Staphylcococus Flashcards

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

Is staphylococcus gram negative or positive

A

Gram positive

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

Brief description of the skin environment

A

The skin has periodic drying and moist areas. It is generally acidic and hyperosmotic and therefore gram positives can cope with big differences in solution (salty to vicious). It has inhibitory substances such as lyzozymes that can attack the cell wall.

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

What areas of the skin are staphylococcus found?

A

They are usually found in moist areas with corynebacterium

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

What are the two common species of staphylococcus

A

Staph Aureus and Staph epidermis

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

What is used to distinguish the two common species of staphylococcus

A

S. aureus- coagulase positive

S. epidermis- coagulase negative

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

S. Aureus

A

This is found in the anterior nares and perineum. They are nosocomial (acquired in a health care setting). 20% permenantely have staph and 60% are transient carriers.

They are found in the mouth as opportunistic pathogens and be responsible for abscess.

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

S. epidermidis

A

These have 100% colonisation and usually found in the skin and mucous membranes. They are nosocomial infection but they tend to cause infection in an immune-compromised patient. They are usually associated with external objects like a catheter

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

MRSA- methicillin resistant staph aureus

A

These are defined by the flucloxacillin resistance and are mainly in nosocomial and elderly patients.

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

Pathogenicity of S. aureus

A

These go from superficial lesions to systemic to toxinoses. Superificial lesions can range from an abscess to scalded skin syndrome where a breakage in the skin can interact with different tissues leading to systemic effects.

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

What virulence factors does staphylococcus have

A
Adhesion
Clots plasma
Kills leucocytes
fibrinogen binding protein
coagulase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Toxinoses

A

TSST-1- rapid progression from high fever, vomitting, diarrhoea, sore throat, muscle pain.

Scalded skin syndrome- this is where it breaks down the cross links of keratin in the skin so have flaky skin.

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

How does toxic shock act

A

This acts by producing superantigens- which leads to the overstimulated of T cells-

Normal T cells- you have an antigen presenting cell that presents substances that are not self to the MHC class 11 - these stimulate T cells and is usually effective in 1-10,000 - which is really effective in normal system.

With superantigens- it does not present itself in the normal hyper variable region but instead presents itself to the outside and you have 1 in 5 cells immune response-

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

What does the release in superantigens do

A

Causes a release in cytokines that cause edema, swelling, blood pressure drops but as more material leaves it becomes thick and vicious- places pressure on the heart which leads to blood clotting.

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

Toxic shock syndrome

A

Fever
Macular rash and desquamation (skin peeling)
hypotension
more than 3 systems involved- death

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

How does attachment occur?

A

Staph A can promote the formation of a blood clot and it has proteins that can stick to the blood clot- FIBROGEN BINDING PROTEIN. This clot can provide a barrier to immune cells so that it is difficult for circulating B cells to gain access.

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

What is coagulase?

A

coagulase forms staphlythrombin that promotes the conversion of fibrinogen to fibrin that leads to clotting. It has the ability to coagulate the plasma

17
Q

How do they evade the host defence?

A

1) protein A- binds antibodies the other way round
2) proteases- degrade antibodies
3) superantigenicity
4) lipases, phopholipases, esterases- destroy tissue, immune cells, take out highly charged molecules,
5) gamma toxin, alpha toxin and PVL
4) coagulase

3) capsule- complex and dense environment- more incapsulated, the more resistant they are- produce an environment beyond the cell wall that causes this protection.

18
Q

Panton Valentin leukocidin

A

destroys a set of immune cells by destroying their cell membrane- leukotoxin

PVL associated with several skin infection

PVL and alpha toxin linked with community acquired - MRSA responsible for necrotising pneumonia

19
Q

Necrotising pneumonia

A

Rapid progression from symptoms that are influenza like to acute respiratory distress and deterioration in pulmonary function.

20
Q

Bacterial infections of the salivary glands

A

This can occur by acute bacterial parotitis, chronic bacterial parotitis and can cause ductal problems, stones and bacteria can also overcome the salivary flow.

21
Q

Acute bacterial parotitis

A

Swelling of the parotid gland that causes fever, pain and purulent secretion

22
Q

What treatment is used against staph A

A

Staph usually produces an enzyme that degrades a penicillin strain.
co-amoxylav treatment-
flucloxacillin ( beta- lactamase resistant)
erythytomycin- usually prescribed in the event of a penicillin allergy.
vancomycin- this is given to MRSA patients intravenously.
Mupirocin- topical decontaminant- up the nose