2. Bacterial Skin infections
Intact
skin is one of the body’s defences
against infection
Normal flora (resident organisms) exist on
the skin
Normal flora become pathogenic when
transported to alternate locations
Break in the normal skin barrier
Uncomplicated skin infections usually
involve 1 or 2 pathogens
Predominant organisms for skin infection
are Staphylococcus and Streptococcus spp
2
4. A. Staphylococcus Aureus &
Streptococcal Infections
S. aureus does not normally reside on
the skin, but may be present transiently,
inoculated from colonized sites such as
the nares (30%), also axillae & vagina.
Colonization is usually intermittent; 10 to
20% of individuals have persistent
colonization
Frequent hand washing reduces the risk
of person-to-person transmission of
cutaneous pathogens.
4
6. Folliculitis
•
Folliculitis is a superficial infection of the hair
follicles characterized by erythematous,
follicular-based papules and pustules.
S. aureus is the usual pathogen, although
exposure to Pseudomonas aeruginosa in hot
tubs or swimming pools can lead to folliculitis.
usually in scalp of children
also in beard, axilla, extremities, buttocks
Causes:
Bacteria (staph.)
Yeasts (pityrosporum)
Chemical or physical injury
•
•
•
6
9. Pseudofolliculitis:
Also called “sycosis barbae”.
Deeper folliculitis of the hair follicles of the beard area in
males due to shaving.
Often the lesions are sterile & poorly respond to antibiotics.
9
11. Furuncle ( Boils )
•
It is an acute, necrotic infection/abscess of a hair
follicle (usually vellus).
•
causative agent: Staphylococcus aureus
firm, red and tender papule that becomes painful
and fluctuant pustule
developed from preceding folliculitis
deep seated
occur in areas that are subject to friction and
perspiration and contain hair follicles (vellus)
(neck, face, axillae, buttocks)
•
•
•
•
11
12.
Precipitating factors:
Poor hygiene
Stress
DM
It may recur at intervals for no apparent cause.
Such patients are carriers to the staph in the nose,
axillae & groins between the attacks.
Carriers may be treated with topical antibacterial
applied to nostrils.
They may also be helped by an antibacterial bath
additives, & a prolonged course of flucloxacillin
12
15. Carbuncle
•
•
•
•
•
•
•
causative agent: Staphylococcus aureus
extend into the subcutaneous fat in areas
covered by thick inelastic skin
more severe and painful than furuncles
multiple pustules
with fever and malaise
usually located at the nape, neck, back and
thigh
blood stream invasion may occur usually as a
result of manipulation causing osteomyelitis,
endocarditis or other metastatic foci
15
16. Carbuncle
•
Carbuncle: S.
aureus A very large,
inflammatory plaque
studded with
pustules, draining
pus, on the nape of
the neck. Infection
extends down to the
fascia and has
formed from a
confluence of many
furuncles.
16
20. Impetigo
Peak incidence aged 2-5 years
Older children and adults also afflicted
M=F
All races susceptible
Nearly always caused by B-haemolytic
streptococci and / or S. aureus
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21. Impetigo
•
•
•
•
•
Contagious Superficial infection of the epidermis
Discrete purulent lesions
Occurs on exposed areas, well localised,
frequently multiple, bullous or non bullous in
appearance initially→characteristic thick yellow
brown crusts
Deeply ulcerated form (extend into the dermis ) =
ecthyma
Systemic symptoms usually absent
21
23.
Non-bullous impetigo is caused by
S.aureus,
streptococci, or both organisms together.
In the nonbullous form the initial lesion is a
small pustule which ruptures to leave an
extending area of exudation and crusting.
The crusts eventually separate to leave
areas of erythema, which fade without
scarring.
23
28. Bullous Impetigo
Scattered, discrete,
intact thin-walled
blisters on the thigh
of a child;
Caused by strains of
S. aureus that
produce exotoxin
causing cleavage in
the superficial skin
layer
28
29. Impetigo: Treatment
topical & systemic antibiotics.
flucloxacillin or 1st gen cephalosporins are
preferred (eg cephalexin, cephradine)
29
30. Staph Scalded Skin Syndome ((lyell’s
disease):
SSSS
Is a toxin mediated epidermolytic
disease characterized initially by painful
tender erythematous skin followed by
widespread detachment of the
superficial layer of the skin
It occurs mainly in newborns and infants
<2 years, and is rare in adults.
