Lecture 23C - Skin Infections Flashcards
What is the cause of acne vulgaris?
blockage of the psilosebaceous unit by propionium bacterium acnes can allow infection and formation of pustules
What are the symptoms of acne?
if the infection is severe and the hair follicle ruptures, scarring can ensue
What does colonisation of the blocked psilosebaceous unit cause?
formation of whiteheads, blackheads and pustules
Treatment of acne vulgaris?
depending on severity
topical benzoyl preoxide
tetracycline might be considered if symptoms are severe
What are the two most common bacteria causing skin infection?
staphylococcus aureus and streptococcus pyogenes
What are vesicles?
smaller fluid filled blisters the size of a pin head (<0.5m in diameter)
What are bullae?
larger fluid filled blister-like eruptions around 1cm (>0.5cm)
What is impetigo?
bacterial infection in the skin which commonly affects face or extremities following injury
What can form with impetigo?
bullae and/or vesicles can form, very contagious
Causative factors of impetigo?
usually caused by S aureus and S pyogenes
Symptoms of impetigo?
non-bullous type has pinhead pustules on red skin which erupt to give yellow-brown crust after skin injury (around 70% of cases)
Bullous type of impetigo?
has larger blisters which release a clear yellow liquid to leave a golden yellow crust (usually S aureus on intact skin)
Treatment of impetigo?
topical treatment with bacitracin or mupirocin
although resistance in some areas
care in playgroups to avoid spreading
often resolves spontaneously
What causes ecthyma?
often progresses from untreated impetigo
poor hygiene, poor ventilation of skin, insect bites, immunocompromised conditions
What is ecthyma commonly associated with?
S pyogenes and S aureus, however other bacterial species can be associated
Signs of ecthyma?
infection penetrates to deeper layers of the skin causing the appearance of painful ulcers
Treatment of ecthyma?
warm compress and antibiotics e.g. dicloxacillin
Folliculitis causes?
infection of hair follicles by S aureus
often affects beards, armpits and back of the neck
Symptoms of folliculitis?
red pustules (furuncles) form and eventually rupture in a few days
Treatment of folliculitis?
should be self limiting
topical clindamycin and erythromycin on affected areas if necessary and antibacterial soap
larger abscesses (carbuncles) may need to be surgically drained
Causes of erysipelas?
involved lymphatic vessels
often caused by S pyogenes and cellulitis by S aureus (inc. MRSA)
What can erysipelas cause?
systemic illness if untreated by passing through lymphatic vessels
Signs and symptoms of erysipelas and cellulitis?
pain ful, warm, red swelling which forms a well defined plaque
Treatment of erysipelas?
penicillin
Treatment of cellulitis?
dicloxacillin
What is erysipelas also known as?
St Anthony’s fire due to red borders round infection
What happens in cellulitis?
the infection has penetrated into subcutaneous tissue
Borders of cellulitis infection?
not well defined, much less than erysipelas
What can cellulitis lead to?
sepsis, requires antibiotic treatment and consideration of hospital admission
What is necrotizing fasciitis?
infection of subcutaneous tissue which can occur after surgery or trauma
What is necrotizing fasciitis caused by?
S pyogenes alone but often involves a mixture of bacteria
Symptoms of necrotizing fasciitis?
starts with war red skin but lesion rapidly expands vertically and horizontally
tissue becomes dark, pustular then necrotic *blackened areas where tissue as died) with gengrene
Treatment of nectrozing fasciitis?
fatal without prompt treatment
surgical intervention required along with parenteral antibiotics such as gentamicin and clindamycin
What happens if the infection becomes gangrenous?
no option other than to remove the leg
Why do physicians mark out infections sometimes?
to make sure it is not progresing
What is lupus vulgaris?
brown nodules on the face caused by mycobacterium tuberculosis
Lugus valgaris treatment?
requires susceptible antibiotic drug combinations
Leprosy?
caused by mycobacterium leprae and lepromatosis
Symptoms of leprosy?
brown nodules, white patches on skin and neuropathy
Treatment of leprosy?
