Skin and Soft Tissue Infection Flashcards

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1
Q

What are the natural defences of the skin?

A
  • Barrier- keratin
  • Acidic sebaceous secretions
  • Immune response via blood supply and lymphatics
  • Mucosal lysozymes, IgA, washing secretions
  • Normal flora
    • Coag negative staphylococci, staph. aureus, Corynebacterium sp., Propionibacterium sp., Candida sp. (fungus)
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2
Q

Describe colonisation

A
  • Does not mean infection
  • Infection involves signs of inflammation
  • > Fever, swelling, redness, pain, loss of function
  • In leg ulcer, surgical wounds, IV- line sites
  • At this point, treat patient not microbiology
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3
Q

How might the skin change in systemic disease?

A
  • Rashes
  • Vesicles, macules, papules
  • Vasculitis, embolic, haemorrhagic lesions
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4
Q

What does SSSI stand for?

A
  • Skin and Skin Structure Infections
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5
Q

What does SSTI stand for?

A
  • Skin and Soft Tissue Infections
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6
Q

What does ABSSSI stand for?

A
  • Acute Bacterial Skin and Skin Structure Infections (ABSSSI)
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7
Q

What are the causative agents of skin infections?

A
  • Staph aureus (MRSA, MSSA)
  • Streptococci (beta haemolytic)
  • Anaerobes
  • Coliforms
  • Other gram negative, e.g. dog bites
  • Fungal
  • Viral features
  • Parasites
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8
Q

Describe the infection Impetigo (epidermis)

A
  • Usually confined to face
  • Vesicels/pustules on erythematpus base
  • Becomes crusty, yellow oozing lesions
  • Bullous or non-bullous (large pocket of fluid)
  • Contagious
  • Diagnosis: clinical (can take swab for culture and sensitivities)
  • Treatment: topical antibiotics or systemic agents, flucloxacillin
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9
Q

Describe the infection Erysipelas (intradermal infection)

A
  • Sharply dermarcated raised edge
  • Patient was systemically well otherwise
  • Swabs all post antibiotics no growth
  • Antistreptolycin O (ASO) titre 1600
  • Streptococci beta-haemolytic (strep pyogenes)
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10
Q

Describe infection Cellulitis (loose subcutaneous tissue/risk factors)

A
  • Staph aureus/strep. cocci beta-haemolytic (strep pyogenes)
  • Risk factors: DM, trauma, dermatitis, peripheral vascular disease
    • Marker outline to check spread
    • Response to antibiotics
  • Those with chronic skin conditions are more likely to develop secondary bacterial infections
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11
Q

Describe infection Lymphangitis

A
  • Group A streptococci beta-haemolytic (strep pyogenes)
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12
Q

Describe abcesses

A
  • Furunculosis infected hair follicles
  • Carbuncles Toxaemia
  • Sebacious or sweat glands
  • Staph aureus including MRSA
  • Drain abcess
  • Could be multifunctional
  • Acidic environment, therefore antibiotic activity limited
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13
Q

Describe bacterial toxins

A
  • Toxic shock syndrome
  • Scaled skin syndrome
  • PVL toxin
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14
Q

Describe possible investigations for SSTIs

A
  • Diagnosis often clinical
  • Blood counts and markers
  • Swabs, pus
  • Blood culture if febrile or septic
  • Serology, e.g. ASO titre
  • Imaging (GAS) or extent of damage
  • Debrided tissue
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15
Q

Give examples of some deeper infections

A
  • Necrotising infections (anaerobes often involved)
  • > Gas gangrene
  • > Necrotising fasciitis (flesh-eating bacteria)
  • Pyomyositis
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16
Q

Describe ‘Cat-scratch disease’

A
  • Bartonella henselae
17
Q

Describe lyme disease

A
  • Erythema chronicum migrans

- Tick bite

18
Q

Give examples of other unusual bacteria

A
  • Cutaneous mycobacteria (similar to TB)
  • Fish tank granuloma, M. marinum
  • Buruli ulcer, M. ulcerans
  • Leprosy, M. leperae
19
Q

What empirical treatment may be used to treat SSTIs?

A
  • Clinicians used 54 different antibiotic agents in initial management of skin infections
  • 40% of patients had modification of antibiotics of which majority were due to treatment failure
  • Around 70% of cases already on antimicrobials 3 months prior to hospitalisation
20
Q

Describe cryptic antibiotic resistances in S. aureus

A
  • Resistant organisms appear to be sensitive to a particular antibiotic phenotypically and can escape routine diagnostic tests
21
Q

Describe viral infections of the skin and mucosae

A
  • HSV, VZV (HZV), CMV, EBV
  • Herpes
  • Primary lesion, systemic in chicken pox
  • Spread up sensory axons to ganglion, latent infection
  • Reactivation results in cold sore (HSV1) or shingles (HSV)
  • Treatment for serious cases acyclovir, valaciclovir or famiciclovir
22
Q

What are other viral infections of the skin and mucosae?

A
  • Papilloma virus- warts
  • Hand, foot and mouth- enteroviruses (may lead to diarrhoea)- pharyngitis and vesicles that burst leaving 5-10 oral painful ulcers, simultaneous lesions on hands and feet
  • Molluscum contagiosum- direct and sexual contact
  • Orf- more common in vets and butchers due to exposed animal contact
  • Small pox
  • Measles
23
Q

Describe higher organisms

A
  • Protozoa (cutaneous leishmaniasis)- satellite region
  • Mites, e.g. scabies- benzyl benzoate used
  • Insects
    • Lice, fleas, maggots and larva