Skin and Soft Tissue Flashcards
what are the different layers of the skin and in what layers do different infections occur?
what are things to consider in relation to infection?
- Site - Possible complications with specific sites (ex; abdo, face)
- Organism
- Host - Diabetes leading to neuropathy and vasculopathy, Immunosuppression, Renal failure, Milroy’s disease, Predisposing skin conditions (ex; atopic dermatitis)
- Environment - Drug-resistant strains (MRSA), Drug interactions, Drug allergies
what is Impetigo?
- Superficial skin infection
- Multiple vesicular lesions on an erythematous base
- Golden crust is highly suggestive of this diagnosis
what organisms are responsible for impetigo?
- Most commonly due to Staph aureus
- Less commonly Strep pyogenes
impetigo is common in who?
•Common in children 2-5 years of age
is impetigo infectious?
•Highly infectious
where on the body does impetigo usually occur?
•Usually occurs on exposed parts of the body including face, extremities and scalp
what are predisposing factors of impetigo?
Skin abrasions
Minor trauma
Burns
Poor hygiene
Insect bites
Chickenpox
Eczema
Atopic dermatitis
what is the treatment of impetigo?
- Small areas can be treated with topical antibiotics alone
- Large areas need topical treatment and oral antibiotics (ex flucloxacillin)
what is Erysipelas?
- Infection of the upper dermis
- Painful, red area (no central clearing)
- Associated fever
- Regional lymphadenopathy and lymphangitis
- Typically has distinct elevated borders
what organism is responsible for Erysipelas?
•Most commonly due to Strep pyogenes
where does erysipelas occur?
- 70-80% of cases involves the lower limbs
- 5-20% affect the face
- Tends to occur in areas of pre-existing lymphoedema, venous stasis, obesity, paraparesis, diabetes mellitus
- May involve intact skin
what is the recurrence rate of erysipelas like?
•High recurrence rate (30% within 3 years)
what is Cellulitis?
- Diffuse skin infection involving deep dermis and subcutaneous fat
- Presents as a spreading erythematous area with no distinct borders
what is responsible for causing cellulitis?
Most likely organisms are Strep pyogenes and Staph aureus
Remember role of Gram negatives in diabetics and febrile neutropaenics
What does cellulitis cause?
- Fever is common
- Regional lymphadenopathy and lymphangitis
- Possible source of bacteraemia
what should you look for in someone with cellulitis>
• Look for predisposing factors
- Diabetes mellitus
- Tinea pedis (athletes foot)
- Lymphoedema
• Patients can have lymphangitis and/or lymphadenitis
what is the Treatment of erysipelas and cellulitis?
- A combination of anti-staphylococcal and anti-streptococcal antibiotics
- In extensive disease, admission for intravenous antibiotics and rest
what are some Hair-associated infections?
- Folliculitis
- Furunculosis
- Carbuncles
what is Folliculitis?
- Circumscribed, pustular infection of a hair follicle
- Up to 5mm in diameter
- Present as small red papules
- Central area of purulence that may rupture and drain
- Typically found on head, back, buttocks and extremities
what organism is responsible for Folliculitis and what symptoms are experienced?
- Most common organism is Staph aureus
- Benign condition
- Constitutional symptoms not often seen
what is Furunculosis?
- Furuncles commonly referred as boils
- Single hair follicle-associated inflammatory nodule
- Extending into dermis and subcutaneous tissue
- Usually affected moist, hairy, friction-prone areas of body (face, axilla, neck, buttocks)
- May spontaneously drain purulent material
what organism is responsible for Furunculosis and what symptoms are experienced?
- Staph aureus most common organism
- Systemic symptoms uncommon
what are risk factors for Furunculosis?
Obesity
Diabetes mellitus
Atopic dermatitis
Chronic kidney disease
Corticosteroid use
what is Carbuncle?
- 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
what is the treatment of hair-associated infections?
- With folliculitis, no treatment or topical antibiotics
- With furunculosis, no treatment or topical antibiotics. If not improving oral antibiotics might be necessary
- Carbuncles often require admission to hospital, surgery and intravenous antibiotics
what is Necrotising fasciitis?
