Skin and soft tissue infections Flashcards
(110 cards)
1
Q
Which bacteria cause impetigo?
A
- S aureus
- Strep pyogenes
2
Q
Which layer of the skin is affected in impetigo?
A
Epidermis
3
Q
Which bacteria cause folliculitis?
A
S aureus
4
Q
Which bacteria cause Erysipelas?
A
Strep pyogenes
5
Q
Which bacteria cause cellulitis?
A
- Strep pyogenes = Common
- S aureus = Uncommon
- H influenzae = Rare
- Other = Rare
6
Q
Which layer of the skin is affected folliculitis?
A
Hair follicle = Dermis
7
Q
Which layer of the skin is affected erysipelas?
A
Infection of the upper dermis
8
Q
Which layer of the skin is affected cellulitis?
A
Deep dermis and subcutaneous fat
9
Q
Which layer of the skin is affected necrotising fasciitis?
A
Subcutaneous fat and fascia, can invade muscle
10
Q
Which bacteria cause necrotising fasciitis?
A
- Strep pyogenes
- Mixed bowel flora
11
Q
What is a golden crust on the skin highly suggestive of?
A
Impetigo
12
Q
How does impetigo present?
A
- Superficial skin infection
- Multiple vesicular lesions on an erythematous base
13
Q
Who is most commonly affected with impetigo?
A
2-5 years of age
14
Q
Where does impetigo often occur?
A
Exposed parts the body:
- Face
- Extremeties
- Scalp
15
Q
Predisposing factors for impetigo?
A
> Skin abrasions > Minor trauma > Burns > Poor hygiene > Insect bites > Chickenpox > Eczema > Atopic dermatitis
16
Q
How do you treat impetigo?
A
> Small areas can be treated with topical antibiotics alone
> Large areas need topical treatment and oral antibiotics (ex flucloxacillin)
17
Q
How does someone present with erysipelas?
A
> Painful, red area (no central clearing)
Associated fever
Regional lymphadenopathy and lymphangitis
Typically has distinct elevated borders
18
Q
Signs and symptoms of erysipelas?
A
> Painful, red area (no central clearing)
Associated fever
Regional lymphadenopathy and lymphangitis
Typically has distinct elevated borders
19
Q
Most common cause of erysipelas?
A
Strep pyogenes
20
Q
Which area of the body is most commonly affected by erysipelas?
A
> 70-80% of cases involved the lower limbs
> 5-20% affect the face
> Tends to occur in areas of pre-existing lymphoedema, venous stasis, obesity, paraparesis, diabetes mellitus
21
Q
What is the reoccurrence rate of erysipelas?
A
High reoccurrence = 30% within 3 years
22
Q
How does cellulitis present?
A
> Spreading erythematous area with no distinct borders
Fever is common
Regional lymphadenopathy and lymphangitis
23
Q
Within diabetics which pathogens can cause cellulitis?
A
Gram negative bacteria
24
Q
Within neutropenics which pathogens can cause cellulitis?
A
Gram negative bacteria
25
Which pathogens most commonly cause cellulitis?
Strep pyogenes
| S aureus
26
What is a common complication of cellulitis?
Bacteraemia
27
Predisposing factors for cellulitis?
- Diabetes mellitus
- Tinea pedis
- Lymphoedema/ Lyphangitis/ Lymphadenitis
28
How do you treat erysipelas and cellulitis?
Anti-staphylococcal and Anti-streptococcal Abx:
> Penicillins:
- Benzylpenicillin, Penicillin V
- Co-amoxiclav
> Cephalosporins:
- 1st generation, cefradine
> Clidamycin
> tigecycline
29
Hair-associated infections?
- Folliculitis
- Furunculosis
- Carbuncles
30
What is folliculitis?
Circumscribed, pustular infection of a hair follicle
31
How does folliculitis presents?
> Small (Up to 5mm) small red papules
> Central area of purulence that may rupture and drain
> Typically on head, buttocks and extremities
32
Most common pathogen causing folliculitis?
S aureus
33
What are furuncles?
- Referred to as boils
| - Single hair follicle-associated inflammatory nodule
34
Which layers of the skin are affected in furuncles?
Extending into dermis and subcutaneous tissue
35
Which areas are most commonly affected in furunculosis?
Usually affected moist, hairy, friction-prone areas of body (face, axilla, neck, buttocks)
36
What are the risk factors of furunculosis?
```
Risk factors include:
> Obesity
> Diabetes mellitus
> Atopic dermatitis
> Chronic kidney disease
> Corticosteroid use
```
37
What is the most common organism that causes furunculosis?
S aureus
38
What is a carbuncle?
- Occurs when infection extends to involve multiple furuncles
- Multiseptated abscesses
39
Most common location of carbuncles?
Often located back of neck, posterior trunk or thigh
40
Risk associated with carbuncles?
