Soft tissue infection Flashcards
Describe impetigo
Typically caused by staph or B-haemolytic strep
Most often found on the face and other exposed areas
The eruption often begins as a single pustule but later develops multiple lesions
It begins as 1-2mm vesciles with erythematous margins
When these break they leave red erosions covered with a golden yellow crust.
Lesions may be pruritic but usually are not painful.
regional lymphadenopathy is common
Rheumatic fever and PSGN are recognised complications
Bullous impetigo is caused by the toxin released by staphylococcus. It is seen primarily in infants and young children - the intial skin lesions are thin walled 1-2cm bullae. DDX include contact dermatitis, HSV infection, superficial fungal infection and pemphigus vulgaris. Gram stain will reveal gram +ve cocci
Oral therapy with flucloxacillin 500mg (12.5mg/kg) QID
For penicillin allergy or for MRSA Bactrim 160/800 (4/20mg.kg) BP for 72 hours.
Describe cellulitis
Inflammatory condition of the skin and subcutaneous tissues
Cardinal feature of cellulitis is inflammation due to increased blood flow.
Pain
The inflammation is typically confluent although it can be patchy
Borders are typically poorly defined
Streaks of inflammation extending proximally from the main area of inflammation along vascular tract is known as lymphangitis and is commonly seen due to strep and bite wound associated Pasteurella multocida
When localized oedema becomes severe epidermal layers can separate leading to vesicles or bullae. This can make it difficult to distinguish cellulitis from other infectious and noninfectious causes of dermatitis.
When the border of an area of cellulitis becomes well demaractated raised and palpable the term erysipelas is used.
Discuss diabetic foot infections
The mose likley organisms in an acute diabetic foot infection are s.aureus and streptocooci. Chronic wounds are more ikley to be polymicrobial with gram + ve and -ve
Pseudomonas is a traditional concern but is uncommon.
Suspect ostemyelitis in all diabetic feet
Will also likely need wound care
List bacteria present with cat/dog bites, fresh water and salt water
Cat/Dog bites – Augmentin
- Pasteurella (canis)/(multocida and septica)
- strep
- staph
- Fusobacterium, bacteroides, prevotella
Fresh water
- Aeromonas myonecrosis
- mycobacterium marinum
Seawater
-Virbrio vulnificus
Discuss signs suggestive of necrotising infection and risk factors for the same + bacteria implicated
Signs
- severe pain out of proportion to clinical signs
- Rapidly progressive
- crepitus
- haemorrahge
- sloughing
- blistering
Risk
- diabetes
- vascular insufficiency
- immunosupression
Typical bacteria -GAS -Staph -enterocci -bacteroides -clostridium species (perfinges) Most are polymicrobial
Discuss necrotising fasciitis
Aggresive infection of the subcutaneous tissues taht spread rapidly along fascial planse.
It is caused by direct extension from a skin lesion in 80% of cases
Two types are described
Type 1- polymicrobial with aerobes and anaerobes
Type 2- monomicobial
Physical finding are intiially those of cellulitis with pain out of proportion. Eventually the skin turns violaceous or ecchymotic. Subsequent inflammation may result in cthe classic sign of so called wodden hard subcut tissues
Discuss Fournier’s gangrene
Necrotising polymicrobial infection of the perineum
Radidly progresses to involve the entire perineum or abdominal wall.
Discuss myonecrosis
Myonecrosis, myositis and pyomyositis refer to infection of muscle which are rare. They may result from local spread of an adjacent infection, penetrating trauma, vascular insufficiency or haematogenous spread.
Discuss management of necrotising infection
ABCD
-Surgical review for potential need for debridement
-Meropenum 1g Q8hrly or piptaz 4.5G Q6hourly
+vancomycin 25mg/kg + clindamycin600mg Q8hourly
If wound has been associated with fresh water cipro is added 400mg Q8hourly to cover for aeromonas which often produce carbapenemase enzymes
Describe strep toxic shock syndrome
Severe toxin mediated syndrome that rapidly progressed to shock with MOF and death.
Invasive group a strep infection often due to M type isolates
Signs and symptoms are caused by progenic exotoxins A and B. These act as superantigens and cause overactivation of T-cell with a massive release of cytokines
Patient have a flu like prodrome followed by high fever, hypotension and tachycardia. ALOC with confusion ic ommon
A diffuse rash is present in 10% of cases which may make differentiation from staph TSS more difficult
Nec fasciitis is present in 50% of cases
Most present wiht shock or quickly develop it
Complications
- DIC
- ARDS
- Renal failure
In contrast to staph TSS , strep TSS is fatal in 30-80% of cases - the epidermolysis typically of staph TSS is not present with strep
Discuss staph toxic shock
Although not as a severe as strep TSS staph TSS remains life threatening. Classic presentation of rash, fever and hypotension.
Menses associated causes have declined dramatically since the elimination of highly absorbent tampons.
Non menstrual cases which currently account for about 50%
-surgical procedures (rhinoplasty, aborption)
-nasal packing
-burns
-IVDU
-Post partum
Similar symptoms to strep TSS but less severe
Desquamation of the skin including the palms and soles eventually occurs 7-14 days after onset. THe overall mortality is below 5% with agressive supportive care
Discuss staph scalded skin
Desqauamting skin disorder caused by exfoliating toxins produced by S aureus. A disease of infants it is rare in odler children and adutls.
SSS is caused by certain strains of s.Aureus that produce epidermolytic toxin A or epiderolytic toxin B - These toxxins act as proteases taht target the protein desmoglein
The severity of the disease ranges from a few blisters at the site of infection to exfoliation of most of the body.
Typically a young child presents with fever irritability and tender red rash. The erythema progresses to bullae formation and subsequent exfoliation of the affected skin. Nikolsky signs +ve.Perioral, perianal and flexural skin may be more affected. Mucous membranse are spared.
Discuss management of toxic shock syndrome
IN Strep TSS - early surgical intervention for debridement
Staph TSS - removal of any inciting cause
Strep TSS - Benpen 2.4g 4 hourly + clindamycin 600mg Q8hourly
Staph TSS - Fluclox 2g + vanc 25-30mg/kg +clinda 600mgQ8hourly + IVIG
