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Year 3 - infection > Skin and Soft Tissue > Flashcards

Skin and Soft Tissue Flashcards

1
Q

what are the different layers of the skin and in what layers do different infections occur?

A
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2
Q

what are things to consider in relation to infection?

A
  • 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
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3
Q

what is Impetigo?

A
  • Superficial skin infection
  • Multiple vesicular lesions on an erythematous base
  • Golden crust is highly suggestive of this diagnosis
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4
Q

what organisms are responsible for impetigo?

A
  • Most commonly due to Staph aureus
  • Less commonly Strep pyogenes
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5
Q

impetigo is common in who?

A

•Common in children 2-5 years of age

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6
Q

is impetigo infectious?

A

•Highly infectious

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7
Q

where on the body does impetigo usually occur?

A

•Usually occurs on exposed parts of the body including face, extremities and scalp

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8
Q

what are predisposing factors of impetigo?

A

Skin abrasions

Minor trauma

Burns

Poor hygiene

Insect bites

Chickenpox

Eczema

Atopic dermatitis

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9
Q

what is the treatment of impetigo?

A
  • Small areas can be treated with topical antibiotics alone
  • Large areas need topical treatment and oral antibiotics (ex flucloxacillin)
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10
Q

what is Erysipelas?

A
  • Infection of the upper dermis
  • Painful, red area (no central clearing)
  • Associated fever
  • Regional lymphadenopathy and lymphangitis
  • Typically has distinct elevated borders
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11
Q

what organism is responsible for Erysipelas?

A

•Most commonly due to Strep pyogenes

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12
Q

where does erysipelas occur?

A
  • 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
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13
Q

what is the recurrence rate of erysipelas like?

A

•High recurrence rate (30% within 3 years)

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14
Q

what is Cellulitis?

A
  • Diffuse skin infection involving deep dermis and subcutaneous fat
  • Presents as a spreading erythematous area with no distinct borders
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15
Q

what is responsible for causing cellulitis?

A

Most likely organisms are Strep pyogenes and Staph aureus

Remember role of Gram negatives in diabetics and febrile neutropaenics

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16
Q

What does cellulitis cause?

A
  • Fever is common
  • Regional lymphadenopathy and lymphangitis
  • Possible source of bacteraemia
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17
Q

what should you look for in someone with cellulitis>

A

• Look for predisposing factors

  • Diabetes mellitus
  • Tinea pedis (athletes foot)
  • Lymphoedema

• Patients can have lymphangitis and/or lymphadenitis

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18
Q

what is the Treatment of erysipelas and cellulitis?

A
  • A combination of anti-staphylococcal and anti-streptococcal antibiotics
  • In extensive disease, admission for intravenous antibiotics and rest
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19
Q

what are some Hair-associated infections?

A
  • Folliculitis
  • Furunculosis
  • Carbuncles
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20
Q

what is Folliculitis?

A
  • 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
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21
Q

what organism is responsible for Folliculitis and what symptoms are experienced?

A
  • Most common organism is Staph aureus
  • Benign condition
  • Constitutional symptoms not often seen
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22
Q

what is Furunculosis?

A
  • 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
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23
Q

what organism is responsible for Furunculosis and what symptoms are experienced?

A
  • Staph aureus most common organism
  • Systemic symptoms uncommon
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24
Q

what are risk factors for Furunculosis?

A

Obesity

Diabetes mellitus

Atopic dermatitis

Chronic kidney disease

Corticosteroid use

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25
Q

what is Carbuncle?

A
  • 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
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26
Q

what is the treatment of hair-associated infections?

A
  • 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
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27
Q

what is Necrotising fasciitis?

A
  • 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

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28
Q

predisposing conditions to Necrotising fasciitis include what?

A

Diabetes mellitus

Surgery

Trauma

Peripheral vascular disease

Skin popping

29
Q

what is type 1 Necrotising fasciitis?

A
  • 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
30
Q

what is type to necrotising fascitis?

A
  • Type II is monomicrobial
  • Normally associated with Strep pyogenes
31
Q

whata re the clinical feastures of Necrotising fasciitis?

A
  • 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
32
Q

what is the management and treatment of Necrotising fasciitis?

A
  • 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%

33
Q

what is Pyomyositis?

A

Purulent infection deep within striated muscle, often manifesting as an abscess

Infection is often secondary to seeding into damaged muscle

34
Q

what are common sites in Pyomyositis?

A
  • Multiple sites involved in 15%
  • Common sites include:
  • Thigh
  • Calf
  • Arms
  • Gluteal region
  • Chest wall
  • Psoas muscle
35
Q

how does Pyomyositis present?

A
  • Can present with fever, pain and woody induration of affected muscle
  • If untreated can lead to septic shock and death
36
Q

what are some predisposing factors to pyomyositis?

