Skin and Soft Tissue Infections Flashcards
(87 cards)
1
Q
2 groups of skin infections
A
Hospital acquired
Community acquired
2
Q
Risk factors for skin and soft tissue infections - host
A
DM leading to neuropathy and vasculopathy
Immunosuppression
Renal failure
Milroy’s disease
Predisposing skin condition (e.g. atopic dermatitis)
3
Q
Where in the skin does impetigo affect?
A
Superficial skin infection only affecting the epidermis
4
Q
Layers of the skin (superficial to deep)
A
Epidermis Dermis Subcutaneous fat Fascia Muscle
5
Q
Who is impetigo common in?
A
Children 2-5 years of age
6
Q
Causative organisms of impetigo
A
Commonly -> staph aureus
Less commonly -> strep pyogenes
7
Q
Is impetigo infectious?
A
Yes - highly infectious
8
Q
Presentation of impetigo
A
Multiple vesicular lesions on an erythematous base
Golden crust
Usually occurs on parts of body including face, extremities and scalp
9
Q
Predisposing factors for impetigo
A
Skin abrasions Minor trauma Burns Poor hygiene Inset bites Chickenpox Eczema Atopic dermatitis
10
Q
Treatment of impetigo
A
Small areas = topical antibiotics alone
Large areas = topical treatment with oral antibiotics (e.g. flucloxacillin)
11
Q
Definition of erysipelas
A
Infection of the upper dermis
12
Q
Presentation of erysipelas
A
Painful, red area (no central clearing)
Assosiated fever
Regional lymphadenopathy and lymphangitis
Distinct elevated borders
13
Q
Most common causative organism of erysipelas
A
Strep pyogenes
14
Q
Where does erysipelas affect?
A
70-80% lower limbs 5-20% face Areas of pre existing - lymphoedema - venous stasis - obesity - paraparesis - diabetes mellitus May involve intact skin
15
Q
Treatment of erysipelas
A
Combination of - anti-staphylococcal (flucocaxillin) and anti-streptococcal (benzylpenicillin) antibiotics extensive disease - admission for IV antibiotics - rest
16
Q
Presentation of cellulitis
A
Spreading erythematous area with no distinct areas Fever Pain Regional lymphadenopathy + lymphangitis Systemic upset
17
Q
Definition of cellulitis
A
Diffuse skin infection involving deep dermis and subcutaneous fat
18
Q
Likely causative organisms of cellulitis
A
Strep pyogenes
Staph aureus
19
Q
Predisposing factors of cellulitis
A
DM
Tinea pedis
Lymphoedema
Obesity
20
Q
Treatment of cellulitis
A
Combination of - anti-staphylococcal antibiotics (flucocloxacillin) and anti-streptococcal antibiotics (benzylpenicillin) Extensive disease - IV antibiotics - rest
21
Q
Definition of folliculitis
A
Circumscribed, pustular infection of a single fair follicle
22
Q
Where is folliculitis commonly found?
A
Head
Back
Buttocks
Extremities
23
Q
Most common organism for folliculitis
A
Staph aureus
24
Q
Definition of furunculosis
A
Infection of a single hair follicle has spread from the follicle to the surrounding tissue
25
What are furuncles commonly referred to as?
Boils
26
What layers of the skin do furuncles affect?
Dermis
| Subcutaneous tissue
27
Where do furuncles usually affect?
Moist, hairy, friction prone areas of the body (face, axilla, neck, buttocks)
28
Most common organism for furunculosis
Staph aureus
29
Risk factors for furunculosis
```
Obesity
DM
Atophic dermatitis
Chronic kidney disease
Corticosteriod use
```
30
What is another name for atophic dermatitis
Eczema
31
Definition of carbuncles
Infection extends to involve multiple furuncles
32
Where are carbuncles found?
Back of neck
Posterior thigh
Posterior trunk
33
Presentation of carbuncles
Multiseptated abscesses
Purulent material expressed from multiple sites
Constitutional symptoms common
34
Treatment of carbuncles
IV antibiotics
| Often require surgery
35
What does the presence of carbuncles indicate?
An underlying cause e.g. HIV as a normal healthy person should not get carbuncles from furunculosis
36
Predisposing conditions to necrotising fasciitis
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DM
Surgery
Trauma
Peripheral vascular disease
Skin popping (PWID into dermis as veins collapsed)
```
37
What does type I necrotising fasciitis involve?
Mixed aerobic and anaerobic infection (diabetic foot, Fournier's gangrene)
38
Typical organisms of type I necrotising fasciitis
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Streptococci
Staphylococci
Enterococci
Gram -ve bacilli
Clostridium
```
39
Typical organisms of type II necrotising fasciitis
Monomicrobial - usually strep pyogenes
40
Presentation of necrotising fascitis
```
Rapid onset
Sequential development of
- erythema, extensive oedema and severe, unremitting pain
haemorrhagic bullae
skin necrosis
Crepitus
Systemic features
- fever, hypotension, tachycardia, delirium, multiorgan failure
Anaesthesia at site of infection
```
41
What is highly suggestive of necrotising fasciitis?
Anaesthesia at the site of infection
42
Treatment of necrotising fascitis
Surgical review mandatory
Antibiotics - broad spectrum
- flucloxacillin, gentamicin, clindamycin
43
Prognosis of necrotising fasciitis
Overall mortality 17-40%
44
Definition of pyomyositis
Purulent deep infection within striated muscle, often manifesting as an abscess
45
What is pyomyositis often secondary to?