requires long term antibiotic treatment
What is the most common infectious fungus?
trychophyton rubrum
What do most fungal infections involve?
trichyphyton, microsporum and epidermophyton
What are the forms of tinea?
tinea pedis
tinea cruris
tinea capitis
tinea corporis
tine unguium (onychomycosis)
What does tinea pedis cause>
athlete’s foot
What does tinea cruris cause?
jock itch in the groin
What does tinea capitis cause?
cradle cap in babies - white coating on the skull of babies
What does tinea corporis cause?
ringworm on the trunk
What does tinea unguium cause?
infection of nails (60% of people over 80)
Treatment of tinea?
terbinafine, clotrimazole or econazole
What are cutaneous fungal infections given the name?
tinea or ringworm
How many adults suffer from tinea pedis?
70%
split skin can cause opportunity for secondary bacterial superinfections to take place
What might be preferred treatment for some types of tinea?
systemic antifungals
What is tinea versicolor?
caused by the widespread yeast malassezia furfur, more common in hot climates
infection of malassezia furfur in the outer layer of the epidermis
Symptoms of tinea versicolor?
results in lightened or darkened pigmentation in patches of the skin in upper body and limbs
Treatment of tinea versicolor?
zinc or selenium sulfide shampoo or topical antifungal agents
How long can it take for normal pigmentation to return?
6 weeks and in this time there can be patches of discoloured skin
What is candidiasis caused by?
the yeast candida albicans, a normal member of the gut flora and genitourinary tract in humans
Symptoms of candidiasis?
inflamed and itchy membranes in moist mucous tissues such as mouth, vagina, armpits etc
What can candidiasis of the mouth be associated with?
an immunocompromised condition or the use of dentures which have not been disinfected properly
Treatment of candidiasis?
topical antifungals, plus possibility of systemic antifungals such as ketaconazole, fluconazole
Herpes simples (1) and cold sores?
85% of the population have antibodies to HSV type 1
virus residues in the dorsal ganglia, until reactivated
Symptoms of HSV 1?
self limiting eruption around mucous membranes of the mouth
Treatment of HSV1?
aciclovir in a cold cream formulation
but cold sores are usually self limiting
Varicella zoster virus?
chicken pox and shingles
during chicken pox, virus travels to sensory ganglia where it remains for life
Symptoms of varicella virus?
pain and paresthesia in an affected dermatome
How does the varicella virus erupt in later years?
in the band of skin (dermatome) supplied by the nerve ganglion which is harbouring the virus
What can shingles cause?
pain and a sensation of tingling, itching, numbness or burning in the affected areas
Treatment of varicella zoster virus?
usually resolves with rest and analgesia, but aciclovir can be used, especially if virus is disseminated
What causes warts?
the human papilloma virus (HPV)
What are warts?
benign skin tumours caused by infection with the human papilloma virus (HPV
Appearance of warts?
dark necrotised blood vessels at the heart of the ward
Common (plane) wart?
(verucca vulgaris)
affects the hands and face and knees and can spread
Plantar wart?
verucca plantaris
grows into the skin of the sole of the foot and can cause pain
Treatment of warts?
will often resolve spontaneously but can be removed by some form of chemical (salicylic acid), cry or surgical ablation
What can some strains of warts increase?
the risk of cervical cancer, but there is not a vaccine against this (Gardasil)
Treatment of warts in children?
waiting to see if they go away
Molluscum contagiosum?
a pox virus transmitted by direct skin contact
Symptoms of M contagiosum?
hyperplasia
raised pink, pearl like, pus filled lesions with a central depression
Treatment of M contagiosum?
often resolves spontaneously but can linger in immunocompromised patients (for months or sometimes yeasrs)
Treatment of M contagiosum in children?
treated conservatively, but broadly similar as for warts with addition of curettage and cantharidin
What is a curettage?
scooping out the virus and papule with a very tine spoon
What is cantharidine?
comes from beetles and is a blister agent
How can M contagiosum be transmitted?
skin contact but can also be sexually transmitted
Common parasitic infections?
scabies and head lice