A

Diabetes mellitus

HIV/immunocompromised

Intravenous drug use

Rheumatological diseases

Malignancy

Liver cirrhosis

37
Q

what organism is responsible for pyomyositis?

A
  • Commonest cause is Staph aureus
  • Other organisms can be involved including Gram positive/negatives, TB and fungi
38
Q

what is the investigation and treatment of pyomyositis?

A

Investigation using CT/MRI

Treatment is drainage with antibiotic cover depending on Gram stain and culture results

39
Q

what are Septic bursitis?

A
  • 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
40
Q

Septic bursitis is often caused form where?

A

•Infection is often from adjacent skin infection

41
Q

whata re some predisposing factors to septic bursitis?

A

Rheumatoid arthritis

Alcoholism

Diabetes mellitus

Intravenous drug abuse

Immunosuppression

Renal insufficiency

42
Q

what are the clinical features of septic bursitis?

A
  • Peribursal cellulitis, swelling and warmth are common
  • Fever and pain on movement also seen
43
Q

what is the diagnosis of septic bursitis based on?

A

• Diagnosis is based on aspiration of the fluid

44
Q

what organisms are responsible for septic bursitis?

A
  • Most common cause is Staph aureus
  • Rarer organisms include:
  • Gram negatives
  • Mycobacteria
  • Brucella
45
Q

what is Infectious tenosynovitis?

A
  • Infection of the synovial sheats that surround tendons
  • Flexor muscle-associated tendons and tendon sheats of the hand most commonly involved
46
Q

what causes infectious tenosynovitis?

A
  • Penetrating trauma most common inciting event
  • Most common cause Staph aureus and streptococci
  • Chronic infections due to mycobacteria, fungi
  • Possibility of disseminated gonococcal infection
47
Q

what is the cliniical features of presentaion of infection tenosynovitis?

A
  • 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
48
Q

what is the treatment of infectious tenosynovitis?

A
  • Empiric antibiotics
  • Hand surgeon to review ASAP
49
Q

what are Toxin-mediated syndromes?

A
  • 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
50
Q

Toxin-mediated syndromes are due to what?

A
  • Mostly due to some strains of Staphylococcus aureus and Streptococcus pyogenes
  • Staph aureus: TSST1, ETA and ETB
  • Strep pyogenes: TSST1
51
Q

what os toxic shock syndrome?

A

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

52
Q

what is the diagnostic criteria for Staphylococcal TSS?

A
  • 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
53
Q

what is involved in Streptococcal TSS?

A
  • 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
54
Q

what is the Treatment of TSS?

A
  • Remove offending agent (ex tampon)
  • Intravenous fluids
  • Inotropes
  • Antibiotics
  • Intravenous immunoglobulins
55
Q

what is Staphylococcal scalded skin syndrome?

A
  • 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
56
Q

what is the management of staphylococcal sclaed skin syndrome?

A
  • Treatment with intravenous fluids and antimicrobials
  • Mortality 3% in children but higher in adults who often are immunosuppressed
57
Q

what is Panton-Valentine leucocidin toxin? and what does it cause and what is the treatment?

A
  • 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
58
Q

what are Intravenous-catheter associated infections?

A
  • Nosocomial infection (in hospital)
  • Normally starts as local SST inflammation progressing to cellulitis and even tissue necrosis
  • Common to have an associated bacteraemia
59
Q

what are risk factors for Intravenous-catheter associated infections?

A

Continuous infusion >24 hours

Cannula in situ >72 hours

Cannula in lower limb

Patients with neurological/neurosurgical problems

60
Q

what is responsible for causing Intravenous-catheter associated infections?

A
  • 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)
61
Q

HOw is a diagnosis of Intravenous-catheter associated infections made?

A

•Diagnosis made clinically or by positive blood cultures

62
Q

what is the treatment and management of Intravenous-catheter associated infections?

A
  • 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
63
Q

what are the different classes of Surgical site infections?

A
  • 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)
64
Q

what organisms are responsible for surgical site infections?

A
  • Staph aureus (incl MSSA and MRSA)
  • Coagulase negative Staphylococci
  • Enterococcus
  • Escherichia coli
  • Pseudomonas aeruginosa
  • Enterobacter
  • Streptococci
  • Fungi
  • Anaerobes
65
Q

what are some patient associated risks for surgical site infections?

A

Diabetes

Smoking

Obesity

Malnutrition

Concurrent steroid use

Colonisation with Staph aureus

66
Q

what are some procedural factors associated risks for surgical site infections?

A

Shaving of site the night prior to procedure

Improper preoperative skin preparation

Improper antimicrobial prophylaxis

Break in sterile technique

Inadequate theatre ventilation

Perioperative hypoxia

67
Q

how is the diagnosis of surgical site infections made?

A
  • 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
68
Q

Conclusion:

A
  • 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

Year 3 - infection (14 decks)

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