- One of the infectious diseases emergencies
- Any site may be affected
Necrotising fasciitis is a rare but serious bacterial infection that affects the tissue beneath the skin and surrounding muscles and organs (fascia). It’s sometimes called the “flesh-eating disease”, although the bacteria that cause it do not “eat” flesh, but release toxins that damage nearby tissue
predisposing conditions to Necrotising fasciitis include what?
Diabetes mellitus
Surgery
Trauma
Peripheral vascular disease
Skin popping
what is type 1 Necrotising fasciitis?
- Type I refers to a mixed aerobic and anaerobic infection (diabetic foot infection, Fournier’s gangrene)
- Typical organisms include
- Streptococci
- Staphylococci
- Enterococci
- Gram negative bacilli
- Clostridium
what is type to necrotising fascitis?
- Type II is monomicrobial
- Normally associated with Strep pyogenes
whata re the clinical feastures 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
what is the management and treatment 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%
what is Pyomyositis?
Purulent infection deep within striated muscle, often manifesting as an abscess
Infection is often secondary to seeding into damaged muscle
what are common sites in Pyomyositis?
- Multiple sites involved in 15%
- Common sites include:
- Thigh
- Calf
- Arms
- Gluteal region
- Chest wall
- Psoas muscle
how does Pyomyositis present?
- Can present with fever, pain and woody induration of affected muscle
- If untreated can lead to septic shock and death
what are some predisposing factors to pyomyositis?
Diabetes mellitus
HIV/immunocompromised
Intravenous drug use
Rheumatological diseases
Malignancy
Liver cirrhosis
what organism is responsible for pyomyositis?
- Commonest cause is Staph aureus
- Other organisms can be involved including Gram positive/negatives, TB and fungi
what is the investigation and treatment of pyomyositis?
Investigation using CT/MRI
Treatment is drainage with antibiotic cover depending on Gram stain and culture results
what are Septic bursitis?
- Bursae are small sac-like cavities that contain fluid and are lined by synovial membrane
- Located subcutaneously between bony prominences or tendons
- Facilitate movement with reduced friction
- Most common include patellar and olecranon
Septic bursitis is often caused form where?
•Infection is often from adjacent skin infection
whata re some predisposing factors to septic bursitis?
Rheumatoid arthritis
Alcoholism
Diabetes mellitus
Intravenous drug abuse
Immunosuppression
Renal insufficiency
what are the clinical features of septic bursitis?
- Peribursal cellulitis, swelling and warmth are common
- Fever and pain on movement also seen
what is the diagnosis of septic bursitis based on?
• Diagnosis is based on aspiration of the fluid
what organisms are responsible for septic bursitis?
- Most common cause is Staph aureus
- Rarer organisms include:
- Gram negatives
- Mycobacteria
- Brucella
what is Infectious tenosynovitis?
- Infection of the synovial sheats that surround tendons
- Flexor muscle-associated tendons and tendon sheats of the hand most commonly involved
what causes infectious tenosynovitis?
- Penetrating trauma most common inciting event
- Most common cause Staph aureus and streptococci
- Chronic infections due to mycobacteria, fungi
- Possibility of disseminated gonococcal infection
what is the cliniical features of presentaion of infection tenosynovitis?
- Present with erythematous fusiform swelling of finger
- Held in a semiflexed position
- Tenderness over the length of the tendon sheat and pain with extension of finger are classical
what is the treatment of infectious tenosynovitis?
- Empiric antibiotics
- Hand surgeon to review ASAP
what are Toxin-mediated syndromes?
- Often due to superantigens
- Group of pyrogenic exotoxins
- Do not activate immune system via normal contact between APC and T cells
- Superantigens bypass this and attach directly to the T cell receptors activating up to 20% of the total pool of T cells instead of the normal 1/10,000
- Massive burst in cytokine release
- Leads to endothelial leakage, haemodynamic shock, multi-organ failure and ?death
Toxin-mediated syndromes are due to what?
- Mostly due to some strains of Staphylococcus aureus and Streptococcus pyogenes
- Staph aureus: TSST1, ETA and ETB
- Strep pyogenes: TSST1
what os toxic shock syndrome?
