Skin and soft tissue infections Flashcards
What us impetigo?
Superficial highly infectious skin infection
Multiple vesicular lesions on an erythematous base
What is highly suggestive of impetigo?
Golden crust
What are the causative organisms of impetigo?
Most common= staph aureus
Less commonly= strep pyogens
Where does impetigo occur?
Exposed areas e.g. face, extremities, scalp
What are the predisposing factors of impetigo?
Skin abrasions
Minor trauma or burns
Por hygiene
What is the treatment of impetigo?
Small areas= topical antibiotics
Large areas= topical treatment an oral antibiotics
What is erysipelas?
Infection of upper dermis
What are the clinical features of erysipelas?
Painful red area, no central clearing
Associated fever
Regional lymphadenopathy and lymphangitis
Distinct elevated borders
What is the commonest cause of erysipelas?
Strep pyogenes
Where is erysipelas most often seen?
Legs
Areas of existing lymphedema, venous stasis, obesity, paraparesis, diabetes mellitus
What is the treatment of erysipelas?
Combination of anti-staph and anti-strep antibiotics
IV antibiotics if severe
What is cellulitis?
Diffuse skin infection involving deep dermis and subcutaneous fat
What are the clinical features of cellulitis?
Spreading erythematous area with no distinct borders
Fever
Regional lymphadenopathy and lymphangitis
What are the most common causative organisms of cellulitis?
strep pyogenes
staph aureus
What are the predisposing factors for cellulitis?
DM
Tinea pedis
Lymphoedema
What is the treatment of cellulitis?
Combination of anti-staph and anti-strep antibiotics
IV antibiotics if severe
What are the hair associated infections?
Folliculitis
Furuncles
Carbuncles
What are the clinical features of folliculitis?
Circumscribed pustular infection of hair follicle
Up to 5mm in diameter
Small red papule
Central area of purulence that may rupture and drain
Where is folliculitis found?
Head
Back
Buttocks and extremities
What is the most common causative organisation of folliculitis?
Staph aureus
What is the treatment of folliculitis?
None or topical antibiotics
What are furuncles commonly referred to as?
Boils
What are the clinical features of furuncles?
Single hair follicle associated with inflammatory nodule
Extending to dermis and subcutaneous tissue
Where do furuncles occur?
Moist, hairy, friction prone areas
What is the most common causative organism of furuncles?
Staph aureus
What are the risk factors for furuncles?
Obesity
DM
CKD
What is the treatment of furuncles?
None
Topical antibiotics
If not improving, oral antibiotics
When do carbuncles occur?
Infection extends to involve multiple follicles
Where do carbuncles often occur?
Back of neck, posterior trunk or thigh
What are the clinical features of carbuncles?
Multiseptated abscesses
Purulent material may be expressed
What is the treatment of carbuncles?
Often require hospital admission, surgery and IV antibiotics
What are the predisposing factors for necrotising fasciitis?
DM
Surgery, trauma
Peripheral vascular disease
Skin popping
What are the types of necrotising fasciitis?
Type I- missed infection, typically strep, staph or enterococci
Type II- mono microbial, associated with strep pyogenes
What are the clinical features of necrotising fasciitis?
Rapid onset
Sequential development of erythema, extensive oedema and severe pain
Haemorrhagic bullae, skin necrosis and crepitus may develop
Anaesthesia at site highly suggestive
What are the systemic features associated with necrotising fasciitis?
Fever Hypotension Tachycardia Delirium Multiorgan failure
What is the treatment of necrotising fasciitis?
Surgical review mandatory
Broad spectrum antibiotics- flucloxacillin, gentamicin, vancomycin
What is pyomyositis?
Purulent infection deep within striated muscle, often manifesting as an abscess
What are the common sites for pyomyositis?
Thigh, calf Arms Gluteal region Chest wall Psoas muscle
What are the clinical features of pyomyositis?
Fever
Pain
Woody induration of affected muscle
What can untreated pyomyositis lead to?
Septic shock and death
What are the predisposing factors for pyomyositis?
DM
Immunocompromised
IV drug abuse
Malignancy
What is the most common causative organism of pyomyositis?
Staph aureus
What are the possible causative organisms for pyomyositis?
Gram + and -
TB
Fungi
What investigations are done for pyomyositis?