Seeding into damaged muscle
46
Common sites of pyomyositis
```
Thigh
calf
arms
gluteal region
chest wall
psoas muscle
```
47
Presentation of pyomyositis
Fever
Pain
Woody induration of affected muscle
48
Predisposing factors for Pyomyositis
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DM
HIV/immunocompromised
IVDU
Rheumatological disease
Malignancy
Liver cirrhosis
```
49
Causative organisms of pyomyositits
Staph aureus most common
gram -ve/+ve
TB
fungi
50
Investigations of pyomyositis
CT/MRI
51
Treatment of pyomyositis
Drainage with antibiotic cover
52
Definition of septic bursitis
infection of the bursae (fluid filled sacs)
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Where are bursae found?
Subcutaenously between bony prominences or tendons
54
most common septic bursae sites
platellar
| olecrannon
55
causes of septic bursitis
adjacent skin infection
| repeated flexion and extension
56
Predisposing factors for septic bursitis
```
rheumatoid arthritis
alcoholism
DM
IVDU
Immunosuppression
Renal insufficiency
```
57
Causative organisms of septic bursitis
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Staph aureus - MOST COMMON
Rarer
- gram -ves
- mycobacteria
- brucella
```
58
Presentation of septic bursitis
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Peribursal cellulitis
Swelling
warmth
fever
pain on movement
```
59
Definition of infectious tenosynovitis
Infections of the synovial sheets that surround tissues
60
Where is the most commonly affected in infectious tenosynovitis?
Flexor muscle associated tendons
| Tendon sheets of the hand
61
What is the most common inciting event of infectious tenosynovitis?
Penetrating trauma
62
Causative organisms of infectious tenosynovitis
MOST COMMON - staph aureus and streptococci
CHRONIC INFECTIONS - mycobacteria and fungi
Possibility of disseminated gonococcal infection
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Presentation of infectious tenosynovitis
Erythematous fusiform swelling of finger
held in a semi flexed position
Tenderness over length of tendon sheath and pain with extension of finger are classical
64
Treatment of infectious tenosynovitis
Empirical antibiotics
| Hand surgeon to review asap
65
What are toxin mediated syndromes often due to?
Superantigens
66
What do toxin mediated syndromes result in?
Endothelial leakage
Haemodynamic shock
Multiorgan failure and death
67
Possible causes of toxic shock syndrome
High absorbency tampons during menstruation
| Small skin infections due to staph aureus secreting TSST1
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What are a lot of toxin mediated syndromes due to? (organisms)
TSST1
69
Presentation of toxic shock syndrome
```
Fever
Hypotension
Diffuse macular rash
3 of the following organs involved
- liver, blood, renal, GI, CNS, muscular
```
70
Investigations of toxic shock syndrome
Isolation of staph aureus from mucosal or normally sterile sites
Production of TSST1 by isolate
Development of antibody to toxin during convalescence
71
What is streptococcal toxic shock syndrome almost always associated with?
Presence of streptococci in deep seated infections such as erysipelas or necrotising fasciitis
72
Streptococcal TSS vs staphylococcal TSS
Strep much higher mortality rate than staph (50% vs 5%)
73
Treatment of toxic shock syndrome
```
remove offending agent (ex tampon)
IV fluids
Inotropes
Antibiotics
IV immunoglobulins (in ITU/HDU)
```
74
Toxins causing toxin mediated syndromes
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Staph aureus
- TSST1
- ETA and ETB
Streptococcus pyogenes
- TSST1
```
75
Causes of staphylococcal scalded skin syndrome
infection due to a particular strain of staph aureus producing the exfoliative toxin A or B
76
Who does staphylococcal scalded skin syndrome affect?
Children but rarely adults as well
77
Presentation of staphylococcal scalded skin syndrome
Widespread bullae and skin exfoliation
78
Treatment of staphylococcal scalded skin syndrome
IV fluids and antimicrobials
79
Pathology of IV catheter associated infections
Starts at local STT inflammation
Progressing to cellulitis
And possibly tissue necrosis
80
Risk factors for IV catheter infections
Continuous infusion > 24 hours
Cannula in situ > 72 hours
Cannula in lower limb
patients with neurological/neurological problems
81
Most common causative organism for IV catheter infections
Staph aureus (MSSA and MRSA)
82
Investigations for IV catheterisation associated infections
Clinically
| +ve blood cultures
83
Treatment of IV catheterisation associated infections
Remove cannula
Express any pus from thrombophlebitis
Antibiotics for 14 days
ECG
84
Prevention of IV catheter associated infections
```
Do not leave unused cannula
Do not insert cannula unless using them
change cannula every 72 hours
monitor for thrombophlebitis
Use aseptic technique when inserting cannula
```
85
Classification of surgical wound infections
class I
- clean wound (other systems not entered)
class II
- clean-contaminated wound (above tracts entered but no unusal contamination)
class III
- contaminated wound (open, fresh accidental wounds or gross spillage from GI tract)
class IV
- infected wound (existing clinical infection, infection present before operation)
86
3 examples of causative organisms of surgical site infection
Staph aureus
Fungi
streptococci
anaerobes
87
Risk factors for surgical site infection
```
DM
Smoking
obesity
malnutrition
concurrent steroid use
colonisation with staph A
shaving of site night prior to the procedure
improper preoperative skin preparation
break in sterile technique
improper antimicrobial prophylaxis
inadequate theatre ventilation
perioperative hypoxia
```
