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skin infections Flashcards

1
Q

What are the three skin and soft tissue infections?

A
  1. Cellulitis
  2. Necrotising fasciitis
  3. Gas gangrene
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2
Q

Define cellulitis

A

Acute infection of skin involving subcutaneous tissue

Precipitant is usually a break in skin

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3
Q

Causes of cellulitis?

A

Staph aureus
Strep pyogenes - Group A beta haemolytic
Group G and C haemolytic streptococci

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4
Q

What are the risk factors for cellulitis?

A 
Previous cellulitis
Diabetes
Lymphoedema 
PVD
obesity 
Skin breaks 
-trauma
-IVD
-insect bite
-fissures in hyperkeratotic skin 
-athletes foot
-leg ulcers
-lower limb eczema
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5
Q

What are the clinical features of cellulitis?

A

Erythema, swelling, hot to touch
well demarcated
evidence of trauma/injury to skin
pt is systemically unwell - febrile tachycardia

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6
Q

How do you manage cellulitis

A

Blood and skin swab cultures & sensitivity
mark boundaries
IV antibiotics
-empiric - flucloxacillin to cover staph and strp pyogenes
-directed- benzylpenicillin for strep pyogenes
manage any underlying cause

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7
Q

Define necrotising fasciitis

A

Destruction of the skin, subcutaneous fat and perimuscular fat with necrotic liquefaction of fatty tissue
Precipitants: stab wound, minor trauma, surgery

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8
Q

Pathogens involved in necrotising fasciitis?

A

–Type 1: Polymicrobial
–Type 2: Group A beta-haemolytic streptococci
–(Type 3: Gas gangrene)

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9
Q

Clinical features of necrotiising fasciitis

A 
severe infection, rapidly progressive 
pain out of proportion to clinical appearance 
shiny skin blisters 
skin color changes as necrosis develops 
pt is systemically very unwell 
high mortality (20-47%)
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10
Q

Management of necrotising fasciitis

A 
•Prompt diagnosis
•Urgent surgical assessment and debridement of dead tissue
•Send tissue for culture and sensitivity
–N.B. Fresh, not in formalin
•Blood cultures

Antibiotics:
–Discuss with consultant microbiologist
–Start smart: Broad-spectrum empiric therapy initially (e.g. Vancomycin + Piperacillin-Tazobactam+ Clindamycin)
–Then focus: If group A strep confirmed, dual therapy (benzylpenicillin plus clindamycin)
•Supportive management in ICU

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11
Q

What is a subtype of necrotising fasciitis? Pathogens involved? Management?

A

Fournier’s gangrene- occurs in perineum
involves full thickness necrosis of perineal skin
may involve penis, scrotum and abdominal wall
severe and disfiguring
Pathogens: polymicrobial – usually involves anaerobes
Management: extensive debridement
broad spectrum antibiotics

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12
Q

What is another name for gas gangrene?

A

Clostridia myonecrosis

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13
Q

Define gas gangrene

A

Necrotising myositis
Pathogens:
Clostridium perfringens
Clostridium Septicum

Precipitated by
–Direct inoculation of wound (trauma or surgery)- C perferingens
–Haematogenous – C. septicum from GIT if colon cancer
(role of immunosupression in malignancy is said to cause C septicum infection)

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14
Q

Clinical features of gas gangrene

A 
–Acute onset of severe pain
–Devitalisation of limb, mottled skin
–Fluid or gas-filled blisters on skin
–Systemically unwell
–Foul odour, crepitus
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15
Q

How do you diagnoses gas gangrene?

A

CT/X ray - gas in tissue

Culture on blood AND wound swab/blister fluid/ tissue

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16
Q

Treatment for gas gangene

A 
–Surgical debridement
–Antibiotic therapy
•Broad spectrum empirically
–Hyperbaric oxygen
–Supportive care in ICU
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17
Q

Other less severe skin and soft tissue infections

A 
Impetigo 
Erisypelas 
Abscesses
Scalding skin syndrome
Diabetic foot ulcer 
Folliculitis 
Carbuncle
Furnuncle 
Acne
Bites
Surgical site infection 
**unlikely to be life threatening
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18
Q

Define impetigo

A 
•Superficial infection of skin, involving epidermis
•Pathogens
–Staph. aureus
–Group A streptococcus
•Epidemiology
–Young children
–Highly infectious
–Outbreaks in creches
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19
Q

