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imed3004 > Skin and Soft Tissue Infections > Flashcards

Skin and Soft Tissue Infections Flashcards

1
Q

How common are Skin and Soft Tissue Infections?

A

One of the most common infections in all age groups

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2
Q

Are SSTIs dangerous?

A

Most are mild but some are limb and life threatening

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3
Q

What skin layer is the first barrier to infection? What happens if this layer is disrupted?

A

Stratum corneum, Disruption allows penetration of pathogens into deeper layers

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4
Q

How can bacteria penetrate into the skin?

A

Disruption of stratum corneum

:Lymphatics

Capillary plexus allows dissemination of pathogens

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5
Q

What else does penetration of stratum corneum cause?

A

Acute inflammatory cells and chemokines

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6
Q

What happens when skin gets infected?

A

Acute inflammation is beneficial

May be exaggerated in severe infections or those producing toxins (leukostasis, venous occlusion, and tissue oedema can result)

May lead to necrosis if vascularity is compromised

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7
Q

How are skin infections diagnosed?

A

Microscopy and culture (Skin swab, tissue, and pus)

Histopathology (Biopsy)

Skin scrapings and nail clippings (Fungal)

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8
Q

Where is fungus most active in a skin infection?

A

In the advancing margin of the lesion

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9
Q

What is the most common cause of impetigo?

A

Group A strep (in non bullous)

Staph aureus in bullous

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10
Q

How is impetigo treated?

A

Topical antibiotic (mupirocin)

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11
Q

What differentiates between a baby getting scalded skin syndrome and bullous impetigo?

A

Whether or not maternal antibodies are preventing dissemination

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12
Q

How is tinea treated?

A

Topical antifungal creams

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13
Q

What tissue gets tinea?

A

Keratinized tissues (feet, body, creases, and scalp)

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14
Q

What is tinea versicolor?

A

A dermatophytosis caused by a yeast that is a normal skin commensal called malassezia furfur. (It causes hyper and hypopigmentation)

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15
Q

What is paronychia?

A

A soft tissue infection around fingernail causing a breakdown of protective barrier between nail and nail fold

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16
Q

What organism causes paronychia?

A

Staph aureus most commonly

Oral flora

Streptococci

Gram negatives

Anaerobes

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17
Q

What causes paronychia?

A

Nail biting

Finger sucking

Manicuring

Artificial nail placement

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18
Q

How is paronychia treated?

A

Warm water soaks 3 - 4 times / day

Antibiotics (Augmentin or clindamycin)

If abscess it is drained

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19
Q

When is paronychia considered chronic?

A

When symptoms are more severe and last for longer than 6 weeks

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20
Q

What are the symptoms of paronychia?

A

Inflammation

Pain

Swelling

Usually after exposure to water (dishwashers, bartenders, swimmers)

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21
Q

What causes chronic paronychia?

A

Candida albicans

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22
Q

How is chronic paronychia treated?

A

Keep dry, warm soaks

Topical antifungals

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23
Q

What is SA folliculitis?

A

Infection of hair follicles / apocrine glands by staph aureus

Itchy papules with central pustule

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24
Q

How is folliculitis treated?

A

Local measures (eg include saline compresses)

Topical antibacterials

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25
Q

What is a SA furuncle?

A

Deep inflammatory nodule, A “boil” often caused by preceding folliculitis

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26
Q

Where are furuncles typically seen?

A

In areas subject to friction/perspiration and contain follicles (neck, face, axillae, buttocks)

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27
Q

What are the risk factors for furuncles?

A

Obesity

Diabetes

Steroids

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28
Q

How are furuncles treated?

A

Application of moist heat is usually sufficient but may require incision and drainage

Antistaphylococcal antibiotics

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29
Q

What is a carbuncle?

A

Multiple furuncles fused together into a huge lump

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30
Q

What other symptoms usually accompany carbuncles?

A

High fever

Unwellness

Pain

Discharging lesions

Deep infection

31
Q

How is a carbuncle treated?

A

Requires surgical drainage and anti-staphylococcal antibiotics

32
Q

What causes erysipelas?

A

Superficial skin infection that involves cutaneous lymphatics

Bacteria most often causative is beta haemolytic group A strep

33
Q

What do erysipelas look like?

A

Fiery red, indurated skin

Clearly demarcated borders

34
Q

where is erysipelas most common?

A

Legs (85%) but also common on face (15%)

35
Q

How is erysipelas treated?

A

IV antibiotics (usually benzylpenicillin or first generation cephalosporin (Cefazolin))

36
Q

What is cellulitis?

A

Acute bacterial infection of the skin and soft tissues

Diffuse spreading erythematous rash

37
Q

What other symptoms precede the cellulitis rash?

A

Fevers and chills can precede onset of rash

Abscesses / Bullae / vesicles may form

Often there is lymphangitis

Regional lymphadenopathy or lymphadenitis (inflamed lymph nodes)

38
Q

What part of the body is most commonly involved in cellulitis?

A

2/3rds involve lower legs

39
Q

What are the predisposing factors to cellulitis?

A

Tinea pedis infection

Venous or arterial ulcers

Primary skin diseases like eczema, psoriasis, dermatitis

Minor trauma, recent surgery

Leg oedema (RHF, venous incompetence, lymphoedema)

40
Q

What causes cellulitis?

A

Rarely identified but commonly associated with beta haemolytic strep

41
Q

How is cellulitis diagnosed?

A

Swab blister fluid (results may be misleading and may come from colonizing bacteria)

Blood cultures

42
Q

How is cellulitis treated?

A

Oral antibiotics for mild cases and IV for severe cases.

Antibiotics are directed at S. aureus and beta haemolytic strep. (Flucloxacillin and 1st gen cephs)

43
Q

What can look like cellulitis that isn’t?

