Bacterial Skin Infections Flashcards
What is Impetigo
Contagious bacterial skin infection
Bacteria causing Impetigo
Staph aureus
Strep pyogenes
Who normally gets impetigo
Children
Impetigo can occur as a complication of what conditions
Eczema
Scabies
Insect bites
Presentation of impetigo
Well-defined honey-coloured lesions with erythematous bases around the nose and face
Ix for impetigo
Clinical diagnosis
+/- bacterial skin culture if treatment isn’t resolving
Tx of impetigo
Localised disease:
1. topical fusidic acid
2. topical retapamulin
If MRSA - topical mupirocin
Extensive disease:
- Oral flucloxacillin
- Oral erythromycin if pen allergic
What advice should be given to children with impetigo about attending nursery/school?
Excluded from school until lesions are crusted and healed, or 48h after commencing Abx treatment
What is cellulitis
Acute bacterial infection of the dermis and subcutaneous fat
Bacteria causing cellulitis
Staph. aureus
Strep. pyogenes (group A beta haemolytic strep)
Risk factors for cellulitis
any breaks in the skin, venous insufficiency/stasis
What is erysipelas
distinct form of superficial cellulitis with notable lymphatic involvement. Raised, sharply demarcated from uninvolved skin
Presentation of cellulitis
pain, swelling, erythema, warmth, systemic upset, +/- lymphadenopathy
Ix for cellulitis
FBC, swab of lesion if surface broken, blood cultures
Mx cellulitis
Flucloxacillin - MSSA
If pen allergic - Doxycycline
What is folliculitis
Inflammatory process involving any part of the hair follicle
Most common cause of folliculitis
Staph. aureus
Presentation of folliculitis
erythematous papules or pustules around hair follicles
What is furunculosis
an acute deep infection of the hair follicles
2 types of furunculosis
Boil > single hair follicle
Carbuncle > collection of hair follicles
Ix for folliculitis
Gram stain
Mx folliculitis if organism unknown
Benzoyl peroxide
Mx folliculitis is MSSA
Cefalexin
Flucloxacillin
Mx MRSA cellulitis
Vancomycin
What is Bullous impetigo
Blistering impetigo - dermal inflammatory response
What can bullous impetigo progress to
Staphylococcal Scalded Skin Syndrome (SSSS)
What is Staphylococcal Scalded Skin Syndrome (SSSS)
Detachment within the epidermal layer by breaking down the desmosomes, caused by the exotoxins A and B which are released by Staph. aureus
Presentation of SSSS
widespread fluid filled blisters that are easily ruptured
Nikolsky sign +
Are the mucous membranes affected in SSSS
No
Most common groups to get SSSS
children < 6 y
immunosuppressed adults
adults with renal failure
Ix for SSSS
Skin biopsy - shows intradermal separation
Histological appearance in TENS
separation along DEJ
Mx SSSS
Supportive care - rehydration, Mx of burns
Tx of primary infection
Parenteral Abx
What is necrotising fasciitis
Bacterial infection of subcutaneous tissue, spreading along fascial planes below the skin surface causing rapid tissue destruction
2 types/causes of necrotising fasciitis
- Mixed anaerobes and coliforms
2. Group A Strep infection
What does necrotising fasciitis NOT affect
the underlying muscle beneath fascia
presentation of necrotising fasciitis
pain +++, disproportionate to visible skin changes
fever
palpitations
tachycardia
hypotension
predisposing risk factors for causing necrotising fasciitis
Diabetes Mellitus Peripheral Vascular Disease Immunocompromised Chronic renal or hepatic insufficiency Herpes Zoster IVDU
How does bacteria get to the fascia in necrotising fasciitis
it is introduced to skin and soft tissue from minor trauma, puncture wounds or surgery
Ix for necrotising fasciitis
FBC, U+Es, CRP, CK, lactate
Blood + tissue cultures
Tx necrotising fasciitis
immediate surgical debridement
+
empirical broad spec Abx
e.g. IV vancomycin + IV Tazocin
what is pitted keratolysis
a superficial bacterial skin infection affecting the soles of feet and sometimes palms of hands
cause of pitted keratolysis
corynebacteria
presentation of pitted keratolysis
smelly feet
white appearance with clusters of punched-out pits
treatment of pitted keratolysis
topical Abx - erythromycin clindamycin mupirocin fusidic acid
bacteria causing syphilis
treponema pallidum (spirochaete)
how many stages of syphilis is there
3
describe primary syphilis presentation
initially macule > papule > ulcerating to form hard chancre
how long after exposure to infection does primary syphilis occur
14-21 days
describe secondary syphilis presentation
symmetrical maculopapular rash over the body, non-itchy, prominent on soles of feet and palms
generalised lymphadenopathy
constitutional symptoms
describe tertiary syphilis presentation
gummas - granulomas in skin, mucosa, bone, joints, viscera
Ix for syphilis
swab of chancre for PCR
Tx of syphilis
IM injection of benzathine benzylpenicillin
What is Lyme disease
tick-borne infection by transmission of Borriela Burgdoferi
What shape is the Borriela Burgdoferi organism
spirochaete
explain the transmission process of Lyme disease
the tick gets the spirochaete from an infected host
the infection is then transmitted to a new host via tick saliva
When is the chance of transmission of Lyme disease from an infected tick most likely to happen
after 48h
1st sign of Lyme disease
Erythema migrans - erythematous bullseye lesions
- a circular rash beginning at the site of the tick bite that gradually expands
How soon does Erythema migrans resolve in Lyme disease
a few days after Tx
if untreated resolves within a month
How soon does Erythema migrans appear after tick bite in Lyme disease
around 14 days after the bite
2nd sign of Lyme disease
Borriela Lymphocytoma
- firm blush/red swelling and tender, local lymphadenopathy
Most common locations for Borriela Lymphocytoma in Lyme disease
children - earlobe
adults - nipple
Non-cutaneous late features of Lyme disease
numbness/arthralgia/facial paralysis/meningitis/arrhythmia
3rd sign of Lyme disease
Acrodermatitis Chronica Atrophicans
- blue/red discolouration progressing to atrophy
How soon does Acrodermatitis Chronica Atrophicans appear after a tick bite in Lyme disease
6/12 months - 8 years after initial infection
Tx of Lyme disease
Solitary lesion - oral doxycycline or amoxicillin 2-3wk course
Severe - IV penicillin/Ceftriaxone 14-21 days
Reaction that can be induced by Lyme disease treatment
Jarisch Herxheimer - fever, malaise, headache due to endotoxin release due to large numbers of organisms being killed
