Initial pilots focused on diabetes and CHF, given the prevalence of these is a 63 year old woman with diabetes who has kept her serum glucose levels under …
|Impetigo and Cellulitis |
Jennifer C Haley, MD, and Antoinette F Hood, MD
Impetigo
Impetigo is a superficial infection of the skin caused by either
streptococcal or staphylococcal organisms, or, on occasion, both It is
most commonly observed during childhood and in those living in warm, humid
climates Poor personal hygiene may predispose individuals to impetigo
Additionally, impetigo is a common complication of insect bites, scabies,
and virus infections Systemic symptoms are rare, but lymphadenopathy may
be present Nonbullous and bullous impetigo represent the primary clinical
subtypes
Nonbullous impetigo
accounts for the majority of cases of impetigo and begins as subtle
vesicles, evolves into superficial pustules and has characteristic
overlying honey-colored crusts Figure 1 Sites of predilection include
uncovered areas such as the face and less commonly, the extremities,
especially following trauma The lesions may be localized or extensive
Staphylococcus aureus and less often group A streptococcusor the two
organisms together are the predominant etiologic agents in nonbullous
impetigo in industrialized nations
Bullous
impetigo
is characterized by localized bullae arising on normal skin Figure 2 The
bullae are easily ruptured and form shallow erosions with an adjacent
yellow-brown crust Bullous impetigo is typically caused by phage group II
Staphylococcus aureus Streptococcus pyogenes is a rare cause of bullous
impetigo in the United States and Europe, but may be a common cause in
developing countries The bullous lesion is caused by an exfoliativetoxin
produced by the bacteria that causes cleavage within the granular cell
layer of the epidermis In children who lack antibodies or in adults with
immunodeficiency or renal failure, systemic absorption of this toxin can
cause the staphylococcal scalded skin syndrome, a generalized eruption
characterized by painful erythema and superficial skin separation
Children, as opposed to adults, usually do not appear seriously ill
In both forms of impetigo, superficial skin cultures confirm the presence
of the responsible bacterial organisms Neither S aureus nor S pyogenes
is part of the normal skin flora Organisms may be spread from infected to
uninfected persons or bacterial colonization may first occur in the nose
and then spread to skin, as S aureus is
present in the nares of
approximately 20 to 30 of the population Topical mupirocin is an
effective therapy for localized nonbullous impetigo whereas systemic
penicillinase-resistant antibiotics are recommended for bullous impetigo
and widespread nonbullous impetigo
Cellulitis
Cellulitis
represents an infection of the soft tissue and may be caused by group A
beta hemolytic Streptococcus or Staphylococcus aureus It is often
associated with impaired lymphatic drainage and may be seen in patients who
have undergone surgical procedures such as lymph node dissections or
saphenous vein harvesting for coronary artery bypass grafts Local trauma,
abrasions and dermatoses such as stasis dermatitis and tinea pedis are
other predisposing factors Cellulitis is a common complication of
intravenous drug abuse
Clinically, cellulitis is characterized by an area of rapidly spreading
erythema The borders are less distinct than in erysipelas see below and
areas of involvement are warm to touch Associated symptoms include
tenderness, fever, malaise and an elevated white blood cell count Facial
cellulitis in children is most commonly caused by Haemophilus influenzae
Usually there is extensive
reddish-blue, unilateral swelling involving the
cheek or periorbital area Figure 3 The cutaneous findings often follow
an upper respiratory tract infection However, there has been a significant
decrease in the incidence of this form of cellulitis since the introduction
of the H influenzae vaccine
Erysipelas
is a distinctive variant of cellulitis that involves the lymphatic vessels
and superficial layers of the skin; it is caused by group A
streptococcusand rarely, S aureus Erysipelas can be distinguished from
cellulitis by its sharp margins and its plaque-like elevation of involved
skin The legs and face are the most common sites of involvement and the
cutaneous findings are often preceded by fever, chills, nausea, vomiting,
headache and arthralgias Recurrences of both erysipelas and cellulitis are
fairly common
In most patients, the diagnosis of cellulitis or erysipelas is made on the
basis of clinical findings A Gram stain of a tissue aspirate or skin
biopsy specimen and blood cultures can sometime provide additional useful
informationIn immunocompromised hosts, tissue cultures of skin may prove
helpful For adults, treatment with systemic antibiotics that offer
coverage for both
staphylococcal and streptococcal organisms is
recommended Children between the ages of 6-36 months should be covered for
H influenzae
Necrotizing fasciitis
is an infection of subcutaneous tissue that results in progressive
destruction of the fascia and fat Given the life-threatening nature of