Clinical features a/w impetigo

A

–Vesicles initially, then golden crusted lesions

–Face (mouth, nose) and extremities

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20
Q

Diagnosis of impetigo

A

Clinical

Culture of exudate

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21
Q

Treatment of impetigo

A

flucloxacillin

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22
Q

Define folliculitis
Pathogens
Diagnosis
Treatment

A

Superficial infection of hair follicles and aporcrine structures
Pathogens: Staph aureus
Diagnosis - clinical (small pruritic papules w. central pustule)
Treatment - often not required ; fluxoxacillin if persistent/ extensive

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23
Q

Define abscess
Pathogen
Treatment

A
  • An abscess is a localised collection of pus
  • Organisms: S. aureus/ polymicrobial
  • Treatment: Incision and drainage
  • Usually no role for antibiotics
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24
Q

define furuncles

Treatment

A
  • Deep inflammatory nodule, usually develops from preceding folliculitis
  • Axillae, buttocks (skin with hair follicles)
  • Spontaneous or surgical drainage
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25
Q

Define carbuncle

A

larger and deeper than furuncle
extending into subcutaneous fat
found in neck, back or thighs
pt may be systemically unwell

26
Q

Define erisypelas and pathogen and clinical features

A

Cellulitis with lymphatic involvement
•Epidemiology: Children, elderly, diabetics
•Organism: Mostly group A streptococcus
•Clinical Features:
–Painful erythematous lesion with elevated, well-defined border
–Face or legs
–May be febrile/ unwell

27
Q

Treatment for erysipelas

A

IV benzyl penicillin (PO switch to oral amoxicillin) or oral antibiotics from outset

28
Q

Scalded skin syndrome definition and clinical features

A
  • Caused by S. aureus producing exfoliative toxin
  • Affects children, neonates
  • Clinical Features: Widespread bullae, exfoliation, diffuse erythematous rash
  • Fever, hypotension, skin tenderness
  • Nikolsky sign: separation of epidermis when pressure applied to skin
29
Q

Treatment for scalded skin syndrome

A

antistaph- flucloxacillin

30
Q

Mortality rate for children and adults

A

children<3%

adults up to 60%

31
Q

Define acne
A/ pathogens
Treatment

A

•Multifactorial skin disorder
•Excess sebaceous secretion by follicles
•Blocked sebaceous gland leads to pustules
•Secondary infection with Propionibacterium spp.
–inflammation and scarring
•Treatment:
–Broad-spectrum antibiotics e.g. Doxycycline

32
Q

Animal bite a/ pathogen
Diagnosis
Treatment

A

•Pathogens: Animal mouth flora as well as staphs/ streps
•Send swab (or tissue if debriding) for culture and sensitivity
•Treatment:
Tetanus prophylaxis
Usually co-amoxiclav
•Discuss with microbiology if deep infection/ osteomyelitis or not resolving

33
Q

Human bite a/ pathogen

Treatment/management

A 
mouth flora - strep / anaerobes
•Management:
–Tetanus booster
–Antibiotics (usually co-amoxiclav)
–Consider blood-borne viruses
–Check for deep infection:
Is there osteomyelitis?
34
Q

How do you categorize diabetic foot infections?

A

Limb threatening vs non limb threatening

35
Q

Define what non limb threatening entails
a/ pathogens
treatment

A

•Cellulitis, no vascular compromise, no abscess
•Pathogens: Staphylococcus aureus, β-haemolytic streptococci
•Treatment (7-14 days):
–Flucloxacillin IV or
–Co-amoxiclav for treatment of non-severe infected diabetic ulcers

36
Q

Define limb threatening diabetic foot infections

Management

A

vascular compromise/gangrene/osteomyelitis/abscess

Management: 
Involve multidisciplinary team
•Endocrinology re glycaemic control
•Diabetes nurse specialist
•Vascular surgeons re drainage/ debridement
•Radiology: is there osteomyelitis?
•Microbiology re antibiotic choice
•Podiatrist
•?OPAT team if osteomyelitis
37
Q

Treatment for severe diabetic foot infection

A

Empiric broad-spectrum cover initially
–e.g. Piperacillin-tazobactam
(covers S. aureus & streptococci/ Gram negatives/ anaerobes)
Often ulcers are colonised with multiple organisms so swabs may not be helpful
–Tissue or bone specimens from debridement or bone biopsy are the specimens of choice to identify the pathogen(s)
–Treatment duration: approx. 14 days if just soft tissue/ 6-12 weeks if bone involvement

38
Q

SSI risk factors

A

•Very common healthcare-associated infection
•Risk Factors:
–Type of procedure
–Patient factors
–Compliance
Surgery type
–Clean (no breach of tract e.g. excision of a skin lump)
–Clean- contaminated (breach of GI/ GU/ Resp etc. tract)
–Contaminated (operating in a contaminated field e.g. post GI perforation)

