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FIM > 12. Staphylococci > Flashcards

12. Staphylococci Flashcards

1
Q

What are the lab results for all staphylococci?

A

Gram positive cocci in clusters

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2
Q

Where does staph aureus colonise?

A

Moist skin folds
Mucosa
Nasopharynx

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3
Q

What is the portal of entry of staph aureus into the body?

A

Ingestion

Break in skin

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4
Q

What factors allow staph aureus to attach to cells?

A

Surface proteins
Capsule
Fibrin/fibrinogen binding protein
Matrix binding proteins

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5
Q

What is the function of coagulase?

A

Produces clots to protect from phagocytosis

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6
Q

What is the function of protein A, which is found on the cell wall of staph aureus?

A

Prevents phagocytosis

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7
Q

What is the function of alpha toxin?

A

Lysis of monocytes and platelets

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8
Q

What does leukocidin/PVL cause?

A

Skin and soft tissue infections

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9
Q

What is the function of staphylokinase?

A

Dissolves clots to allow spread

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10
Q

What is the function of hyaluronidase?

A

Breaks down hyaluronic acid in connective tissue which allows further spread

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11
Q

What 3 methods can staph aureus use to cause damage to the host?

A

Direct
Enzymes
Toxins

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12
Q

How does staph aureus cause direct damage to the host?

A

Peptidoglycan wall increases cytokine release

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13
Q

What 2 types of toxins are released by staph aureus?

A

Superantigens Eg. toxic shock syndrome toxin, enterotoxin

Exfoliative toxins Eg. epidermolytic toxin

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14
Q

How does staph aureus spread?

A

Person to person or via environment

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15
Q

What is the difference between a furuncle and a carbuncle?

A

Furuncle is a single collection of pus with a single point of drainage
A carbuncle is a collection of boils which have multiple points of drainage

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16
Q

Name the skin and soft tissue infections caused by staph aureus?

A 
Folliculitis
Mastitis
Styes
Boils
Impetigo
Cellulitis
Necrotising fasciitis
Scalded skin syndrome
Toxic shock syndrome
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17
Q

What systemic infections are caused by staph aureus?

A 
BSI
Endocarditis
Pneumonia
Osteomyelitis
Septic arthritis
18
Q

What are the risk factors for endocarditis?

A

IV catheter
SSI
Surgical valve replacement

19
Q

What are the risk factors for pneumonia?

A

Influenza
CF
on ventilator

20
Q

How is osteomyelitis diagnosed?

A

Bone biopsy
Direct needle aspiration
MRI

21
Q

What investigations take place when toxic shock syndrome is suspected?

A 
History
FBC
U&E
Lactate
Wound swab
22
Q

How is toxic shock syndrome managed?

A

Rapid IV antibiotics
Resus
Care for wounds

23
Q

What toxin mediated infections are due to staph aureus?

A

Food poisoning
Scalded skin syndrome
Toxic shock syndrome

24
Q

What is Nikolsky’s sign?

A

Peeling of layers of skin in scalded skin syndrome

25
Q

What groups of people is scalded skin syndrome most common in?

A

Neonates
Immune compromised
Renal failure

26
Q

What are the symptoms of toxic shock syndrome?

A

Fever
Low BP
Rash

27
Q

What are the possible complications of toxic shock syndrome?

A

Renal failure

CNS and muscular involvement

28
Q

What is the method of resistance present in MRSA?

A

Altered penicillin binding protein

Causes resistance to most beta-lactam antibiotics

29
Q

What gene causes MRSA?

A

mecA

30
Q

Which antibiotics can still be used for an MRSA infection?

A

Vancomycin
Linezolid
Daptomycin

31
Q

What infections are caused by community acquired MRSA?

A

Skin infections

Pneumonia

32
Q

What toxin is present in MRSA?

A

PVL

33
Q

How are staph aureus infections managed?

A 
History and clinical exam
Blood tests
Microbiology specimen depends on site of infection
Radiology
Antibiotics if needed
34
Q

What blood tests are useful in a staph aureus investigation?

A

FBC
CRP
U&E
lactate

35
Q

What is the preferred antibiotic for MSSA?

A

Flucloxacillin

36
Q

Which antibiotics are used for MRSA?

A

Vancomycin

Teicoplanin

37
Q

What sorts of infections are caused by staph epidermidis?

A

Infections associated with prosthetic devices as it forms a biofilm

38
Q

What infection is caused by staph saprophyticus?

A

UTI (cystitis)

39
Q

Which staphylocci are coagulase positive and which are negative?

A

Aureus is positive

Epidermidis and saprophyticus are negative

40
Q

How does mannitol salt agar differentiate between sub species of staph?

A

Aureus ferments and turns yellow

Epidermidis remains pink

41
Q

How is mannitol salt agar selective?

A

Staph can withstand high levels of salt, as it colonises on skin
High salt levels can stop other bacteria growing

42
Q

What susceptibility test is used to differentiate between staph saprophyticus and epidermidis?

A

Novobiocin

Saprophyticus is resistant

FIM (44 decks)

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