this disease, the responsible organisms are commonly known as flesh-eating
bacteria, and typically include group A streptococcus or a mixture of
facultative aerobic and anaerobic bacteria The extremities are the most
common sites of involvement If this disease is not recognized and treated
promptly, it can rapidly progress and result in shock and multi-organ
failure Predisposing factors for necrotizing fasciitis include penetrating
injuries, burns, surgical procedures, diabetes mellitus, childbirth, and
even minor cuts The clinical manifestations of this infection include
erythema, edema and pain followed by a dusky blue discoloration of the skin
or the formation of bullae, which rapidly become hemorrhagic Fulminant
gangrene manifesting as myonecrosis and spread of the disease along fascial
planes may then occur, unless there is rapid intervention
It is often difficult to distinguish
necrotizing fasciitis from cellulitis
In its early stages, a frozen section of a biopsy specimen examined for
organisms may be useful in making the diagnosis In addition, a Gram stain
and culture of a biopsy specimen may help establish a definitive diagnosis
However, if the diagnosis of necrotizing fasciitis is suspected, these
procedures should not delay appropriate treatment and surgical exploration
Preoperatively,magnetic resonance imaging may be useful in determining the
depth of involvement Treatment includes both surgical debridement of
necrotic tissue and intravenous antibiotics Poor prognostic factors
include: 1 age greater than fifty years; 2 underlying diabetes mellitus
or peripheral vascular disease; 3 delay of diagnosis and surgical
debridement by greater than a week; and 4 involvement of the trunk
References
1 1 Bisno AL, Stevens DL Current Concepts: Streptococcal infections of
skin and soft tissues N Engl J Med 1996;334:240-245
2 2 Hirschmann JV Bacterial infections of the skin In:Principles and
Practice of Dermatology Sams WM Jr,Lynch PJ eds Second Edition,
Churchill-Livingstone: New York, 1996, pp79-88
3 3 Lee PK, Zipoli MT, Weinberg AN,
Swartz MN, Johnson RA Pyodermas:
Staphylococcus aureus, streptococcus,and other gram-positive bacteria
In: Fitzpatricks Dermatology in General Medicine Freedberg IM, et
al edsSixth Edition, McGraw-Hill: New York, 2003, pp 1843-1855
4 4Weinberg AN,Swartz MN, Tsao H,Johnson RA Soft tissue infections:
erysipelas, cellulitis,gangrenous cellulitis and myonecrosis In:
Fitzpatricks Dermatology in General Medicine Freedberg IM, et al
edsSixth Edition, McGraw-Hill: New York, 2003, 1883-1895
Figure Legends
Figure 1 Impetigo contagiosa Honey-colored crusted lesions on the face
of a young adult National Library of Dermatologic Teaching Slides
Figure 2 Bullous impetigo Intact vesicles and blisters on otherwise
normal appearing skin National Library of Dermatologic Teaching Slides
Figure 3 Cellulitis due to Hemophilus influenza Prominent edema of the
upper and lower eyelids with faint erythema Left Ill-defined erythema on
the cheek of an infant Right National Library of Dermatologic Teaching
Slides
Questions - Impetigo and Cellulitis
1 A
4-year-old girl develops vesicles with honey-colored crusts around her
nose The most likely organism is:
A Streptococcus pyogenes
B Staphylococcus aureus
C Haemophilus influenzae
D Pseudomonas aurginosa
E Mixed bacterial flora
2 A 50-year-old man with renal failure develops blisters over his stomach
followed by widespread erythema and superficial sloughing of his skin
Culture of lesions will show:
A Streptococcus pyogenes
B Staphylococcus aureus
C Haemophilus influenzae
D Pseudomonas aurginosa
E No bacteria
3 Following a motor vehicle accident, a 22-year-old woman develops severe
pain, swelling and a dusky blue discoloration of her right arm What is
your diagnosis?
A Erysipelas
B Cellulitis
C Impetigo
D Necrotizing fasciitis
E Undetected fracture
4 Predisposing factors for the development of necrotizing fasciitis
include:
A Burns
B Surgical procedures
C Diabetes mellitus
D Childbirth
E All of the above
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|Answers - Impetigo and Cellulitis |
1 A 4-year-old girl develops vesicles with honey-colored crusts around her
nose The most likely organism is:
A Streptococcus pyogenes
B Staphylococcus aureus
C Haemophilus influenzae
D Pseudomonas aurginosa
E Mixed bacterial flora
Answer: B Staphylococcus aureus
2 A 50-year-old man with renal failure develops blisters over his stomach
followed by widespread erythema and superficial sloughing of his skin
Culture of lesions will show:
A Streptococcus pyogenes
B Staphylococcus aureus
C Haemophilus influenzae
D Pseudomonas aurginosa
E No
bacteria
Answer: E No bacteria
3 Following a motor vehicle accident, a 22-year-old woman develops severe
pain, swelling and a dusky blue discoloration of her right arm What is
your diagnosis?
A Erysipelas
B Cellulitis
C Impetigo
D Necrotizing fasciitis
E Undetected fracture
Answer: D Necrotizing fasciitis
4 Predisposing factors for the development of necrotizing fasciitis
include:
A Burns
B Surgical procedures
C Diabetes mellitus
D Childbirth
E All of the above
Answer: E All of the above
Source:cdc.gov
