Skin and soft tissue infection Flashcards
1
Q
What is impitigo?
A
Superficial skin infection
2
Q
Impetigo is caused by what?
A
Most commonly due to Staph aureus
Less commonly Strep pyogenes
3
Q
Features of impetigo?
A
- Multiple vesicular lesions on an erythematous base
- Golden crust is highly suggestive of this diagnosisa
4
Q
Who is impetigo common in?
A
- Common in children 2-5 years of age
- Highly infectious
- Usually occurs on exposed parts of the body including face, extremities and scalp
5
Q
Predisposing factors for impetigo?
A
- Skin abrasions
- Minor trauma
- Burns
- Poor hygiene
- Insect bites
- Chickenpox
- Eczema
- Atopic dermatitis
6
Q
What is the treatment for impetigo?
A
- Small areas can be treated with topical antibiotics alone
- Large areas need topical treatment and oral antibiotics (ex flucloxacillin)
7
Q
What is erysipelas?
A
- Infection of the upper dermis
- Painful, red area (no central clearing)
8
Q
Common features of erysipelas?
A
- Painful, red area (no central clearing)
- Associated fever
- Regional lymphadenopathy and lymphangitis
- Typically has distinct elevated borders
9
Q
Erysipelas is caused by what?
A
- Most commonly due to Strep pyogenes
10
Q
Erysipelas affects where?
A
- 70-80% of cases involves the lower limbs
- 5-20% affect the face
11
Q
RF for erysipelas?
A
- Tends to occur in areas of pre-existing lymphoedema, venous stasis, obesity, paraparesis, diabetes mellitus
- May involve intact skin
- High recurrence rate (30% within 3 years)
12
Q
What is cellulitis?
A
- Diffuse skin infection involving deep dermis and subcutaneous fat
- Presents as a spreading erythematous area with no distinct borders
13
Q
Causative organisms for cellulits?
A
- Most likely organisms are Strep pyogenes and Staph aureus
- Remember role of Gram negatives in diabetics and febrile neutropaenics
14
Q
What are the common features of cellulitis?
A
- Fever is common
- Regional lymphadenopathy and lymphangitis
- Possible source of bacteraemia
15
Q
What are the predisposing factors for cellulitis?
A
- Diabetes mellitus
- Tinea pedis
- Lymphoedema
- Patients can have lymphangitis and/or lymphadenitis
16
Q
What are the treatments for erysipelas and cellulitis?
A
- A combination of anti-staphylococcal and anti-streptococcal antibiotics
- In extensive disease, admission for intravenous antibiotics and rest
17
Q
What are the hair associated infections?
A
- Folliculitis
- Furunculosis
- Carbuncles
18
Q
What organism causes folliculitis?
A
- Most common organism is Staph aureus
- Benign condition
- Constitutional symptoms not often seen
19
Q
What are furuncles commonly known as?
A
- boils
- Single hair follicle-associated inflammatory nodule
- Extending into dermis and subcuta
20
Q
Causative organism for furunculosis?
A
- Staph aureus most common organism
- Systemic symptoms uncommon
21
Q
What are carbuncles?
A
- Occurs when infection extends to involve multiple furuncles
- Often located back of neck, posterior trunk or thigh
- Multiseptated abscesses
- Purulent material may be expressed from multiple sites
- Constitutional symptoms common
22
Q
Which hair associated infection requires admission?
A
Carbuncles
- Carbuncles often require admission to hospital, surgery and intravenous antibiotics
23
Q
What is necrotising?
A
- One of the infectious diseases emergencies
- Any site may be affected
24
Q
RF for necrotising fasciitis?
A
- Diabetes mellitus
- Surgery
- Trauma
- Peripheral vascular disease
- Skin popping
25
What are type 1 and type 2 necrotising fasciitis?
* Type I refers to a mixed aerobic and anaerobic infection (diabetic foot infection, Fournier’s gangrene)
* Type II is monomicrobial
26
What are the organisms for type 1 and 2 necrotising fasciitis?
Type 1
* Streptococci
* Staphylococci
* Enterococci
* Gram negative bacilli
* Clostridium
Type 2
* Type II is monomicrobial
* Normally associated with Strep pyogenes
27
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 suggestive of this disease
28
Management of necrotising fasciitis?
* Surgical review is mandatory
* Imaging may help but could delay treatment
* Antibiotics should be broad spectrum
* Flucloxacillin
* Gentamicin
* Clindamycin
* Overall mortality ranges between 17-40%
29
What is pyomyositis?
* Purulent infection deep within striated muscle, often manifesting as an abscess
* Infection is often secondary to seeding into damaged muscle
30
What are presentations of pyomyositis?
Predisposing factors
* Can present with fever, pain and woody induration of affected muscle
* If untreated can lead to septic shock and death
* Predisposing factors include
* Diabetes mellitus
* HIV/immunocompromised
* Intravenous drug use
* Rheumatological diseases
* Malignancya
31
Causative organism of pyomyositis?
•Commonest cause is Staph aureus
32
What is septic bursitis?
•Infection is often from adjacent skin infection
33
Dx for septic bursitis?
* Peribursal cellulitis, swelling and warmth are common
* Fever and pain on movement also seen
* Diagnosis is based on aspiration of the fluid
* Most common cause is Staph aureus
34
What is infectious tenosynovitis?
* Infection of the synovial sheats that surround tendons
* Staph aureus and streptococci
35
What is TSS?
* Toxic Shock Syndrome
* Known since 1927 but interest increased in 1980s due to association with the use of high-absorbency tampons during menses
* Can also be due to small skin infections due to Staph aureus secreting TSST1
* Mostly due to some strains of Staphylococcus aureus and Streptococcus pyogenes
36
Dx criteria for staphylococcoal TSS?
* Fever
* Hypotension
* Diffuse macular rash
* Three of the following organs involved
* Liver, blood, renal, gatrointestinal, CNS, muscular
37
Treatment of TSS?
* Remove offending agent (ex tampon)
* Intravenous fluids
* Inotropes
* Antibiotics
* Intravenous immunoglobulins
38
Notable features of IV catheter associated infections?
* Nosocomial infection
* Normally starts as local SST inflammation progressing to cellulitis and even tissue necrosis
* Common to have an associated bacteraemia
* Risk factors for infections
* Continuous infusion \>24 hours
* Cannula in situ \>72 hours
* Cannula in lower limb
* Patients with neurological/neurosurgical problems
39
What are the most common causative organisms for IV cath associated infections?
* Most common organism is Staph aureus (MSSA and MRSA)
40
How do we treat IV cath associated infections?
* Treatment is to remove cannula
* Express any pus from the thrombophlebitis
* Antibiotics for 14 days
* Echocardiogram
41
Common causes of surgical site infections?
* Staph aureus (incl MSSA and MRSA)
* Coagulase negative Staphylococci
* Enterococcus
* Escherichia coli
* Pseudomonas aeruginosa
* Enterobacter
* Streptococci
* Fungi
* Anaerobes
42
RF for surgical site infections?
Patient associated:
* Diabetes
* Smoking
* Obesity
* Malnutrition
* Concurrent steroid use
* Colonisation with Staph aureus
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
43
Dx for 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)
* Antibiotics to target likely organisms