Toxic shock syndrome (TSS) is a rare but life-threatening condition caused by bacteria getting into the body and releasing harmful toxins.
It’s often associated with tampon use in young women, but it can affect anyone of any age – including men and children.
TSS gets worse very quickly and can be fatal if not treated promptly. But if it’s diagnosed and treated early, most people make a full recovery.
• Can also be due to small skin infections due to Staph aureus secreting TSST1
what is the 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
what is involved in Streptococcal TSS?
- Almost always associated with presence of Streptococci in deep seated infections such as erysipelas or necrotising fasciitis
- Mortality rate is much higher than Staphylococcal (50% vs 5%)
- Treatment necessitates urgent surgical debridement of the infected tissues
what is the Treatment of TSS?
- Remove offending agent (ex tampon)
- Intravenous fluids
- Inotropes
- Antibiotics
- Intravenous immunoglobulins
what is Staphylococcal scalded skin syndrome?
- Infection due to a particular strain of Staph aureus producing the exfoliative toxin A or B
- Characterised by widespread bullae and skin exfoliation
- Usually occurs in children but rarely in adults as well
what is the management of staphylococcal sclaed skin syndrome?
- Treatment with intravenous fluids and antimicrobials
- Mortality 3% in children but higher in adults who often are immunosuppressed
what is Panton-Valentine leucocidin toxin? and what does it cause and what is the treatment?
- It is a gamma haemolysin
- Can be transferred from one strain of Staph aureus to another, including MRSA
- Can cause SSTI and haemorrhagic pneumonia
- Tends to affect children and young adults
- Patients present with recurrent boils which are difficult to treat
- Treat with antibiotics that reduce toxin production
what are Intravenous-catheter associated infections?
- Nosocomial infection (in hospital)
- Normally starts as local SST inflammation progressing to cellulitis and even tissue necrosis
- Common to have an associated bacteraemia
what are risk factors for Intravenous-catheter associated infections?
Continuous infusion >24 hours
Cannula in situ >72 hours
Cannula in lower limb
Patients with neurological/neurosurgical problems
what is responsible for causing Intravenous-catheter associated infections?
- Most common organism is Staph aureus (MSSA and MRSA)
- Commonly forms a biofilm which then spills into bloodstream
- Can seed into other places (ex endocarditis, osteomyelitis)
HOw is a diagnosis of Intravenous-catheter associated infections made?
•Diagnosis made clinically or by positive blood cultures
what is the treatment and management of Intravenous-catheter associated infections?
- Treatment is to remove cannula
- Express any pus from the thrombophlebitis
- Antibiotics for 14 days
- Echocardiogram
- 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
what are the different classes of Surgical site infections?
- Class I: Clean wound (respiratory, alimentary, genital or infected urinary systems not entered) (shown in picture)
- Class II: Clean-contaminated wound (above tracts entered but no unusual contamination)
- Class III: Contaminated wound (Open, fresh accidental wounds or gross spillage from the gastrointestinal tract)
- Class IV: Infected wound (existing clinical infection, infection present before the operation)
what organisms are responsible for surgical site infections?
- Staph aureus (incl MSSA and MRSA)
- Coagulase negative Staphylococci
- Enterococcus
- Escherichia coli
- Pseudomonas aeruginosa
- Enterobacter
- Streptococci
- Fungi
- Anaerobes
what are some patient associated risks for surgical site infections?
Diabetes
Smoking
Obesity
Malnutrition
Concurrent steroid use
Colonisation with Staph aureus
what are some procedural factors associated risks for surgical site infections?
Shaving of site the night prior to procedure
Improper preoperative skin preparation
Improper antimicrobial prophylaxis
Break in sterile technique
Inadequate theatre ventilation
Perioperative hypoxia
how is the diagnosis of surgical site infections made?
- 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
Conclusion:
- Most infections of skin are easily recognised and treated
- Some infections need urgent attention:
- Necrotising fasciitis
- Pyomyositis
- Toxic shock syndrome
- PVL infections
- Venflon-associated infections
•Treat or manage underlying predisposing factors
