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MBChB3 > Skin And Soft Tissue Infection > Flashcards

Skin And Soft Tissue Infection Flashcards

1
Q

Describe the microbiome of the skin

A
  • coagulase negative staphylococci
  • corynebacterium sp.
  • areas of skin with less acidic pH = S. aureus, S. pyogenes
  • sweat + sebaceous glands = anaerobe P. Acnes
  • fungi + mites
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2
Q

What characterises impetigo?

A

Golden encrusted skin lesions with inflammation localised to the dermis. Tends to be well circumscribed. Contagious.

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3
Q

What is the causative organism and treatment of impetigo?

A
  • S. aureus
  • usually mild + self limiting
  • can treat with topical fusidic acid (well circumscribed) or systemic antibiotics if needed
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4
Q

What characterises tinea?

A
  • superficial fungal infection in skin/nails
  • very common (esp on feet - athletes foot)
  • diagnosis made on skin scrapings
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5
Q

What are the causative organisms and treatment of tinea?

A

Most common causes = microsporum, epidermophyton, trichophyton

Treatment with topical therapy in non-severe cases involving skin alone = clotrimazole or terbinafine cream

Systemic therapy in severe cases involving hair/nails = terbinafine/itraconazole

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6
Q

What characterises a soft tissue abscess

A
  • infection within the dermis/fat layers with development of walled off infection and pooled pus
  • most commonly begins on lower limbs and tracks through the lymphatic system and may involve localised lymph nodes
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7
Q

What is the causative organism and treatment of soft tissue abscesses?

A
  • usually B-haemolytic strep (group A strep + S. aureus most common)
  • limited antibiotic penetration so usually surgical drainage is best
  • no antibiotics needed if abscess fully drained and no surrounding cellulitis
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8
Q

Describe the Eron classification of cellulitis

A

Class I = no signs of systemic toxicity or uncontrolled comorbidities
Class II = systemically unwell or systemically well with comorbidity which can complicate or delay resolution of infection
Class III = significant systemic upset (confusion, tachycardia, hypotension) or unstable comorbidities that may interfere with response to treatment, or limb-threatening infection due to vascular compromise
- Class IV = the person has sepsis/severe life-threatening infection (eg. Necrotising fasciitis)

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9
Q

Describe the management of cellulitis

A
  • Class I = primary care management with oral antibiotics
  • Class II = short term hospitalisation and discharge on outpatient parenteral antibiotic therapy (OPAT) - ceftriaxone
  • Class II/IV = urgent hospital admission
    (Risk of life-threatening infection/facial cellulitis = urgent hospital admission)
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10
Q

What antibiotics are given for class I cellulitis?

A

Treatment to cover S. aureus + S. pyogenes
Oral:
1st line = flucloxacillin
2nd line = doxycycline, clarithromycin, clindamycin
(7 day treatment)

IV:
1st line = flucloxacillin
2nd line = vancomycin
(Can be switched to oral therapy in 48-72hrs)

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11
Q

What are the possible complications of cellulitis?

A
  • local = severe tissue destruction
  • distant = septic shock
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12
Q

Describe the cause and presentation of streptococcal toxic shock

A
  • group A streptococcus
  • primary infection within throat/skin/soft-tissue
  • patients present with localised infection, fever and shock
  • can have diffuse, faint rash over body/limbs
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13
Q

Describe the treatment of streptococcal toxic shock

A
  • surgery (aggressively seek out abscesses for drainage)
  • antibiotics = penicillin + clindamycin (reduce toxin production)
  • severe cases = pooled human immunoglobulin
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14
Q

Describe the characteristics of necrotising fasciitis

A
  • immediately life threatening soft tissue infection with deep tissue involvement
  • rapidly progressive with extensive tissue damage requiring extensive surgical debridement
  • surgical emergency
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15
Q

What are signs and symptoms of necrotising fasciitis?

