Skin and Soft Tissue Infections Guide

Skin and Soft Tissue
Infections
 Lecture objectives : Define and describe
common infections that affect the skin, soft
tissues, bones and joints.
 Recognize the clinical manifestations and
differential diagnosis of infections that involve
the skin, soft tissues, bones and joints.
 Comprehend the general principles of
antimicrobial therapy, i.e. organism-based
treatment and empirical therapy.

Infections
 Skin and soft tissue infections can be
caused by either direct penetration of a
pathogen or by hematogenous spread
of the pathogen from the initial site.
 Skin and soft tissue infection can be
classified on the basis of the anatomic
level at which infection, i.e., either
superficial or deep.

Symptoms of skin infections
 Skin inflammation that begins in a
small area and spreads. This
includes:
 Redness
 Pain or tenderness
 Swelling
 Warmth
 Blisters
 A red streak (possibly)

Symptoms of skin infections
 A red streak (possibly)
 Swollen lymph nodes
 Fever or chills
 Fatigue
 Irritability
 Loss of appetite, nausea, or
vomiting

Infections
 Infections by either group A streptococci,
staphylococci or anaerobic bacteria are
particularly important causes of more serious
forms of disease.
 Classification of clinically distinguishable
cutaneous infections caused by streptococcus
pyogenes: Impetigo, Ecthyma, Cellulitis,
Erysipelas and Necrotizing fasciitis.

Infections
 Impetigo is a superficial infection of the skin
caused by group A streptococci or S. aureus
it begins as a transient vesiculopustular lesion
that quickly ruptures and exudes serous fluid
which then dries to form a characteristic dry
thick honey (golden) crust.
 A bullous type, particularly in children,
suggest bullous impetigo caused by S.
aureus.
 Ecthyma is a deeper form of impetigo with
ulceration and scarring, commonly on the
legs and associated with trauma or debility.

Infections
 Differential diagnosis : the differential
diagnosis of impetigo includes contact
dermatitis, herpes simplex and varicella.
 Contact dermatitis may be suggested by the
history or by linear distribution of the lesions,
and culture should be negative for
staphylococci and streptococci.
 Herpes infection usually presents with
grouped vesicles or discrete erosions and may
be associated with a history of recurrences.
Viral culture and Tzanck smears of the
lesions are positive.

Infections
 Treatment : topical antibiotics are not as
effective as systemic antibiotics. Two percent
mupircon ointment (Bactroban) used three
times daily after hygenic measures for 10
days, may be effective for limited disease.
 Crusts and weepy areas may be treated with
with compresses, and washcloths and towels
must be segregated and washed separately.

Infections
 For large areas, fever or toxicity- or if there is
concern a nephritogenic strain may be
causative, then systemic antibiotics should be
given.
 Penicillin is the drug of choice for impetigo,
and if S. aureus is suspected a penicillinase-
resistant penicillin such as cloxacillin or
dicloxacillin, 250mg orally qid daily, is usually
effective and should be used.Erythromycin
250mg four times daily, is a reasonable
alternate for the penicillin-allergic patient.

Infections
 Erysipelas is a superficial form of cellulitis that
classically occurs on the cheek; It is almost
always caused by group A streptococci. This
infection is seen primarily in children and the
elderly.
 Erysipelas is a bright red to violaceous raised
lesion that is sharply demarcated and
expands rapidly in a centrifugal fashion.
 Vesicles or bullae may occur. Fever, pain,
malaise and chills are generally present, but
bacteremia is uncommon.

Infections
 Treatment with IV penicillin 1-2 million units
every 4 hours and clindamycin 900mg q8h IV
is curative, but defervescene is gradual.
 Cellulitis, a diffuse spreading infection of the
subcutaneous tissue, may be due to one of
several organisms, usually gram-positive
cocci, though gram-negative rods (E. coli,
Pasturella multocida, Erysipelothrix and
Vibrio) may also be responsible.

Infections
 Cellulitis is said to occur after a break in
the skin, but this is often not apparent.
 The lesion is hot and red and linear
streaks of erythema and tenderness
indicate lymphatic spread
(lymphangitis).
 Regional lymph node enlargement and
tenderness are common.