Constitutional symptoms are common
41
How to treat hair-associated infections - folliculitis?
No treatment or topical antibiotics are required
42
How to treat hair-associated infections - furunculosis?
> No treatment or topical antibiotics are required
| > Oral antibiotics might be necessary if not improving
43
What is necrotising fasciitis?
> An infectious disease emergency
| > Necrotic
44
Which area of the body is most commonly affected in necrotising fasciitis?
Any site can be affected
45
Predisposing conditions in necrotising fasciitis?
```
Predisposing conditions include:
> Diabetes mellitus
> Surgery
> Trauma
> Peripheral vascular disease
> Skin popping
```
46
Type I necrotising fasciitis?
Type I refers to a mixed aerobic and anaerobic infection (diabetic foot infection, Fournier’s gangrene)
47
Common organisms in type I necrotising fasciitis?
```
Typical organisms include:
> Streptococci
> Staphylococci
> Enterococci
> Gram negative bacilli
> Clostridium
```
48
Common organisms in type II necrotising fasciitis?
Monomicrobial = Strep pyogenes
49
What is anaesthesia at the site of an infection highly suggestive of?
Necrotising fasciitis
50
Clinical features of necrotising fasciitis?
> Rapid onset
> Sequential development of erythema, extensive oedema and severe, unremitting pain
> Haemorrhagic bullae, skin necrosis and crepitus may develop
>Systemic features include fever, hypotension, tachycardia, delirium and multiorgan failure
>Anaesthesia at site of infection is highly
51
Imaging or not in necrotising fasciitis?
Imaging may help by could delay treatment
52
Which antibiotics are used in necrotising fasciitis?
- Flucloxacillin
- Gentamicin
- Clindamycin
53
If necrotising fasciitis is suggested what should be reviewed?
Surgical review
54
What is the overall mortality in necrotising fasciitis?
17-40%
55
What is pyomyositis?
Purulent infection deep within striated muscle, often manifesting as an abscess
56
What does pyomyositis often occur secondary to?
Often secondary to seeing into damaged muscle
57
Which areas of the body are commonly affected by pyomyositis?
```
Multiple sites involved in 15%:
> Thigh
> Calf
> Arms
> Gluteal region
> Chest wall
> Psoas muscle
```
58
How does someone present pyomyositis?
- Fever
- Pain
- Woody indication of affected muscle
59
What is the risk of untreated pyomyositis?
Untreated septic shock and death
60
Predisposing factors for pyomyositis?
```
Predisposing factors include:
> Diabetes mellitus
> HIV/immunocompromised
> Intravenous drug use
> Rheumatological diseases
> Malignancy
> Liver cirrhosis
```
61
What is the most common causes of pyomyositis?
S aureus
62
What are other organisms other than S aureus cause pyomyositis?
Gram positive/negatives, TB and fungi
63
Investigations in pyomyositis?
CT/MRI
64
Treatments in pyomyositis?
Treatment is drainage with antibiotic cover depending on Gram stain and culture results
65
What is septic bursitis?
> Bursae are small sac-like cavities that contain fluid and are lined by synovial membrane
> Located subcutaneously between bony prominences or tendons
66
What is the most common sites of septic bursitis?
Most common include patellar and olecranon
67
What does septic bursitis usually occur due to?
Often from adjacent skin infections
68
What are the predisposing factors of septic bursitis?
```
Other predisposing factors include:
> Rheumatoid arthritis
> Alcoholism
> Diabetes mellitus
> Intravenous drug abuse
> Immunosuppression
> Renal insufficiency
```
69
How does septic bursitis present?
```
> Peribursal cellulitis
> swelling
> warmth at the site
> Fever
> Pain on movement also seen
```
70
How is septic bursitis diagnosed?
Aspiration of the fluid
71
What is the most common organism that causes septic bursitis?
S aureus
72
What other organisms causes septic bursitis other than S aureus?
- Gram negatives
- Mycobacteria
- Brucella
73
What is infectious tenosynovitis?
Infection of the synovial sheats that surround tendons
74
What is the most common site of tenosynovitis?
Flexor muscle-associated tendons and tendon sheats of the hand most commonly involved
75
What is the most common cause of tenosynovitis?
Penetrating trauma
76
What is the most common organism of tenosynovitis?
- S aureus
| - Streptococci
77
What is the most common organism in chronic tenosynovitis?
- Mycobacteria
| - Fungi
78
What is a risk associated with tenosynovitis?
Disseminated gonococcal infection
79
How does infectious tenosynovitis present?
> Erythematous fusiform swelling of the finger
> Semiflexed position
> Tenderness over the length of the tendon sheet and pain with extension of finger
80
How to treat infectious tenosynovitis?
- Empiric Abx
| - Hand surgeon to review ASAP
81
Diagnostic criteria for Staphylococcal TSS?