30
31.
Etiology
Staph aureus phage group II (types 71 and
55) which produce exfoliatin toxins that
disseminates systemically.
The site of infection and production of the
toxins is remote (Not in the skin). (purulent
conjunctivitis, otitis media, omphalitis).
31
32. •
Course and prognosis
– With adequate antibiotic treatment the
superficially denuded skin heals in 3-5 days
with no scarring.
– Without therapy, death occurs due to fluid
and electrolyte loss and Sepsis
– Treatment:
– Hospitalization with IV fluid replacement and
systemic antibiotics ( Flucloxacillin or 1st
generation cephalosporins)
32
33. SSSS
•
Staphylococcal
scalded-skin
syndrome In this
infant, painful, tender,
diffuse erythema was
followed by
generalized epidermal
sloughing and
erosions. S. aureus
had colonized the
nares with perioral
impetigo, the site of
exotoxin production.
33
35. Ecthyma
lesion of neglect—develops in
excoriations; insect bites; minor trauma
in diabetics, elderly patients, soldiers,
and alcoholics. ( more common in
debiliated patients ).
Caused by strep.pyogenicus & staph
Usually on upper posterior thighs or
buttocks
Vesiculopustule -erosion-ulcer covered
by a crust
Treatment (topical or Oral Abx)
35
39. Infected eczema :
Eczema with exudates, crusts & inflammation.
The cause is due to persistent scratching & using
topical steroids.
Cause: staph & strept.
Treatment: weaker topical steroids & topical
antibiotics, systemic antibiotics if necessary.
Commonly in atopic eczema.
39
41. Erysipelas
•
•
•
•
•
Diffuse spreading skin infection without
underlying suppurative foci
Red tender lesions raised above level of
surrounding skin, clear line of demarcation
of involved tissue.
Usually involves lower extremities,
classically butterfly area of face
The patient looks ill & feverish.
Cavernous sinus thrombosis is an
important complication on face
involvement.
41
42. Erysipelas
More common among infants, young
children, and older adults
Almost always caused by B-haemolytic
strep (usually Group A, but can be
caused by serogroups C or G)
Rarely Group B streptococci or S.
aureus be involved, also H.influenzae
type b
An area of broken skin forming portal of
entry, may be found ( ex. Tenea pedis )
42
43. Erysipelas
•
Erysipelas of face:
group A
streptococcus
Painful, well-defined,
shiny, erythematous,
edematous plaques
involving eyelids,
cheeks, and the nose
of an elderly febrile
male. On palpation the
skin is hot and tender.
Portal of entry was
conjunctivitis
43
44. Erysipelas
•
Erysipelas of leg: S.
aureus The lower leg
is red, hot, tender,
and edematous.
Erythematous plaque
is well defined. The
infection is recurrent
with interdigital tinea
pedis as the portal of
entry.
44
47. Cellulitis
Also a diffuse spreading skin infections
without underlying suppurative foci
Extends more deeply than erysipelas to
involve subcutaneous tissues and lacks
distinctive anatomical features as
erysipelas
47
49. Cellulitis
Usually due to Beta Hemolytic
streptococcus (commonly Gp A, less
commonly from B, C or G) , also
H.influenzae type b in childern
S. aureus less frequently, often result
from penetrating trauma including
injection sites
49
50. Cellulitis
•
Cellulitis of cheek:
H. influenzae
Erythema and edema
of the cheek of a
young child,
associated with fever
and malaise. H.
influenzae was
isolated on culture of
the nasopharynx
50
51. Cellulitis
•
Cellulitis of arm: S.
aureus Cellulitis with
abscess formation
and blistering
occurred as a
puncture wound
infection in a
construction-site
worker. The lower
arm had to be
debrided down to the
facia and grafted.
