Skin and Soft Tissue Infections Flashcards

1
Q

What are the different areas where a skin or soft tissue infection can occur?

A
Epidermis - Impetigo
Follicle - Folliculitis
Dermis - Erysipelas
Subcut Fat - Cellulitis (also affects deep dermis)
Fascia - Necrotising Fasciitis
Muscle
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2
Q

What host factors may predispose to developing a skin and soft tissue infection?

A

Diabetes
Immunosuppression
Renal Failure
Milroy’s Disease (congenital lymphadenopathy in legs)
Predisposing skin conditions - e.g. atopic dermatitis

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3
Q

What is impetigo?

A

A superficial skin infection common in young children that is highly infectious.

Golden crust, multiple vesicular lesions on erythematous base.

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4
Q

Where does impetigo tend to occur?

A

Exposed body parts; e.g. face, extremities and scalp

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5
Q

What organisms typically cause impetigo?

A

Usually staph aureus.

Sometimes strep pyogenes.

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6
Q

What are some predisposing factors for impetigo?

A
Skin abrasions
Minor trauma
Burns
Poor Hygiene
Insect Bites
Eczema
Chicken Pox
Atopic Dermatitis
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7
Q

How do you treat impetigo?

A

Topical Abx

For large areas may add an oral abx like flucloxacillin

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8
Q

What organism commonly causes erysipelas (upper dermis infection)?

A

Strep pyogenes

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9
Q

Where does erysipelas most commonly occur?

A

Lower limbs and then the face

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10
Q

What factors increase the risk of erysipelas?

A
Milroy's Disease
Venous Stasis
Eczema
DVTs
Obesity
Paraparesis
Diabetes
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11
Q

What is the recurrence rate of erysipelas?

A

1/3 in 3 years

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12
Q

What are the common organisms in cellulitis?

A

In most patients: 50:50 staph aureus:strep pyogenes.

In diabetics and febrile neutropenics:
About 33:33:33 staph aureus:strep pyogenes:gram negative

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13
Q

What is the typical appearance of cellulitis?

A

Spreading red area of no distinct border, fever, lymphadenopathy and lymphangitis. Shiny oedematous skin.

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14
Q

What are some predisposing factors for cellulitis?

A

Diabetes
Tinea Pedis
Lymphoedema

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15
Q

How do you treat cellulitis?

A

Cover strep pyogenes and staph aureus - can do a combination but usually just give flucloxacillin, IV vancomycin or cotrimoxazole.

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16
Q

What are 3 different types of hair associated infection?

A

Folliculitis - superficial or deep, where only one follicle is involved
Furunculosis - infection all the way to subcut that normally only involves one follicle
Carbuncles - skin abscess where multiple follicles are involved in an area

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17
Q

What does folliculitis look like?

A

Circumscribed, pustular infection of hair follicle up to 5mm in diameter.
Head, back, buttocks and extremities.

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18
Q

What is the most common organism in folliculitis?

A

Staph aureus

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19
Q

What does furunculosis look like?

A

Boils - single hair follicle inflammatory nodule extending into dermis and subcut fat.
Moist, hairy, friction-prone areas

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20
Q

What common organism is found in furunculosis?

A

Staph aureus

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21
Q

What are risk factors for furunculosis?

A
Obesity
Diabetes
Atopic dermatitis
CKD
Chronic steroids
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22
Q

Where do we typically find carbuncles?

A

Neck, posterior trunk or thigh

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23
Q

What do carbuncles look like?

A

Multiseptated abscesses

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24
Q

How do you treat hair associated infections?

A

Folliculitis/Furunculosis - leave it or topical abx. If worse then maybe oral.
Carbuncles - admit, surgical drainage, possible IV abx

