skin infections

Question 1

What are the three skin and soft tissue infections?

Answer 1

1. Cellulitis
2. Necrotising fasciitis
3. Gas gangrene

Question 2

Define cellulitis

Answer 2

Acute infection of skin involving subcutaneous tissue

Precipitant is usually a break in skin

Question 3

Causes of cellulitis?

Answer 3

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

Question 4

What are the risk factors for cellulitis?

Answer 4

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

Question 5

What are the clinical features of cellulitis?

Answer 5

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

Question 6

How do you manage cellulitis

Answer 6

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

Question 7

Define necrotising fasciitis

Answer 7

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

Question 8

Pathogens involved in necrotising fasciitis?

Answer 8

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

Question 9

Clinical features of necrotiising fasciitis

Answer 9

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%)

Question 10

Management of necrotising fasciitis

Answer 10

•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

Question 11

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

Answer 11

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

Question 12

What is another name for gas gangrene?

Answer 12

Clostridia myonecrosis

Question 13

Define gas gangrene

Answer 13

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)

Question 14

Clinical features of gas gangrene

Answer 14

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

Question 15

How do you diagnoses gas gangrene?

Answer 15

CT/X ray - gas in tissue

Culture on blood AND wound swab/blister fluid/ tissue

Question 16

Treatment for gas gangene

Answer 16

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

Question 17

Other less severe skin and soft tissue infections

Answer 17

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

Question 18

Define impetigo

Answer 18

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

Question 19

Clinical features a/w impetigo

Answer 19

–Vesicles initially, then golden crusted lesions

–Face (mouth, nose) and extremities

Question 20

Diagnosis of impetigo

Answer 20

Clinical

Culture of exudate

Question 21

Treatment of impetigo

Answer 21

flucloxacillin

Question 22

Define folliculitis
Pathogens
Diagnosis
Treatment

Answer 22

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

Question 23

Define abscess
Pathogen
Treatment

Answer 23

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

Question 24

define furuncles

Treatment

Answer 24

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

Question 25

Define carbuncle

Answer 25

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

Question 26

Define erisypelas and pathogen and clinical features

Answer 26

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

Question 27

Treatment for erysipelas

Answer 27

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

Question 28

Scalded skin syndrome definition and clinical features

Answer 28

* 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

Question 29

Treatment for scalded skin syndrome

Answer 29

antistaph- flucloxacillin

Question 30

Mortality rate for children and adults

Answer 30

children<3% | adults up to 60%

Question 31

Define acne A/ pathogens Treatment

Answer 31

•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

Question 32

Animal bite a/ pathogen Diagnosis Treatment

Answer 32

•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

Question 33

Human bite a/ pathogen | Treatment/management

Answer 33

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

Question 34

How do you categorize diabetic foot infections?

Answer 34

Limb threatening vs non limb threatening

Question 35

Define what non limb threatening entails a/ pathogens treatment

Answer 35

•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

Question 36

Define limb threatening diabetic foot infections | Management

Answer 36

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 ```

Question 37

Treatment for severe diabetic foot infection

Answer 37

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

Question 38

SSI risk factors

Answer 38

•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)

Question 39

How do you classify SSI

Answer 39

superficial deep/incisional organ/space

Question 40

What pathogens are involved in SSI

Answer 40

* 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)

Question 41

Prevention of SSI

Answer 41

•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

Question 42

What are some viral skin infections

Answer 42

warts cold sores hand foot mouth disease

Question 43

Common cause of warts

Answer 43

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

Question 44

Treatment for HPV

Answer 44

* Childhood: self-resolution * Excision, salicylate & lactic acid ointment * Freezing, cryoprobe or liquid nitrogen

Question 45

cold sores causative agent

Answer 45

Coldsores caused mostly by HSV-1 | •May get more severe infection in immunocompromised patients

Question 46

diagnosis of cold sore

Answer 46

clinical , viral swab for PCR

Question 47

Treatment for cold sore

Answer 47

aciclovir topical - cold sores systemic - immunocompromised

Question 48

what causes hand foot mouth disease

Answer 48

cox sackie A and other enteroviruses | appears in children - highly contagious

Question 49

diagnosis of hand foot mouth disease

Answer 49

–Clinical –Vesicular fluid for viral PCR –Throat swab

Question 50

What are some fungal skin infections?

Answer 50

Candida Ringworm Pityriasis versicolor

Question 51

Define candidiasis

Answer 51

``` •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 ```

Question 52

Diagnosis and Tx of candidiasis

Answer 52

``` •Diagnosis: –Clinical appearance –Swab •Treatment: –Topical: Clotrimazole –Oral: Fluconazole ```

Question 53

Define ringworm | A/ pathogens

Answer 53

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

Question 54

Diagnosis and Treatment for ring worm

Answer 54

•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

Question 55

``` Pityriasis versicolor a/ pathogen clinical features diagnosis treatment ```

Answer 55

•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

Question 56

What are two parasitic skin infections?

Answer 56

Scabies | Lice

Question 57

Define scabies

Answer 57

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

Question 58

Clinical features of scabies

Answer 58

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

Question 59

Treatment for scabies

Answer 59

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

Question 60

Define lice types clinical features treatment

Answer 60

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)