Infections
 Progression and systemic symptoms are
quite variable, but most patients are
febrile.
 In cases of venous stasis, the only clue
to cellulitis may be a new localized area
of tenderness.

Skin and Soft Tissue Infection

Infections
 Two potentially life threatening entities that
can mimic cellulitis, a painful, red, swollen
leg. They are deep venous thrombosis and
necrotizing fascitiis.
 The presence of a positive Homans sign or
palpable venous cord may suggest DVT, but
these are insensitive signs.
 If clinical suspicion is high an imaging
modality should be utilized for DVT.

Infections
 The diagnosis of necrotizing fasciitis should
be suspected in a patient with a toxic
appearance, bullae, crepitus or anaesthesia of
the involved skin, overlying skin necrosis, and
laboratory evidence of rhabdomyolysis or
DIC.
 While these findings may be present with
severe cellulitis and bacteremia, it is essential
to rule out necrotizing fasciitis because rapid
surgical debridement is essential.

Infections
 Therapy with parenteral antibiotics, with a
penicillinase-resistant pcn, IV nafcillin or
oxacillin 2gm q4h or cefazolin 1gm q8h IV or
unasyn 3gm q6h, usually suffices.
 In mild cases or following the initial
parenteral therapy, dicloxacillin or cephalexin,
500 mg qid orally for 7-10 days, is usually
adequate.

Infections
 Necrotizing fasciitis, pyomyositis and
myonecrosis are examples of deeper
infections of the skin and soft tissues.
 Necrotizing fasciitis is an uncommon severe
infection of the subcutaneous tissue that
results in destruction of fascia and fat.
 It is grouped under the classification of
necrotizing soft tissue infections that include
clostridial cellulitis, synergistic necrotizing
cellulitis (Meleney’s gangrene), and gas
gangrene.

Infections
 necrotizing fasciitis due to group A
streptococcus previously called
streptococcal gangrene, has been
known for years, with a dramatic
increase in the recognition and
reporting of such infections.

Infections
 Moreover, these infections are
commonly associated with the early
onset of shock and organ failure.
 Predisposing factors include varicella,
penetrating injuries, minor cuts, burns,
splinters, surgical procedures,
childbirth, blunt trauma, and muscle
strain.

Infections
 The most common primary site is the
extremities.
 The first cutaneous clue to fasciitis is diffuse
swelling of an arm or leg, the skin may
appear normal or have a red or dusky hue,
followed by the appearance of bullae filled
with clear fluid, which rapidly takes on a
maroon or violaceous color.
 In some instances crepitus may be present.

Infections
 In situations in which there is no cutaneous
evidence of infection, yet severe pain and
symmetric swelling are present or fever with
unexplained severe musculoskeletal pain is an
important clue to necrotizing fasciitis.
 Plain radiographs, CT or MRI, can be useful
in locating the site and depth of infection.

Infections
 Although necrotizing cutaneous infections are
classified into specific entities (ie, fasciitis,
clostridum myonecrosis) based on clinical
characteristics and etiology, the initial clinical
manifestations are not distinctive.
 Regardless of the etiology, the primary
therapy is emergent surgical debridement and
treatment with antibiotics that are active
against streptococci, clostridium species, and
mixed aerobes and anaerobes.
 Clindamycin and pen G IV or Ceftriaxone 2gm
q12h IV .

Infections
 Pyomyositis is a deep infection of muscle
usually caused by S. aureus and occasionally
by group A streptococci or enteric bacilli.
Most cases occur in warm or tropical regions,
and most among children.
 Patients present with fever and tender
swelling of the muscle;Following exercise or
muscle injury, the skin is usually minimally
involved.

Infections
 The diagnosis can be readily made, if
suspected, by needle aspiration and x-rays.
Surgical debridement and appropriate
antibiotics are curative (nafcillin-oxacillin or
vanco 1 gm q12h IV).
 Myonecrosis or clostridial gas gangrene
generally occurs after a contaminated injury
to muscle (knife or GSW).
 Within 1-2 days of injury, the involved
extremity becomes painful and swollen. Gas
present in tissue may be obvious by physical
exam, x-ray or CT.

Infections
 Furuncles and carbuncles are subcutaneous
abscesses caused by S. aureus.
 The lesions are red, tender nodules that may
have a surrounding cellulitis. They often drain
spontaneously.
 If fluctuant, these lesions should be incised
and drained in conjunction with antibiotics,
especially if systemic symptoms or cellulitis is
present.