39
Q

How do you classify SSI

A

superficial
deep/incisional
organ/space

40
Q

What pathogens are involved in SSI

A
  • Staphylococcus aureus (most common irrespective of type of surgery)
  • Beta-haemolytic streptococci
  • GNBs (mostly only seen post-clean-contaminated or contaminated surgery)
  • Anaerobes (post-clean-contaminated or contaminated surgery)
  • Coagulase-negative staphylococci (if prosthetic material)
41
Q

Prevention of SSI

A

•Pre-op: optimise risk factors such as diabetes mellitus
MRSA decolonisation for some procedures
•Intra-op: skin asepsis, choice/timing of antibiotic prophylaxis, surgical technique, theatre conditions, glycaemic control, oxygenation, no shaving, short duration procedure
•Post-op: removal of drains, asepsis when reviewing wound

42
Q

What are some viral skin infections

A

warts
cold sores
hand foot mouth disease

43
Q

Common cause of warts

A 
HPV 
Genital warts -STI
Common warts
•Children
•Infection by direct contact
•Palms, wrists, dorsum of hand
•DNA virus infects epidermal cells -hypertrophy &amp; multiply leading to keratinised nodular papilloma
44
Q

Treatment for HPV

A
  • Childhood: self-resolution
  • Excision, salicylate & lactic acid ointment
  • Freezing, cryoprobe or liquid nitrogen
45
Q

cold sores causative agent

A

Coldsores caused mostly by HSV-1

•May get more severe infection in immunocompromised patients

46
Q

diagnosis of cold sore

A

clinical , viral swab for PCR

47
Q

Treatment for cold sore

A

aciclovir
topical - cold sores
systemic - immunocompromised

48
Q

what causes hand foot mouth disease

A

cox sackie A and other enteroviruses

appears in children - highly contagious

49
Q

diagnosis of hand foot mouth disease

A

–Clinical
–Vesicular fluid for viral PCR
–Throat swab

50
Q

What are some fungal skin infections?

A

Candida
Ringworm
Pityriasis versicolor

51
Q

Define candidiasis

A 
•Candida spp. are normal flora in skin folds, bowel
•Candida spp. can also cause skin infections
–Erythema, plaque-like lesions
–Under breasts, in groin
–Itchy, sticky exudate
•Precipitants
–Antibiotics
–Steroids
–Pregnancy
–Immunosuppression
52
Q

Diagnosis and Tx of candidiasis

A 
•Diagnosis:
–Clinical appearance
–Swab
•Treatment:
–Topical: Clotrimazole
–Oral: Fluconazole
53
Q

Define ringworm

A/ pathogens

A

•Skin infection caused by dermatophyte fungi
•Organisms:
–Trichophyton spp.
–Epidermophyton spp.
–Microsporum spp.
•May be acquired from other humans/ animals

54
Q

Diagnosis and Treatment for ring worm

A

•Diagnosis:
–Clinical
–Skin scrapings for microscopy and culture
•Treatment:
–Tinea pedis/ Tinea corporis:
•Topical terbinafine 1st line
•Or oral terbinafine or itraconazole
–Tinea capitis:
•Oral terbinafine or itraconazole 1st line
•Plus ketoconazole shampoo to prevent spread

55
Q 
Pityriasis versicolor 
a/ pathogen 
clinical features
diagnosis
treatment
A

•Caused by Malassezia furfur (filamentous fungus)
•Rash, pale brown macules on chest, back
•Common in tropics
•Diagnosis: clinical appearance, skin scrapings
•Treatment:
–Topical ketoconazole shampoo to scalp and skin

56
Q

What are two parasitic skin infections?

A

Scabies

Lice

57
Q

Define scabies

A

Caused by scabies mite- Sarcoptes scabiei which burrows in epidermis
highly infectious caused by sharing beds for example - seen in household, boarding schools

58
Q

Clinical features of scabies

A

–Characteristic burrows in finger webs
–Itch ++ (worse at night)
–‘Norwegian scabies’: diffuse crusted lesions (same parasite but in immunocompromised patients)

59
Q

Treatment for scabies

A

topical permithrin- need to leave on overnight and can be messy
washing clothes and sheets

60
Q

Define lice
types
clinical features
treatment

A

aka pediculosis
Headlice –Common in children, outbreaks in schools, spread by direct contact
–‘Nits’ (eggs) attached to bases of hairs
–Itch/ papular lesions
–Treatment: Malathion or 1% permethrin. Fine combing to remove nits. Bathing/ washing clothes
•Body lice (Pediculus humanus)
•Pubic lice (Phthirus pubis)

CNS infections (4 decks)

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