CT/MRI
What is the treatment of pyomyositis?
Grainage
Antibiotics
What is septic bursitis?
Small bursae- small sac like cavities containing fluid and lined by synovial membrane
Located subcutaneously between bony prominences or tendons
Where is septic bursitis most often found?
Patellar or olecranon regions
What are the predisposing factors for septic bursitis?
DM
IV drug abuse
Immunosuppression
Alcoholism
What are the clinical features of septic bursitis?
Peribursal cellulitis, swelling, warmth
Fever
Pain on movement
How is septic bursitis diagnosed?
Aspirate fluid- not always done
What is the most common causative organism of septic bursitis?
Staph aureus
What are the possible causative organisms of septic bursitis?
Staph aureus
Gram -
Mycobacteria
Brucella
What is the treatment of septic bursitis?
Antibiotics
What is infectious tenosynovitis?
Infection of synovial sheets surrounding tendons
What are the most common locations for infectious tenosynovitis?
Flexor muscle associated tendons
Tendon sheets of the hand
What is the most common inciting event for infectious tenosynovitis?
Trauma
What are the causative organisms of infectious tenosynovitis?
Staph aureus and strep most common
Chronic due to mycobacteria or fungi
What are the clinical features of infectious tenosynovitis?
Erythematous fusiform swelling of the finger
Held in semiflexed position
Tenderness over length pf tendon sheet and pain with extension are classic
What is the treatment of infectious tenosynovitis?
Empiric antibiotics
Hand surgeon to review
What are toxin mediated syndromes often due to and why?
Superantigens- they can bypass normal immune system and attach directly to T cell receptors
What are the most common causative organisms of toxin mediated syndromes?
Staph aureus
Strep pyogens
What are the causes of toxic shock syndrome?
High absorbency tampons- most common
Staph aureus skin infection
Strep
What are the diagnostic criteria for staph aureus toxic shock syndrome?
Fevere Hypotension Diffuse macular rash At least 3 organs involved Isolation of staph aureys
What is strep in toxic shock syndrome associated with?
Deep seated infections and high mortality
What is the treatment of strep causing toxic shock syndrome?
Urgent surgical debridement of infected tissues
What is the treatment of toxic shock syndrome?
Remove offensive agent IV fluids Inotropes Antibiotics- v high dose IV immunoglobulins
What causes staphylococcal scalded skin syndrome?
Particular strain of staph aureus producing exfoliative toxin A or B
What are the clinical features of staphylococcal scalded skin syndrome?
Widespread bullar and skin exfoliation
Usually in children
What is the treatment of staph scalded skin syndrome?
IV fluids and antimicrobials
What is Panton-Valentin leucocidin toxin?
Toxin that can be transferred from one strain of staph aureus to another
Can cause haemorrhagic pneumonia
What are the clinical features of Panton-Valentin leucocidin toxin?
Tends to affect children and young adults
Recurrent boils which are difficult to treat
What is the usual progression of IV catheter associated infections?
Local inflammation
Progress to cellulitis and even necrosis
What is commonly associated wth IV catheter associated infections?
Bacteraemia
What are the risk factors for IV catheter associated infections?
Cannula in situ >72 hours
Cannula in lover limb
What is the causative organisms of IV catheter associated infections?
Staph aureus
How are IV catheter associated infections diagnosed?
Clinical or positive blood diagnosis
Echo for complications
What is the treatment of IV catheter associated infections?
Remove cannula
14 days antibiotics
What are the types of surgical site infection?
Class I= clean wound, systems not entered
Class II= clean contaminated wound, no unusual contamination
Class III= Contaminated wound
Class IV= infected wound
What are the possible causative bacteria of a surgical site infection?
Staph aureus Staph, strep and enterococci Fungi Anaerobes E. coli Pseudomonas aeruginosa
What are the personal risk factors for surgical site infection?
DM Smoking Obesity or malnutrition Steroid use Staph aureus colonisation
What are the procedural risk factors for surgical site infection?
Shaving site prior evening
Improper pre-op skin prep
Improper antimicrobial prophylaxis
Break in sterile technique
How is surgical site infection diagnosed?
Pus/tissue culture- deep if possible
What is the treatment of surgical site infection?
Antibiotics