Infections
 Folliculitis is a superficial infection of hair
follicles. The lesions are crops of red papules
or pustules that are often pruritic.
Staphylococci, yeast, and occasionally,
pseudomonas species are the responsible
pathogens.
 Local treatment with cleansing and hot
compresses is usually sufficient. Topical
antibacterial (bactroban-cleocin) or antifungal
agents also may be helpful.

Infections
 Ecthyma gangrenosum is an ulcerating lesion
associated with disseminated gram-negative
rod infection, commonly pseudomonas, and
observed in neutropenic patients.
 Treatment should be started with an
aminoglycoside and plus a 3rd
generation
cephalosporin (ceftazidime) until the results
of biopsy, culture and sensitivity are known.

Infections
 Paronychia is an infection of the soft
tissue around the nails due to S. aureus
when acute.
 Chronic infection may involve candida
or herpes simplex (herpetic whitlow).

Infections
 Herpetic skin infections: Subclinical
primary infection with the herpes
viruses is more common than clinically
manifest illness.

Infections
 Each persists in a latent state for the
remainder of the host’s life. With HSV and
VZV, virus remain latent in sensory ganglia,
and upon reactivation lesions appear in the
distal sensory nerve distribution.
 Herpes 1 and 2 affect primarily the oral and
genital areas, respectively. Varicella-zoster
virus is HHV 3.
 Disease manifestations are referred to as
either chickenpox or shingles (zoster).

Infections
 Fungal skin infections, or Mycotic
infections are traditionally divided into
two principal groups: superficial and
deep. We will only discuss the
superficial infections

Infections
 Dermatophytosis is a superficial infection of
the epidermis due to dermatophytic fungi,
Trichophyton, Microsporum, and
Epidermophyton species. Athlete’ foot and
ringworm are examples.
 These fungal infections may be confused with
eczema.
 Candidiasis is a red, tender edematous rash
occurring in moist body parts and caused by
C. albicans

Infections
 The diagnosis of fungal infections of the skin
is usually based on the location and
characteristics of the lesions and on the
following laboratory examinations, 10% KOH
preparation or culture.
 Dermaphytosis of the trunk (tinea
corporis,cruris-capitum) can be caused by
several species (T. rubrum-mentagrophytes)
resulting in inflamed patches with scaling
and, at times vesiculopapular borders with
central clearing.

Infections
 Tinea versicolor, a common superficial fungus
infection caused by Pityrosporon orbiculare, is
identified by scaling, red to brown or white
patches over the neck, trunk, and upper
arms. As the name implies, the lesions vary in
color.
 Either topical or systemic agents can treat
fungal infections of the skin and in general
topicals are preferred, e.g. miconazole,
clotrimazole, ciclopirox, or terbinafine creams.

Bone and Joint Infections
 This class of infections includes those
localized to the skeletal system and adjacent
structures, septic bursitis, septic arthritis and
osteomyelitis.
 Inflammation of the synovium-like cellular
membrane overlying bony prominences may
be secondary to trauma, infection, or arthritic
conditions such as gout, rheumatoid arthritis
or osteoarthritis.
 Septic bursitis is almost always caused by
staphylococcus aureus.

 The two most common sites are the
olecranon and prepatellar bursae. In
most instances, there is a history of
prior infection or irritation of the skin
overlying the bursa.
 Acute swelling, redness and peeling are
frequently present.

 The absence of fever does not exclude
infection, and one—third of those with
septic olecranon bursitis have no fever.
Bursal fluid analysis averages 50k wbc/
ml.
 Treatment involves nafcillin or oxacillin
IV and repeated aspirations. Followed
by oral dicloxacillin for 3-4 weeks.

 In adults, almost all cases of infective
arthritis of natural joints occur through
hematogenous spread.
 Occasionally, intra-articular trauma can
result in septic arthritis. This disease
process can be polyarticular or
monoarticular.

 Causative organisms for infective
arthritis include bacteria, viruses,
myocbacteria and fungi.
 S. aureus is the most common cause of
septic arthritis. In sexually active young
adults, N. Gonorrhea is a frequent
pathogen.

