Skin and Soft Tissue Infections Flashcards
2 groups of skin infections
Hospital acquired
Community acquired
Risk factors for skin and soft tissue infections - host
DM leading to neuropathy and vasculopathy
Immunosuppression
Renal failure
Milroy’s disease
Predisposing skin condition (e.g. atopic dermatitis)
Where in the skin does impetigo affect?
Superficial skin infection only affecting the epidermis
Layers of the skin (superficial to deep)
Epidermis Dermis Subcutaneous fat Fascia Muscle
Who is impetigo common in?
Children 2-5 years of age
Causative organisms of impetigo
Commonly -> staph aureus
Less commonly -> strep pyogenes
Is impetigo infectious?
Yes - highly infectious
Presentation of impetigo
Multiple vesicular lesions on an erythematous base
Golden crust
Usually occurs on parts of body including face, extremities and scalp
Predisposing factors for impetigo
Skin abrasions Minor trauma Burns Poor hygiene Inset bites Chickenpox Eczema Atopic dermatitis
Treatment of impetigo
Small areas = topical antibiotics alone
Large areas = topical treatment with oral antibiotics (e.g. flucloxacillin)
Definition of erysipelas
Infection of the upper dermis
Presentation of erysipelas
Painful, red area (no central clearing)
Assosiated fever
Regional lymphadenopathy and lymphangitis
Distinct elevated borders
Most common causative organism of erysipelas
Strep pyogenes
Where does erysipelas affect?
70-80% lower limbs 5-20% face Areas of pre existing - lymphoedema - venous stasis - obesity - paraparesis - diabetes mellitus May involve intact skin
Treatment of erysipelas
Combination of - anti-staphylococcal (flucocaxillin) and anti-streptococcal (benzylpenicillin) antibiotics extensive disease - admission for IV antibiotics - rest
Presentation of cellulitis
Spreading erythematous area with no distinct areas Fever Pain Regional lymphadenopathy + lymphangitis Systemic upset
Definition of cellulitis
Diffuse skin infection involving deep dermis and subcutaneous fat
Likely causative organisms of cellulitis
Strep pyogenes
Staph aureus
Predisposing factors of cellulitis
DM
Tinea pedis
Lymphoedema
Obesity
Treatment of cellulitis
Combination of - anti-staphylococcal antibiotics (flucocloxacillin) and anti-streptococcal antibiotics (benzylpenicillin) Extensive disease - IV antibiotics - rest
Definition of folliculitis
Circumscribed, pustular infection of a single fair follicle
Where is folliculitis commonly found?
Head
Back
Buttocks
Extremities
Most common organism for folliculitis
Staph aureus
Definition of furunculosis
Infection of a single hair follicle has spread from the follicle to the surrounding tissue
What are furuncles commonly referred to as?
Boils
What layers of the skin do furuncles affect?
Dermis
Subcutaneous tissue
Where do furuncles usually affect?
Moist, hairy, friction prone areas of the body (face, axilla, neck, buttocks)
Most common organism for furunculosis
Staph aureus
Risk factors for furunculosis
Obesity DM Atophic dermatitis Chronic kidney disease Corticosteriod use
What is another name for atophic dermatitis
Eczema
Definition of carbuncles
Infection extends to involve multiple furuncles
Where are carbuncles found?
Back of neck
Posterior thigh
Posterior trunk
Presentation of carbuncles
Multiseptated abscesses
Purulent material expressed from multiple sites
Constitutional symptoms common
Treatment of carbuncles
IV antibiotics
Often require surgery
What does the presence of carbuncles indicate?
An underlying cause e.g. HIV as a normal healthy person should not get carbuncles from furunculosis
Predisposing conditions to necrotising fasciitis
DM Surgery Trauma Peripheral vascular disease Skin popping (PWID into dermis as veins collapsed)
What does type I necrotising fasciitis involve?
Mixed aerobic and anaerobic infection (diabetic foot, Fournier’s gangrene)
Typical organisms of type I necrotising fasciitis
Streptococci Staphylococci Enterococci Gram -ve bacilli Clostridium
Typical organisms of type II necrotising fasciitis
Monomicrobial - usually strep pyogenes
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
What is highly suggestive of necrotising fasciitis?