51
52. Cellulitis: Investigation &
Management
Blood cultures: low yield unless very severe
Needle aspirations / skin biopsies unnecessary in
typical cases
D.DX: Acute dermatitis, gout, herpes zoster,
acute lipodermatosclerosis
Therapy: targeted at streptococci +/- S. Aureus
Flucloxacillin, clindamycin, erythromycin all
suitable unless resistance common in community
Severely ill pts: flucloxacillin, 1st gen cephalosporin
Penicillin allergy: Clindamycin or vancomycin. In
uncomplicated cases, treat for 5 days
52
53. Necrotizing Fasciitis
a rare subcutaneous infection that tracks along
fascial planes and extends well beyond superficial
signs of infection
53
54. Necrotizing Fasciitis
Caused by: S. pyogenes, S.aureus, and
anaerobic streptococci
Community acquired
Present in the limbs
Underlying cause: diabetes, arteriosclerotic
disease, venous insufficiency
Mortality is high: 50-70% in pts with
hypotension and organ failure
54
56. Necrotizing Fasciitis: Diagnosis
Suspect when there is:
Failure to respond to initial antibiotic
therapy
Hard wooden feel of subcutaneous
tissues
Systemic toxicity
Bullous lesions
Skin necrosis or ecchymosis
Appearance of tissue at operation,
samples for culture best obtained from
deep tissues
Blood culture results
56
57. Necrotizing fasciitis: Treatment
Surgical intervention: major therapeutic
modality
Usually returns 24-36 hrs after first
debridement, daily thereafter till no need
for further debridement
Aggressive fluid administration
Antimicrobial therapy until operative
procedures no longer needed, obvious
clinical improvement and fever absent for
48-72 hours
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58. Scarlet Fever
Scarlet fever (SF) is an acute infection of the tonsils, skin, or other
sites by an exotoxin-producing strain of Streptococcus
pyogenes, associated with a characteristic toxigenic
exanthem.
Epidemiology and Etiology
Age of Onset
Children.
Incidence
Much less than in the past.
Etiology
Usually group A -hemolytic S. pyogenes (GAS). Uncommonly
S. aureus.
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59. History
• Incubation Period
Rash appears 1 to 3 days after onset of
infection.
• Exposure
Household member(s) may be a
streptococcal carrier
• Site of Infection
Pharyngitis; tonsillitis. Infected surgical or
other wound. Impetiginous skin lesion.
59
60. Physical Examination / Skin Lesions
exanthem Finely punctated erythema
has become confluent
(scarlatiniform);
petechiae can occur and have a
linear configuration within the
exanthem in body folds (Pastia's
line).
Desquamation: Exanthem fades
within 4 to 5 days and is followed
by browny desquamation on the
body and extremities and by
sheetlike exfoliation on the palms
and soles
60
61. Physical Examination / Mucous Membranes
white and red strawberry
tongue Bright red tongue
with prominent papillae on
the fifth day after onset of
group A streptococcal
pharyngitis in a child. The
white patches at the back
of the tongue represent
residuals of the initial white
strawberry tongue.
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62. Management
Symptomatic Therapy
Aspirin or acetaminophen for fever and/or pain.
Systemic Antimicrobial Therapy
Penicillin is the drug of choice because of its
efficacy in prevention of rheumatic fever. Goal is to
eradicate throat carriage.
For penicillin-allergic patients:
Erythromycin
Azithromycin
Clarithromycin
Follow-Up
Reculture of throat recommended for individuals with
history of rheumatic fever or if a family member has
history of rheumatic fever.
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Ecthyma: ulcerative pyoderma of the skin caused by group A beta-hemolytic streptococci
Omphalitis: infection of the umbilical cord stump
Initially, findings of acute cellulitis (local redness, edema, heat, and pain in the involved area), typically occur on an extremity. Characteristic findings appear within 36 to 72 h after onset: the involved area becomes dusky blue in color; vesicles or bullae appear containing initially yellowish, then red-black fluid. Infection spreads rapidly along fascial planes resulting in extensive necrotic sloughs . Bullae rupture, and extensive, sharply demarcated cutaneous gangrene develops. At this point the area may be numb, and the black necrotic eschar (Fig. 22-28) with surrounding irregular border of erythema resembles a third-degree burn. The eschar sloughs off by the end of 1 week to 10 days. Peripheral areas of involvement develop about the initial site of infection.