 Gonococcal infection may present as a
bacteremic illness with polyarticular
tenosynovitis and skin lesions, or as a
monoarticular septic arthritis.
 Other common causative agents are
streptococcus, group A streptococci and
salmonella.

 Viral agents associated with infectious
arthritis are rubella, mumps, hepatitis B
and parvovirus.
 These are usually a polyarthritis with
minimal joint effusions, and a result of
the host immune response.

 Tuberculous and fungal (sporothrix) arthritis
is usually monoarticular and an indolent,
chronic disease.
 The joints commonly affected are the knee,
hip, ankle and wrist.
 As a general rule, patients with inflammatory
chronic monoarticular arthritis should have a
synovial biopsy for culture and histology.

 The synovial fluid should be gram-
stained and cultured, analyzed for cell
count, glucose and crystals.
 Blood cultures should be obtained in all
cases of suspected septic arthritis (prsp
and ceph 3).

 Osteomyelitis, in general bone infections
develop in three ways: by hematogenous
spread, secondary to contiguous infection, or
by direct inoculation during surgery, as a
result of trauma.
 The term acute osteomyelitis is used clinically
to signify a newly recognized bone infection;
the relapse of a previously treated, or
untreated infection is considered a sign of
chronic disease.
 Clinical signs persisting for more than 10 days
correlate roughly with chronic osteomyelitis.

 Hematogenous osteomyelitis develops mostly
in prepubertal children and in elderly patients.
In children, infection is usually located in the
metaphyseal area of long bones (tibia-femur),
usually as a single focus.
 The clinical features of this form of
osteomyelitis are typically, the acute onset of
chills, fever and malaise, local pain, and
swelling over a bone.
 Blood cultures are often positive for the
infection.

 Other individuals at risk of hematogenous
osteomyelitis are IVDA ( S. aureus and P.
aeruginosa) as well as patients with urinary
catheters, patients with hemoglobinopathy, in
which salmonella and pneumococcus often
infect infarcted regions of bone.
 In most instances, physical examination
distinguishes septic arthritis from acute
osteomyelitis, because range of motion is
preserved in osteomyelitis.

Bone and Joint Infectins
 Vertebral infection, is the principal form of
osteomyelitis occurring in adults, typically it
involves two adjacent vertebrae and the disk
space between them.
 Neck or back pain and fever are the main
symptoms. Acute spinal epidural abscess is a
surgical emergency.
 Blood cultures are often negative, so needle
biopsy for cultures and histology are the
procedures of choice.

 Bone scan helpful and sensitive but not
specific and does not distinguish very well
bone infection vs. Soft tissue infection.
CT/MRI can reveal periosteal reaction-cortical
destruction when regular x-rays are normal.
 In the event of failure to establish a diagnosis
via biopsy, empirical therapy for 4-6 weeks
with nafcillin or oxacillin plus a 3rd
cephalosporin or vanco for MRSA. ESBL
(timentin,unasyn,zosyn) are alternatives.

 Osteomyelitis from a contiguous focus of
infection-prosthetic joint replacement,
decubitus ulcer, neurosurgery and trauma are
frequent causes of soft tissue infections that
can spread to bone. S. aureus and S.
Epidermidis are the most frequent organisms.
 A traumatic incident often associated with
osteomyelitis is either a human or an animal
bite. Human bites if deep enough, may result
in osteomyelitis caused by anaerobic mouth
flora.

 Cat bites notoriously result in the
development of osteomyelitis because the
thin, sharp, long cat’s teeth often penetrate
the periosteum. Both cats and dogs harbor
pasturella multocida, as part of their oral
flora, which is a frequent pathogen in this
setting.
 Therapy is with PCN G or augmentin or
fluoroquinolones plus clindamycin.

 Chronic osteomyelitis results from untreated
or inadequately treated bone infections.
Some patients have tolerated chronic
osteomyelitis for decades with intermittent
episodes of disease activity manifested by
local pain and drainage from a sinus tract.
 Complications include an anemia of chronic
disease, and occasionally amyloidosis-
fibrosarcoma. Diagnosis and cure are best
effected by surgical debridement and long
term antibiotics directed at organisms from
the surgical specimen.

Skin and Soft Tissue Infections Guide

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