Anaesthesia at the site of infection
Treatment of necrotising fascitis
Surgical review mandatory
Antibiotics - broad spectrum
- flucloxacillin, gentamicin, clindamycin
Prognosis of necrotising fasciitis
Overall mortality 17-40%
Definition of pyomyositis
Purulent deep infection within striated muscle, often manifesting as an abscess
What is pyomyositis often secondary to?
Seeding into damaged muscle
Common sites of pyomyositis
Thigh calf arms gluteal region chest wall psoas muscle
Presentation of pyomyositis
Fever
Pain
Woody induration of affected muscle
Predisposing factors for Pyomyositis
DM HIV/immunocompromised IVDU Rheumatological disease Malignancy Liver cirrhosis
Causative organisms of pyomyositits
Staph aureus most common
gram -ve/+ve
TB
fungi
Investigations of pyomyositis
CT/MRI
Treatment of pyomyositis
Drainage with antibiotic cover
Definition of septic bursitis
infection of the bursae (fluid filled sacs)
Where are bursae found?
Subcutaenously between bony prominences or tendons
most common septic bursae sites
platellar
olecrannon
causes of septic bursitis
adjacent skin infection
repeated flexion and extension
Predisposing factors for septic bursitis
rheumatoid arthritis alcoholism DM IVDU Immunosuppression Renal insufficiency
Causative organisms of septic bursitis
Staph aureus - MOST COMMON Rarer - gram -ves - mycobacteria - brucella
Presentation of septic bursitis
Peribursal cellulitis Swelling warmth fever pain on movement
Definition of infectious tenosynovitis
Infections of the synovial sheets that surround tissues
Where is the most commonly affected in infectious tenosynovitis?
Flexor muscle associated tendons
Tendon sheets of the hand
What is the most common inciting event of infectious tenosynovitis?
Penetrating trauma
Causative organisms of infectious tenosynovitis
MOST COMMON - staph aureus and streptococci
CHRONIC INFECTIONS - mycobacteria and fungi
Possibility of disseminated gonococcal infection
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
Treatment of infectious tenosynovitis
Empirical antibiotics
Hand surgeon to review asap
What are toxin mediated syndromes often due to?
Superantigens
What do toxin mediated syndromes result in?
Endothelial leakage
Haemodynamic shock
Multiorgan failure and death
Possible causes of toxic shock syndrome
High absorbency tampons during menstruation
Small skin infections due to staph aureus secreting TSST1
What are a lot of toxin mediated syndromes due to? (organisms)
TSST1
Presentation of toxic shock syndrome
Fever Hypotension Diffuse macular rash 3 of the following organs involved - liver, blood, renal, GI, CNS, muscular
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
What is streptococcal toxic shock syndrome almost always associated with?
Presence of streptococci in deep seated infections such as erysipelas or necrotising fasciitis
Streptococcal TSS vs staphylococcal TSS
Strep much higher mortality rate than staph (50% vs 5%)
Treatment of toxic shock syndrome
remove offending agent (ex tampon) IV fluids Inotropes Antibiotics IV immunoglobulins (in ITU/HDU)
Toxins causing toxin mediated syndromes
Staph aureus - TSST1 - ETA and ETB Streptococcus pyogenes - TSST1
Causes of staphylococcal scalded skin syndrome
infection due to a particular strain of staph aureus producing the exfoliative toxin A or B
Who does staphylococcal scalded skin syndrome affect?
Children but rarely adults as well
Presentation of staphylococcal scalded skin syndrome
Widespread bullae and skin exfoliation
Treatment of staphylococcal scalded skin syndrome
IV fluids and antimicrobials
Pathology of IV catheter associated infections
Starts at local STT inflammation
Progressing to cellulitis
And possibly tissue necrosis
Risk factors for IV catheter infections
Continuous infusion > 24 hours
Cannula in situ > 72 hours
Cannula in lower limb
patients with neurological/neurological problems
Most common causative organism for IV catheter infections
Staph aureus (MSSA and MRSA)
Investigations for IV catheterisation associated infections
Clinically
+ve blood cultures
Treatment of IV catheterisation associated infections
Remove cannula
Express any pus from thrombophlebitis
Antibiotics for 14 days
ECG
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
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)
3 examples of causative organisms of surgical site infection
Staph aureus
Fungi
streptococci
anaerobes
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