A
  • rapidly progressive
  • pain out of proportion to clinical signs
  • severe systemic upset
  • presence of visible necrotic tissue
  • late signs = fascial oedema + gas in soft tissue
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16
Q

Type I necrotising fasciitis

A

Polymicrobial
- usually complicates existing wounds, including surgical wounds
- microbiology usually shows a mix of gram positives, gram negatives and anaerobes

17
Q

Type 2 necrotising fasciitis

A

Group A streptococcus
- usually occurs in previously healthy tissue, typically on limbs
- may follow a minor injury such as a scratch/sprain
- microbiology usually shows monobacterial infection with S. pyogenes only

18
Q

Describe the treatment of necrotising fasciitis

A

Broad spectrum antibiotic therapy:
- flucloxacillin
- benzylpenicillin
- gentamicin
- clindamycin
- metronidazole
* surgical review

19
Q

What are the common pathogens that can complicate bite wounds?

A
  • staphylococci
  • streptococci
  • anaerobic organisms
  • pasteurella (mammal bites)
  • capnocytophagia (mammal bites)
20
Q

Describe the treatment of bite wounds

A

Antibiotics:
1st line = co-amoxiclav
2nd line = doxycycline + metronidazole

Surgical treatment: early exploration + debridement of complications (eg. Tendon sheath infection)

Prophylactic treatment: antibiotics in high risk, tetanus, rabies (if cannot be excluded eg. Bat scratches/bites)

21
Q

Describe the considerations required for hospital acquired infection

A
  • vascular access sites should be checked (high risk for bacteraemia)
  • MRSA infection
22
Q

What are common infections for people who inject drugs?

A
  • S. aureus predominates but infections often polymicrobial
  • high rates of bacteraemia + disseminated infection (S. aureus bacteraemia, DVT + pulmonary abscesses triad)
    *BBV testing required for every patient
23
Q

What is PVL staphylococcus and its associations?

A
  • virulence factor carried by some S. aureus
  • associated with recurrent soft tissue boils and abscesses (over months/years)
  • necrotising chest infections
24
Q

What is the treatment of PVL staphylococcus?

A
  • antibiotics (MRSA/MSSA, clindamycin to reduce toxin production)
  • decolonisation therapy (+ household contacts) = topical chlorhexidine for skin/hair, nasal mupirocin ointment, washing of sheets/towels
25
Q

Describe the characteristics, diagnosis + treatment of HSV

A
  • type I = stomatitis (cold sore)
  • type 2 = genital herpes (vesicular, may be painful)
  • recurrent = virus latent in sensory nerve ganglia
  • diagnosis = clinical, blood/vesicle fluid PCR, sometimes serology
  • treatment = aciclovir (topical, oral, IV)
26
Q

Describe characteristics, diagnosis + treatment of VZV (chickenpox)

A
  • often self-limiting in children
  • highly infectious (side room management) = contagious from day 8-21
  • congenital abnormalities (if pregnant)
  • causes pneumonitis in adults (more severe infection)
  • diagnosis = vesicle fluid PCR
  • treatment within 48hrs of symptoms = aciclovir PO/IV
27
Q

Describe characteristics, diagnosis + treatment of VZV (shingles)

A
  • reactivation of dormant VZV (dorsal root ganglia)
  • dermatomal distribution
  • isolate until last crop of vesicles crusted (reduces risk of transmission)
  • treat only high risk patients = aciclovir
  • pain management = NSAIDs, gabapentin
28
Q

Describe burn injuries and its common pathogens

A
  • microbial colonisation caused by loss of protective barrier and commensal organisms
  • extent of burn injuries increases susceptibility to infection
  • common organisms = group A strep, S. aureus (toxin production can be problem)
  • opportunistic organisms = pseudomonas, bacillus
  • complication = TSS (children), biofilm
29
Q

What are the 3 zones in burns?

A
  • coagulation
  • stasis
  • hyperaema
30
Q

What is the treatment of burn wound infections?

A
  • debridement of dead/severely infected tissue
  • topical antiseptics/antimicrobials
  • systemic antimicrobials
  • tetanus (consider)
  • prophylactic systemic antibiotics (not usually indicated)

MBChB3 (100 decks)

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