurex, rapid agglutination will occur using any three of these components

40
Q

What will cause rapid agglutination in the Staphaurex Plus test?
(3)

A

Reaction between fibrinogen and coagulase

Binding between Protein A and the Fc portion of IgG

Binding between MRSA capsular polysaccharide and specific IgG

41
Q

Explain in your own words how the Staphaurex Plus test works
(4)

A

Test latex beads are coated in porcine fibrinogen which will detect coagulase

Latex bead also coated with IgG antibodies

IgG anti capsular polysaccharide to detect MRSA capsule

Fc portion of IgG will detect Protein A

42
Q

What is the DN’ase test?

A

Deoxyribonuclease Agar

Nutrient agar that has 0.2% DNA added

43
Q

How is DN’ase agar used?
(5)

A

Spot inoculate DNase agar and incubate overnight

Flood with 1 molar HCL

HCL precipitates DNA which turns the medium cloudy

DNase-positive cultures -> DNA is unavailable for precipitation so there will be a clear zone around the inoculum e.g. S. aureus

DNase negative will have no zone of clearing e.g. CNS

44
Q

What automation is used in the identification of Staphylococcus
(5)

A

VITEK GP Card - biochemical reactions
MALDI-TOF -> protein profile

These are used to ID S. aureus and speciate Coagulase negative staff if it’s required

Molecular ID systems- real time PCR detection systems such as the Xpert MRSA/SA assay can be used
- these target protein A (SA) or mecA (meth resistance) DNA sequences
- mostly used in MRSA surveillance for direct screening or confirmation of MRSA from nasal swabs

45
Q

How does the Xpert MRSA/SA assay work?
(2)

A

Molecular ID system which uses real-time PCR

It detects targets such as Protein A (found in S. aureus) or mecA (found in methicilin resistant strains) DNA sequences

46
Q

When is the Gene Xpert used for Staphylococci

A

Used in MRSA surveillance -> for direct screening or confirmation of MRSA from nasal swabs

47
Q

What test do you carry out on Coagulase negative staph to speciate them?

A

Automated VITEK/MALDTOF

Novobiocin resistance

48
Q

How do you carry out the novobiocin test, what are the results
(4)

A

Nutrient agar with novobiocin discs

Lawn inoculum

S. aureus/CNS are novobiocin susceptible

S. saprophyticus are novobiocin resistant

49
Q

How is methicillin susceptibility performed?

A

Using cefoxitin

50
Q

What are the three classifications of S. aureus infection

A

Superficial infection
Serious infection with S. aureus
Serious infection with MRSA

51
Q

How is a superficial staph infection treated?

A

Topical = mupirocin

Oral = augmentin

52
Q

How is a serious infection with S. aureus treated?

A

Requires aggressive treatment including incision and drainage of lesions

Systemic antibiotic needed = Methicillin

53
Q

How is a serious infection with MRSA treated?

A

Aggressive treatment including incision and drainage of lesions

Systemic antibiotic = Vancomycin

2.2 Microbiology (60 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions