Download Bacterial Skin Infection

1.
Direct infection of skin : impetigo, ecthyma,
folliculitis, furunculosis, carbuncle, sycosis.
2.
Secondary infection: eczema, infestations,
ulcers, …etc.
3.
Effect of bacterial toxin: staph.-associated
scalded skin syndrome (SSSS), toxic shock
syndrome.

Direct inf. of skin or subcut. tissue: Impetigo,
ecthyma, cellulitis, vulvovaginitis, perianal inf.,
strepto. ulcers, blistering distal dactylitis,
necrotizing fasciitis.

2ry inf.: eczema, infestations, ulcers, …etc.

Tissue damage from circulating toxin: scarlet
fever, toxic shock-like syndrome.

Skin
lesions
sensitivity
to
attributed
strepto.
to
allergic
antigens:
hyper-
erythema
nodosum, vasculitis.

Skin dis. provoked or influenced by strepto. inf.:
psoriasis especially guttate forms.
 Mechanical
disruption
(inflammations, abrasions)
 Prolonged use of steroids, topical or
systemic
 Presence of systemic illnesses (DM,
malignancy)
 Immunosuppression
 Malnutrition
 Anaemia
 Acute
contagious skin infection
caused mostly by staph. Aureus and
strept.
 Affects children mainly esp. in
summer times.

1- Non-bullous impetigo:
◦ Caused by staph., strept. or both organisms.

2- Bullous impetigo:
◦ Caused by staph aureus.
•
Staph. aureus or gp A stretp. (GAS) or both “mixed
infections”.
•
May arise as 1ry inf. or as 2ry inf. of pre-existing
dermatoses, e.g. pediculosis, scabies & eczemas.
•
An intact st. corneum is probably the most
important defense against invasion of pathogenic
bacteria.
•
A
thin-walled
vesicle
on
erythematous base, that soon
ruptures & the exuding serum
dries to form yellowish-brown
(honey-color) crusts that dry &
separate
leaving
erythema
which fades without scarring.
•
Regional adenitis with fever
may occur in severe cases.


Sites: Exposed parts eg.
face & extremities. Scalp
(in pediculosis). Any part
could be affected except
palms & soles.
Complications: Poststreptococcal acute
glomerulo-nephritis
“AGN” especially in
cases due to strepto.
pyogenes M. type 49.
•
Circinate impetigo:
with peripheral
extension of lesion &
healing in the center.


Crusted impetigo:
on the scalp
complicating
pediculosis. Occipital
& cervical LNs are
usually enlarged &
tender.
•
Ecthyma (ulcerative
impetigo): adherent
crusts, beneath which
purulent irregular ulcers
occur. Healing occurs
after few wks, with
scarring.

Site: more on distal
extremities (thighs &
legs).


Age: all ages, but
commoner in
childhood & newborn
(impetigo
neonatorum).
Site: face is often
affected, but the
lesions may occur
anywhere, including
palms & soles.

The bullae are less
rapidly ruptured
(persist for 2-3 days)
& become much
larger. The contents
are at first clear, later
cloudy. After rupture,
thin, brownish crusts
are formed.

Treatment of predisposing causes: e.g.
pediculosis & scabies.

Remove the crusts: by hydrogen peroxide.

Topical antibiotic: e.g. tetracycline, bacitracin,
gentamycin, mupiracin (Bactroban®), Fusidic acid
(Fucidin®).
•
Systemic antibiotics are indicated especially in the
presence of fever or lymphadenopathy, in
extensive infections involving scalp, ears, eyelids
or if a nephritogenic strain is suspected, e.g.
penicillin, erythromycin & cloxacillin.
•
Azithromycin (Zithromax®) 2 caps 500 mg daily for
3 days in adults.
•
In erythromycin-resistant S. aureus: amoxicillin +
clavulanic a. (Augmentin®) 25 mg/kg/day.

inflammatory disease of the hair follicles,
which may be infectious or non-infectious.
Superficial Folliculitis
(Bockhart’s Impetigo)

a dome-shaped
pustule at the orifice
of a hair follicle that
heals within 7-10
days.


Caused by staph
aureus and affects
mainly extremities
and scalp.
Topical steroids are a
common predisposing
factor.
Sychosis Vulgaris
•
Recurrent red follicular papules
or pustules centered on a hair,
usually remain discrete over the
beard or upper lip, but may
coalesce to produce raised
plaques studded with pustules.
•
DD: pseudofolliculitis of the
beard, T. barae.
Pseudofolliculitis

from penetration into
the skin of sharp tips
of shaved hairs.
•
It is a staphylococcal infection
similar to, but deeper than
folliculitis & invades the deep
parts of the hair folliculitis.
•
Occasionally several closely
grouped boils will combine to
form
a
carbuncle.
The
carbuncle usually occurs in
diabetic cases. The site of
election is the back of the
neck.


Cellulitis is an infection of subcutaneous
tissues.
Ersipelas: It’s due to infection of the dermis &
upper subcutaneous tissue by gp A
streptococci. The organism reaches the
dermis through a wound or small abrasion. It
is regarded as a superficial “dermal” form of
cut. cellulitis.




Erythema, heat,
swelling and pain or
tenderness.
Fever and malaise
which is more severe in
erysipelas.
In erysipelas: blistering
and hemorrhage.
Lymphangitis and
lymphadenopathy are
frequent.

Edge of the lesion:
well demarcated and
raised in erysipelas
and diffuse in
cellulitis.
•
Recurrences may lead to lymphedema.
•
Subcutaneous abscess.
•
Septicemia.
•
Nephritis.
•
Systemic antibiotics, especially penicillin, e.g.
benzyl penicillin 600-1200 mg IV/6 hrs or
cephalosporines.
•
Rest, analgesics.
Erythrasma
•
It is mild, chronic,
localized superficial
infection of skin by
Coryn. Minutissimum.
•
Clinically: sharplydefined but irregular
brown, scaly patches
•
usually localized to
groins, axillae, toe clefts
or may cover extensive
areas of trunk & limbs.
Obesity & DM may
coexist.
•
Coral red fluorescence
under wood’s light.
•
Topical treatment with azole antifungal agents
for 2 weeks or topical fucidin.
•
Erythromycin orally.
A mother brings 5 yr
old Johnny to
surgery. He has
developed this rash,
which is weeping and
crusting.
What is the diagnosis?

A highly infectious skin disease, which
commonly occurs in children.

What is the likely causative organism?


The causative organism is usually Staphylococcus
Aureus or can be strep pyogenes.
What is the treatment?

Treatment:
 Mild localised cases - use topical antibiotic
Polyfax
 Widespread or more severe infections – use
systemic antibiotics, such as flucloxacillin (or
erythromycin if penicillin allergic)
A: He does not have to be excluded from school
so long as he is on antibiotics
B: He has to remain off of school for 5 days from
the onset of the lesions
C: He must remain off of school until the lesions
have crusted or healed
D: He must remain off of school until he has
completed the antibiotic course.
A 27 year old business
man attends surgery
complaining of pain
and itching in the
beard area. You
examine him and see
the following:
What is the Diagnosis?



Inflammation of the
hair follicle.
Presents as itchy or
tender papules and
pustules at the
follicular openings.
Complications
include abscess
formation and
cavernous sinus
thrombosis if upper
lip, nose or eye
What is the causative organism?
Most common cause is Staph Aureus.
Other organisms to consider include:
Gram negative bacteria – usually in
patients with acne who are on broad spec
antibiotics
Pseudomonas (“Hot tub folliculitis”)
Yeasts (candida and pityrosporum)





What is the treatment?





Topical antiseptics such as Chlorhexidine
Topical antibiotics, such as Fusidic acid or
Mupirocin
More resistant cases may need oral antibioics such
as Flucloxacillin
Hot tub folliculitis – ciprofloxacin2
Gram negative – trimethoprim
What is the most common causative organsism?

Streptococcus – Group A Strep Pyogenes.
Others include Group B, C, D strep,
Staphylococcus Aureus, haemophilus influenzae
(children) and anaerobic bacteria (e.g Pasteurella
spp. After animal bites)






Oral Flucloxacillin or erythromycin if allergic
Co-amoxiclav in facial cellulitis
If severe systemic upset, may require admission
for IV antibiotics.
After the acute attack has settled, especially in
recurrent episodes – consider the underlying
cause
Painful red nodule
 Deeper
Staphylococcal abscess of the
hair follicle
 Coalescence of boils leads to the
formation of a carbuncle
 Treatment is with systemic antibiotics
and may need incision and drainage.
 Consider looking for underlying
causes, such as diabetes
Thank You