Skin Infections Flashcards
How can antibiotics lead to skin conditions
Kill normal flora leading to pathogenic overgrowth
Characteristics of epidermis to prevent infection
Dry - unfavourable for pathogens
Desquamates constantly
Chemical barrrier - eccrine, apocrine, and sebaceous glands, oleochemicals acid
Colonisation by non pathogenic skin flora
Dysbiosis
disruption to the microbiome resulting in an imbalance in the microbiota
Normal skin flora benefits
Produce molecules that inhibit colonisation from other species
Remains stable
Educates immune response
Why does the normal skin flora thrive on the skin better than pathogenic flora
Adapted to harsh dry environment and sparse butrients
3 main microenvironment on the skin
Moist - axilla perineum toe webs
Oily - hands face trunk
Dry - upper arms legs
Microorganism forming 90% of normal skin flora
Staphylococcus epidermidis
What pathogen causes folliculitis
Staphylococcus aureus
Pseudomonas aeruginosa - hot tub folliculitis
Folliculitis
Infection and inflammation of 1 or more hair follicles forming a pimple with a white top or barbers itch
Folliculitis treatment
Oral antibiotic
Retinoic acid
Which of folliculitis, cellulitis, erysipelas, scalded skin syndrome, impetigo, and necrotising fasciitis are superficial bacterial infections and which are deep
Superficial - Folliculitis, impetigo
Deep - cellulitis, erysipelas, scalded skin syndrome, necrotising fasciitis
What bacteria cause impetigo
Staphylococcus aureus
Streptococcus pyogenes
How does impetigo present
Red sore near mouth/nose which breaks leaking pus and forming HONEY coloured scabs
Does impetigo cause permanent scarring
Not usually
Impetigo treatment
Most cases resolve untreated in a few wks
Mild - 1% hydrogen peroxide cream
Severe/spread to other areas - Oral/topical antibiotic
Cellulitis
Infection of the dermis and subcutaneous fat
What bacteria cause cellulitis
Staphylococcus aureus
Streptococcus pyogenes
Most common cellulitis sites
Legs
Face
Erysipelas
Cellulitis of the face
Differences between cellulitis and erysipelas
C affects anywhere on body e effects face
C effects dermis and sub cut fat, e effects only dermis
E has sharper borders
C can be caused by staphylococcus aureus or streptococcus progenies, erysipelas only streptococcus pyogenes
Cellulitis and erysipelas treatment
Oral antibiotics
What bacteria causes scalded skin syndrome
Staphylococcus aureus
Scalded skin syndrome
denudation of the skin caused by exotoxin producing strains of the Staphylococcus species forming widespread fluid filled blisters which easily break
How do exotoxins of staphylococcus aureus cause scalded skin syndrome
Destroy Desmosomes holding keratinocytes in granulosum and spinosum layers together
What is Nikolskys sign and what is a condition that causes a positive sign
top layers of the skin slip away from the lower layers when rubbed
Scalded skin syndrome - twisting pencil rubber on blister breaks blister
Scalded skin syndrome treatment
Conservative - rehydration + antipyretics, usually complete resolution within 10 days
Parenteral antibiotics
Most common locations of necrotising fasciitis
Abdomen
Groin
Necrotising fasciitis treatment
Surgical debridement
Empiric antibiotics
Hyperbaric oxygen
Empiric antibiotics
antibiotics that are administered during the period prior to the receipt of blood culture and antibiotic susceptibility test results
What HPV types cause viral warts and veruccas
1, 2, 4, 7, 22, 63
3, 19 and 28 cause flat warts
How does HPV cause viral warts and veruccas
DNA virus infects basal cells of epidermis -> proliferation of infected basal keratinocytes -> lesions
What happens to untreated viral warts and veruccas
Cleared by immune system within 2 years
Viral wart and veruccas treatment
Topical salicylic acid
Fluorouracil cream
Cryosurgery
Surgical curettage
CO2 Laser treatment
What lesions are caused by herpes simplex type 1 and sometimes type 2 on the mouth and fingers
Mouth - cold sore
Finger - hepatic whitlow
Herpes virus treatment
Topical or oral antivirals
What causes Herpes zoster/shingles
Reactivation of varicella zoster virus
Where does Herpes zoster virus integrate in the body and stay dormant
DRG of sensory neurones
How does shingles present
Single wide stripe rash down one side of body
Often down 1/2 of face and tongue
Postherpetic neuralgia
Long term pain in skin affected by shingles after shingles has resolved
How long after onset of shingles can antivirals be administered to reduce severity
72hrs
What type of pathogen causes molluscum contagiosum
Virus
How are molloscum warts spread
Contact
Fomites
How long do molluscum/water warts last
Years
Molloscum/water warts treatment
Usually resolves without treatment
Severe/in genital area - OTC wart treatments, cryo surgery
What type of pathogen causes Candida albicans and pityriasis versicolour
Yeast
What conditions are caused by opportunistic growth of Candida albicans
Genital thrush
Intertrigo
Oral plaques
Paronychia
Predisposing factors to Candida albicans opportunistic infection
Moist enviro
Obesity - skin folds
Diabetes
Immunosuppression
Antibiotics
Repeated hand washing and nail biting - paronychia
Where is Candida albicans found normally
Mouth
GI tract
Overgrowth of pityrosporum orbiculare yeast causes what condition
Pityriasis versicolour
Pityriasis versicolour appearance
Brown/pink scaly patches, lighter than normal skin on darker skin, darker on Caucasian skin
How does pityriasis versicolour change throughout the year
Clears during winter, reappears during summer
What makes pityriasis versicolour more common
Hot humid climate
Heavy sweating
Pityriasis versicolour treatment
Anti fungal shampoo - ketaconazole
Selenium sulphide
Anti fungal creams
Dermatophyte
Multicellular fungal filaments or hyphae that reproduce by spore formation
Tinea
Fungal skin infection within stratum corneum, hair , or nails
Aka ringworm
3 genera of tinea
Microsporum
Trichophyton
Epidermophyton
5 sites of ringworm
Tinea corporis - body and limbs
Tinea cruris — groin
Tinea pedis - athletes foot
Tinea capitis - scalp
Onychomycosis - nails
Tinea treatment
Topical anti fungals
Oral anti fungals - severe
What causes symptoms of scabies
Allergic reaction to mites
How do scabies spread
Prolonged skin to skin contact
What is the more severe form of scabies
Crusted scabies
Scabies treatment
Permethrin, ivermectin, and crotamiton orally or washes
Scabies symptoms
Rash
Intense Pruritis worse at night
Why do scabies symptoms persist for weeks after removal of mites
Fecal matter from mites irritates skin until sloughed off
What mute causes scabies
Sarcoptes scabiei
What bacteria causes Lyme disease
Borrelia
Lyme disease first symptom
Erythema migrans - expanding red bulls eye rash at site of tick bite
Lyme disease treatment
Tick removal
Antibiotics 1-4wks
What bacteria cause leprosy
Mycobacterium leprae
Mycobacterium lepromatosis
Appearance of leprosy skin lesions
Pale/pink patches often insensitive to temperature or pain
Leprosy treatment
Rifampicin
Dapsone
Clofazimine
Leishmaniasis
Tropical disease causes by trypanosomes spread by sandflies. Cutaneous form most common
Leishmaniasis skin lesions
Open sore at site of sandfly bite which heals in a few months - 18months leaving a scar
What sepsis complication is associated with cutaneous necrosis
Disseminated Intravascular coagulation