A

Varicose veins (venous stasis)

Erythema nodosum (drug allergies and shit like that)

Pyoderma gangenosum

44
Q

How common are surgical site infections?

A

Very common

2nd most common healthcare associated infection

45
Q

What are the costs of surgical site infections?

A

60% extra hospital days

40% extra hospital costs

> 7 days extra in-patient stay

46
Q

How are surgical site infections classified?

A

Based on how deep the infection has gone:

Superficial incisional
= skin + subcutaneous tissue

Deep incisional
= involving deeper soft tissue

Organ/Space SSI
= Involves any part of
anatomy other than incision,
opened or manipulated
during op
47
Q

What microbes cause surgical site infections?

A

Usually patient’s own flora

Staph aureus

May be hospital acquired organisms so could be antibiotic resistant (Rarely from medical staff though)

48
Q

How are surgical site infections diagnosed?

A

Bad smell or purulent discharge

Fever raised inflammatory markers

Microscopy and culture of discharge (note: beware colonisers, infecting organisms can be patient’s flora, and may require deep collection at operation)

49
Q

How are surgical site infections treated generally?

A

Drainage, debridement, washout, pus must come out completely

50
Q

How are surgical site infections treated if in superficial layer?

A

Anti-staph agent (flucloxacillin)

51
Q

How are surgical site infections treated in deep incisional cases?

A

Also cover aerobic gram negative bacilli and anaerobes (tazocin)

52
Q

What is an important thing to watch out for with surgical site infections?

A

Antibiotic resistant organisms. Liaison with ID/microbiologists is super important.

53
Q

Why are cat and dog bites dangerous?

A

They can involve deep structures

Tendon sheaths can be infected

Bones and joints can be infected

(Cat bites more dangerous because they penetrate rather than crush as is the case in dogs)

54
Q

What bacteria can be seen in cat and dog bites?

A

pasteurella multocida (gram negative, pleiomorphic)

Capnocytophaga canimorsus (gram negative, usually dogs, overwhelming infection in persons without a spleen)

Staphylococci

Streptococci

Anaerobes

55
Q

How are cat and dog bites managed?

A

Wounds are debrided and irrigated

Low threshold for antibiotic treatment because they can get really bad.

Broad spectrum antibiotics used (Tazocin or augmentin)

56
Q

What are indications for urgent treatment of cat and dog bites?

A

Delayed presentation (>8 hours)

Puncture wounds that can’t be debrided (cats > dogs)

Wounds on hands, feet or face

Wounds with underlying bone/joint/tendon involvement

57
Q

What infections are associated with fresh water lacerations?

A

Aeromonas hydrophila

58
Q

What infections are associated with fish and crayfish spikes?

A

Erysipeloid

Erysipelothrix

Rhusiopathiae

59
Q

What infections are associated with sea water exposure?

A

Vibrio species

60
Q

What infections are associated with fish tank exposure?

A

Mycobacterium marinarum

61
Q

What infections are associated with garden or soil exposure?

A

Nocardia

Mycobacterium

Sporothrix schenckii

62
Q

How are diabetic foot infections managed?

A

Surgical debridement

Aircast boots, plaster casts, orthotics

Broad spectrum antibiotics (tazocin, ertapenem)

Good glycaemic control (Better wound healing, physicians also manage other co-morbidities and risks)

63
Q

What is the difference between type 1 and type 2 necrotizing fasciitis?

A

Type 1 is polymicrobial and seen in diabetics and elderly. This is the most common type.

Type 2 is monomicrobial and may follow minor trauma and is caused by group A strep or S. aureus

64
Q

How does necrotising fasciitis take place?

A

Bacteria enter deep tissues

Developes into swelling, inflammation, thrombosis

Eventually ischaemia and necrosis

Pus tracks along fascial planes

Spread into lymphatics and bloodstream

65
Q

What are the clinical features of necrotising fasciitis?

A

Systemic toxicity

Pain

Swollen discoloured skin

Blistering then dusky skin

Cutaneous gangrene, wood-hard tissues

66
Q

How is necrotising fasciitis diagnosed?

A

Clinical suspicion if pain and systemically unwell

Lab tests: Neutrophilia, high CRP, end organ involvement such as kidneys and liver (Abnormal function tests)

Radiology (CT) - gas within thigh

Microbiology (Blood culture, skin swabs, blister fluid, surgical tissue samples)

67
Q

How is necrotising fasciitis treated?

A

It is considered a medical and surgical emergency:

Surgical debridement (aggressive repeated surgeries)

Antibiotics empiric IV therapy: Meropenem, vancomycin, clindamycin

Targeted intravenous therapy (Penicillin + clindamycin)

Adjunctive therapy (intensive care)

68
Q

What antibiotics cover all possible causes of necrotising fasciitis?

A

Meropenem: Gram positives, negatives, and anaerobes

Vancomycin: MRSA

Clindamycin: Gram positives and turns off toxin production

GAS: Penicillin + clindamycin

69
Q

What is the mortality rate of necrotising fasciitis?

A

High mortality rate (20 - 40%)

Early diagnosis may save lives

70
Q

What causes clostridial myonecrosis?

A

Penetrating injuries which consist of soil and faecal material.

Usually clostridium species specifically C. perfringens

71
Q

What type of bacteria are clostridium species?

A

Anaerobic and form spores

72
Q

What people get fournier’s gangrene?

A

SSTI found in elderly, diabetics, obese patients, and alcoholics

73
Q

What is fourniers gangrene?

A

Breach in bowel mucosa, leak into perianal area

74
Q

What structures are involved in other deep rapidly spreading SSTIs?

A

Scrotum

Penis

Perineum

These spread to abdominal wall and legs

imed3004 (50 decks)

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