> Fever
> Hypotension
> Diffuse macular rash
> Three of the following organs involved:
- Liver
- blood
- renal
- gatrointestinal
- CNS
- muscular
> Isolation of Staph aureus from mucosal or normally sterile sites
> Production of TSST1 by isolate
> Development of antibody to toxin during convalescence
82
When does Streptococcal TSS most commonly occur?
In deep seated infections such as erysipelas or necrotising fasciitis
83
Which TSS Strep or Staph has higher mortality rate?
Streptococcus 50% vs 5%
84
How is streptococcal TSS treated?
```
> Urgent surgical debridement of infected tissues
> Remove offending agent (ex tampon)
> Intravenous fluids
> Inotropes
> Antibiotics
> Intravenous immunoglobulins
```
85
What is Staphylococcal scalded skin syndrome?
> Infection due to a particular strain of Staph aureus producing the exfoliative toxin A or B
> Widespread bullae and skin exfoliation
86
Who is most commonly affected by staphylococcal scalded skin syndrome?
Most common in children but rarely in adults
87
What is the treatment of staphylococcal scalded skin syndrome?
> IV fluids and antimicrobials
88
What is the mortality rate?
Around 3% in children but higher in adults who often are immunosuppressed
89
What is Panton-Valentine leucocidin toxin?
Gamma haemolysin
90
What is the big issue with Panton-Valentine leucocidin toxin and S aureus?
Can be transferred from one strain of Staph aureus to another, including MRSA
91
What can Panton-Valentine leucocidin toxin cause?
SSTI and haemorrhagic pneumonia
92
Who is commonly affected by Panton-Valentine leucocidin toxin?
Children and young adults
93
How does someone present with Panton-Valentine leucocidin toxin?
Recurrent boils which are difficult to treat
94
How do you treat Panton-Valentine leucocidin toxin?
Antibiotics that reduce toxin production
95
IV-catheter associated infections progression?
1) Local SST inflammation
2) Cellulitis
3) Tissue necrosis
4) Can cause bacteraemia
96
Risk factors for IV-catheter associated infections?
```
Risk factors for infections
> Continuous infusion >24 hours
> Cannula in situ >72 hours
> Cannula in lower limb
> Patients with neurological/neurosurgical problems
```
97
What is the most common organism that causes IV-catheter associated infections?
Staph aureus (MSSA and MRSA)
98
How does Risk factors for IV-catheter can infections?
> Commonly forms a biofilm which then spills int bloodstream
> Can seed into other places (Endocarditis, osteomyelitis)
99
How are IV-catheter associated infections diagnosed?
Clinical or by positive blood cultures
100
How is IV-catheter associated infections treated?
1) Remove cannula
2) Express any pus from the thrombophlebitis
3) Abx for 14 days
4) Echo to rule out endocarditis
Prevention is key!
101
How can you prevent IV-catheter associated infections?
Prevention more important:
> Do not leave unused cannula
> Do not insert cannulae unless you are using them
> Change cannulae every 72 hours
> Monitor for thrombophlebitis
> Use aseptic technique when inserting cannulae
102
Classification of surgical site infections - Class I?
Class I: Clean wound (respiratory, alimentary, genital or infected urinary systems not entered)
103
Classification of surgical site infections - Class II?
Class II: Clean-contaminated wound (above tracts entered but no unusual contamination)
104
Classification of surgical site infections - Class III?
Class III: Contaminated wound (Open, fresh accidental wounds or gross spillage from the gastrointestinal tract)
105
Classification of surgical site infections - Class IV?
Class IV: Infected wound (existing clinical infection, infection present before the operation)
106
Organisms thar cause surgical site infections?
```
> Staph aureus (incl MSSA and MRSA)
> Coagulase negative Staphylococci
> Enterococcus
> Escherichia coli
> Pseudomonas aeruginosa
> Enterobacter
> Streptococci
> Fungi
> Anaerobes
```
107
Risk factors for surgical site infections - Patient associated?
```
Patient associated:
> Diabetes
> Smoking
> Obesity
> Malnutrition
> Concurrent steroid use
> Colonisation with Staph aureus
```
108
Risk factors for surgical site infections - procedural factors?
```
Procedural factors:
> Shaving of site the night prior to procedure
> Improper preoperative skin preparation
> Improper antimicrobial prophylaxis
> Break in sterile technique
> Inadequate theatre ventilation
> Perioperative hypoxia
```
109
Diagnosis of surgical site infections?
> Importance of sending pus/infected tissue for cultures especially with clean wound infections
> Avoid superficial swabs – aim for deep structures
> Consider an unlikely pathogen as a cause if obtained from a sterile site (ex bone infection)
110
Which skin/tissue infections require urgent attention?
```
> Necrotising fasciitis
> Pyomyositis
> Toxic shock syndrome
> PVL infecitons
> Venflon-associated infections
```