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25
What are some predisposing factors for necrotising fasciitis?
``` Diabetes Surgery Trauma Peripheral vascular disease Skin popping ```
26
How many types of necrotising fasciitis are there?
4 - only look at 2 though
27
What is type 1 necrotising fasciitis?
Mixed aerobic and anaerobic infection Common in diabetic foot and Fournier's gangrene
28
What organisms can cause type 1 necrotising fasciitis?
``` Streptococci Staphylococci Enterococci Gram negative bacilli Clostridium ```
29
What is type 2 necrotising fasciitis?
Monomicrobial infection - normally associated with strep pyogenes (Very painful leg)
30
What are the features of necrotising fasciitis?
Rapid onset Extensive oedema and severe, unremitting pain Haemorrhagic bullae, skin necrosis and crepitus Systemic features, sepsis and death. Anaesthesia at site of infection
31
What is mortality for necrotising fasciitis?
17-40%
32
What is treatment for necrotising fasciitis?
ABCDE - IV fluids Surgical review Broad spectrum abx (flucloxacillin, gentamicin, clindamycin)
33
What is pyomyositis?
Muscle abscess normally in the lower limbs - direct progression of cellulitis or seeding of another infection (IE)
34
What are common sites for pyomyositis?
``` Thigh Calf Glutes Psoas Arms Chest wall (Multiple sites in 15%) ```
35
What are predisposing factors for pyomyositis?
``` Diabetes HIV/Immunocompromised IV drug use Rheumatological diseases Malignancy Liver cirrhosis ```
36
What organisms cause pyomyositis?
Usually staph aureus other gram positives/negatives, TB, fungi
37
How do you investigate pyomyositis?
CT/MRI
38
How do you treat pyomyositis?
Drainage and abx
39
What is septic bursitis?
Infection of the synovial sacs/bursae at joints close to bone, tendons and skin. Infection often spreads from nearby skin.
40
Where are the most common areas for septic bursitis?
Patella and olecranon
41
What are some predisposing factors for septic bursitis?
``` Rheumatoid arthritis Alcoholism Diabetes IV Drug Use Immunosuppression Renal insufficiency ```
42
What is the most common cause of septic bursitis?
Staph aureus | rarer include gram negatives, mycobacteria and brucella in farmers and abroad
43
What is infectious tenosynovitis?
Infection of the synovial sheaths around tendons - commonly in the hands, fingers and toes
44
How does infectious tenosynovitis appear?
Red swollen semi-flexed finger that can't move properly. Excrutiating pain on extension of finger.
45
What are the most common organism in infectious tenosynovitis?
Staph aureus and streptococci. Chronic - mycobacteria and fungi If not think gonorrhoea
46
What is the treatment for infectious tenosynovitis?
Empirical antibiotics and hand surgeon review.
47
What are toxin mediated syndromes?
Syndromes occur as a result of toxins produced by infecting bacteria. Superantigens produced by gram positive bacteria are a common culprit. These pyrogenic toxins stimulate T-cells directly - activating up to 20% of them and causing a massive burst of cytokine release.
48
What are some consequences of the massive cytokine release in some toxin mediated syndromes?
Endothelial Leakage Haemodynamic shock Multi-organ failure Death
49
What organisms can cause toxin mediated syndromes?
Mostly: Staph aureus - causing TSST1, ETA and ETB Strep pyogenes - causing TSST1
50
How do you diagnose staphylococcal TSS?
Fever Hypotension Diffuse Macular Rash 3 of (liver, blood, kidneys, GI, CNS, muscle) involved Isolated staph aureus in mucosal/sterile sites Production of TSST1 by isolate Antibody development to toxin
51
Where does streptococcal TSS tend to come from?
Deep seated infections such as erysipelas and necrotising fasciitis
52
How do you treat strep TSS?
FAST - 50% mortality so need urgent surgical debridement of infected tissues
53
How do you treat TSS generally?
``` Remove offending agent IV fluid Inotropes Abx IV immunoglobulin ```
54
What toxin produces Staphylococcal Scalded Skin Syndrome?
Exfoliative toxin A or B from staph aureus IV fluid and antimicrobials
55
What tends to occur as a result of Panton-Valentine Leucocydin toxin from staph aureus?
Recurrent boils and haemorrhagic pneumonia in children and young adults
56
What are risk factors for IV catheter associated infections?
Continuous infusion >24h Cannula in situ >72h Cannula in lower limb Neurological/neurosurgical problems
57
What common organisms are found in IV catheter associated infections?
MSSA and MRSA
58
What are some complications of the resulting bacteraemia from seeding IV catheter associated infections?
Endocarditis and osteomyelitis
59
How would you treat an IV cannula associated infection?
Remove cannula Express pus Abx for 14 days Echocardiogram to be safe
60
What are the 4 classes of surgical site infection?
I: Clean wound (respiratory, alimentary, genital or infected urinary systems not entered) II: Clean-contaminated wound (above tracts entered but no unusual contamination) III: Contaminated wound (Open, fresh accidental wounds or gross spillage from the gastrointestinal tract) IV: Infected wound (existing clinical infection, infection present before the operation)
61
What can cause a surgical site infection?
``` Staph aureus (incl MSSA and MRSA) Coagulase negative Staphylococci Enterococcus Escherichia coli Pseudomonas aeruginosa Enterobacter Streptococci Fungi Anaerobes ```